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Re: Preamps



Jerry,

ARR preamps have been used successfully for both satellite and eme.  I
heard my first 2m eme signals using a P144VDG with a broken-down old
cushcraft satellite antenna with one element missing!  The problem is
protecting the preamp from wx and accidental transmissions.  If You
transmit into it by mistake the GasFet will be fried instantly; no second
chance.  Then you are faced with replacing a delicate static-sensitive
device {I have way too much experience doing this}.  

For satellite, I really recommend you look at ARR's model MSP144VDG.  It
uses the same device but automatically switches out the preamp in transmit
for power levels up to 160w!  The enclosure is designed for antenna mount
and is wx-proof.  It costs a little more [$209.95], but you will need only
one coax run and have a worry free setup.  According to ARR the NF is 0.55
dB, so supposedly you lose .05 dB over the P144VDG.  For satellite
operation this will not matter.  Any preamp giving .7-.8 dBNF is adequate
at 144 due to sky noise and today's man-made noise.  For 432 pretty much
the same.

You can view ARR's complete line at:  http://www.advancereceiver.com

SSB Electronics makes a comparable model, as does Lunar, and Kuhne.  But
you will likely spend more.

Regarding omni antennas, AO-40 is theoretically supposed to be workable
with a dipole over a ground screen using 50w on mode-UV, but my experience
tells me that you would probably find that you would be limited to passes
near earth and not always have access.  Unlike AO-13, you will not need a
super-satellite antenna system. But a moderate 2m beam {6-10 elements} and
70cm beam {10-14 elements} will greatly improve performance.  Circular
polarized beams will be better than horz or vert only beams.  The Leo sats
move fast and have a short pass, so auto-tracking directional antennas are
desirable.  For AO-40 you do not need auto-tracking as you will need to
move your antenna only every half hour or so.  And then, only to peak up
the signal.

It will be some months before AO-40 is commisioned for general use, so you
have time to become familiar with what is needed.  I would expect ham
magazine articles will be addressing station needs for working AO-40.

Now all of the above is my opinion.  You should gather input from others to
make an informed descision.  A good place to start is the amsat web page
and from amsat publications.  IMHO for a full understanding of AO-40, one
should get a copy of "P3G to P3D".  And hang out on this list.  Many others
will be asking some of the same questions you may have!

Ed

At 11:08 AM 12/10/00 -0600, you wrote:
>Excuse me if this is not the proper place to pose questions regarding a
>new-comer to satellites establishing his station.
>
>As I see it, regardless of what I choose to work (Analog, digital or
>others), I will need good preamps.  I am considering the ARR SP144VDG &
>SP432VDG models.  My question is about "pole mounting" at the antennas.
>These do not appear to be constructed for such.  Are there other models
>from ARR (or other brands) for outside pole mounting?
>
>Possibly, some of you may suggest an weather tight enclosure.
>
>Truthfully, I am really starting from the ground floor on this and doing
>a lot of reading.  I still have to make the decision of what mode of
>satellites to start with.  It probably will be the analog sats till I
>get the hang of it and progress from there.  Again, I'll have to decide
>upon antennas too.  Are the Omni's that effectual?
>
>Thanks for your input.
>
>Jerry  N5GPC
>Grand Prairie, TX
>
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