[NLRS] FT-857D PTT out?

[Chris Elmquist]

On Wednesday (09/14/2005 at 07:02PM -0500), Gerald wrote:
> 
> 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.

I am quite familiar with this issue but I am curious how people actually
do it in practice.  Do you forego the use of the PTT switch on the mic
and have some other XMIT button?  What happens if the radio is accidently
put into VOX mode and you sneeze?  How do you make this sequencing work
in all modes SSB, CW, VOX, etc?

As I have mentioned to others, my dream radio for transverter use would
have an RTS (request to send) output and a CTS (clear to send) input.
(hey, I'm a computer guy :-)  ) RTS would go true when you initiate
transmit from any method-- PTT, VOX, CW, etc. but no RF would be produced
until CTS went true.  If you were running without a transverter, you just
loop RTS to CTS and the radio works normally.  If you are sequencing
then you start the sequence when RTS goes true and the last thing the
sequencer does is drive CTS true... and then RF comes up and off you go.

But I haven't found a radio that works like this yet.  I mod'd my FT-736
so it does... but it's a lot of screwing around.

But I seem to see most people running DEM transverters without any
sequencing.  They just key the transverter with the PTT-L output from
the IF rig and seem to get by.  It sure makes it easier because then
the PTT switch on the mic still works... as does VOX, CW, etc.

Chris NØJCF

-- 
Chris Elmquist   mailto:chrise at pobox.com   http://www.pobox.com/~chrise