[amsat-bb] ICOM 706G phase noise

David G0MRF g0mrf at aol.com
Sat Nov 1 14:49:26 UTC 2014

Hi again
It appears the IC706 does transmit low level wideband noise over most of the VHF/UHF spectrum when in 'transmit' mode.
My issue was solved with a cavity filter in the TX output line. Now the 2m receive is nice and quiet.  I'll investigate replacing the cavity with a High pass filter which should have a lower insertion loss and be much smaller.
Also......Thanks to DG0ER for my first QSO on AO-73 earlier today. - Success at last.
-----Original Message-----
From: Paul Stoetzer <n8hm at arrl.net>
To: David G0MRF <g0mrf at aol.com>
CC: amsat-bb <amsat-bb at amsat.org>
Sent: Fri, 31 Oct 2014 17:34
Subject: Re: [amsat-bb] ICOM 706G phase noise


Try a diplexer on either the transmit or receive side (whichever works
better) with the common port to the antenna, the appropriate band port
hooked to the radio, and the other band port left disconnected. If
your Icom is putting something out on 2m when transmitting on 70cm,
that should filter it out.


Paul, N8HM

On Fri, Oct 31, 2014 at 12:41 PM, David G0MRF <g0mrf at aol.com> wrote:
> Hi all.
> Inspired by the FUN on the YouTube videos from the car park at Baltimore, I've 
been trying to set up a satellite station using two independent radios. An 
IC706G on 70cm transmit and an FT736R on 2m receive.
> Antennas are  a 4 ele yagi ( horizontal ) on 2m receive with an AMSAT-UK 
filtered preamp. Transmit antenna is a 9 ele Tonna mounted vertically.
> Antennas are on a rotator using a fibreglass boom about 1.8m long.
> The problem:  Whenever I press the 70cm transmit 'button'  - ptt on SSB, or 
key on CW I get S8 noise on the 2m receiver. (and S6 without the preamp)
> Note...This does not appear to be RF overload as I can turn the power down to 
minimum on SSB, even remove the microphone and the noise level remains.
> On CW the noise level is constant when the 706 is in transmit mode. It does 
not appear and disappear with each dot or dash.
> My conclusion is that on 70cm the IC706G is transmitting something on 2m 
whenever it is in it's transmit mode.- possibly phase noise.
> Has anyone else come across this issue with ICOMs or is it just this one? and 
is there a known minimalist solution.
> Many thanks
> David  G0MRF
> _______________________________________________
> Sent via AMSAT-BB at amsat.org. AMSAT-NA makes this open forum available
> to all interested persons worldwide without requiring membership. Opinions 
> are solely those of the author, and do not reflect the official views of 
> Not an AMSAT-NA member? Join now to support the amateur satellite program!
> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb


More information about the AMSAT-BB mailing list