[aprssig] EB-432/PCSAT2/APRS Question

[John Ronan]

On 25 May 2006, at 00:00, Robert Bruninga wrote:

>> 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.

And that's where I think the vertical was 'better', but thats just a  
gut feeling.
>
> 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 simple 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.
>
Ok, I'm slightly confused now.. I though the eggbeater (with radial  
kit, which I have), increased the horizontal gain and reduced the  
overhead gain.  Then again I never mentioned that the first time  
around, apologies.

> 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.
>
Does that still hold when the radial kit is included?

> 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.
Thats a good question... bearing in mind that I'm 'flying blind' to a  
certain extent.. and just trying things.  If anyone could suggest any  
methodology that I could use to approach this it would be of great help.

One of the reasons I am using the Soundmodem is that it will decode  
1200 and 9600 baud packets simultaneously.

I also have a 9600 baud modem that I will try tonight instead of the  
soundmodem.  It may just be that the software demodulator needs  
tweaking somehow (audio levels/filter response maybe).   The hardware  
modem should (in theory, I think) be better able to cope with  
variations.  And at least it will rule that out.

Thanks for the help.

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