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Re: [TenTec] OmniVI: question about T/R control logic

To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] OmniVI: question about T/R control logic
From: Ken Brown <ken.d.brown@hawaiiantel.net>
Reply-to: ken.d.brown@hawaiiantel.net, Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Sun, 13 Dec 2009 10:33:44 -1000
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
Hi Allan,

     You are correct about much of the logic going on inside 
microprocessor chips in the Omni VI. Yet there is still a lot of T/R 
control logic going on is simple resistor/transistor/diode circuitry in 
the Omni VI, and a lot can be learned from the schematics.

     My best guess it that "keying" the key or PTT input of the Omni VI 
does all of the antenna switching and receiver muting stuff BEFORE the 
TX EN signal comes back from the amplifier to say "Ok everything is 
ready, now you can really transmit" I do not suggest risking equipment 
damage, or hearing loss, based on a guess though. One way to confirm 
what happens in what order would be to use a dual trace oscilloscope. 
One input could be the PTT or Key input. Then you could probe around 
other places, with and without the TX OUT and TX EN jumper in place, and 
determine the time relation between keying input and PIN diode 
switching, and the dependency (or not) of the TX EN signal.

DE N6KB

Allan Taylor wrote:
> I now have a pair of OmniVIs and would like to use them in a sort of
> poor-man's SO2R. Actually I
> believe what I want to do is called SO2V but will actually be with two
> radios. What I would like to do
> is to have both radios functional on receive, and have the alternate
> radio's (radio B) T/R PIN diode switch activated when the primary
> radio(radio A)  is transmitting, thus protecting the front end of the
> alternate radio (radio B). Thus the question: Does the PIN diode
> switch activate a) when the key is pressed/entered, b) when the signal
> from the QSK loop / amp is returned, or c) at some other time. The
> easiest solution would be to use radio A's QSK loop in some way to
> activate radio B's T/R PIN switch. As the control logic is inside a
> chip rather than in hardware, staring at the schematic does no good.
>
> Any takers for this question??
>
>   
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