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

[Edward Cole]

At 04:19 AM 5/30/2009, Bob Bruninga wrote:
> > 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
>
>Bob, WB4APR

I've posted this before, but maybe it helps to repeat.  When AO-51 
launched, I used a 19-inch mag-mount mobile whip on a steel ground 
plane to copy telemetry on 435-MHz using a preamp.  Signals were 
quite adequate.  Probably low horizon AOS/LOS was limited (too long 
ago to remember).  But very simple to implement and use as Bob 
states.  I have two Lindenblad antennas under construction so will 
play with them (using my 435 preamp) when I get them up.  I am 
preoccupied with finishing my 1296-eme station with 16-foot dish.  In 
July, I should be able to re-assemble the old AO-40 tracking 
super-array of antenna as can be seen on my website.

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73, Ed - KL7UW              BP40iq, 6m - 3cm
144-EME: FT-847, mgf-1801, 4x-xp20, 8877-600w
1296-EME: DEMI-Xvtr, 0.30 dBNF, 4.9m dish, 60/300W  (not QRV)
http://www.kl7uw.com       AK VHF-Up Group
NA Rep. for DUBUS: dubususa at hotmail.com
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