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Help with Spectra VCO

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Big BOB
Posts: 185
Joined: Tue Sep 04, 2001 4:00 pm

Help with Spectra VCO

Postby Big BOB » Fri Jan 07, 2005 11:47 pm

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?

Thanks,

Big BOB

VE3TUH
Posts: 269
Joined: Fri May 24, 2002 3:14 pm
What radios do you own?: more than I should...

450 Spectra

Postby VE3TUH » Sat Jan 08, 2005 7:08 am

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.

Randy

kc7gr
Posts: 1027
Joined: Wed Mar 13, 2002 4:00 pm
What radios do you own?: Motorola, Icom, Sunair (HF).

Three Words: Conductive-Ink Pen

Postby kc7gr » Sat Jan 08, 2005 5:42 pm

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).
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Bruce Lane, KC7GR
"Raf tras spintern. Raf tras spoit."


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