Icom F121 Receiver Sensitivity Problems

Forum dedicated to discussion on Icom Commercial Radio products such as F70, F80, F1721, F2821, F9011, F9021, F9411, F9521, F9511HT.
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d119
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Joined: Fri May 13, 2005 9:31 pm
Location: The Internet

Icom F121 Receiver Sensitivity Problems

Post by d119 » Wed Jan 11, 2012 1:51 pm

Is anyone aware of any known issues with the ICOM IC-F121 series VHF radios that causes receiver sensitivity to go to crap?

I have two units exhibiting this problem. One opens squelch at 15uV (not .15uV, 15uV!) and the other is even worse, needing about 60uV to open the squelch.

I have adjusted the squelch on both units and also performed the BPF alignment using the CS-F100ADJ software. I am using a Motorola R2600 to align the radios and am an experienced RF technician by trade.

There's definitely a hardware issue going on here. Anyone experienced this problem and know of any solutions short of sending it off to Icom for repair?

I am not an ICOM fan, but we have a non-profit that really needs these radios working and I'd like to help them out.

Thanks!

jpeted307
Posts: 2
Joined: Mon Feb 06, 2012 11:53 pm

Re: Icom F121 Receiver Sensitivity Problems

Post by jpeted307 » Tue Feb 07, 2012 12:22 am

the problem is the 2nd BPF, the 450khz filter. They are a bit of a pain to change as the entire ckt board has to be removed because the filter is mounted on the bottom of the board.

eh2677
Posts: 4
Joined: Sun Dec 13, 2009 3:57 pm

Re: Icom F121 Receiver Sensitivity Problems

Post by eh2677 » Thu May 17, 2012 8:47 pm

It does seem to be a common problem for the 450kHz Ceramic Filter to fail and have the radio become "numb". In VHF radios I replace the 450F TOKO ceramic filter (+ or - 6kHz or 12kHz total) to a 450H (+ or - 3kHz or 6kHz total) ceramic filter. I do this to make the radio more selective because adjacent VHF channels/frequencies are now 7.5kHz and a 12kHz filter is simply too wide so will hear the channel you are on plus the adjacent frequency above and below. Of course there are other issues with the radio but this will help make the radio more selective when it isn't scanning at least.

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