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Re: Preamp bypass circuit




  One thing to bear in mind when talking about
sequencers is that some radios (such as the  ft736
and uniden hr2510) throw stray RF out the antenna 
ports even when the radio is not transmitting,
so even a sequencer doesn't guarantee long life
for anything on a shared t/r path.

  -al
  WB1BQE




Doug Braun NA1DB wrote:
> 
> I like your idea, but it should go even further:
> 
> Instead of a "TX inhibit" input, there should be a "TX enable" input.
> (The difference being that if you have nothing hooked up to the input,
> the radio does not transmit.)
> 
> There should also be an "TX request" signal that is generated from the
> mike's PTT button, the VOX, the front-panel Xmit button, the TNC port's
> xmit input signal, etc.  "Normal" users would jumper the two signals
> together, either with a real jumper plug, or a software-controlled virtual
> jumper.
> 
> People who need to use sequencers or delays would break the jumper and
> connect the two signals to their own circuitry.  This way, they could still
> use the stock PTT/Xmit switches, and everything would be 100% foolproof.
> Problems like broken wires or accidentally-pulled-out plugs would
> not cause a disaster.
> 
> I am really surprised that $2000 specialty satellite radios do not
> already work this way.
> 
> Another beef:  My IC821 has a "preamp" button, and when you turn it
> on, it puts 12 volts DC on the output only when receiving.  But
> there is no way to program the radio to provide a delay between the
> time the voltage is dropped, and the transmitter actually starts
> up...
> 
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