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Re: AO-40 Portable, Duplexers, and Down Converters, and only 2 cables?

Hello Bill,

my comments are added....

Bill Acito W1PA wrote:

>As I continue to plan for FD, I may be faced with the situation of
>having my AO-40 antennas 50 or 100' from my rig set-up.
>With the thought of trying to minimize the amount of cabling I have to
>lug around, and assuming I use a dish with a AIDC downconverter, a
>safety bias-tee (not the power option from the FT-847), and already have
>the duplexers handy, could I do the following:
>r|--2m--[Bias Tee]----|                  |-----AIDC-----Dish
>i|                    |Dup>----------<Dup|
>g|--70cm--------------|                  |--------------70cm Beam
>Assuming the duplexers provide a DC path for the AIDC.

BIG assumption, may pass dc low impedance to the 70cm driven element 
which is grounded
therefore you may have a dead short at DC...

The 70cm rig may react to a low impedance at DC.....

The Duplexer must be able to handle the required current draw..... in 
addition to the RF current.....
overall power rating is DC plus RF power

You must have high isolation on the duplexer inputs AND outputs.
 i.e., high isolation from 2M to 70 cm on both the input and output sides.

>How much power could I run and not smoke the AIDC --- what would happen
>first, Leila siren, or downconverter smoke?  :-)

depends on the isolation from 2M to 70cm within the duplexer.....

>(If I only plan to run AO-40 only, I could also use one rotor tilted at
>45 deg, and therefore have one run of coax and one rotor cable between
>the operating station and the antennas).

The S2 downlink dish will probably need more elevation control than to 
be fixed at 45 degrees....
I use 2 rotator control cables, az and el.... in my permanent setup.

The YAESU G5400B and requires 6 conductors for az and another 6 
conductor cable for el control.
I added 2 each 8 conductor rotator control cables and I have 4 each 
spares for yagi polarization control
DC power and PTT control ( ground to TX) to hard switch mast mounted 
Standard rotator control cable like BELDEN 8405 is 8 conductor,
You have to go out of your way to find 6 conductor.....

Most mast mounted preamplifiers/relays  will RF sense and switch to TX 
mode on TX up to 100W,
but with hard PTT control, the same preamplifier/relays  can handle at 
least 1/2 KW if sequenced properly

The downconverter does not have to be fed DC on the IF coax. convert it 
to a external separate
 DC input fed on another pair of wires from the shack. Put a gell cell 
at the downconverter...

Stan, WA1ECF

>Feel free to punch holes in this idea. :-)
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