Saturday, October 16, 2010

New Project - 2304 MHz Transverter - Tuning the Front End

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:  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.

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