[amsat-bb] Re: Antenna suggestions for mounting on vehicle for sat work.

Ted k7trkradio at charter.net
Thu May 24 13:47:28 PDT 2012

Lee, there is a construction article in Chap 6 of the ARRL Satellite
Handbook (too complicated for me)

But the reality is that it is easy to manually turn the RS rotor with the
control box from the comfort of your chair just following the azimuth
showing on your sat program and listening with your ear...this will get you
close enough. I have the Elk on a RS rotor with Bob's fixed elevation.
(Worked good enough for VUCC #226)  

Of course, the original question was about mobile installation, so unless
you have a long extension cord or a generator....... hi hi

73, Ted, K7TRK

-----Original Message-----
From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] On
Behalf Of Lee Maisel
Sent: Thursday, May 24, 2012 1:00 PM
To: Bob Bruninga; amsat-bb
Subject: [amsat-bb] Re: Antenna suggestions for mounting on vehicle for sat

 Thanks Bob!!!!

That is extremely helpful, and most likely what I will do.   Now, is 
there a computer interface somewhere for these RS rotators?


Bob Bruninga wrote:
>> The company that comes out with an AZ/EL unit that 
>> is about $200 is going to sell a million. 
> Radioshack already does.  Its called a TV rotator, and I would buy one
before they are no more!.  For LEO satellites one does not need elevation
98% of the time and with a modest beam (ARROW type) you can have a $70
system.  Tilt the beam up about 15 degrees so that you still have max gain
on the horizon where satellites spend 1/3rd of all their pass times below 20
degrees.  Track then in AZ only.
> As the satellite gets above about 30 degrees and starts to roll off a dB
or so of beam gain, remember that at that elevation the satellite is HALF as
far away so it is now 6 dB stronger!  This remains true up to over 45
degrees, where you may be down 3 dB on the beam but the signal is 10 dB
closer to you!  The break-even point is above about 70 degrees.  BUT!
Remember, the satellite is only above 70 degrees less than 2% of all pass
times.  Simply not worth spending another $700 for an elevation rotator for
1 minute a day of better access.
> Also, do NOT be tempted to tilt above about 15 degrees or you are going to
lose gain on the horizon where you need it most.  Lots of folks put it up
higher because it seems logical, but they are ignoring the very significant
DISTANCE factor at low elevations (sketched to scale on the web page). 
> Please take a look at the plots on http://aprs.org/rotator1.html
> Its an old page, but the drawings are always valid.
> Bob, WB4APR

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