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[TenTec] RE: Omni VI RF Spike

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Subject: [TenTec] RE: Omni VI RF Spike
From: chestert@pressroom.com (Chester Alderman)
Date: Wed, 07 Jan 1998 19:29:41 -0500
>I ran my AL-80b from my Omni VI for several years with only one small
>problem.   The Omni emits a large spike of RF upon keydown for a
>fraction of a second, resulting in overdrive on many amps (this spike
>can exceed 100w.)  Many rigs do this from both sides of the pond,

For every 'horror' story, there are 'success' stories! I have been running
my Omni VI into a Titan amp for over six years; I always monitor the RF
waveform via a pickup wire hanging in my Johnson KW match box tuner,
connected to a Tektronic 100 MHz o-scope; and I run only CW. I specifically
look at the leading edge of my waveform to make sure the leading edge does
not get quicker than about 4 ms, because I don't want to produce key
clicks, especially when running at 1500 watts out. I have never observed
anything other than a rather smooth transition during the leading edge of
the RF waveform, whether sending at 20 wpm or at 60 wpm. 
I do know what an 'RF spike' looks like, because the IC-781 that I have
produces a trememdous RF spike, either barefoot or into a 50 ohm dummy load
or into the Titan amp. 
If your Omni VI does not produce an RF spike when it is loaded into your
antenna or when it is loaded into a dummy load, maybe some 'tweaking' of
the amplifiers input matching circuit could have solved the problem?

>This issue was addressed in the Technical column of  "73"  magazine (I
>think it was Feb. 96') after my query to them as neither Ameritron nor
>Ten Tec could provide a solution.  Ameritron's answer was lower drive,
>Ten Tec support's answer was to run one of their amps, and they wouldn't
>speculate on other amps from other manufacturers.  

Perhaps you did get a correct answer, but it was not acceptable to you. I
don't think a manufacturer should be required to make their radio play
correctly into anyone else's amplifier, however, they SHOULD be required to
make it play correctly into a 50 ohm non-reactive load! I don't like the
fact that the Omni VI will not send CW at speeds any greater than about 70
wpm, but even though I got an answer from TenTec, I understand the
technical reason for it, and it is a 'livable' compromise for me. For
higher speeds, I just switch to my Corsair II, but when I'm chasing DX or
contesting or normal rag chewing, 'there ain't nothing going to replace my
Omni VI!!
By the way, the answer I (and one other person I know) got from Icom about
the IC-781 RF spike was 'Yes, we know about it, but we will not fix it'!
>You can see this yourself on any oscilloscope.  The AL-80b typically
>handled the spike as long as I didn't push it (input drive power) too
>far.  If anyone's interested, I can look up the articles and the letter
>I sent to 73 and input them here.  The AL-80b will work, just don't
>input too much drive from the exciter and you will be ok.
>73 de Dave  KB6JOX   

Chester Alderman
W4BQF -- Tom

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