[amsat-bb] Circular Antennas

[Dino Papas]

We used the M2 eggbeaters as our back up ARISS antenna system; because of a technical issue at the last minute we actually ended up doing the ISS QSO on the eggbeaters vs. the tracking yagi with polarization switching, phew!  With 600 some odd kids sitting behind us when the astronaut answered we were pretty relieved.  Probably knocked a minute or so off the Q&A period but the audience never knew the difference.  Talk about sweating bullets for a few moments!

73 - Dino KL0S

> On Aug132016, at 1249 PM, Robert Bruninga <bruninga at usna.edu> wrote:
> 
> Noting wrong with "circulars".  Whats wrong is expecting to hear a weak
> signal on the horizon using no gain.
> 
> Eggbeaters are great antennas that give good circular polarization at all
> elevation angles to cover the whole sky and are great for non-tracking
> ground stations listening to strong signals from space (the ISS for
> example).  But by definition, you cannot hear "all of space above the
> horizon" without giving up gain everywhere.
> 
> Space tracking satellites is not homogeneous.  You need TEN times the gain
> down near the horizon compared to overhead.  Any antenna designed to hear
> everywhere upwards equally is going to be ten times worse on the horizon
> where it needs gain the most.  And satellites spend more than 70% of their
> time below something like 22 degrees.
> 
> Please see: http://aprs.org/LEO-tracking.html
> 
> Bob, WB4APR
> 
> On Fri, Aug 12, 2016 at 5:14 PM, Dave Mann <cwo4mann at comcast.net> wrote:
> 
>> My experience with the M2 eggbeaters left something to be desired.  The
>> 70cm antenna was deaf without a gasfet preamp.  I use the 2m one as my
>> local repeater and simplex antenna now.
>> 
>> I've read other comments here about limitations, but I'm still not
>> convinced circulars are a bad thing.
>> 
>> That's about all the advice I can render.
>> 
>> 73
>> Dave
>> N4CVX
>> 
>> 
>> Sent from my iPad
>> 
>>> On Aug 12, 2016, at 13:40, Gerald Payton <gp_ab5r at outlook.com> wrote:
>>> 
>>> Trying to get back into satellite radio from the early 2000s, I wonder
>> what happened to circular helical antennas.  Are they out of fashion now?
>>> 
>>> 
>>> 73,
>>> 
>>> Jerry  AB5R
>>> 
>>> EM12kh
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