[ICOM] IC-7000 AM Modulation Problem

[Adam Farson]

Larry, Gary,

Actually, I suspect that Icom are overstating the  case by claiming 40W AM
(resting carrier) output for a 100W-class rig. The maths don't add up.

A solid-state transmitter is peak-power-limited. If it is rated at 100W PEP,
the maximum permissible carrier output is 25W. Increasing the output above
the -6 dB point relative to PEP rating will cause the ALC to level the total
output (carrier and sidebands) at 100W when modulating. This will lead to
carrier starvation and distortion, as discussed in my AM article:

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

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: 04 April 2006 10:55
To: ICOM Reflector
Subject: Re: [ICOM] IC-7000 AM Modulation Problem

Thanks Gary,

No, I did not know the IC-7000 was only capable of only 40 Watts in the Am
mode.  However, I did check the modulation at various power levels. I think
I did check modulation  with carrier levels set as low as 10 Watts. The low
modulation problem never improved.

73,Larry/K3JRR


----- Original Message -----
From: "Gary" <n6lrv at cox.net>
To: "ICOM Reflector" <icom at mailman.qth.net>
Sent: Tuesday, April 04, 2006 05:24
Subject: Re: [ICOM] IC-7000 AM Modulation Problem


> Larry I was with ya all the way till the end of your email when you 
> mentioned
> you set the carrier output power to 25 watts, etc. etc.
> You realize (I hope) that the IC-7000 is only capable of 40 watts max 
> output
> power in AM mode on HF & 6m right? It's even less for 2m and 70cm (20w and

> 14w
> respectively).
> Gary
>
> Larry Harrison wrote:
>
>> 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
>>
>> ----
>> 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/



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