[amsat-bb] Re: Polarity questions
w4as at bellsouth.net
Fri Sep 19 14:11:34 PDT 2008
I gotta hand it to the guys who do it with a handheld, and an arrow
antenna. I hear them all the time, they have good signals. They are
standing up, figuring out where to point the antenna, when and where
to turn it, up and down, sideways, and keep up with doppler, and log
the signals and somehow also talk; I don't know how they do it!
This morning I worked a station on one of the birds who was using a
vertical, he was weak, but we made the qso.
I personally enjoy experimenting, and seeing what works best for me.
I don't just throw money at something and hope it somehow gets
better. Not to knock the guys who really know their stuff, the guys
who built the satellites and control them. But as I've said before -
the main issue with the amateur satellites at this time is that they
are UNDERUTILIZED. Just listen during a pass and many times you won't
hear anyone, and most of the time you will end up talking to the same
people over and over again. I hope that statement doesn't waken up
the "we don't have a HEO" complainers!
73 de W4AS
On Sep 19, 2008, at 2:44 PM, Clint Bradford wrote:
>>> ...20-dB, assuming the signal is pure circular polarization.
>>> ...linear, then -3 dB.
>>> ...difference between RHCP and LHCP is 20 dB
>>> ...difference between Horizontal and Vertical Linear is 20 dB
>>> ...difference between (RHCP or LHCP) and (Horizontal or Vertical)
> is 3 dB
>>> ...the VHF/UHF Manual handbook says 20 -30dB
>>> ...in the real world, expect around 20~25dB loss from being
> completely cross-polarized
>>> ...Between linear and circular, expect about 3dB loss.
> Ahh, thank goodness for the engineers...
> Just know that to get started working the FM satellites, you do not
> need to spend much to make successful contacts...Working AO-51 from
> Southern California (which some claim is not a "real world") at a Watt
> or so with an HT and Arrow Antenna is a breeze, and the polarization
> of the Yagi makes no difference in quality of TX/RX signal.
> And as you refine your satellite comms requirements, you can spend
> more money!
> Clint Bradford, K6LCS
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