...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 909-241-7666
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 Sebastian
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 909-241-7666 _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Hi Sebastian,
On 9/19/08, Sebastian w4as@bellsouth.net wrote:
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!
I'm one of these guys :-) Even if lately I'm not much active on the birds, since is still a good period for weak signal work. After some practice you learn how to use all your four hands and do things correctly HI. By far the worst problem working birds this way is when someone wants to chat (when in facts you can only exchange quick contacts with this setup) and tells you that your doppler tuning isn't perfect. Signals on birds are quite strong even with 4 elements on V and 8 on U since you can always find the best polarization quickly and easily. By the way, logging is easy with a recorder, I just record some time marks at the start of the pass then I rewind at the end of the pass and transfer all contacts on paper or whatever with the correct time.
73 Francesco IZ8DWF (alway worked /P also as IZ5DWF and IS0FKQ).
participants (3)
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Clint Bradford -
francesco messineo -
Sebastian