> What if I fed > the output from two VERTICAL antennas into the K3 receivers in diversity > mode, fed the audio output of both receivers into the A and B channels > of the computer sound card, and used an application that introduced an > adjustable delay in one audio channel before summing the two channels > and doing the D/A translation back to monaural audio? Wouldn't that > have the exact same effect as being able to adjust the phase of the > incoming RF, and therefore the directivity of the 2 element vertical > array?
Yes, I think that would work fine. There are two issues that I can think of: While the main and sub receivers are phase-coherent, the actual phase difference between them is random. I believe that if you change frequency it is not guaranteed that the phase difference will be the same. So every time you change frequency you may have to re-adjust the phase delay to get the antenna to "point" in the right direction. The other issue is that the antennas must be no more than 1/2 wavelength apart to get a clean, single-lobe response in the directivity pattern. Al N1AL On Thu, 2010-09-16 at 01:37 -0700, David Gilbert wrote: > Several weeks ago, I believe that Wayne posted a message asking what > kind of different uses people were coming up with for their K3. One > thing I've been playing with lately is feeding the signals from two > horizontally polarized antennas at different heights on my tower into > the Main and Sub receivers of my K3 in diversity mode. Since the > relative phase between the two signals is preserved in the translation > to audio, I can feed the audio from the two receivers into the A and B > channels of my computer sound card and compare the relative phase using > a dual-trace sound card oscilloscope program like Zelscope. By knowing > the vertical distance between the two antennas I'm hoping to be able to > calculate the arrival angle of the signal in real time. I say "hoping > to" because so far I don't have a distant stable, unmodulated carrier to > work with ... the best DX carriers have come from 40m BC stations but > the modulation screws up the triggering. Once I get the methodology > worked out a bit better I'll ask someone in Europe to throw a carrier on > frequency for me. > > Playing around with this stuff got me thinking, though. What if I fed > the output from two VERTICAL antennas into the K3 receivers in diversity > mode, fed the audio output of both receivers into the A and B channels > of the computer sound card, and used an application that introduced an > adjustable delay in one audio channel before summing the two channels > and doing the D/A translation back to monaural audio? Wouldn't that > have the exact same effect as being able to adjust the phase of the > incoming RF, and therefore the directivity of the 2 element vertical > array? I'm pretty sure that today's computers could certainly handle > the computation. There wouldn't be any constraints on the amount of > delay so the array should be continuously steerable through an entire > 360 degrees, and since the delay would be imposed digitally there > wouldn't be any frequency dependency. Ideally the two feedlines would > be of equal construction and equal length, but even if they weren't it > would be fairly easy to characterize their relative phase delay as a > function of frequency. I think mutual coupling even become a non-issue > if the verticals are non-resonant. Non-resonant antennas might be the > way to go anyway since such unlimited control over phase means that > spacing between them would be less of an issue, and therefore the same > pair of verticals could be used on more than one band as long as the > spacing was wide enough. > > Why wouldn't this work? The PCM data format is pretty straightforward > and I can't believe that the application would be that complicated to > write. I must be missing something but nothing jumps out at me. If it > worked, it could even be a feature in a next generation K3 (maybe even > the current one) .... all it would take is some means to adjust the > delay since everything else (two phase locked receivers, DSP processing > for both RF and audio) is already there. > > In the case of the K3, all of this would only apply to reception, of > course, although it almost seems like a transceiver could be engineered > that used the desired delay determined from the receiver to set a > corresponding delay for two identical tone-modulated transmitter chains > driven from the same oscillator. I suspect a pair of phased > transmitters would have pretty limited appeal, though ... certainly > they'd be an expensive way to get just two or three db steerable gain. > > Fun stuff to think about, in any case. > > 73, > Dave AB7E > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
