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Re: Ruining $4 Attenuators



Dave, and FT-847 users:

Just a note to let you know that there is a modification to separate the Rx
from the Tx antenna connection which has been documented by DL4MEA (I don't
have the url here at work).  Basically the RG-174 jumper inside the radio
coming from the Rx to the internal antenna T/R circuits is broken and
brought out thru the back ventilation slots using a sma female panel
connector (a feedthru style will fit in the slot without drilling).  Now
you just connect your AO-40 convertor directly into the FT-847 Rx sma with
zero risk of transmitting into it.  If you bring out the other (T/R) cable
end, as well, then a mere jumper restores the radio to normal transceive
thru the main antenna connector.

I plan to make this mod for both 144 and 432.  I will run the 2m cables
thru a SP6T coax relay (surplus) to allow me to connect all sorts of
devices (transvertors for microwave bands) to the FT-847 receiver (and one
relay position will jumper back to restore T/R operation).  The radio is
easily restored for resale by pulling the sma's inside the cabinet and
using an sma barrel!

73, Ed

At 02:35 PM 8/6/02 -0700, Dave Guimont wrote:
>
>>The first thing your 2m rig should see is something like the RF power
>>protector sold by SSB electronics. It's pricey, but has saved both my step
>>attenuator and UEK-3000 twice so far.
>>
>>FT-847 > Protector > MFJ Step Attenuator > 80' LMR-400 > UEK 3000 d/c
>
>Very good, Hasan, I got mine from DEM, I think about $50; it will take the
full
>power of my Icom 821 ~30watts.  Pretty cheap insurance in my opinion..A coax
>switch selects the link, and I don't have to worry about not switching.
>I think most of us have blown at least one converter or preamp!!
>
>Now I can use my 2M uplink for AO7 with complete safety.  Prior to 
>acquiring the
>DEM protection I disconnected  the 2M xmit inside the rig...Not too 
>convenient if
>I want to xmit on 2M for any reason...
>
>
>
>            73, Dave wb6llo@amsat.org
>                    Disagree: I learn....
>
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