Re: [amsat-bb] DEM converter mounting

["Edward R. Cole" <al7eb@xxxxxxxxxxxxx>]

>From: David Reinhart <wa6ilt@bellatlantic.net>
>How are people who have bought the DEM converter mounting it?  The photo
>DEM has on their web site shows a plain box and their text indicates
>that their housing decisions took into account  mounting their helical
>antenna on the box to make a single package.  Basically I'm concerned
>about maintaing the weatherproof integrity of the box and keeping
>mounting hardware away from the circuitry.
>
>Also, are people mounting their various converters on the crossboom or
>on the vertical mast?  The obvious problem with putting it on the
>crossboom is that the connectors will be more exposed to weather, except
>when the antennas are vertical.  Anybody using some kind of gimbal mount
>so that the connectors can always be on the bottom of the box?

Dave,

I am not using the DEM preamp, so this reply diverges slightly.

1.  In order to obtain min NF, my preamp [Kuhne MKU-232A], which is built
with a male-N on the input, is directly connected to the helix N-female
panel jack using a right-angle N-adapter.  

2.  I will place the preamp inside a Radio Shack plastic box [6x3x2 inch]
to wx-shield it [it will be not sealed tight but be open at the bottom for
the output coax which drapes downward].  The box will be attached directly
to the back of the helix reflector plate sealed with a little RTV around
the opening for the helix connector.

3.  From here I run the LMR-400 coax along the feed support arm, back of
dish, around rotator and down main mast where the two Drake converters are
mounted in a vertical position with the F-connectors down.  The LMR-400
connects to a N-tee with two RG-11 phasing lines that split the signal to
the two converters.  Because of the complexity of cables and two converters
I chose to mount them below any rotating hardware.  They are also within
reach [4-foot] for maintenance or testing [from my flat roof], but barely
above the snow level in winter.

4.  Separate RG-6 lines connect the outputs [123 & 435 MHz IF's] to the
FT-847.

5. Both Drakes will be modified for external 13.8 vdc power fed from a
roof-mounted power supply.  Both preamps will be powered at the same time.

6.  The 13.8vdc/8-amp power supply is mounted inside a NEMA wx-tight box
along with a 50w 432 PA, 432 preamp, and the 144/1268 Mode-L Tx converter.
The box sits on the non-penetrating roof-frame that supports the satellite
antenna array [a wooden 2x4 frame with small tripod tower using cement
block ballast].  This is situated directly above the radio room with cables
going over the roof edge and thru the exterior wall into the spare bedroom
that is used for a radio room.

7.  I have two 2-1/2 inch holes in the exterior wall [a third to be added
this summer] which will be fitted with rigid electrical conduit nipples and
right-angle breakouts going into an outside cable box [a sort-of vault].
>From there the cables either go to the roof or thru PVC conduits trenched
into the lawn to the various towers.

8.  The satellite array is mounted on a 10-foot mast with a G-5400 rotator
on top with a five-foot cross-boom.  One end holds the 21-foot M2-436CP42
RHCP yagi; the other the 33-inch dish with the 12-foot 45-loop yagi for 1296.

I will use heat-shrink tubing over most of the connectors with additional
electric tape and Scotch-Kote sealant.  This I need to get done soon as we
are about to go into the rainy season [late-July/August... then snow].  But
today was a balmy 69F!

Well that is probably more detail than you were looking for, but do you
know a ham that doesn't love to "talk" equipment?

73, Ed
Beacon acquired at 0400 utc and running especially strong >S-9; 318/325
good CRC, so far.

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