[amsat-bb] Re: Info needed.

[Edward Cole]

Rod,

Here are some general suggestions for any station setting up for 
observing HEO's:

At 12:06 PM 2/14/2007, Stargate wrote:
>Hi all,
>         Well, It's time to start considering antennas for my 
> satellite station.
>(tax refund:-) I am trying to pack as many modes into my station as I can. I
>have the following so far....
>
>Yaesu FT-847
>AOR 8600 MK2 receiver (dc-3ghz)
>Icom IC-706MK2G
>Mirage 2530 (300 watt 2 meter amplifier)
>Astron RS-70M power supply
>G-5500 rotor
>LVB tracking board
>SAT688 tracking board
>Orbitron tracking software
>Andrew CF2P coax (2.7db loss 100' @ 450mhz)
>
>         I will be running the coax in about 50-70' runs from the shack to the
>antennas.

Chose coax to keep your losses below 1-dB.  You might consider 
running 1/2-inch hardline for transmit.

>I would like to have mode S receive as well but the loss gets rather high
>with this coax so hardline or a mast mounted
>downconverter may be the way I go.

Mode-S requires a low noise front-end (usually a good preamp, 
immediately followed by the downconverter.  The preamp should be 
mounted on the dish feed or no more than 2-feet of coax from the 
feed.  Place the downconverter at the dish so that you may run 
light-duty coax back into the shack (I ran 60-foot of 
RG-58).  Placing the preamp/converter with long coax runs after the 
dish feed will result in failure.  Do not do that.  I can only guess 
on what size dish is needed for P3E or Eagle, but probably a 3-foot 
will do fine (that was the min size that worked well on AO-40).  Do 
not think of using a helical beam...nearly all who tried them on 
AO-40 were dissatisfied.

A trick to avoiding big low-loss coax is to locate your Tx amplifiers 
at the antenna.  This will require a wx-tight box and probably a 
12-volt power supply co-located with the amp(s).  The only frequency 
that one can get away with ordinary coax is 144-MHz.  432 and 1268 
need low-loss cable.  Above 1.2 GHz one should mount equipment at the antenna.



>         I'm pretty sure I want circular polarized antennas unless 
> someone talks me
>out of it. Switchable for LHCP or RHCP??

Switchable is great but many of us have gotten along fine with 
RHCP.  Others have used linear-pol and if the antennas are large 
enough that works fine.  ON receive one will get spin modulation 
fading more pronounced using linear antennas.

>Whatever VHF and UHF antennas I choose will also be used for terrestrial
>work as well. Unfortunately, my terrestrial work is somewhat limited due to
>the topography of where my house is. I will also be adding mast mounted
>preamps sometime in the future.

For terrestrial linear-pol is probably indicated so that might make 
your decision.  I ran RHCP on 432 terrestrially with no issues 
(realizing that half my signal was wasted in cross-pol).


>         I'm confusing myself with all the modes and options so what do you
>recommend?

I'm sure others will make some suggestions so that may help (or 
not).  Although getting ready now has your station able to go with 
the launch of the new satellites, we do not know for sure how well 
they will perform until they are up there.  So some may want to wait and see.

I have all my antennas from AO-40 so no reason for me to wait.  If I 
were purchasing everything, I might hold off on some items until more 
is known on satellite requirements (did the mode-whatever survive, etc.).


73,
Ed - KL7UW
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