[amsat-bb] Re: Re eggbeater performance - mobile

jeff kb2m kb2m at comcast.net
Sat May 30 05:35:34 PDT 2009

 When I used to do a lot of driving for work I used to use a 1/4 wave, and a
high gain vertical antenna to work the birds. I would switch between the
high gain when the bird was coming up to the 1/4 wave when it was up 15
degrees or so. Then back to the high gain vertical when it was getting back
down below 15 degrees or so.    Another good trick was to use the 1/4 for TX
only, and listen with  1/2 of an Arrow (with pre-amp) for the 70cm, D/L out
the drivers window, this would give you near armchair copy, when pulled over
of course ! 

73 Jeff kb2m

-----Original Message-----
From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] On
Behalf Of Bob Bruninga 
Sent: Saturday, May 30, 2009 8:19 AM
To: mikehooles; amsat-bb at amsat.org
Subject: [amsat-bb] Re: Re eggbeater performance - mobile

> For mobile work on AO27, SO50, AO51 
> a 2 metre quarter wave whip is all 
> you need... to work the LEO's mobile
> and the satellite is 15 degrees or 
> more above the horizon,

Absolutely, For a 19.5" whip in center of roof:

1) Has 5 dBi gain above 20 deg on 2m
2) Has 7+ dBi gain above 30 deg on 70cm
3) Is an omni
4) does not sacrifice 3 dB for circular
5) Above 25 deg, satellite is 6 to 10 dB closer!
6) works the birds solid for the center of high passes
7) Simplicity at its best!

Read about it: www.aprs.org/rotator1.html

Disadvantage:  The only disadvantage is TIME.  On the above web page you can
also see that satellites spend 70% of their daily pass times below 25
degrees.  BUT!  For those best passes in the morning and the evening (or
whenever) you can make solid contacts while mobile for about 5 minutes.

Also note, that you do NOT need any tracking program to predict passes.
AO51 schdule repeats evry 5 days for example.  Just write down the CENTER
pass of the morning and evening for each day for 5 days.  Update those 10
times on a small 3/5" card on the dash about once a month or so will predict
all passes whenever you are mobile.  There will be a pass 100 minutes
earlier and 100 minutes later each day too.  So you can predict all 6 passes
a day from those same 10 times.

See how: www.aprs.org/MobileLEOtracking.html

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