Alan Bloom wrote:
As I recall, signals at VHF/UHF tend to become horizontally polarized
after propagating long distances, no matter what the polarization of
the transmit antenna. That's why horizontal polarization is
traditionally used for SSB/CW (DX-oriented communications) and
vertical for FM (mostly local communications).
Remember that 50 MHz is "kinda-sorta" a VHF band. In truth, it has properties
of both HF and VHF frequencies. The main propagation mode on 6M is
sporadic-E -- and in a few more years (we all fervently hope and pray) a
little F2! Sporadic-E especially is oftentimes very dynamic, with a lot of
deep QSB as the E-cloud shifts, travels, grows stronger, and dissipates. I've
always suspected, due to this fact, that diversity reception on 6M would be a
real boon, especially on multiple-hop long haul paths, as well as during
marginal E openings where signals are generally weak with deep QSB. No, I
haven't tried it, but I suspect it would be killer for sporadic-E propagation.
I plan to experiment with that next summer after I have my K3 and hopefully
second receiver module.
Bill W5WVO
(certified 6M nut)
Al N1AL
On Sun, 2007-12-30 at 15:33, Mike Scott wrote:
I am building a 3-element 6-meter quad while waiting for my 2nd
batch K3. Before final build a new thought...
Instead of building a quad I could alternatively make the spreader
arms a little longer and configure two cross-polarized 3-element
yagis. The thought would be to drive two receivers in polarization
diversity.
Does anyone have any experince with the value of polarization
diversity at 50 MHz? I am inexperienced on this band. I know
everyone goes horizontal polarization for VHF weak signal work but
once the signal gets refracted back to ground level the actual
polarization may be rotated.
BTW, Lyle have you thought about ways to optimumly combine diversity
receiver outputs other than just piping them into seperate ears? I
could imagine actually calculating a time averaged received
polarization angle and differential delay between channels and then
combining...
Mike Scott-AE6WA
Tarzana, CA (DM04/near LA)
QRP-ARCI #12326/ KX1 #1311/ Swan 350C
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