[ICOM] IC-7000 AM Modulation Problem

[Adam Farson]

Hi Larry,

There could be a problem in the way the 7000's DSP algorithm generates AM.
In the IC-756Pro series, AM works really well. 

Have you had a look at the carrier and sidebands on a spectrum analyser, for
test-tone and voice modulation? The spectral content and amplitude of the
sidebands may give an indication of what is going on. With the spectrum
analyser connected, it may also be useful to do a swept baseband measurement
with a single tone in the range 200 Hz to 2.9 kHz, with 1 kHz as reference,
and take a screenshot if possible. If you find an anomaly, this will be hard
evidence that you can submit to Icom America. I would suggest 100 Hz or 300
Hz RBW.

I made a little study of AM in he 756Pro series. (I have not actually
operated AM since 1963, but that is a story for another evening.)

http://www.ab4oj.com/icom/pro_notes.html#AM

http://www.ab4oj.com/icom/dsp_am.html 

Cheers for now, 73,
Adam VA7OJ/AB4OJ


-----Original Message-----
From: icom-bounces at mailman.qth.net [mailto:icom-bounces at mailman.qth.net] On
Behalf Of Larry Harrison
Sent: 03 April 2006 22:13
To: ICOM Reflector
Subject: [ICOM] IC-7000 AM Modulation Problem

Hi All,

I recently purchased an IC-7000.  A fine radio in all respects except my
radio will only modulate 30% or less with VOICE.
It will modulate 100% with a 1000 Hz tone.

Is there anyone else who owns an IC-7000 with this problem.

If you have never checked your IC-7000 on AM, would you please do so to find
out what your 7000 does on AM.

I have found several postings on eHam.net by others who have reported this
problem.
I have contacted ICOM Re this matter, and have received an unfavorable
response from them.

Please email via the Reflector or directly to me, harrisonl at comcast.net if
any of you are experiencing this problem.

I operate AM as well as SSB, and CW. I sure would appreciate any help from
any of you as my IC-7000 transmitter is totally useless on AM.  Sure hate to
have spent $1499 for a radio that has a problem, that so far has not been
resolved.

By the way, the AM modulation percentage problem has been confirmed with the
built in wattmeter, an oscilloscope, IFR-1200S communications service
monitor and a Bird 43 Peak Reading Wattmeter. All testing was performed with
the carrier set at 25 Watts (1/4th of 100 Watts for proper head room).

73
Larry K3JRR

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