Thank you Guy for the best explanation I've ever read on how diversity reception works in a contest-like environment. I hope others found it as enlightening as I did, and if you haven't done so already, that you'll share it on some wider venue such as QST. 73, Gary, K6KV
-----Original Message----- From: guyk...@gmail.com [mailto:guyk...@gmail.com] On Behalf Of Guy Olinger K2AV Sent: Thursday, November 11, 2010 7:13 PM To: Gary Gordon Cc: Barry N1EU; elecraft@mailman.qth.net Subject: Re: [Elecraft] [K3] Enhancement request - audio mixing This reply is not speculation. We used orthogonal antennas and dual RX K3's in diversity mode at N4A in the IOTA on Core Banks NC this summer. It worked very well, and we had the high North America island expedition score for LP, beating all but one of the North America HP scores. A pair of three band inverted vees running NW/SE and NE/SW fed with 450 line feed and tuned via a 4:1 balun and the K3 antenna tuners. What happens is that with both RX on that you do not get the nature of signal separation you are expecting. You get phasing separation because the antennas will decode any polarization off pure vertical and pure horizontal into the same kind of separation you have listening to a conversation in a crowded room. Signals not low angle frequently came in on a rotating polarization, moving back and forth from one ear to the other. What was quickly clear was that if we turned off the SubRX, the moving back and forth is converted into rapid deep QSB that defeats copy. The LOUD stations tended more to be in one ear or the other, but those are easy to work. The WEAK signals on 40m particularly, would be affected by this rotating polarity. The same rotation was heard on the band noise, some of the guys having a hard time listening to this rotating background. I was constantly cleanly copying signals that sounded like they were starting on a fadeout but just rotated through my head to the other side instead. One has to hear it to understand it. The complexity you seem to be recommending was unneeded for our best score ever. We knew that to transmit, the predominant signals needed to be in the LEFT ear. The ANT button just toggled that for us. We used the config menu to label one ant "NEAST" and the other "NWEST" so that came up on the display when we switched it. This was never a confusion and it was used competently right off the bat by all the operators. You're transmitting to the signal in your left ear. If it's in the right, hit the ANT button. If what's in the right ear is making it hard to hear, just hit the SUB button. Mixing the channels when doing diversity RX seems to me anyway to just muddle it and reduce the benefits. To use the K3 in the way described for N4A requires that the subrx is set up to use the non-TX antenna of the ANT1 ANT2 pair. This of course is not compatible with using AUX for diversity listening on RX only antennas for 160 because that is not internally switched. I have solved that by getting the K3 back panel from Elecraft with the "ANT3" BNC hole punched into it, and a miniplug to BNC cord, which I shortened on the BNC end. I used this to bring out the "other" antenna jack from KANT3 to the K3 back panel at ANT3. Then to do this kind of thing at FD or next year's IOTA just patch ANT3 to AUX RF and leave the SubRX listening on AUX RF. Having used this at N4A, I find NOT having it at home is like something is missing, and I'm designing my station forward to take advantage of it. 73, Guy. On Thu, Nov 11, 2010 at 6:39 PM, Gary Gordon <ga...@gary-gordon.com> wrote: > I've been paying close attention to this thread, having purchased > the K3 sub-receiver with the intent of using it next Field Day with my two > "very-orthogonal" 40M antennas. My question is, has it been thought through > how the capability of having two receivers and two antennas works best in a > contest? I sense from this thread that it is distracting to not be able to > hear only the chosen antenna in both ears. It makes me wonder, could a > different optional mode for the K3's antenna switch help satisfy this wish? > > Ideas are cheap, and one that comes to mind is this: When listening > to two antennas, a TAP of the ANT switch would feed what's in the left ear > into both ears. If instead a slightly longer HOLD of the ANT switch was > made, what was heard in the right ear would then be fed into both ears, and > also select the XMIT antenna. After the contest exchange, any further tap > of the ANT switch would revert the receivers to putting their separate > signals into each ear, maybe assigning the last active antenna to the left > ear. > In use in a contest, then, if the desired station were strongest in > the right ear, the operator would press the ANT switch for one second, work > the station (hearing it in both ears), and finish with one tap of the ANT > switch to returned reception to its prior dual-receiver mode. > Note that such a mode might be implemented as an option. If set to > that mode, then a K3 would enter that mode when the diversity mode was > invoked. > My post is not a "request", but rather a question that, given the > power of dual receivers and antenna switching, has the best way to use this > capability in a contest been worked out? > Thanks > Gary K6KV ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
