[amsat-bb] Advice for a portable ground station

Clayton Coleman kayakfishtx at gmail.com
Fri Jan 16 14:29:19 UTC 2015


I am not a fan of using RG-58 for satellite portable.  I've worked
with too many people trying to use 5-10' runs of RG-58 only to see
them become very frustrated at their inability to work SO-50.  Keep
your feedline as short as possible if you are using RG-58.  Remember,
not all RG-58 is created equal.

My preferred feedline is LMR-240uf (UltraFlex) for portable use.  It's
a little more expensive but I can easily get away with a 10' length
between the Arrow and my transceiver.  Use quality connectors
installed on quality feedline.  Try to avoid gender-changing adapters
if possible.

A lot of published material on the Internet and in print specifically
talks about FM satellites like AO-27 and AO-51.  They had great
downlink signals compared to SO-50.  With SO-50 being our only FM
bird, we need to set realistic expectations that extended whips and
RG-58 coax are not going to perform as well as they did on the former
FM satellites.

Fox-1 series satellites, on the other hand, should be a game-changer
and open the door again for more modest portable stations.

73
Clayton
W5PFG

On Fri, Jan 16, 2015 at 1:06 AM,  <tom.wz9u at gmail.com> wrote:
> The lack of a fully searchable archive for this list has made this post necessary, my apologies for a noob-style query.
>
>
> I’m gradually assembling a portable ground station for the FM satellites, primarily using John Heath’s (G7HIA) article “Down-to-Earth Satellite Communications” (PDF), focusing on his “Awesome” configuration:
>
>
> Dual-band HT
>
>
> Diplexer
>
>
> 2m amplifier
>
>
> 70cm preamplifier
>
>
> Arrow II antenna
>
>
>
> In that article he uses RG58 coax, perhaps 15-20 feet max.  Is there a better choice that also works in that application?  Considering the lengths involved, price per foot is not really an issue.
>
>
> He also calls out an RF choke at the feed point of the 70cm antenna, but gives no detail about its material or construction.  It looks to me like a few turns of RG58 on some type of ferrite core.  I’ve spent hours Googling for information (commercial or DIY) and have come up mostly empty-handed.  All the “meaty” stuff is for HF only.
>
>
> A final question concerns the various connectors involved.  The illustrations in that article aren’t the best, but it seems that he’s using BNC terminators on all the cables, and BNC-to-UHF adapters where required.  I’m concerned (perhaps too much) about cumulative losses, both from the coax and all those adapters.
>
>
> My goal is a tripod-mounted antenna, operating on battery power from various parks and forest preserves nearby.
>
>
> Can anyone clarify my understanding here?
>
>
> Tom WZ9U
>
>
>
>
> Sent from Windows Mail
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