[NLRS] DEM 10g Amp question...

[W0ZQ@aol.com]

I would be concerned with running your "24v spiked declining to 12v on 
transmit" control line into your TTL input on the new amp if the new amp is running 
on only +12 vdc.  The reason for my concern is that the +24 vdc would be 
exceeding your amps Vcc rail (+12vdc) and that can make current flow in undesired 
directions.   In addition, it may actual tend to clamp the "24vdc" due to this 
forward conduction problem and cause your 24 vdc relay not be get pulled in 
... yet another problem.   I may work due to the units design, but without 
looking at it my recommendation is to not do it.

Another caution when you tie together multiple PTT control lines.   When your 
IF rig is not transmitting it's PTT control input line (that goes to ground 
when your transmit) is open (high impedance).   When this happens you are 
connecting the two PTT output lines to each other and you may have current flow 
between the two depending on how those two PTT sensing circuits work (the PTT 
sensing circuit in your transverter and the one in your amp).   To assure that 
there are not "funny" current paths I always use a series diode in the PTT 
control line so that current can only flow out of the PTT control line and not into 
it .... the PTT line from the amplifier and the PTT line from the transverter 
should each have a series diode with the anode towards the unit (transverter 
or amp) and the cathodes tied together (common).   The common cathodes then go 
to the PTT input line on your IF rig.   This way when your are not t
ransmitting no current can flow out of one PTT port into the other; the diodes block 
it.   

For whatever it counts, I'm running about 1.2 watts on 10 GHz without a 
sequencer .... the +12 vdc for my amps Vcc is controlled by the transverter and my 
IF rigs PTT line goes to the transverter so this MAY help some .... dunno.   A 
sequencer is a good idea.   On the other hand perhaps this isnt too much of 
an issue until you get a bit more power.   

73, Jon
W0ZQ





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