Diversity at 50 MHz
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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 No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.516 / Virus Database: 269.17.12/1202 - Release Date: 12/29/2007 1:27 PM _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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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). 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 > > > > > No virus found in this outgoing message. > Checked by AVG Free Edition. > Version: 7.5.516 / Virus Database: 269.17.12/1202 - Release Date: 12/29/2007 > 1:27 PM > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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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). Exceptionally interesting thread... K1JT (of WSJT fame) has been doing some experimenting with dual polarization reception using two identical setups, preamps, receivers, etc, connected to horizontal and vertically polarized antennas. Each receiver requires a separate baseband feed to Linrad to decode (4 channels) that is then fed to a second computer over a dedicated Ethernet crossover cable which is running MAP65. Results have been outstanding. Here is a link describing MAP65: http://physics.princeton.edu/pulsar/K1JT/MAP65_Quick_Start.txt My question would be, are there two separate IF outputs on the K3 if you have two receivers installed? Better yet, can you get I and Q outputs for both receivers separately at the rear panel to feed into a 4 channel soundcard, and then along to a computer running Linrad and then on to a second computer running MAP65? Rick Kunath, k9ao _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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Since the two receivers in the K3 are identical and use the same
frequency reference, I presume that when they are tuned to exactly the same frequency the IF outputs should be phase-coherent (with an unknown but constant phase offset). Anybody know if that's correct? Al N1AL On Sun, 2007-12-30 at 17:52, Rick Kunath wrote: > 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). > > Exceptionally interesting thread... > > K1JT (of WSJT fame) has been doing some experimenting with dual > polarization reception using two identical setups, preamps, receivers, > etc, connected to horizontal and vertically polarized antennas. Each > receiver requires a separate baseband feed to Linrad to decode (4 > channels) that is then fed to a second computer over a dedicated > Ethernet crossover cable which is running MAP65. > > Results have been outstanding. > > Here is a link describing MAP65: > > http://physics.princeton.edu/pulsar/K1JT/MAP65_Quick_Start.txt > > My question would be, are there two separate IF outputs on the K3 if you > have two receivers installed? > > Better yet, can you get I and Q outputs for both receivers separately at > the rear panel to feed into a 4 channel soundcard, and then along to a > computer running Linrad and then on to a second computer running MAP65? > > Rick Kunath, k9ao > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Rick Kunath
Hello Rick!
> My question would be, are there two separate IF outputs on the K3 if you > have two receivers installed? There are two IFs, and independent 8.215 MHz IF buffers. The KXV3 only allows a single IF to be connected at the moment, so you'd need to hijack or add a rear panel BNC to have access to both IFs at the same time. > Better yet, can you get I and Q outputs for both receivers separately at > the rear panel ... ? The 15 kHz IF is not brought to the rear panel. I and Q are done in the DSP, and the DSP has only stereo outputs. However, it *might* be possible to incorporate a special mode where the LINE OUT represented I and Q from one receiver, and PHONES/SPKR the I and Q of the other receiver. You'd then need to isolate the PHONES and be careful with level settings, etc. The PC application would need to independently compensate for any phase or amplitude shift from the different AF paths. The bandwidth from these would be about 5.2 or 5.3 kHz. The K3 with second receiver will have high correlation between the receivers, as the synthesizers are derived from the same reference oscillator, the same oscillator is used for the conversion from 8.215 MHz to 15 kHz, and the ADC sampling is done by a common clock on the main DSP board. Have a gr8 '08! Lyle KK7P _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Rick Kunath
Very interesting thread indeed.
My activities on 50MHz primarily take place on dxpeditions, limited to just six meters. I have often wondered about setting up a second antenna, spaced several wavelengths away from the primary ant, to try diversity reception on terrestrial E and F2 propagation. JT65, while very interesting and helpful, are more difficult for dxpeditioners due to the high duty cycle requirement for the amplifiers. Has anyone here tried two antennas yet with K2 or K3? Personally, I can't wait for the opportunities coming our way over this next cycle. 73 Dick, K5AND _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: Diversity at 50 MHz
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In reply to this post by Alan Bloom
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 >> >> >> >> >> No virus found in this outgoing message. >> Checked by AVG Free Edition. >> Version: 7.5.516 / Virus Database: 269.17.12/1202 - Release Date: >> 12/29/2007 1:27 PM >> >> _______________________________________________ >> Elecraft mailing list >> Post to: [hidden email] >> You must be a subscriber to post to the list. >> Subscriber Info (Addr. Change, sub, unsub etc.): >> http://mailman.qth.net/mailman/listinfo/elecraft >> >> Help: http://mailman.qth.net/subscribers.htm >> Elecraft web page: http://www.elecraft.com > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Mike Scott-7
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... For what it's worth many folks take the 3dB hit and combine the horizontal and vertical feeds with a quadrature combiner (or you can phase lag the horizontal and vertical antennas by 90 phase degrees). This goes a long way towards reducing signal fade via polarization rotation. This is, of course, combining in the RF domain which I don't think is what you were seeking. The other folks in this thread suggest the polarization issues are not too big a deal in the 6M band. Perhaps. One thing is for sure... your high water mark in complexity need not exceed your dual Yagi with both feeds ending up in your station where you can then select or combine with arm chair comfort. That kind of flexibility would be cool. > > > Mike Scott-AE6WA > Tarzana, CA (DM04/near LA) > QRP-ARCI #12326/ KX1 #1311/ Swan 350C > > > > > No virus found in this outgoing message. > Checked by AVG Free Edition. > Version: 7.5.516 / Virus Database: 269.17.12/1202 - Release Date: 12/29/2007 > 1:27 PM > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: Diversity at 50 MHz
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> The other folks in this thread suggest the polarization issues are not
> too big a deal in the 6M band. Perhaps. One thing is for sure... your > high water mark in complexity need not exceed your dual Yagi with both > feeds ending up in your station where you can then select or combine > with arm chair comfort. That kind of flexibility would be cool. -------------------------------------------------------------- During the great solar cycle of the late 1950's a VE3 neighbour of mine observed that on East - West 6m F2 paths a vertically polarized antenna often provided better copy than a horizontal antenna, while a horizontal antenna was always better on North - South paths. I suspect that one reason might be that the East - West paths tend more or less to follow lines of equal geomagnetic latitude, perhaps in ducts, while the North - South paths cross these lines and signals 'hop'. It would be interesting to be able to select vertical or horizontal or circular polarization from the comfort of the shack not only when working F2 paths but also when working long haul auroral Es, a case where the polarization of an arriving signal might be changing a fair amount - a speculation. 73, Geoff GM4ESD _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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