Help with Spectra VCO

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Help with Spectra VCO

Post by Big BOB »

I have a 450-480 Spectra. I have loaded some 440 frequencies into it and can't get the VCO to lock. It seems that no matter what length I make the stripline it stays in the original band split. Does anyone have any suggestions why its not moving?


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450 Spectra

Post by VE3TUH »

I think you may have trouble going down to 440 with a 450 spectra. I have one also, and tried it, and was not real happy with the results. From what I recall, it had something to do with the pin voltages going to the vco, it would either rx but not tx well, or the other way around. Same luck with a 403 split, trying to bring it up. It was possible to get the radio close to where I wanted it, but performance degraded to unsatisfactory above 450. The only real answer is to get a range 2 model. If anybody has a range 2 radio, I would gladly trade for it. I could give up any of vhf high split, uhf range 1 or 3, 800, or a 900 mhz radio.

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Post by kc7gr »

I ran into a similar situation when I got my UHF Spectra (a Range 3 -- 450-482-- mid-power). I found that two modifications were needed to make it usable on 440.

(1) Place a small stripe of conductive ink on the VCO substrate, right at the end of the microstrip capacitor zone, to drop the thing's center frequency a bit. That took care of the FAIL 001 error, but I had one other issue. Specifically...

(2) Receive sensitivity below about 449.5MHz was the pits with a Range 3 front-end board. I ended up replacing said front-end board with a Range 2 part (about $150 or so from Motorola).

The radio has been working beautifully ever since, all across the 440 amateur band.

Keep the peace(es).
Bruce Lane, KC7GR
"Raf tras spintern. Raf tras spoit."
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