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Author Topic: Antenna shootout methods  (Read 7493 times)
M6GOM
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« Reply #15 on: October 10, 2012, 02:55:37 PM »

They're not scientifically normalized, the measuring methodology is poor at best, so the resulting data isn't much more than a brag tape!

The 80's-90's CA 75m mobile shootouts were well run by RF engineers. Power delivered to the antenna was measured and normalized, i.e. factored into the results. A ferrite rod receiving antenna on a pole was used to minimize the effects of human bodies. The RF measuring device was borrowed from Lockheed. The compiled results of three of those shootouts are at:

http://www.w5dxp.com/shootout.htm

I see two photos on that page with two antennas mounted completely differently. Might as well be trying to compare an apple to an orange.
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W8JI
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« Reply #16 on: October 10, 2012, 05:58:02 PM »

I can. The Hamstick should be on the top, Hi-Q second, and the bugcather with large hat last.
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W5DXP
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« Reply #17 on: October 10, 2012, 07:51:42 PM »

I see two photos on that page with two antennas mounted completely differently. Might as well be trying to compare an apple to an orange.

Those two photos are from two different years but they were about equal in performance. The second one was just to see how well I could do with stuff from my junk box - I tied for first place.
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
W5DXP
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« Reply #18 on: October 10, 2012, 07:54:43 PM »

I see two photos on that page with two antennas mounted completely differently. Might as well be trying to compare an apple to an orange.

Those two photos are from two different years using the same mount on the same GMC pickup but they were about equal in performance. The second one was just to see how well I could do using nothing but stuff from my junk box - I tied for first place.
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
K0BG
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« Reply #19 on: October 11, 2012, 06:39:34 AM »

Tom, you ask about the problems with shootouts, and I can think of several right away. The main one is the ground conductivity.

I have a large field behind my house where I can park my vehicle. Parking there early in the morning and you tune to the lowest SWR, within a hour the SWR will climb several points. This is particularly evident if there has been a bit of moisture the night. Even driving just 10 feet away, the SWR changes quite a bit.

At the last shootout I attended, we started at about 10 am. The last vehicle checked was at 1:30 pm. Just for fun, we rechecked the first two vehicles. The difference would have placed one of the vehicles 4 spots down from where it was originally. The temp at 10 am was about 80°, and at 1:30 pm about 95°.
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G4ZOW
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« Reply #20 on: October 11, 2012, 07:40:00 AM »

Has anyone ever accurately compared the FS when switching a Scorpion with a HiQ on the same mount on the same vehicle?

Or are either side afraid of the result?

If this were carried out in public I'd invest in the winning antenna.

G4ZOW/M
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K0BG
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« Reply #21 on: October 11, 2012, 02:36:09 PM »

Yes it has. By me personally. Buy the Scorpion!
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G4ZOW
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« Reply #22 on: October 14, 2012, 07:51:08 AM »

Thanks Alan  Smiley

...and can you confirm it can take the 'full load' on 160m without arcing all over the place?

David G4ZOW
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K0BG
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« Reply #23 on: October 14, 2012, 12:10:54 PM »

I don't own a 160 meter model, but the 680 easily handles the legal limit here (1,500 dead carrier).
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