I am surprised that no posting has questioned these measurements! It seems
to me that specifying impedance without including the phase angle ( or R +-
jx ) is of little use in understanding what is happening. Am I missing
something?
Could it be that the impedance is of little concern when trying to determine
how to best install radials so that the issue of impedance terminology was
ignored?
k7puc
----- Original Message -----
From: <Dinsterdog@aol.com>
To: <towertalk@contesting.com>
Sent: Friday, May 13, 2005 9:07 AM
Subject: [TowerTalk] 4080V test get interesting per W8JI suggestions
>I have no idea why I didn't test things at the antenna but chalk it up to
> new born twins....
>
> Here are the 80M results:
>
> 3.770Mhz 3.789MHz 3.826Mhz
>
> 42 ohm impedance 42 ohm impedance 55 ohm impedance
>
> 2:1 SWR 1.4 SWR 2.0 SWR
>
> Bandwidth at 2:1 is only 56 Khz. Manual states 100Khz at 2:1 Had 30Khz
> more
> bandwidth in the shack. Coax feedline was making a difference here.
>
> Take the radials off and Boom!
>
> 3.870Mhz 3.883Mhz 3.910Mhz
>
> 80 ohm impedance 80 ohm impedance 85 ohm impedance
>
> 2.0 SWR 1.6 SWR 2.0 SWR
>
> 40 Khz of bandwidth.........? I thought it would go higher with a less
> efficient antenna. A 94Khz jump in resonant point.
>
> THE 40M results:
>
> 7.132Mhz 9.972Mhz 6.846Mhz
>
> 80 ohm impedance 50 ohm impedance 48 ohm impedance
>
> 2.0 SWR 1.2 SWR 2.0 SWR
>
> 286Khz bandwidth as advertised, or close enough. Resonant point slightly
> lower by 10Khz than measured in shack.
>
>
> 40M Results with No Radials-
>
> 7.213Mhz 7.286MHz 7.392Mhz
>
> impedance 60 ohms impedance 70 ohms impedance 90 ohms
>
> 2.0 SWR 1.6 SWR 2.0 SWR
>
> Conclusion: I still have a 8-10 ohm difference in impedance when
> comparing
> 40 meters to 80 meters at the feed point with or without radials
> attached.
> So it is the antenna. I had a suggestion emailed to me that it is
> because
> the 80M antenna portion is a 1/4 design and the 40M antenna is a 1/2 wave
> design. This would explain the size of the 40M coil considering the
> antenna
> itself is almost a quarter wave in length for 40 meters.
>
> Also, it goes to show the huge difference even a small radial field can
> make. I use very heavy insulated hard copper wire but if you saw my puny
> back
> yard, you would wonder why I am even trying a low band array.
>
> Any input on these numbers is appreciated except by SWR critics. This
> all
> about impedance and the effect it can have in an array. If this was just
> a
> stand alone antenna, I would not be putting the effort in. Also, I don't
> plan
> to operate below 7.000Mhz. I was using an analyzer. I just can't wait
> for
> those questions.
>
> Thank you= And thank you to those with some excellent suggestions-
>
> 73
>
> Paul N0AH
> _______________________________________________
>
> See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
> Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with
> any questions and ask for Sherman, W2FLA.
>
> _______________________________________________
> TowerTalk mailing list
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>
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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