[amsat-bb] Re: Good mobile antennas to use

[Clayton Coleman W5PFG]

My recommendation is to use separate antennas for the uplink and
downlink.   You might not be satisfied using a standard whip antenna
for the downlink.  There are too many nulls.  It is obvious to many
satellite users when someone is running this configuration.  Why?
Because typically the person doing this does not realize they are
losing the bird for periods of time during the pass.  I've seen this
more and more lately.  It is demonstrated when a user comes on, says
"mobile" but they cannot hear anyone coming back to them.  I'm not
saying it cannot be done (many do it successfully,) but there will be
a lot of passes you cannot work because you can't hear.  On busy
passes of AO-51 and AO-27, not using something better to receive the
downlink will give you a real handicap.

This is why I use a separate downlink antenna, typically a 3-element
folded beam such as K5OE's design or the Arrow 3-element.  Sometimes I
will use a full 7-element Arrow for the receive if the pass is low
angle or the terrain is unforgiving.   The downside to sticking a
small yagi out the window is you cannot be in motion.  I just orient
my car in a safe place with my driver's side facing the east or west,
depending on the pass.

If you do want to be in motion, you should look at using a small UHF
eggbeater-type antennas or a similar design to the http://Antennas.us
quadrifilar helix.  Even those may not be perfect but will work far
better than cheating with a whip antenna.  I personally have listened
to many passes on the Antennas.us model but feel that if I want to
reliably make contacts, I will do that from a fixed position in the
car.

73,

Clayton
W5PFG

On Wed, Sep 14, 2011 at 5:28 PM, John Geiger <aa5jg at fidmail.com> wrote:
>
> I am looking to get on the FM satellites while mobile and activate some
> different grids.  Can anyone recommend a good mag mount dual band antenna to
> use for satellite work?  Does the MFJ 1/4 wave mag mount antenna do pretty
> good on the sats?  I am guessing a 1/4 wave will cover more of the pass than
> a 5/8 wave would.
>
> 73s John AA5JG
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