[VHFcontesting] pre-amp hookup help

[Jeff Townsend]

You should be able to use ALC to cut the transmitter off until the sequencer allows transmit.

W6PQL does that on his amplifier control board.

http://www.w6pql.com/amplifier_control_board.htm <http://www.w6pql.com/amplifier_control_board.htm>

Go down to the "Blocking RF From The Driver” section where he explains how it works.


> On Feb 8, 2022, at 12:20 PM, Chris Lumens <chris at lumensoutdoors.org> wrote:
> 
> Hey, everyone.  I've been thinking about this for some time but haven't
> gotten it figured out.  It's only mildly off topic for this group.
> 
> The extremely short story is that I want to add a 70cm mast mount preamp
> for my home satellite setup.  That doesn't seem too hard - sequencers,
> bias tees, etc. - but of course it's the details that make it difficult.
> 
> I have two antennas and two radios.  The radios are an FT-818 and an
> IC-7000.  Several years ago while roving, I broke the headphone jack on
> my IC-7000 and according to Icom, fixing it requires replacing the whole
> face place, which is expensive.
> 
> Therefore, instead of what most people do, I have a TX radio and and RX
> radio.  Some sats have a 2m downlink/70cm uplink, and some have the
> reverse so that means I have to switch the cables back and forth between
> the two radios.
> 
> That is what makes adding a pre-amp hard, as far as I can tell.  It
> could potentially be hooked up to either radio and that could change
> several times in a given day.  That means I don't want to have a manual
> step involved, because one day I will forget to do it and that'll blow
> up the pre-amp.
> 
> I could fix this by buying a replacement face plate ($), a second FT-818
> ($$), or an IC-9700 ($$$) but I really don't want another radio right
> now.  If I could get the pre-amp out of the way by simply sending a
> signal down the coax, I could probably fix this by also buying a 2m
> pre-amp, ensuring there's always a pre-amp that needs to get out of the
> way.
> 
> My other concern is: I'm not sure a sequencer alone is gonna fix my
> problems.  When I key up the mic, there will be RF present on the coax
> before the sequencer has gotten time to act.  I don't believe the
> IC-7000 has any sort of TX inhibit, so I don't know how to tell the
> radio to not actually transmit until things have switched over.
> 
> Any clever ideas for dealing with these two problems?  Thanks!
> 
> -- 
> Chris Lumens - KG6CIH
> Hike * MTB * XC Ski * Haskell
> Research - Experimentation - Testing - More Testing
> _______________________________________________
> VHFcontesting mailing list
> VHFcontesting at contesting.com
> http://lists.contesting.com/mailman/listinfo/vhfcontesting

Jeff Townsend
WB8LYJ