[aprssig] EB-432/PCSAT2/APRS Question

[Robert Bruninga]

>I purchased an EB-432 before christmas... for PCSAT2...
>Previously, I was using a Dual Band Co-linear, 

Well the colinear will have more gain down on the horizon where 
you need it most.  Remember that LEO satellites spend 67% of 
their time in view below 20 degrees, it is the horizon where you 
need the gain.

>with the pre-amp in- line instead of the surge protector 
>and I seemed to be getting better  
>results with it (more telemetry decoded).

You should use a pre-amp no matter what antenna
you use.

>Testing with a terrestrial station (and the EB-432) a S1, 1200 baud  
>signal is decoding almost every second go.. switch on the Pre-Amp and  
>the signal is going to up a S9+10.

As I assume it should...

>Bearing in mind that I was able to get at least a few packets per day  
>decoded with the TH-D7 and a 19" whip sitting on a biscuit tin lid,  
>this is kind of a let down.

Yes, the TH-D7 has a good receiver and being no coax loss, it
should do pretty well.    The Eggbeater in theory is a good
hemispherical omni dual-poarized antenna.  But the problem is,
you do not need or want that for listening to LEO satelites.

A simpl e whip will work better on average.  Remember, the 
EggBeater is to give you omni gain at all angles including straight 
up.  But low satellites are above 45 degrees less than 5% of the 
time.  SO you sacrifice gain 95% of the time where the satellites
are most of the time, for a little more gain where the sateliltes
are less than 5% of the time.

The Egg beater in my opinion has no value for most
low orbiting AMateur satellites.  AND it loses 3 dB compared to
a whip antenna because it is dual polarized.

Though, with the horizontal polarization, there are
times when it will be better.  But I would rather
stick with vertical and have 3 dB better HALF the time than
lose 3 dB ALL THE TIME just to pick up something when
the signal may be more horizontal.

>Any thoughts appreciated.

I appreciate your report.  And I would appreciate it if you
would so some careful testing.  You are confirming what I
have always said, that the Eggbeater is not a good antenna
for our typical LEO amateur satellites that are currently
in use.  The Eggbeater is ideal for higher satellites that
have more power so that it can hear them on the horizon.
Such as WX satellites and any commercial satelites.

But for our weak amateur satellites, the Eggbeater just
does not have enough gain on the horizon where the
satellites are almost 70% of the time to be of any
real value.

If you could document and compare these results, it
would make a great AMSAT article.

Bob, WB4APR
Regards
de John
EI7IG
--
John Ronan <jronan at tssg.org>, +353-51-302938
Telecommunications Software &  Systems Group,  http://www.tssg.org 




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