[ICOM] IC-7000 AM Modulation Problem

[Sheldon Daitch]

If you have access to a fairly decent scope, you can use some different techniques
for measuring AM modulation.

See figures 4, 6 and 7 at:

http://www.icycolors.com/nu9n/scope_your_audio.html

If I recall correctly, you don't even need any pickup boxes, just
enough RF signal to get the good figure 4 trace on carrier power
without modulation.

Figures 6 and 7 will show with tone modulation, but you can
see the carrier cutoff, which is considered 100 percent negative
modulation, even on voice modulation, assuming the transmitter will
go to that level.

73
Sheldon
WA4MZZ



msole at loxinfo.co.th wrote:

> If you are using a regular, AVERAGE reading meter to observe modulation then a tone that
> gives 100% and speech that gives about 30%. Seems absolutely correct to me. I'd say your
> radio is working fine. What does your power meter show on SSB where power equates to
> modulation?
>
> 73
> Martin, HS0ZED
>
> Quoting Larry Harrison <harrisonl at comcast.net>:
>
> > Hi David.
> >
> > The modulation takes place in DSP. It could be the way the 7000's DSP
> > algorithm generates AM.
> > It does not matter how hard you hit the audio, you only get 30% modulation
> > on voice.
> >
> > Many others have reported the same problem.
> >
> > I also emailed Rob Sherwood of Sherwood Engineering, Inc. to find out if he
> > by any chance had tested the IC-7000 AM modulation.  Rob said he had tested
> > the IC-7000 and also found only 30% on voice and 100% on tone.
> >
> > Seems we all are up against a stone wall. ICOM alleges that the 7000 meet
> > their specifications and refuses to even acknowledge the problem.
> >
> > In an email back to me ICOM stated :
> >
> > on 03/30/2006
> > "The attached picture is from the testing that we did. You can see with the
> > HM-103 held of to the speaker of the monitor the radio is almost modulating
> > at 100%. If the meter in the upper left was at the 12 o'clock position that
> > would be 100% modulation." (WITH A TONE NOT VOICE)
> >
> > on 04/01/2006
> > "We did try testing the modulation of the radio with voice. According to our
> >
> > technicians when they modulate with voice they see what they would expect to
> >
> > see. They said that the radio is functioning fine and performing to the Icom
> >
> > specifications."
> >
> > "they see what they would expect to see" (This can mean anything from 0% to
> > 100%.  This is a vague and non answer.)
> >
> > Go Figure!
> >
> > 73,
> > Larry K3JRR
> >
> >
> >
> > ----- Original Message -----
> > From: "David J. Ring, Jr." <n1ea at arrl.net>
> > To: "ICOM Reflector" <icom at mailman.qth.net>
> > Sent: Friday, April 07, 2006 05:53
> > Subject: Re: [ICOM] IC-7000 AM Modulation Problem
> >
> >
> > > Hi Larry,
> > >
> > > I was reading your posts - and I have a couple of questions.  Forgive me
> > > if
> > > you've already answered them.
> > >
> > > You mention that you modulated your AM signal with a tone, and it
> > > modulated
> > > 100%.
> > >
> > > But with voice only 30%.
> > >
> > > That is really puzzling!
> > >
> > > Have you tried feeding an audio amplifier (at microphone level plus 15 dB)
> > > into the microphone connection?  Or perhaps going into the rear AUX "din"
> > > connector (I don't have that model, but other recent ICOM's have this.).
> > >
> > > I'd make a tape recording with my voice hitting 0 VU and then with a tone
> > > hitting 0 VU and feed it into the microphone connector - then the AUX
> > > connector.  Of course the modulation "should" peak the same - unless the
> > > TONE control is set differently to favor one or the other.
> > >
> > > This is too strange!
> > >
> > > 73
> > >
> > > David N1EA
> > >
> > >
> > > ----
> > > 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/
> >
>
> ----
> 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/