[Antennaware] Dual output K9AY
n4zr at contesting.com
Tue May 26 02:59:17 PDT 2009
Thanks for the quick reply, Andy. I am no theoretician, but I recall
a discussion of the K9AY loop in which one well-qualified engineer
asserted that it could/should be viewed as a close-spaced array of
two short near-verticals, phased by the wire between them. If this
is in fact the mode of operation, then feeding each "vertical"
separately, while retaining the top connection between them, seems
like a real muddle from the standpoint of phasing. Modeling two
side-by-side loops also wouldn't really be faithful to the real-world
antenna, would it?
At 06:49 PM 5/25/2009, Andy Ikin wrote:
>Thank you for looking into the modelling feature.
>The reason for trying to model the Dual output was to determine the
>phase relationship verses freq. required to increase the rear null
>by subtracting some of the front lobe from the rear. I did some work
>on this in May 2001, but ran into problems with the phasing. Misek
>uses this technique on his Steerable Wave antenna in his Beverage
>Handbook. However his Phasing system is not wide-band.
>The test set-up was to use 2 x 9:1z xmfr at each ends of the loop at
>the junction of the ground wire. Both xmfr outputs connect
>to Phasing box. One channel is a variable 0-165ns delayline
>(terminated 50R). The other channel has the amplitude control. The
>phasing box provides a constant 50 Ohm input for any phase or
>amplitude setting. Also the phase delay is constant for variations in Freq.
>First I wired the K9AY xmfrs so that the Phasing box would combine
>in-phase plus the 0-165ns delayline. Result no increase in gain.
>Next I re-wired K9AY xmfrs so that the Phasing box would combine
>anti-phase plus the 0-165ns delayline. The gain dropped by approx.
>6dB, however, the rear null could be simply adjusted to upto -50dB
>with just tweaking the Phase and amplitude control. Across the MW
>band the average delay was 65ns, so most of the null adjustment was
>with the amplitude balance. The max null was far higher than using
>remote variable termination. The results were much better than I
>had in 2001 with the improvement in the phasing system.
>Btw, this technique doesn't work with RC phasers e.g. MFJ and Dxeng
>except over a narrow bandwidth i.e. the knob fiddling becomes
>tedious with changes with freq.
>Getting back to the model, my thoughts are to simulate the Dual
>output K9AY is to model 2 K9AY close together and take the source
>from each antenna.
>----- Original Message ----- From: "Pete Smith" <n4zr at contesting.com>
>To: "Andy Ikin" <andrew.ikin at btopenworld.com>; <antennaware at contesting.com>
>Sent: Monday, May 25, 2009 10:19 PM
>Subject: Re: [Antennaware] Dual output K9AY
>>Andrew, I am very suspicious. Running this model in Multinec
>>(NEC2) and 4NEC2, it appears to be very sensitive to the value of
>>the assumed ground resistance. At 200 ohms, it gives me a peak
>>gain -18.4 versus average of -26. At 100 ohms the figures are
>>-15.4 and -23.2, and at 50 ohms -12.4 and -20.2. At 5 ohms the
>>values are -3.1 vs -11. The reference single-feed version gives -26 vs -34.
>>I ran the same dual feed arrangement with another model of the
>>loop, as modified by W7EL. He uses a pair of 50-foot radials
>>perpendicular to the plane of the loop in lieu of a direct ground
>>connection, Real-Sommerfeld ground and no series resistance to
>>ground. That model gives quite similar results, -9.8 dB vs
>>-17.95. The reference single-feed version gives -25.9 vs -33.94.
>>I can't explain the results, but I fortunately, it should be fairly
>>easy to test. an 8 to 16 dB difference in signal strengths between
>>the reference loop and the dual-feed design should really be
>>obvious. I'll be interested to see how your tests come out.
>>73, Pete N4ZR
>>At 04:57 AM 5/25/2009, you wrote:
>>>Pete, Guy, Gary and Terry;
>>>Please see attached files. The original K9AY model ( K9AY _ALT.EZ
>>>) is, I believe one from Terry but with the 200 Ohm res. in the
>>>ground wire as per a model from Gary.
>>>The Dual opt K9AY.EZ is with the 390 Ohm load replace with a Source.
>>>Btw, I am going to test it this morning using a varible delayline
>>>Phasing Unit . If the model is right then the correct phasing from
>>>500kHz to 2MHz is a 54ns delayline!!!!
>>>Andrew (G8LUG not active )
>>>----- Original Message ----- From: "Pete Smith" <n4zr at contesting.com>
>>>To: "Andy Ikin" <andrew.ikin at btopenworld.com>
>>>Sent: Sunday, May 24, 2009 10:08 PM
>>>Subject: Re: [Antennaware] Dual output K9AY
>>>>Can you put the model file somewhere we can download it? EZNEC
>>>>or NEC-2 or? This potentially looks very interesting, either
>>>>with switchable phasing or maybe with a phaser in the shack, like
>>>>the DX Engineering or MFJ units.
>>>>73, Pete N4ZR
>>>>At 04:53 PM 5/24/2009, you wrote:
>>>>>I have been trying to model a Dual Output K9AY I.e. taking
>>>>>another output from where the termination is normally placed.
>>>>>Then combine the two equal amplitude outputs with a small phased shift:
>>>>>10 deg. at 500kHz; 20 deg.at 1MHz; 30 deg. at 1.5MHz, 37 deg. at 1.85MHz.
>>>>>This provides the typical K9AY pattern. However, the gain 8dB
>>>>>higher at 1.85MHz and 22dB higher at 0.5MHz compared to the K9AY.
>>>>>I have yet to verify the model. However, does the model change stack-up??
>>>>>Antennaware mailing list
>>>>>Antennaware at contesting.com
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