[ICOM] IC-7000 AM Modulation Problem

[Larry Harrison]

Adam

Yes this is what I thought all along.  That is why I used 25 watt carrier in 
my original post and tests. The PEP output at 100% modulation would be 100 
Watts. (4 X Carrier)  meeting the PA PEP rating for any 100 Watt PEP 
transmitter.

Regards, 73
Larry K3JRR


----- Original Message ----- 
From: "Adam Farson" <farson at shaw.ca>
To: "'ICOM Reflector'" <icom at mailman.qth.net>
Sent: Tuesday, April 04, 2006 18:12
Subject: RE: [ICOM] IC-7000 AM Modulation Problem


> 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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> ----
> 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/
>