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Drake 2880 power/TX Protection/IF thoughts



After reading various comments:

>I know one can do the mod and apply power through a hole
> > drilled in the case. Is there a cheap power inserter idea around?
>
>The Drake is probably going to require mods in any event, and the
>power feed mod appears to be relatively non-noxious, so I'm not
>quite sure why you hope to avoid it.
>

I figure I'd spew out some of my ideas I have for my FT-847 and the Drake, 
or any Mode-S converter--  This rig can be set up to
put +13.8V up the coax on receive for a pre-amp... Either get a Ramsey 
electronics RF sesnsed switch and set it up for "pre-amp switching" (nice in 
case somehow power stays applied during TX) or use a relay to switch the 
Drake in on DC power from the rig via a RF choke.. (At 2m a standard relay 
works ok in this app... there are several inexpensive PC mount relays 
available from DigiKey or Down East Microwave good for 432 MHz).  On the 
other side of the relay, 50 Ohm termination.. That *might* save the thing if 
it's transmitted into.

The other idea along the same line of thought is for TX protection is to use 
the DEM TC (transverter control) in a seperate box for a transverter 
interface (as I do VHF contests also and have a couple of transverters) and 
add a transistor inverter to do the switching of this device through the 
"pre-amp" dc output of the 2m IF on the 847.
(The transverters will be switched to "transmit" if the unit is 
disconnected, or if the DC voltage goes away, i.e. on transmit)  This is 
actually what I'm probably going to do for units that operate at a 2m IF.. 
I'll post details after I get the unit and build it up.

Idea number two is to leave the 120 MHZ IF (or find another around 220 MHz 
that is convienient and far away from the broadband noise on TX at 2m, 70cm 
and 1269 MHz) and then build a second downconversion (7th Overtone OSC and a 
SBL 1 mixer?) stage to 50 MHz for the 847.  This would be nice in that it 
wouldn't interefere with either U/S or L/S-- thus not requiring two 
downconverters.  I'm going to research this further. This would be great if 
I can get it to work.  The second downconversion could be in the shack, and 
also work as the power inserter and TX protection...

Idea #3 is to use a seperate RX rig and send power to the unit via a 
seperate wire (Get some "DirectTV" RG-6 with the ground wire attached at 
WalMart) and, yes drill a small hole in the Drake case-- fit snugly with a 
feedthru cap or feedthru filter, and put a dab of RTV in it at the same 
time, and the unit is still waterproof...

I still think it is going to be desireable for people to get a HEMT LNA for 
those units as 6.5 dbNF is still not terribly good-- so I agree that they 
will probably need serious surgery anyway.. I don't think I'd fear the 
"feedthru" cap mod..

Fred W0FMS
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