开云体育

TRA 921 clarifier

g1inf #1663 Hello, folks, Has anyone any experience with fitting a clarifier (tx and rx) to the synth on a TRA 921? I've acquired a couple of these radios, and one of the applications I intend for one of them has frequency allocations at xxxx.5 kHz. I'm guessing I need to pull the reference osc crystal, but I'd rather get sound advice before plunging in. Best regards, Pete.
Jim Butch All Messages By This Member #1665 开云体育 Pete: ? I have modified two TRA-921's to work on 60M.? This is not a clarifier, but it is very simple to do.? The MHz knob on the radio selects a crystal oscillator for each 1 MHz band from 2 to 7 MHz.? The PLL synthesizer does the 100 KHz, 10 KHz and 1 KHz selection.? I simply found the crystal for the 5 MHz band and put a 12 pf capacitor in parallel with it.? You may have to "tweak" this value a bit to get it just right.? I did this by selecting the capacitor from several on hand.? This offsets the entire 5 MHz band down 500 Hz, but it will take you less than 15 minutes to put the mod in the radio.? This mod?will require you to tune to the next higher 1 KHz position on the dial, while on 60M. ? I thought about replacing the desiccator with a pot and put a?varicap diode?on the reference oscillator,?but I have not got around to it yet.? This would reduce the frequency stability a bit.? It is very good now. ? This radio also have very good true AM modulation and?a true AM detector along with a good AM IF filter.??For those who?check into any of the military?radio AM nets, it is?better than most packsets. ? Good luck, ? Jim Butch wb8cdx ? ?

Previous Topic Next Topic