[NLRS] FT-857D PTT out?

[Gerald]

On Wed, 2005-09-14 at 16:06 -0500, Chris Elmquist wrote:
> 
> How do you guys using FT-857D as IF radios obtain a PTT or keying signal
> to key the external transverter?
> 
> Unless I missed something when looking at the manual, I didn't see a
> PTT output from that radio as stock.  Seemed to be only PTT inputs on
> the various back panel connections.
> 
> Just curious...
> 
> Thanks.  Chris NØJCF
> 

Unless the 857 is indeed very unique, you don't want to key the
transverter with a PTT output. You want to have a sequencing circuit
that keys the transverter, preamp, and main antenna relay, THEN when
those relays have had maybe a tenth of a second to settle in the
transmit side you can key the exciter. Most often the exciter puts out
RF at the same time or faster than it puts out a control line. There
should be a PTT output on the linear connector though.

I know in the FT-726 that RF appears before the control output by a few
milliseconds. That's hard on relays and receiving stuff that gets hit by
transmitter power before the control signal arrives. I know it cost me a
GaAsFET in one preamp. The control output of the 726 comes from a relay
that's powered by a TX+12 volt. The same TX+12 that runs the transmitter
stages with a diode antenna switch. That just about guarantees a 10 ms
delay for the control output. Hence the need for external sequencing.

-- 
73, Jerry, K0CQ
Dr. Gerald N. Johnson, electrical engineer
All content copyright, Dr. Gerald N. Johnson