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
Amen.
1/4 wave simple 19.5" whip is ideal not only for VHF, but also has almost 7 dBi gain on UHF above 25 degrees. So it performs very well on high elevation passes.
Any mobile gain antenna optimized for mobile operation will, by definition, perform worse for satellites than the raw 19" whip.
See http://aprs.org/astars.html about 80% down the page discusses it.
Bob, WB4APR
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of John Geiger Sent: Wednesday, September 14, 2011 6:28 PM To: AMSAT-BB Subject: [amsat-bb] Good mobile antennas to use
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 _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
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 [email protected] 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 _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
participants (3)
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Bob Bruninga -
Clayton Coleman W5PFG -
John Geiger