kd0ar's Ham Blog

Useful Microwave Test Gear

2011-09-14T21:31:00.000-04:00

About 6 months ago, I ordered a VFO kit using an Si570 DDS chip. The unit is self contained with a 2-line display and an optical encoder switch to change frequency down to 1 Hz resolution. If I recall the specs on the Si570, I believe it is accurate to 25ppm. It puts out 10 dBm from 3.5 - about 260 MHz. There are other models which go all the way up to 1400 MHz. I got the lowest cost unit that goes to 260 MHz, which is adequate for its intended purpose. The units are available on http://www.sdr-kits.net/

I bought it so that I can use it as a reference oscillator for various brick oscillators. I have 2 bricks in my possession, one on L band, the other on 6200 or so MHz.

Here is a test setup showing the unit in operation, referencing my L band brick:

Software Defined Radio - What Is It

2010-12-08T22:01:00.000-05:00

Over the past year or so, I have made mention of the SDR (Software Defined Radio) in some facebook posts. I get questions from time to time, so I thought I would write a little bit about how this works and what it is, exactly.

I have 2 different SDR's actually. One is a receiver only, the other is a transmitter / receiver. Both of my radios cover the HF (shortwave) bands, from 1.6 - 30 MHz. The radios are kits, yea, you have to build them. They are a PC board which you have to populate the board with the parts. You supply the case for it, but the newest versions supplies all of the connectors.

The finished radios - Softrocks have no knobs, no volume control, no tuning dial, nothing. It is a black box with an antenna connector, a USB port, and 1 or 2 audio connectors, depending on if your board is receive only or is a transceiver and a power connector.

The USB port is used to tune the radio. The software which you use with this board sends tuning code to the board via the USB. It also automatically selects the band filters for the frequency youre dialed to.

The audio connector on the board sends a stereo audio frequency signal to the sound card. This signal is audio, but there is a slight phase difference between channels that is derived by the mixer on the board. Actually, there are 2 mixers on the board, with a common local oscillator , however, one mixer is fed a phase delayed signal from the local oscillator (90 degrees). The outputs of the 2 mixers therefore has a slight phase shift in the mixed down signals.

In transmitting, the transmitter basically reverses the above process, amplified and transmitted to about 1 watt, which I feed into a small linear amplifier outboard.

Because of this special stereo audio, the DSP chip in your sound card and the associated software is able to distinguish between upper sideband, lower sideband, AM, narrow band FM, double sideband (with or without carrier), DRM...anything you might want to receive.

The software (there are several different programs available) displays the entire spectrum that the soundcard sample rate allows. For instance, if your sound card is capable of a 96 Kbps sample rate, you are able to see 96KHz of spectrum at one time on your display. Lets say you are looking at the 49 meter shortwave band at night, you will see a spectrum analyzer display that is just under 100 KHz wide, and you will see every station within that bandwidth on the display. The software is calibrated in dBm, and you can see which signals are stronger or weaker and what frequency theyre on. A simple mouse click will allow you to select any signal that you can see. The demodulated output appears at your line output of your sound card.

One of the biggest features of this technology is the filtering. By "grabbing" and dragging the audio passband window in the software, you can continuously vary the bandpass and center frequency of the filter so you can eliminate annoying heterodynes and other interference from the sighal you want to actually listen to. There are preset filters, which vary from 2.4 KHz to 16 KHz in the AM mode (there are other filters for SSB). One can select one of these filters and modify them any way you want to enhance the intelligibility if the signal you want to hear.

Synchronous detection on AM is available in some programs that allow you to listen to shortwave stations in the presents of "selective fading" Selective fading is a phenomenon where the carrier fades, but the sidebands arent faded. This causes severe distortion during the fade, but the synchronous detector eliminates that problem by injecting a phase locked BFO to the carrier frequency, simulating the original carrier, and since the BFO does not fade, you will never know there was a selective fade going on (unless you look at the display).

All of these features are in the software. The hardware part is just a mixer and oscillator that produces an audio baseband signal for which the software can do its work. The hardware end of it is extremely simple. There are receivers available for as little as $20. The all band receivers are about $50 or so. When these are used with a good quiet sound card, the performance is quite unbelieveable.

I hope this answers a lot of questions as to what this technology is about. This is a basic, non-technical explanation. There are more in-depth websites that describe the technology in far greater detail.

2304 Yagi

2010-11-13T16:17:00.001-05:00

Being I got some power out of the transmitter, I had an idea a couple of days ago, and thought about building a yagi antenna for 2304.

I went with the DL6WU design, but with a twist. Instead of doing the folded dipole and balun, I went instead with the WA5VJB unbalanced half - folded driven element. Everything else about the yagi is in accordance to DL6WU's calculations.

I have 10 elements built so far. The longest element is about 60 mm long, and the boom length is 12 inches (305 mm). The entire antenna is made from hobby brass, the boom is 1/4 inch square brass. The elements are 1/16 inch diameter brass rod.

Here is a photo of the driven element. The driven element is insulated from the boom. At first I could not get the SWR down on the driven element. Some adjusting of the driven element length, shape and spacing to the first director, I got the return loss down to -30 dB or more. I cannot measure below that level of reflected.

As you can see, the antenna is quite small. The antenna appears to have decent directivity. Although I have not yet completely tested it with a weak signal source, placing my hand in front of the antenna causes wild fluctuations in the reflected power, but moving my hand around the sides and to the rear of the antenna shows very little change in reflected power. This kind of tells me that the RF is being radiated off the front of the antenna, which is what we are looking for.

The antenna will be extended to about 2 feet. I wanted to try to see if I could make this work with 10 elements before I waste the additional brass (and time) with a longer antenna.

I used the VK5DJ Yagi Calculator program to design this antenna. The driven element was designed by me, using the principle that WA5VJB used on his 1296 & lower antenna. The length was arrived at empirically, trimming the length and spacing between the DE and 1D. The odd shape of the hairpin does not seem to affect anything, its just how I happened to bend the DE.

I still need to package up the transverter and actually finish it. The antenna experiment was a little bit of a distraction to break some of the monotony of the rest of the project, besides, I had some ideas after talking to N6NB, Wayne at the Packrats VHF conference regarding his Quagi design. Since his designs were done on an antenna range, with a limited number of elements, I posed the question "How do you think your principles would work on a long boom design, such as the DL6WU design - using his director calculations, but replacing the reflector and driven element with your quad elements". His reply was that it should work. Although I did not go with the quad elements on this design, I did think that the WA5VJB driven element should work with this antenna, which apparently it does.

2304 MHz Transverter - Photos

2010-11-08T19:56:00.000-05:00

As I promised, here are some photos of the nearly completed 2304 rig.

This is the complete rig

One of the modified RF amplifiers with the cover off.

The other amplifier.

Mixer and IF Attenuator

Bandpass filter

Unused amplifier module.

Modified MMDS unit.

So these are the pictures of how this thing looks right now. The amplifiers are not bolted down to the aluminum panel yet. I have yet to install a T/R switch and I need to come up with some kind of power distribution. This unit takes +20V, -20V and +12V to make it all work.

2304 MHz Transverter - Its almost done!

2010-11-07T23:23:00.000-05:00

I know I promised a posting describing the filter and other modules that I'm using in this project, but I thought I would wait until I had gotten some of it actually working. Since I am now getting a useable amount of power out, I felt it was time to write a little. Today I built an IF attenuator to drop the 144 MHz IF level from 250 mW down to 1 mW to feed the mixer.

I then started hooking up the modules that I had built up. The LO was fed through a commercial low level amplifier module that was part of an amplifier chain which I will describe in a couple of paragraphs down this entry. Measured LO was about +16 dBm. The mixer wants between +10 and +20 dBm, so this level is perfect. From there, the output goes into the LO port of the mixer. The IF port goes to the 24 dB attenuator that I just built, and from there goes to the FT-817.

The RF port is connected to the band pass filter. This is a 3 pole inline resonator filter that had to be modified slightly to get it to tune 2.4 GHz. This filter does have a cool feature that is worth talking about. It has 2 notch filters incorporated in it. I tuned one notch to the LO frequency, the other to the image. This should be one clean transverter! The LO and image look to be down better than 80 dB because of these notch filters. The tuning of the bandpass filter is quite sharp as well.

From the band pass filter, the RF goes through my 2- mmic preamp I built from Down East. I'm only seeing about 20 dB of gain, however, so I'm not sure if there is a problem or not. I'm getting 0 dBm out of the preamplifier.

WA3TTS gave me some surplus 1.85 - 2 GHz hardware, including a filter and an amplifier chain. The amplifier chain consists of 5 modules. I'm not certain how much input power is required to drive the entire chain to its rated 5 watts, but my guess is about a milliwatt or 2. The modules all needed to be retuned to 2.4 GHz. The modules are built one stage per module, and are built on ceramic circuit board material and have etched tuning and matching circuitry with no tuning adjustments. The modules that I've tuned so far have been tuned with my Dremel tuning tool - carefully grind away printed capacitors and tuning lines. This is opposite of most microwave commercial hardware, as most surplus is designed to operate above the amateur bands, such as the MMDS unit that I added material to its internal PC filters to get it to cover the ham band. Because these units operate below the band, the opposite has to be done - copper has to be removed. Because the copper is either vacuum deposited or etched on ceramic, an X-Acto knife was pretty much useless. I then attempted grinding away the traces carefully with a fine grinding bit on the dremel tool. With the unit powered up and the covers off the modules, I connected the power meter to the output of the first module through the attenuator, and applied drive from the IF. I then began grinding the input network in the module while watching the power meter. As the power came up, I continued until I saw no more increase. I did the same with the output network. I'm seeing about 10 dB of gain thru each of 2 modules I have done so far. Currently I'm getting +23 dBm out of the last amplifier.

Well, thats where I am with the project right now. I still have a 5 watt PA to tune. All of the modules have to be mounted down to the chassis, and the T/R switching still has to be built. The receiver is working, and the transmit is working at the 200 mW level, and the next thing I think I'm going to do is install the T/R relay and try to make a short range contact with what I have so far. The 5 watt PA will be more difficult to tune, as it consists of a pair of devices which will have to be balanced somehow. I'm not entirely certain how I'll retune it, but once I figure out a gameplan on tackling it, you can bet I'll be posting a procedure right here. Check back soon for the info!

2304 MHz Transverter - Significant Progress Made #1

2010-10-31T22:43:00.000-04:00

Welcome back! Today was a good day. Got a LOT done on the transverter with the help of WA3TTS. There was so much that we did, I can't write it all in one post, or in one night. I'm going to split this up into several postings. Question is, where to start.

First thing, and probably a very important thing is we checked the LO level and spectrum. The level is much lower than I expected, I'm getting about -3dB at the SMA connector on the receiver brick. The good news is it is VERY clean, all spurs are down by more than 60 dB, and the nearest spur is over 100 MHz away from the intended LO freq. My plans have changed slightly because of this. Since I have 2 of the Down East ERA2 2 stage amplifier boards. I plan on taking the unbuilt board, and cut it in half, making 2 single mmic boards. I will then use one of these boards to amplify the LO. These boards should have about 15 dB of gain, so I should get about 12 dBm out of the amplifier, enough to properly drive the mixer. I'm certain that if i fiddle with the LO probe, I could increase this level, but since the LO is so clean, I am almost tempted not to mess with it. At least I know how much RF is there, it wont be difficult getting the level up to where it needs to be.

While I was there, I finished the mixer module. We added a filter (more about this on the next post), and measured -20 dBm at the RF port of the mixer. We only used the available -3dBm from the LO source. A signal generator simulated the IF, tuned to 144 MHz. The mixer output saturated at +6 dBm. I believe that when I increase the LO level to +10 - +13 dBm, the output level will increase dramatically.

We did not test the 2 stage low power amplifier. It is ironic to think however, that the -20 dBm coming out of the mixer matches perfectly the 2 stage gain of 30 dB, and in theory, I would end up with the +10 dBm that I'm shooting for at the output of this amplifier. I believe it would be better, however to drive the LO to the +10 dBm level and run less IF energy into the mixer, thinking the linearity would probably be better coming out of the mixer.

As you can see from what is presented here, the rig is almost ready to hook to an antenna. All that it needs is a good filter following the mixer, and perhaps a bit more power. Tomorrow I'll write about a filter that we retuned and some of the really cool features of this filter. We'll also talk a little bit about power amplification too. I'll leave the cliffhanger here... Lets just say, I got a solid state power amplifier that will provide meaningful power for portable work. It will need some work to get it to run on 2304, so will be experimenting with that soon also.

Stay tuned, keep the dish pointed this way, and check this frequency soon for the next update. 73 for now.

2304 MHz Transverter - A Little Bit About the TX Mixer

2010-10-28T17:37:00.000-04:00

While I'm waiting for the parts to come to repair the ABPM, I thought I'd write a little something about the mixer that I'll be using with this rig. The mixer I'm going to use is an old Vari-L DBM-184 flatpack double balanced mixer. The specs on this device, although it is a rather old device shows some promise according to the datasheet. It will accept up to a +20 dBm LO, the LO to RF isolation is about 20 dB, and is good to 2500 MHz on the RF port. The conversion loss is about 8 dB, which is typical for a DBM. Its 3 dB compression point is +6 dBm, which I would assume is the output power, which corresponds to an IF drive level of +14 dBm when used with a +20 dBm LO. I will not be driving this device that hard though, figuring on driving the device with about 0 dBm, and between +10 - +13 dBm on the LO port.

I picked up 2 of these mixers at the 2010 Packrat (Mt. Airy VHF Club) VHF Conference.

I am in the process of packaging the mixer in a brass box, just slightly larger than the mixer itself (3/4 inch square), with SMA connectors connected to all 3 ports. This will make the unit a "module" which is how I like to build things, especially when working with the microwave bands. This method of construction allows one to substitute different components, so one can experiment to find the best performing module for this particular combination of parts.

Basically, the planned signal path will be something like this:
From the LO tap in the CalAmp RX converter, LO will be amplified using a MSA-0386 in a homebrew amplifier run at saturation, feeding the DBM-184 mixer. The IF will be an attenuated 144 MHz TX signal from the FT-817nd, feeding 0 dBm into the IF port of the mixer. The RF port will feed a 3 resonator BPF designed by G0ORY, details of which appear here. From the filter, the RF will be amplified by the already constructed ERA-2 mmic amplifier. From that point, I'm unsure as to what the final power output will be, but I am hoping I will find an amplifier that will provide a couple of watts on the band. What I use will depend on what the pocketbook will allow, as well as what power supply I have available.

Once again, stay tuned, as work progresses, I will post again.

2304 MHz Transverter - Transmitter Construction

2010-10-23T18:40:00.000-04:00

After what seemed like forever, the ABPM (All Band Power Meter) arrived from Down East Microwave. I had also ordered 2 ERA-2 amplifier boards at the same time. I had the power meter built that evening, and went to test it, and the microwave detector does not work. The parts in that section are extremely tiny, and I'm thinking I popped the detector chip. I think it was probably my fault. I also believe I'm losing my touch, as I'm having more difficulty working with surface mount parts due to their size. I think I need to invest in one of those big magnifyers with the light in the head if I plan on continuing to work on this sort of thing.

Anyway, the power meter will read from about -20 dBm to +10 dBm in 2 bands - HF thru 500 MHz, and from 500 MHz to 10 GHz. The low frequency sensor is working perfectly. I got this shipment yesterday.

Today, I built one of the ERA2 dual mmic amplifiers. I am going to use this as a transmit amplifier to get to the 10 milliwatt level. 10 milliwatts is a magic power level, as many higher power amplifiers are designed to input 10 milliwatts to get you from 1 watt to 100 watts, depending on what you are planning.

The ERA2 preamp boards are tiny as well, but I didnt have too much trouble building this one. The 0805 chip caps are small, but fortunately, in these amplifiers, they're not too close together, and the circuit for a mmic amplifier is very simple. These boards are nice high quality boards, made of Teflon, and have plated through via's. These amplifiers provide about 30 dB of low level amplification, and will output up to 20 milliwatts at the 1 dB compression point.

This is a photo of the amplifier board. As you can see, it is quite small. Of course, I have no way to test it until I have the mixer finished. I am currently working on that now, but I'm short one SMA connector to make that happen.

I still need to finish the mixer, and I also need to make a bandpass filter to place after the mixer that will pass 2304 MHz, but block the 2160 LO and 2016 MHz image. I am going to use a 3-resonator type filter similar to the one I made for my 1296 rig. Things start to get rather small on 2304 MHz, the resonators are less than an inch long on this band. Its a good thing I have a micrometer. I'll have the filter swept before I use it on the air. If it's not selective enough, I'll use a cavity filter instead (or in addition to). 2304 is an awkward band in that it is more difficult to homebrew components such as the filters. Cavities for 2304 are about 1 1/2 inches high, which makes them somewhat on the large size if you are trying to build small. The resonator filters are less than an inch, and they require some level of precision for them to work well.

Once I get the mixer and filter built, I'll post again, and let you know how it all plays together. Once I get to the 10 milliwatt level, I may attempt to make a contact on the rig if I can find someone with the capability to operate that band without having to drive too far.

Stay tuned, the next update will be coming soon!

New Project - 2304 MHz Transverter - Tuning the Front End

2010-10-16T16:34:00.001-04:00

OK, I got the ambition to hook it all up today and start tuning the receiver. I used a very crude setup. The only signal source I have that will generate a signal near 2304 MHz is the second harmonic of the local oscillator in my 1296 transverter. I used that as the signal source.

I had to set up the signal source about 20 feet away from the workbench to keep the RF from being picked up directly on the 13 cm circuit board. I put a homebrew 1/4 wavelength antenna on the input side of a 0 - 50 dB attenuator, then fed the other side of the attenuator into the RF in on the converter. I used my FT-817 as the IF. Tuned to USB, I easily spotted the signal very close to 144 MHz on the IF. The signal was about an S-2 with 0 dB of attenuation inline with the little 3 cm long antenna. I began snowflaking the hairpins, adding small strips of copper to the hairpins where I saw an increase in signal and soldered them in place. There were a couple places that gave huge increases in gain, in the middle of the filter. After about 2 hours work, I was able to get the signal up to about an S-7 with 20 dB of attenuation in line with the little whip antenna I was using as a pickup.

The frequency stability appeared to be quite good, there was some drift when I first powered it all up, but that quickly settled down after it was on for about 5 minutes or so. I did not have to touch the VFO dial in the IF rig after that time.

The next step will be in building the transmit side of the transverter. I am still waiting on my order to come in from Down East- one of W1GHZ's power meters and a couple of MMIC low level amplifier boards. I need the power meter in order to tune the TX filter which I have yet to build.

Oh, I'm using this article as a guide to my conversion: http://www.qsl.net/g0ory/2.3g/31732/31732.html No sense reinventing the wheel, being Adam already did the hard part.

Stay tuned, when I start on the TX portion, you can bet I'll talk about it here.

New Project - 2304 MHz Transverter

2010-10-14T22:03:00.000-04:00

Its been so long since I've posted in here, I almost forgot I had this blog site. I haven't been very active since my last post, but I feel its time to document a new project that I just started today. This is a major project for me. What I'm doing is building up a transverter for 2304 MHz, partially from scratch, partly from an old MMDS receive converter. I'm building this unit around the California Amplifier model 31732 MMDS downconverter. These units were originally used to receive over the air cable television. I have successfully retuned one for Amsat Oscar 51 (AO51) ham satellite S band downlink on 2401.200 MHz. The converter is extremely sensitive and they appear to be stable enough to use as a basis for this project. This is the first time I've attempted to build my own microwave rig from either converting surplus or scratchbuilt.

The design goal for this transverter is to build a portable 13 cm station. Power output of a couple of watts, and later perhaps as much as 75 watts using converted surplus. This band is easy to do this with, being there is a nice variety of surplus hardware that can be used on these frequencies. The project will use the MMDS converter for the entire receive chain, including the LO. A probe (first modification) is installed just above the LO filter striplines, and exits the chassis to an SMA connector to be used to drive the TX mixer.

The TX mixer, bandpass filter and low level transmit amplifier will be homebrew, external to the MMDS whitebox. A surplus double balanced diode ring mixer will be used as the transmit mixer. From the RF port, a homebrew 3 resonator filter will pass only the LO + IF output of the mixer, then will be amplified to approximately +10 dBm, which will drive a commercial PA, which, depending on what I use, will run anywhere from 2 to 75 watts, depending on the model I'm able to acquire.

The first modification I have done was to install the TX LO probe to tap off some 2160 MHz energy to drive the TX mixer. This involved milling down a lip on the case of the converter and installing an SMA connector with a 30 mm probe inside the whitebox.

Today, I received the necessary crystal to change the frequency of the LO synthesizer to output the 2160 MHz. The crystal frequency is calculated by taking the operating frequency (2304) minus the IF frequency (144), then dividing the result (2160) by 256 (8.4375). This is the frequency of the crystal I ordered. I ordered this crystal from International Crystal, and it came in today. I installed the crystal, and checked the frequency, and it netted on frequency with very little effort. The output from the probe seems to be enough to drive the TX mixer.

The next step will be in tuning the receiver printed circuit bandpass filter, lowering its frequency from 2500 MHz down to 2300 MHz. My next post will describe the procedure, and will keep you informed as to my progress. So until then, I'll have to wait until I get some RG59 and some connectors so I can hook up the IF rig to the unit and start adjusting the hairpins on the pc board.

Cell Phone Interference on the Softrock Series SDR

2010-04-17T19:05:00.001-04:00

Ever since I built my first Softrock, I was plagued by the usual buzz sound caused by a cell phone in close proximity to the radio. It was so bad with the rig, that the phone could be anywhere within about 15 feet (or more) and the interference was still quite noticeable. I had some success reducing it slightly by putting ferrites on the cables going to the radio, but could never reduce it to the point where it would not be annoying - until today.

The following modification should work on any of the Softrock sets, although I tested it on a TX/RX 6.3.

On an old scrap circuit board in my junk box, I found some molded RF chokes. The particular value I found were 4.7 microhenries. I installed one in series with the B+ line at the power jack in my shielded metal chassis thats holds the radio. This reduced the interference substantially. I then bonded the B-, shield of the serial connector and the grounds of the 2 audio connectors as well as the ground of the USB cable in my 6.3, and that reduced the interference to the point where I no longer hear the interference with the phone in my pocket, about 3 feet away from the unit.

I tried the inductor on the B- side of the power supply also, but when I did so, the interference came back to about the same level as it was before I began.

As an added bonus, by making this modification, I was able to also reduce the center "hump" substantially as well. My analyzer screen in PowerSDR is now almost totally flat across the passband of the sound card.

If you have this type of interference on your V9 or 6.3, I strongly recommend doing this mod. I assume the inductor value isn't critical, so long as the value is relatively small. It seems that there is not enough capacitance between windings on the inductor I used to pass the 800 MHz garbage.

Progress Made on 1296 Rig

2010-03-06T21:22:00.001-05:00

Well, we figured out the problem with the 1296 rig, but I'm unsure how to fix the problem. Apparently there has been no oscillation problem all along, the local oscillator chain is producing harmonics that are causing some strange mixing products. We had a strong output on around 1250 mhz that was always at the output anytime the transverter was keyed. This signal goes away when the oscillator is detuned so that it stops oscillating, but is always there anytime the oscillator is going. The signal levels are equal to the desired 1296 signal when driven by the IF rig. So when the rig is running, I had an output on 1296 and a carrier at 1250 (or thereabouts). We traced the problem to a dirty LO chain.

We were able to clean it up substantially by inserting a 3 pole BPF between the 10 mW transverter output and the next amplifier stage. The correct way to fix this in my opinion would be to incorporate another of these filters in the output of the LO chain. We didnt get that far with it today though.

When we hooked up the 2W PA, there was no output from the amp, and we didnt have time to troubleshoot it. It was working when we began testing, so I am guessing it is something simple, such as a short in the RF path somewhere. Since the TX is now clean, I can now troubleshoot the amp and try to maximise the output power.

Another possible problem with the dirty LO is that of receive performance. With a dirty LO, the receiver will be receiving on 2 different frequencies, cutting the gain down by 3dB (or more) on the desired 1296 MHz, and also increasing the noise by 3 dB (or more), I never really noticed a receive problem with the exception of the RF stage oscillating, which was a confirmed problem. So, with that discovery, work can begin cleaning up the LO, and eventually I should get a 1296 rig on the air , hopefully before summer.

1296 Transverter Progress

2010-03-03T21:59:00.001-05:00

For quite awhile, I have been battling a low power problem with an older circa 1995 Down East Microwave 1296-144 transverter. At first I thought the PA was blown, I removed it and installed an outboard PA with no success. Eventually I replaced the entire transmit chain with still no improvement.

Most recently, I replaced the mixer IC. The original mixer chip is no longer made, however a newer model which spec's somewhat better than the original was installed.

I never reinstalled the PA module. I am going to do some testing very soon with the +10dBm output from the driver. If everything checks out, I'll continue to use the outboard 2W module, then feed that into the 30W PA. Keeping the rig this way, in my opinion would be more versatile as far as making improvements and upgrades on the circuit. Because everything is interconnected using UT-141 copper hardline, things such as bandpass filters and amplifier replacements can be more easily tried.

I am hoping to put the rig on a spectrum analyser and power meter to determine if the transverter is working properly. If it is, I plan on operating some 1296 up on the Lake, as well as possibly some mountaintop operations this summer. Stay tuned to my blog, I'll report here on the performance once I am able to make the proper tests.

Softrock 6.3 RXTX with USB Control

2010-03-03T20:01:00.000-05:00

I ordered and built the USB I2C controller board for my Softrock 6.3 RXTX. Adding this option opens up a whole new world for your Softrock. Not only does it allow you to tune the entire bands, but also allows you to have general coverage receive capability with the rig.

It also allows external programs to take control of the radio. This is REALLY cool, as you can run Powersdr in the background and use software such as fldigi and WSPR to actually control the frequency. Fldigi logging works great too, as it can read the frequency of the radio and it puts that into the log automatically.

Another added feature is you no longer need the serial cable to key the transmitter. This is all done now via the USB port. Of course, you still need to set up virtual com ports so the additional software can communicate PTT to Powersdr.

I have been using PowerSDR v.1.19.3.15 with this new setup. This version has been designed for use with CURRENT firmware in your softrock, and it works quite well. I find the audio is less choppy with this version as well, and it's a lot prettier on the screen with its customizable skins.

Upgrading your Softrock with this little $11 board is more than worth adding the option.

On a sidenote, the other night I thought I would try some digital communications running barefoot 1 watt from the radio, and worked a fellow in Arkansas using Olivia 500/16 on 40 meters. I was running 1 watt, he was running 40 watts and was using a Flex-5000. We maintained contact for 1 1/2 hours, talking about SDR in general. Was a real fun QSO. I'm looking forward to working my first Softrock to Softrock rig, as I think that would be quite interesting.

Softrock and the Digital Modes

2010-02-13T19:38:00.004-05:00

Today I was experimenting with setting up PowerSDR-SR40 for use with fldigi and other digital software, and I got everything talking to each other. When everything is working together, it makes operating digital so easy. So far, I got PSDR working with fldigi and Ham Radio Deluxe. I'm planning on getting it working with MMSSTV and EasyPal Digital SSTV program. I dont think there will be any problems, as they should set up the same as the ones I already got working.

There are 2 programs you will need in order to make everything play nice. First is "Virtual Audio Cable". it can be downloaded from here: http://software.muzychenko.net/eng/vac.html

When you get it, you will need to create 2 virtual sound devices. There are good instructions at the above website on doing this. One will be needed for receive, the other for transmit.

The other program you will need, and you will only need it for software that also controls the radio, such as fldigi and Ham Radio Deluxe, and that is "com0com", This creates virtual com ports to link the control aspects together. It can be gotten here: http://com0com.sourceforge.net/

You will need to create 1 pair of com ports for most applications. There are excellent pdf directions on how to do this at the above website.

Then go into Powersdr and set up the "CAT" section. Although some software will work using the identifier set for "SDR-1000", I've had better luck setting up emulating a TS-2000. Under CAT control, set the com port as the lower com port number that you created in the virtual com ports, I used COM5. Fldigi will use COM6 under its CAT settings. I used RIGCAT in Windows to control the SDR, and it plays nice. I have had some problems getting the external programs to control PTT, so I just use VOX for that. I used to use VOX in my Yaesu too when I ran digi modes.

To get audio to the programs, you need to set up virtual audio cable. I used Virtual Audio Cable #1 for audio out from PSDR and VAC #2 for the TX input audio. These settings will be found in the VAC tab in the audio settings in PSDR. The audio settings in fldigi are just the opposite - VAC2 is the output device, and VAC 1 is the input.

Once everything is talking, fldigi will read the frequency of the radio and you can then use the logger in fldigi, and it works like any other radio would with CAT control.

Ham Radio Deluxe sets up in a similar fashion.

To listen to your receive audio, should you choose to do so, VAC has a little utility called an Audio Repeater. You can set that up to input the proper VAC device as the input, and your soundcard that you use for your speaker audio as the output of the repeater.

There you have it, a basic overview as to how to set up different software so they will talk to eachother. Once they talk, operation is a breeze. I worked a little bit of the RTTY contest, and worked about 25 contacts in less than an hour with only 15 watts of TX power.

Good luck, and I hope this helps you get things working with your Software Defined Radio.

SoftRock v6.3 RXTX+Xtall

2010-02-09T22:00:00.004-05:00

About 2 weeks ago, I finished building a SoftRock v6.3 RXTX+Xtall SDR transceiver. I ordered the transceiver and 3 power amp, low pass TX filters, so I can cover 80 meters thru 10 meters.

The 6.3 TXRX is a 1 watt PEP transceiver capable of running whatever frequency bands that you supply PA's for. The standard kit allows for 16 presettable (with a 4 section DIP switch) frequencies. Each frequency is tunable over a span of 96 KHz with the software, with the preset dip switch setting being the center of that tuning range. All modes are possible, including SSB, AM, NB FM, and all of the digital modes, including Slow Scan Television using outboard software.

Most of my operation so far has been on WSPR on the 40 meter band, however I have operated SSB on 20 and 40 meters, and have worked a couple of countries using an outboard HFPack amplifier at about 15 watts. The performance is nothing short of remarkable, and have gotten exceptional audio reports while using a VERY cheap computer microphone.

Operating an SDR transceiver requires the use of 2 different sound cards. I use one card that works as the digital signal processor for the radio and the other to drive the speaker on receive and mic for transmit. For the radio card, you want the best sound card you can get, with the lowest noise and highest sample rate. 92 khz sample rate cards are available with noise floors in excess of -100 dB, and they are common and inexpensive. I bought a Soundblaster Audigy card for this purpose, but with many soundblaster internal cards, there is some phase shifting in the card, and I couldnt get a good balance without setting the phase and amplitude all over the place. I've used an older USB card such as the Soundblaster Live external card and that works pretty well. The external cards apparently do not suffer from the phase shifting that the internal cards do.

With the bare transceiver with the fixed frequency settings, the only software that is useable with it is a special version of PowerSDR, called;PowerSDR-SR40 and is available at http://powersdr-sr40.sourceforge.net/. All other versions do not allow you to transmit if the fixed frequency is enabled. There is, however an add on module that allows USB control of the Si570 oscillator that allows continuous tuning, which I ordered but have not received yet.

I will write more stories on this radio, and will detail a little more precisely on setting up this radio for use. It is a fun little rig, and for roughly a $100 investment, you will have yourself a very capable little radio.

New 2 Meter Radio

2009-11-12T18:32:00.001-05:00

With all the driving I do with my job, I decided to purchase a new ham radio for my van. I drove up to Amateur Electronic Supply in Cleveland and picked up the new Yaesu FT-1900R. The one I wanted was discontinued, but this is looking more and more like it is a better radio.

One thing that has concerned me is that the new mobile 2 meter rigs run 50+ watts. This one is 55 watts, and the package is so tiny, I was afraid that there wouldnt be enough heat sink to dissipate the kind of heat that a 50 watt final would produce. Turns out the entire bottom of the radio is finned heat sink, and it runs really cool with no temperature rise. Could they be running a class E PA in their rigs now? It would make sense.

Now for the operation of the rig... For a new radio, it is relatively convenient. You do need to reference the user manual, however, as programming the radio involves a few keystrokes, especially when you need to use CTCSS to access a repeater. You can also name the channels so you dont have to remember the frequencies when you tune thru the memories.

Operating the radio is a breeze once its set up. Power level is changed between 4 steps using a front panel button, tuning can be direct entry via the DTMF microphone (standard equipment), or by turning the tuning knob. The receiver has a hot .2 microvolt sensitivity, and the transmit audio is nice and clean. I've made a few QSO's on the radio from the mobile, and I am very pleased with it.

I also started a yahoo group on this radio, and if you have one, you're welcome to join it. The url is at
http://groups.yahoo.com/group/ft-1900r/

E-H Antenna

2009-09-22T16:55:00.004-04:00

Because of my limited space for antennas, I decided to do a little experimenting with an E-H Antenna. An E-H Antenna is a tiny HF and MW antenna. Originally designed for AM broadcast stations, these antennas supposedly operate with extremely high efficiency, but come in a very small package.

More information at http://www.eh-antenna.com/

I built one for the 30 meter band. The antenna is about 2 feet long, and have the antenna resonant close to the 30 meter band. According to my SWR meter, it currently runs about a 2:1 SWR on 10.139 MHz. I could get the swr down even lower by adjusting the matching coils. I did a rough tuning on mine, and got it close enough for now.

I've read mixed reports by hams who have built these antennas for themselves. Many say they dont work. Here is what I've found so far:

On receive, it seems to pick up a fair amount of noise, but that could be due to antenna placement. I dont have the antenna up very high, only about 10 feet.

On transmit, it appears to do fairly well, even at this height. Signal reports are about even using WSPR. I chose WSPR as an antenna testing mode because every station "advertises" their transmit power, so I can compare transmit vs receive efficiency easily. There is a difference, as my untuned 20 meter hamstick (going thru a tuner in the shack) consistently runs about 10 dB weaker on transmit than in my receiver.

Although this is not paint a complete picture, it does tell me that it works equally well, (or equally poor) between receive and transmit. When I am able to test the antenna when its up a bit higher, I'll be able to make better comparisons.

Watch for me on the 30 meter WSPR freq. I'll be beaconing using this antenna for awhile.

10 GHz Mountaintop Operations

2009-09-20T07:32:00.003-04:00

Saturday, Sept. 19 (2009) was the first time I have operated from a mountaintop on 10 GHz, and I'd like to share some observations from this particular trip. Because this was the first time I have operated from this location, Blue Knob, PA EN00rg, I'd like to tell you what I learned from this trip.

Mountaintop operations such as this tests the capability of your equipment beyond what I have experienced along the lake. Things such as receive sensitivity, pointing accuracy, etc are tested. On this trip, most of the signals are much weaker then what I experienced on Lake Erie.

One thing that was noticed readily on this trip, although our most experienced operator on site, KB8VAO said that this was a fluke, but the 2 meter band conditions were far better than the conditions on 10 GHz. Typically, signals on 10 GHz are much stronger than on 2 meters. Now I have noticed this up on the lake, but I figured this was caused by the duct over the lake being much smaller, and not able to support 2 meters. However, on the mountain, stations in New England were extremely strong on 2 meters, but almost imperceptible on 10 GHz. Many stations had to be worked on CW because the signals were so light. Most of the contacts were a struggle, especially the ones over 100 km away.

Although band conditions were such that there was a 2 meter opening, and 10 GHz seemed flat in comparison, I still managed to break my old personal distance record and worked Vermont which was just under 600 KM away. It was hit and miss for awhile, signal was quite weak, and had to be done on CW. I think next trip, I'm going to bring some form of headphones. I have found that headphones will give you about a 10 dB advantage, at least for me when working extremely weak CW.

The next week or 2, I'm going to compile an equipment checklist, I forgot to bring my code key, and had to borrow one to make the contact.

I worked about a dozen stations total from the mountain, ranging from 60 KM to 600 KM.

PowerSDR-IQ with the SoftRock v9.0 Lite+USB Xtall

2009-09-08T17:50:00.005-04:00

I've been running the Softrock Xtall+Lite v9.0 with the individual band pass filter boards for several months before I broke down and purchased the Electronically Switched Bandpass Filter about a month ago. Ever since I got it, I had problems getting PowerSDR to switch the filter automatically. I know the filter works because it works fine using Winrad. Today, I got powersdr-iq working with the filter using a fancy little trick that I discovered.

The first thing I did was to uninstall powersdr-iq. I went into windows explorer and deleted what was left in the installed folder. I then went and reinstalled powersdr-iq.

Now here is where it gets tricky. If there is a .dll file in the installed directory called "ExtIO_PMSDR.dll", rename it to something like "EXTIO_PMSDR1.dll". Then go and download ExtIO_Si570.dll and save it in your powersdr-iq folder. Rename the file to "ExtIO_PMSDR.dll". Run Powersdr-iq. Go to setup > General > USB and UNCHECK BOTH boxes under AVR. Then go to the ExtIO tab, under General and check "PM-SDR Enable". Click the "Toolbox" button. You will get another box pop up. If you have Winrad installed and working with the dll for the Softrock, this box will look familiar. If you need help with this box, here's what you need to do with it.

Under "BPF", check "Enable". Normally the info in the band boxes would have for Band 0 1.8 to 4 mhz. I built my BPF so that band 0 is 50 - 54 MHz, so I changed those numbers. I also changed Band 1 to 3 to 7 MHz. You may not have to do this, but by experimenting with the cutoff freq's for MY individual filter, I found these numbers to work best.

I have posted to the usergroups regarding this problem, but it sure seemed that I was the only one that had this problem. I find that hard to believe, but now that I have this new dll installed, I can fully customize the filters, and they switch just like in winrad, probably because its the same software snippet that Winrad uses!

If you have noticed this problem too, give this fix a try. At the very worst, you might need to uninstall psdr and start over. This is all experimental software, and I'm sure that if youre using this stuff, you've probably uninstalled and reinstalled more than once anyway. Its worth a try. Let me know if it works for you too.

1296 update

2009-09-02T17:56:00.003-04:00

I had just finished rebuilding my 1296 rig and assembled the modules. I added a 3 pole bandpass filter between the transverter output and the 10 dB gain block that drives the 2 watt PA. When I initially tested, I wasnt getting any power out of the rig, so I proceeded to test for RF at each stage.

I was getting the usual milliwatt or two out of the transverter., but at the output of the filter, there was nothing. I retuned the filter for max output. I lost about 3 dB thru the filter.

After hooking up the low level amplifier, the measured output was about +8 dBm. A little lower than I expected, but it's enough to drive the 2 watt amplifier to a useable output level. A quick check at the 2 watt PA output indicated a healthy output. I then determined that I had the antenna relay hooked up backward, RX line going to the TX port, etc.

Once I got it all hooked up, there was an oscillation, which I cured by shielding the low level amplifier. The output is a little low, i think, but I still believe it is enough to so some good mountaintop work. I believe I can get a little more out of the transverter, however, so I'm sure I can get the power level up to where it should be. I guess the level to shoot for is +10 dBm out of the low level amplifier. So, it looks like I'm capable of getting on 1296 now.

1296 2W Amp Update

2009-08-22T10:11:00.003-04:00

I got the 2 watt 1296 amplifier working Friday evening. I have had some problems with it when I was working on it. Let me give you a history before I go on.

The active device is a Motorola SML7008, which is known to work on 1296, but with slightly reduced RF output. This was aquired on eBay as a kit.

A couple weeks ago, I installed the circuit on an aluminum pallet ready to install in the enclosure that I planned on using. After it was assembled, I installed a couple of SMA connectors, connected it to a 20V Dell laptop power supply, terminated the input and put my power sensor on the output.

When I powered it up, the unit oscillated. I tried all of the usual fixes - conductive foam, etc... to no avail. The PC board that came with the kit used single sided material, with 2 mounting holes for the board and the active chip is flange mounted with 2 holes.

The fix was...I installed some flashing on the top side of the board, wrapped it around to the bottom, and screwed the board down against the flashing to the aluminum pallet. This is what eventually fixed the amp.

Now, when I was testing the amplifier earlier, I discovered the transverter power output was a tad bit low. This amplifier likes 10 milliwatts on the input for full output. I'm getting about 2 mW. The output spectrum isnt as clean as I'd like either, so I'm planning on building a 3 resonater filter and will place that on the output of the transverter, and a MMIC amplifier following that, to drive the 2 watt amplifier. I'm guessing the filter will have about 3 dB or so of loss, so the MMIC should work out just fine. I will probably be using a MSA-1105 for the active device. I still need to look up the device specs, gain, etc., but I believe it should work out. Once I get this done, I'll be packaging the thing up and will try some line of sight contacts with it using one of my 10 element yagi's. Of course I'll keep you posted as to how it comes along.

WSPR Beaconing

2009-08-22T09:10:00.005-04:00

Along the same lines as PropnetPSK, I ran across another system that looks promising, WSPR. Pronounced "Whisper", and is an acronym for "Weak Signal Propagation Reporter". This is the kind of thing that looks quite interesting, so I downloaded it and installed and ran it for a couple of days.

This looks to be a great mode. It decodes signals up to about -29 dB below the noise floor, uploads the spots to a realtime database and plots them on a google map. Most stations run about a watt or two, with some running a couple hundred milliwatts. This is an USB digital mode. Bandwidth is a whopping 6 hz! It does not take much power to be heard.

There are stations on most of the HF bands, however most are concentrated on 30 meters. Again, I would like to see some activity on bands like 2 meters, as being the extremely weak signal properties of this mode, it would be beneficial in showing enhancements on the VHF bands. So far, I have not seen any activity on 2 meters.

Although this is an excellent mode, I dont have a good working antenna for 30 meters, so my transmitted signals are typically down about 15 dB from others on the band. Until more activity starts to show up on bands above 10 meters, my activity on this mode will be limited, I believe. This is a personal preference, I would operate more if I had a 30 meter hamstick, which I may end up getting at some point, but for now, I will probably keep beaconing on PropnetPSK.

10 GHz & Up Cumulative Contest Part 1

2009-08-18T20:46:00.005-04:00

Part one of the 10 GHz & Up contest was August 15 & 16th, 2009. I operated Sunday for a couple of hours on Lake Erie along with WA3TTS and KB8VAO at grid EN91kt. I would have stayed all day like they did, but I was on call at work for 13 radio stations, so I cut it short, just in case.

Although I only operated from about 9AM - noon, I managed to work 10 stations. A large number of VE3's were roving across the lake, into Michigan and around to Ohio. Unfortunately, I did not work them all at every stop, as I left around noon.

Veteran microwave operator, KB8VAO operated the lake both Saturday & Sunday. I dont know how many QSO's he had, but I'm sure he did quite well, as the band was even better on Saturday than Sunday.

Mike, WA3TTS worked 20 QSO's on Sunday. He spent all day there, and this was his first time out on the lake operating with any real seriousness. Mike was up on the lake last year during a microwave activity day running a milliwatt or 2, but his receiver was confirmed working perfectly. Now that Mike has had a taste of some 10 GHz operation, I'm sure he will be quite active in the future. Mike is also planning on building a beacon for 1296 and 10 GHz.

This was a really fun event. It adds a new dimension when you get to operate with other microwaver's. Steve coordinated the operation because he was running the most power and was the most experienced among us. I have to thank Steve because if it wasnt for him, I dont believe we would have done as well as we have.

Now for the 2nd part of the contest, there is talk that Saturday, we operate from Lake Erie again, and from Blue Knob, a mountain in south central Pennsylvania. I have never done a mountaintop operation before, so I'm sure that will be an interesting operation. From what I hear, the long haul DX possibilities are nothing short of incredible, so I cant wait to do something from there. I went to the mountain last summer to check it out, but havent operated the mountain. You can see for miles in every direction, so no doubt, 10 GHz will go a long way from there.

Software Defined Radio

2009-08-12T20:11:00.005-04:00

Something I've been playing around with, on and off over the past few months has been Software Defined Radio, or SDR for short. A few months ago, I ordered a kit receiver from Tony, KB9YIG. He has been continuing the "Softrock" series originally sold by the American QRP Club. The latest "Softrock 40's" currently are synthesized, and are controlled totally by computer. The theory is a bit deep as to how these work, but for simplicity, I'll say that the sound card in a computer does all of the demodulation of the signals.

This opens up a whole new world of radio. Here, a small pc board, which costs about $50 will tune the HF bands thru 6 meters, and do it so well, it rivals almost any radio on the market. The features of the radio is only limited by the software used in conjunction with it. Using this radio, and a program called "PowerSDR", the receiver will tune, general coverage from 1.6 MHz thru 30 MHz, or from 3.5 MHz thru 52 MHz. It will also receive all modes, USB, LSB, CW, AM, FM and DRM. Using external software, the receiver will receive all of the amateur digital modes (PSK, SSTV, Olivia, Hellscreiber, etc), and with Dream software, will also decode shortwave DRM Broadcasts.

Tonight, I listened to Radio Canada International for about an hour, running Dream, listening to their digital broadcast. They did a commentary, News, etc, which is what you would normally hear on a government operated shortwave station, but they also played some music - Gospel, Jazz, etc. I will say, the quality was almost as good as FM broadcast quality. Absolutely no noise whatsoever, and the frequency response and distortion were exceptionally great!

Of course, the receiver will listen to the analog AM broadcasts, as well as SSB and CW with no additional software.

The display shows a panoramic view of the frequency domain (It looks like a spectrum analyser), and by using different sound card sample rates, you can see anywhere between about 50 KHz to about 200 KHz of spectrum using 48K thru 192K sample rates respectively, provided your sound card is capable of the faster rates. I usually run the 48K rate, as the 96K rate my sound card sounds choppy.

Originally, I purchased this device as an aid to finding rain scatter signals on 10 GHz (with the appropriate converters), however, this is just so cool, that I have been using it as a general coverage receiver.

I just purchased a electronically switched bandpass filter kit for the input of the receiver. The way I have been using this so far has been by changing out little monoband filter boards that cover sections of the HF spectrum. The kits, including the bandpass filter are mostly surface mount devices, and the parts are extremely tiny. There are special techniques for building with these components. I'm finding my eyesight isnt as good as it used to be when I was younger, as I've been having trouble seeing what I'm doing. I can only work on it for about half an hour at a time till my eyes get "buggy".

The link to this really cool project can be found at http://www.wb5rvz.com/sdr/
Hope you try one of these, you'll have a blast with it! They also make a version that transmits also.

Absorptive SWR Bridge for the Microwave Bands

2009-08-08T18:44:00.010-04:00

A number of years ago, I built an antenna tuner with a very simple SWR meter built in. This SWR meter worked using the Wheatstone Bridge theory, and the indicator was an LED. This meter worked well on HF using 2 watt transmitters. It had occured that since most microwave work is at similar power levels, why one of these meters wouldnt work on VHF and above.

I therefore built a meter similar to the one I used. I found an article on W1GHZ's site, that was very similar to what I was using. Here I thought this was a new idea for a microwave reflectometer, but Paul thought about it before me. I did, however use his circuit, and I also made a few modifications to his circuit to make it better. The schematic is shown. Click on the image for a larger view.
Basically, this is a wheatstone bridge. The three 50 ohm resistors, along with the output port, which if the impedance equals 50 j0 ohms, there will be a null across the 100 ohm resistor, and therefore no diode current. If however, the resistance is anything other than 50 ohms, an imbalance occurs, and RF will be present across the 100 ohm resistor, as well as across the diode. The imbalance current is read on the meter, and can be calibrated as SWR. One feature that is inherent with this type of meter is that it always presents a load near 50 ohms to the source, preventing any kind of burnout of the PA. The disadvantage of this type of circuit is that it cannot be left in the circuit, as it will have approximately a 6 dB loss.

The resistor with the "*" can be found experimentally, or replaced with a potentiometer of about 10 K or so to adjust the meter for a full scale reading with no load connected. To measure forward power to calibrate the meter, remove the antenna or output connection. To measure reflected, simply reconnect the antenna or device being measured. The power handling of this device is quite low, so don't transmit into the meter running more than a couple of watts for very long. My meter will calibrate with 1 watt applied. This meter will work using standard leaded resistors and chip capacitors up thru 432 MHz. To make the unit null on 902 MHz and above (probably thru 2304), you must replace all the resistors with chip resistors. Remember, any path carrying RF should be made with 50 ohm stripline.

My present meter is using the standard metal film leaded resistors, and the null is very good on 432 mhz. I use sma connectors for the guzinta and the guzoutta. I used what I had available as far as the resistors and caps are concerned. I have leaded resistors but no leaded caps, so I used all chip caps for mine.

This device can be used from HF - SHF, but it is a QRP meter. I wouldnt load more than 5 watts into this device.

If you have any questions on this meter, please leave a comment. I will try to answer any questions you may have. I hope that some of you may find this device useful, as it makes antenna tuneup easy, and protects the final of your radio while youre tuning!

1296 amp, and other things....

2009-08-03T22:09:00.003-04:00

Today I built up my 2 watt amplifier for 1296 (23 cm). Basically, the board was built, I just mounted it to an aluminum pallet and built a small brass enclosure, mounted sma connectors and power connection.

I tested the thing out using a reduced voltage. I hit it with 12 volts, the unit takes 20 - 24 volts. Turns out it needs like 15 - 16 volts for it to start working, and of course, I had nothing coming out. A phone call to Mike, WA3TTS confirmed that I needed more voltage. I have a couple of old Dell laptop power supplies that are good for about 20 volts at 2 - 3 amps, which should work ok running this amp, which I will use. I will set that up another day, because I need to make this idiot proof, cuz....well, lets say, I've been known to be an idiot sometimes! ha ha... Dont need 20 volts on the transverter or the IF radio.

I also installed Windows XP on my shack pc. It had Vista in it, and I found that my software defined radio did not work in Vista, and besides, this computer is REALLY slow running Vista. Now everything is working again. Just set up Propnet-PSK again, but I have it set up as a lurker station on 10 meters. I'll get the PTT RS-232 working in the next day or 2.

I also volunteered to help out with a local public service event here in New Middletown tomorrow (tuesday). Theyre having a village "party" at the village park, and it kicks off with a parade. I'm to help organize the parade and provide communications for the parade. I did this last year too. Its one reason amateur radio exists, to provide communications as a public service. I therefore am helping to justify our frequencies by helping out in local events.

Well, I havent been doing that much radio wise lately, as the blog shows. The 1296 rig is still my current project, but its time to start packaging the rig, and putting the system together. Once the 2 watt amp is working, then I'll need to rebuild my 30 watt amplifier, then we'll be pretty well set up. Of course I'll keep you posted! 73 for now...

10 Element 1296 Yagi Works!

2009-07-14T20:12:00.002-04:00

Just finished building and tested a 10 element yagi for 1296. This antenna replaced the larger yagi that did not appear to work. This one received the source just fine. Being it is only 21 inches long (boom length), it did not perform like the 4 foot long antennas that I had tested earlier, it still seems to have the gain and directivity that I would expect out of a 10 element yagi.

The software that I used to design this antenna suggests that the antenna can be lengthened without having to change the current element lengths or spacings. Therefore, I'll add another segment to this antenna at a later time to increase its size to something that should be more useful.

This antenna was a new design, as I used very small diameter elements (1/16 inch). Most yagis on 1296 use 1/8 inch elements, which in my opinion might be a little large for this band. Although the software can design working antennas with different diameter elements, I went with 1/16 inch aluminum to keep the weight down, and I'm thinking the thinner elements might provide a little more gain.

The next step is to get these antennas tested for return loss. I still have no idea how they perform in that manner, and do not have the instruments to test. I did run across an article online telling how to build a directional coupler that works from 2 meters up thru 1296, which I just might decide to build. I think I have all the necessary parts to build it.

1296 Antenna Testing

2009-07-12T14:29:00.003-04:00

I just finished doing some tests on my 3 1296 yagi's. The first was a WA5VJB wood boom yagi, the second, was designed on VK5DJ's calculator, the third was a loop yagi. Knowing that the loop yagi works reasonably well, it was the antenna to beat.

This test was done in a rather unscientific manner. The signal source was a 48 MHz oscillator using ambient radiation from its open enclosure, located about 50 feet away from the antenna under test. The 27th harmonic was weak but quite noticable in the receiver. I did not use any metering to determine gain from one antenna to another, but just compared them all "by ear". I have no way of determining the return loss of the antennas under test. The "antenna range" was not ideal either, located between 2 metal structures about 50 feet apart. I was able to notice decent directivity and antenna gain between the antennas I tested. I figure that the directivity would give some indication of gain. Anyway, here are the results of this test:

The WA5VJB 10 element yagi compared favorably to the 19 element looper. Directivity and apparent gain were too close to call which one was the winner. The 18 element yagi that was designed using the VK5DJ calculator could barely hear the signal source. I therefore measured the dimensions of this antenna, and realized I had built this antenna for the satellite portion of the band (1268 MHz). I will be redesigning another antenna using this design, but tuned to the proper frequency.

Keep in mind, this was a very unscientific test. I meant to do this to see if there was a noticeable difference in the performance of these antennas. Because I built the VK5DJ antenna some time ago, I hadnt realized it was built for the satellite portion of the band. I will run a new test on this antenna once it is built.

I printed out 2 different designs using the VK5DJ Antenna Calculator. One was for a 10 element yagi, the other for an 18 element model. The element lengths and spacing are identical for the first 10 elements, which suggests that a 10 element version could be built, and later the antenna extended to at least 18 elements at a later date. Therefore, I will construct the 10 element version, then will extend it at a later date, if the 10 element version checks out.

1296 MHz Station

2009-06-22T08:51:00.002-04:00

Finished building another 1296 MHz antenna last night. I have been experimenting with yagi antennas for the 23 cm band lately. Planning on doing some antenna comparisons this weekend. The new antenna was designed using the VK5DJ calculator. This particular antenna has 15 elements on a 3 foot boom. Over the winter, I built one of the WA5VJB "Cheap Yagi's", but have not been able to test it yet. I hope to be able to compare these two antennas over the weekend. This latest antenna was built on a 1/2 inch diameter round boom and is of all metal construction. The "Cheap Yagi", as with all of these antennas was built using a wood boom, in this particular example, I used a 3 foot 1/2 inch wooden dowel for the boom, and brass brazing rod for the elements. When I'm able to check the return loss on these antennas, I'll post the info here. I have a low power signal source that I can use to do relative gain measurements on these antennas. It will be interesting as to how these antennas compare to eachother.

kd0ar audio captured in a video

2009-06-19T21:06:00.003-04:00

I found something that is WAY too cool. N0SSC captured me on video while he was making a contact on satellite AO-51. I've always been curious to see how I sounded on the satellite, and I seem to have been hitting it good that day!
The url to the YouTube video is at http://www.youtube.com/watch?v=ywECT739etI

More PropNET info

2009-06-17T16:34:00.002-04:00

I spoke of PropNET in a previous post. Allow me to direct you to more information and the maps it generates to show where the propagation is happening. First, the display info can be had at http://propnet.org/index3rp.shtml . This link will allow you to set up the band and area of the country you are interested in. When you have that set up, click the "Catches" link just under the table.

Now for the software which you'll need to participate in this project. You can find the software here: http://sourceforge.net/project/showfiles.php?group_id=250959&package_id=306760&release_id=671918

leave a comment on this post if you have problems, or twitter me at http://twitter.com/kd0ar if you need more information.

PropNET PSK

2009-06-16T23:53:00.002-04:00

I discovered something rather interesting a couple days ago, called propnet psk. Basically, it used psk31 to beacon, looking for propagation. The way it works is a special soundcard based program is used, you set it up for the band you want to beacon on, and input info like your grid square, power, antenna height, etc. It builds a special code to let others know your operating conditions. The beacons if heard by other beacon ops gets posted automatically to a website, showing areas of propagation. Currently there is activity on 30 meters, 10 meters, 6 meters and 2 meters. 10 meters is the most popular right now, but would like to see more of this going on 2 meters.

This could be a really good indicator of 2 meter band openings if there were more operators on this mode operating on 2 meters.

WA5VJB Cheap Satellite Yagi

2009-06-15T22:13:00.002-04:00

Well, I was a bit bored tonite. I've been having trouble with the 2 meter portion of my satellite antenna lately. I think water got into the balun and screwed it all up. So, I've been working on replacing the VHF portion of the antenna with a 3 element version of WA5VJB's Cheap Yagi.

This antenna is an interesting design. It uses half of a folded dipole (Kinda like a 'J' shaped element) for the driven element. With the driven element alone, the SWR and feed resistance is VERY low, but when the reflector is brought real close, the SWR goes down. The spacing is strange, something like 8 inches between the driven and reflector, and the director is about 18 -19 inches in front. I'm not sure how this works, but apparently it does.

When I get the VHF portion done, I need to build the UHF one, and tune it to 432 MHz and sweep it to see how flat the SWR is between 432 and 436 MHz. The current antenna has horrid performance on AO-7, but it seems to receive well on AO-51's downlink.

Will keep you up to date as to how the antenna is coming along. My analyzer's battery is dead and is charging now, so looks like I'm done playin for tonite.

10 GHz short range experiment

2009-06-14T23:09:00.000-04:00

Today I took part in a shortrange experiment on 10 GHz. Because I have not made a contact in a long time, Steve, KB8VAO came over, calibrated the gear, and he ran mobile on 10 GHz. Yes, mobile, running a 10 slot alford slot antenna on a magnet mount on his car. I was able to work him over a 2 km range. Range was poor because of the trees in the path. The experiment did, however accomplish a couple things. 1. Because his rig is phase locked to a stable, calibrated source, I was able to determine that 10368.1 MHz corresponds to 144.128 MHz on my IF rig.

Second, I was able to determine that my 2 watt amplifier was working properly, as his rig runs 8 watts, and we had similar copy even over the weaker paths.

I was running the offset dish on my end, tripod mounted in my driveway, DB6NT transverter (g2 model), into a DEMI 3 watt amplifier.

I believe Steve was running a DEMI transverter with an 8 watt PA into the slot, trunk mounted.