For the ARISS events that have recently concluded in the UK with Tim Peake, we used the following setup for the bulk of the contacts.
1x Wimo X Quad with vertical, horizontal, crossed left & right polarisation switching. http://wimo.de/xquad-antennas_e.html
1x Wimo Crossed yagi, 2x10 element http://wimo.de/yagi-antennas-wimo_e.html Model WX220with fixed right hand polarisation.
Both antennas had mast head preamps, were fed via (separate) 50m lengths of Ecoflex 15+ coax cables to the radio (TS2000X) through a common RF path of a PA and Bird wattmeter.
Whilst I don't have precise numbers on the times we switched polarisation, there were far too many occasions on all contacts where the XQuad, albeit shorter/smaller gain and with switched polarisation etc outperformed the larger, higher gain, fixed polarisation crossed yagi during the ARISS contacts. The crossed yagi however, appeared to be better when the ISS was on the horizons.
You cannot prescribe a setup that will be 100% perfect in all circumstances - as we say here "pays your money, takes your choice". It is about what the operator is prepared to invest in terms of equipment vs the expected return.
For us here in the UK, we prefer to maintain the flexibility on the XQuad but have the crossed yagi for safety. Besides who else has tried transporting a 2x10 element crossed yagi from site to site! Oh, and one other point that was important for us, was the difference between having six space craft docked to the station and not having six craft docked. That made a big difference from TCA to LOS.
73
Ciaran M0XTD
-----Original Message----- From: AMSAT-BB [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Robert Bruninga Sent: Wednesday, June 01, 2016 5:11 PM To: dan@post.com; AMSAT-BB amsat-bb@amsat.org Subject: Re: [amsat-bb] Polarization (attitude mostly)
Having the RHCP/LHCP switch is better than not having it since it gives you one more ace in the hole. Sure, it might only provide true value for a few seconds due to all the other variables, but when it occurs, it is nice to have for such high visibility events (especially if someone else is buying the hardware)... but for me personally, I'd probably not bother with the complexity for just a few more seconds of null avoidance...
Just an opinion.
Bob, Wb4aPR
-----Original Message----- From: AMSAT-BB [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Daniel Cussen Sent: Wednesday, June 01, 2016 5:00 AM To: AMSAT-BB Subject: Re: [amsat-bb] Polarization (attitude mostly)
I pushed back on that requirement due to cost and availability issues, but went ahead and installed the polarity switch on our CP antennas. With certainty I can tell you that at random times it made a huge difference in downlink signal
level.
There was discussion on the ARISS OPs mailing list as to what to recommend to schools and what would give best "bang for buck" I am still not 100% convinced that a RHCP/LHCP switch is indeed necessary for ARISS contacts. The only way to confirm would be one station with both RHCP and LHCP both receiving at the exact same time and logging or recording the results. Most/all stations that have said the switch helped have not compared in real time not switching. Over time the ISS signal can vary wildly, in particular the solar panels can totally block the signal completely from time to time. There is a couple of stations with dual VHF circular systems (mostly ARISS tele-bridge ground stations) and I have asked them to help. Until we have real world comparisons at least in the case of the ISS, I am not sure a switch is needed. Can someone do tests to check? _______________________________________________ Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb _______________________________________________ Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb