[amsat-bb] Re: Polarity questions

n3tl@bellsouth.net n3tl at bellsouth.net
Fri Sep 19 16:23:09 PDT 2008


" ... and the polarization of the Yagi makes no difference in quality of TX/RX signal."

I know I haven't been working the satellites nearly as long as Clint and many others - and with all due respect, my friend - I have to disagree with the above statement. I routinely work passes during which I swing my Arrow through, and sometimes beyond, 90 degrees to maintain signal quality. There also have been times when a quick twist of the wrist has made the difference between making a contact and getting a new grid square ... and not. 

I don't-at-all disagree with the concept that working AO-27, AO-51 and SO-50 isn't terribly difficult with a handheld station. Frankly, that has really (and pleasantly) surprised me. However, I do believe that adjusting polarity when hand-holding the Arrow provides improved performance during many passes. 

73 to all,

Tim

-------------- Original message from Clint Bradford <clintbrad4d at earthlink.net>: -------------- 


> >>...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 at 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 


More information about the AMSAT-BB mailing list