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!!!!
>
>73
>
>Andrew (G8LUG not active )
>
>
>
>----- Original Message ----- From: "Pete Smith" <n4zr@contesting.com>
>To: "Andy Ikin" <andrew.ikin@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:
>>>Hello guys,
>>>
>>>
>>>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??
>>>
>>>73
>>>
>>>Andrew Ikin
>>>_______________________________________________
>>>Antennaware mailing list
>>>Antennaware@contesting.com
>>>http://lists.contesting.com/mailman/listinfo/antennaware
>>
>
>
>
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