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
