[NLRS] FT-857D PTT out?

[jcplatt1 at mmm.com]

98% of us are using IF rig (FT817, FT857, FT897, HR2600, FT100, TS930, etc)
generated PTT control signals to switch transveters either directly or
through a simple interface circuit as Dave mentioned.    Almost always the
IF drive level to the transverters mixer is of such low level that the IF's
T/R timing isn't critical.      This is time proven, time tested.

If you are using an amplifier after the transveter, some Op's simply use
the amp's built in RF switching.    The up side to this approach is that it
is easy to implement and gosh, it works.  The down side is that it is slow
to go back to receive, plus it can lead to relay failure ala contact
pitting due to hot switching.    Most amplifiers have a PTT-in control line
and most transverters has a PTT-out control line .... simply connect these
together after making sure that they are PTT-H or PTT-L signals, etc.
Again, a time tested approach and pretty easy.     Sequencing is not
required.

Where things get more dicey is if you use a preamp or perhaps at microwave
frequencies where relays do not have as good an isolation as they do at
VHF/UHF.      In these cases, a sequencer is indeed a good idea, especially
if you run higher power.     I ran 1 watts on 10gig using the simple T/R
switching scheme described above with no problems.    When I went to 6
watts I added sequencing.

For the basic VHF/UHF 6m thru 2304 station, using your IF rig to directly
key your transverter and using your transverter to then key any amplifiers
is "state of the art".     Using an external preamp MAY require the use of
a sequencer.    For my home station, the only band that I have a preamp on
is 902, and that's because I have an older style DEM transverter that has a
somewhat higher noise figure.    Todays VHF rigs and transverter have
PLENTY of sensitivity and if you are using high quality coax (LMR400 on 6m
thru 432, 7/8 on 902 and up) a preamp is actually harmful to your operating
(as it decreases your stations reliability and decrease your receivers
dynamic range).    EME and microwaves is a different story.

Regarding IF rigs for 222 transverters, I prefer to find a way to reduce
the output power of the IF rig.    On 222 I am currently using a older
style transverter with a HR2600.   The HR2600 has been internally modified
to deliver 100mW .... an easy modification.     I would look for a way to
modify the IF rig so that it delivers low power (and that isnt using the
ALC voltage).     That's my preference.    Others have successfully used
the DEMI high power interface.

73, Jon
W0ZQ