[amsat-bb] Re: ISS and PCsat SATgates

[Bob Bruninga <bruninga@xxxxxxxx>]

Someone asked about my reference to a 1/4 wave ground plane antenna:

> > 3) OMNI SATgate gain should shoot for angles above 10 degrees.  Use a 1/4
> > wave whip over a ground plane.  This antenna has a broad lobe that will
> > hear the satellite the other 70% of the time when it is above 10 degrees
> > and the satellite is 6 dB or more closer.
> >
> > 4) The 5/8th wave has all of its gain on the horizon.  At all angles above
> > 15 degrees, the 1/4 wave does several dB better AND the bird is 6 dB or
> > more closer.  Between 30 to 50 degrees, for example the 1/4 wave is 11
> > dB or more better!
> > <snip>
>
> So, are you talking about a 1/4 wave antenna with ground plane at 90
> degrees? How many elements should I have on the ground plane? 3, 4
> elements?

No, sorry, I did confuse things.  I am talking about a 1/4 wave vertical
whip over a "ground plane" like the roof of a car, or a 1 meter or so
piece of chicken wire or something to act as a "large ground plane".  This
is what gives the high angle lobe above 10 degrees.

A "ground plane" antenna that consists of a vertical over 4 radials has a
radiation pattern identical to a Dipole.  That is, it puts the major lobe
on the horizon just like a vertical dipole.

Hope that helps...

 de WB4APR@amsat.org, Bob

PCsat WEB  page     http://www.ew.usna.edu/~bruninga/pcsat.html
ISS-APRS FAQ:       http://www.ew.usna.edu/~bruninga/iss-faq.html
CUBESAT Designs     http://www.ew.usna.edu/~bruninga/cubesat.html
APRS LIVE pages     http://www.ew.usna.edu/~bruninga/aprs.html
APRS SATELLITES     http://www.ew.usna.edu/~bruninga/astars.html
MIM/Mic-E/Mic-Lite  http://www.toad.net/~wclement/bruninga/mic-lite.html

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