[Elecraft] Diversity at 50 MHz

[Bill W5WVO]

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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