[ICOM] 756 pro III noise

[Walt - WB2VSJ]

Jim,

That's what I was getting at in my first reply.  You want to have a shielded
termination on the rcvr ant input.  Even a short piece of unshielded wire
will act as an antenna and pull in any local QRN.

What does the ICOM's spectrum scope display look like?   Is the noise broad
band or does it peak on certain frequencies?

What happens if you turn on the attenuators? 

Is the Noise Blanker effective in reducing the noise?

Try having  PRO III powered up and while it is  receiving the noise, then
turn on the second radio. With  the second radio see if you can hear if any
noise is being generated by the PRO III.

Walt

-----Original Message-----
From: icom-bounces at mailman.qth.net [mailto:icom-bounces at mailman.qth.net] On
Behalf Of Jim Hargrave
Sent: Tuesday, October 12, 2010 9:15 PM
To: ICOM Reflector
Subject: Re: [ICOM] 756 pro III noise

Jim,

Have you actually shorted the antenna connection? Does it go away?
Is the noise on all bands or just 40M?
Does it stop if you reduce the receiver RF gain?
What happens if you turn off the AGC?

     73's Jim
      W5IFP

> -----Original Message-----
> From: icom-bounces at mailman.qth.net
> [mailto:icom-bounces at mailman.qth.net]On Behalf Of Jaime Gomez
> Sent: Tuesday, October 12, 2010 8:08 PM
> To: ICOM Reflector
> Subject: Re: [ICOM] 756 pro III noise
>
>
> Thanks, Walt, the noise is present even without anything connected to 
> the antenna input.
> 73,
>
> Jim, HK1N
>
>
> On Tue, Oct 12, 2010 at 7:06 PM, Walt - WB2VSJ <wb2vsj at earthlink.net> 
> wrote:
>
> > What's it do with the rcvr  input terminated?  i.e. dummy load.
>  Only 40M?
> >
> > -----Original Message-----
> > From: icom-bounces at mailman.qth.net 
> > [mailto:icom-bounces at mailman.qth.net]
> > On
> > Behalf Of Jaime Gomez
> > Sent: Tuesday, October 12, 2010 7:26 PM
> > To: ICOM Reflector
> > Subject: [ICOM] 756 pro III noise
> >
> > This afternoon I was testing one of the new antennas for 40 mt, all 
> > of a sudden I started hearing a very strong (s9 in the meter)
> pulsing noise, it
> > pulses at about 15 cycles per second, after a lot of checking I
> found that
> > the noise is produced in the radio, it is present without any 
> > external connection to it and doesn't matter which power supply
> connected, I tested
> > 3
> > different power supplies, the noise is definitely in the radio.
> I connected
> > another one and no noise.
> > Anyone who has experienced something like this? Any hints about 
> > where to check?
> >
> > Appreciate any help, because it will be quite difficult to
> re-export it for
> > repairing and CQWW is close.....
> >
> > --
> > Jim, HK1N
> > ----
> > Your Moderator: Dick Flanagan K7VC: icom-owner at mailman.qth.net
> Icom Users
> > Net: Sundays, 1700Z, 14.316 MHz Icom FAQ: http://www.qsl.net/icom/ 
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> >
> > ----
> > Your Moderator: Dick Flanagan K7VC: icom-owner at mailman.qth.net Icom 
> > Users Net: Sundays, 1700Z, 14.316 MHz Icom FAQ: 
> > http://www.qsl.net/icom/ To support QSL/QTH.net: 
> > http://www.qsl.net/donate.html
> >
>
>
>
> --
> Jim, HK1N
> ----
> Your Moderator: Dick Flanagan K7VC: icom-owner at mailman.qth.net Icom 
> Users Net: Sundays, 1700Z, 14.316 MHz Icom FAQ: 
> http://www.qsl.net/icom/ To support QSL/QTH.net: 
> http://www.qsl.net/donate.html

----
Your Moderator: Dick Flanagan K7VC: icom-owner at mailman.qth.net Icom Users
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support QSL/QTH.net: http://www.qsl.net/donate.html