[ICOM] Re:ICOM] TX audio on 775

[Igor Sokolov]

> Igor,
> Are you testing into a dummy load? If not I would suggest you try
> that and listen to a
> monitor receiver in the shack.

Did just that.

> Nothing else hooked up to the radio except mic and dummy load and AC
> power cord?

Correct

> If you reduce power output does the distortion go away or is it reduced?

Does not change

> If you can look at the RF envelope via a oscilloscope does the wave
> form look clean or
> like maybe a bias problem in the PA?

It looks clean.

> Try disconnecting the Rx jumper in the back of the radio and then re-test.

Will ask if that had been done. Just do not know now.

> Bruce

Thanks Bruce

73, Igor UA9CDC

>
> At 12:16 PM 10/16/2006, Igor Sokolov wrote:
> >The problem persists with DSP disabled. So it does with the compressor
> >disabled.
> >
> >73, Igor UA9CDC
> >
> >
> >
> > > It is possible to disable the DSP in the 775 and have all SSB
generation
> > > done in analog rather than digital fashion.  Would be interesting to
see
> >if
> > > the problem persists after the DSP is disabled for Tx.  (It can be
> >disabled
> > > from the front panel menu).
> > >
> > >
> > > ----- Original Message -----
> > > From: "Adam Farson" <farson at shaw.ca>
> > > To: "'ICOM Reflector'" <icom at mailman.qth.net>
> > > Sent: Sunday, October 15, 2006 1:25 PM
> > > Subject: RE: [ICOM] Re:ICOM] TX audio on 775
> > >
> > >
> > > > Hi Clete,
> > > >
> > > > Correction...it is not a compandor; it is a compressor. There is no
> > > > complementary expansion function in the receiver.
> > > >
> > > > In the IC-775 series, the compressor is an analogue circuit in the
455
> >kHz
> > > > TX IF chain. In the newer IF-DSP-based Icom transceivers (IC-756Pro
> > > > series,
> > > > IC-7800, IC-746Pro, IC-7000) it is a process in the DSP algorithm.
> > > >
> > > > I remember the old echo suppressors from my years in the telecom
> >industry.
> > > > They were analogue, and DSP-based adaptive echo cancellers replaced
> >them.
> > > >
> > > > There is a general article on compression on my website.
> > > >
> > > > http://www.ab4oj.com/icom/ssbcomp.html
> > > >
> > > > Cheers for now, 73,
> > > > Adam VA7OJ/AB4OJ
> > > >
> > > >
> > > >
> > > > Scanned for viruses by Blue Coat
> > > > http://www.WinProxy.com/
> > > > ----
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> > > > Icom Users Net: Sundays, 1700Z, 14.316 MHz
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> > >
> > > ----
> > > Your Moderator: Dick Flanagan K7VC, icom-owner at mailman.qth.net
> > > Icom Users Net: Sundays, 1700Z, 14.316 MHz
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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/
>
> ----
> 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/