Bob,
So that all may fully understand:
Most LEO’s use monopoles or dipoles (on VHF/UHF) which are actually linear and not circular polarization, but the birds are spinning and tumbling therefore the polarization can be H, V or any angle. If you use H or V pole at the ground station the fading may be as high at 30dB therefore it is recommended to use circular polarization at the ground station as maximum fade would be around 3 dB whatever the satellite polarization may be.
I suggest that you use RHCP without polarisation switch, except if you wish to spend some money to experiment with same. I have the possibility to switch polarization but it is not used at all.
Hope this help.
73
Jean Marc (3B8DU)
On Dec 15, 2018, at 1:40 AM, Mark D. Johns [email protected] wrote:
On Fri, Dec 14, 2018 at 10:58 AM Bob Hammond [email protected] wrote:
Do you use polarity switches on your yagis? If you do, is it worth
the effort?
No and no.
I had polarity switching on long yagis back in AO-10 & AO-13 days and it was helpful. But for the LEO satellites we have now, it's rare to have a fade so deep that one can't copy. -- Mark D. Johns KØJM / MØGZO / ex-9H3DJ / ex-KØMDJ Brooklyn Park, MN USA EN35hd
"Heaven goes by favor; if it went by merit, you would stay out and your dog would go in." ---Mark Twain
Greg,
73s,
Bob W7OTJ
On Mon, Nov 26, 2018 at 10:08 AM Greg D [email protected] wrote:
That's pretty much what I did, though with different antennas. Also put the AO-40 dish on the other side of the rotor from the 23cm helix, so it went 70cm, 2.4gig, rotor, 23cm, 2m. Put things as far away from each other as you can, without running out of crossboom.
I was very concerned about having the 70cm beam (uplink) so close - inches - to the 2.4 ghz dish (downlink), but it was fine. Good input filtering in the 2.4 ghz Khune preamp, I guess. More recently, Mode L/v on AO-92 seems ok too, with the 23cm antenna near the 2m, but I have a lot less power on 23cm than I did with AO-40 on 70cm.
Greg KO6TH
Bob Hammond wrote:
I'm putting the following antennas on an 8-foot fiberglass crossboom:
M2 2MCP8A, 143-148 MHz C{ Gulf Alpha 70cm 8x8 CP WiMo Helix 23
I'm not sure how to calculate the proper spacing on the crossboom. I assume the 2m antenna should go on one end and the 70cm antenna on the opposite end. Can I mount the 23cm helical antenna very near the
rotator
without harm since it has the solid reflector behind the helix?
Bob W7OTJ (was WL7CQX) _______________________________________________ Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership.
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Sent via [email protected]. 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 [email protected]. 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