[amsat-bb] Re: Re eggbeater performance - mobile
bruninga at usna.edu
Sat May 30 05:19:13 PDT 2009
> 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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