Hi Paul,
I would say your problem is on 40 not 80. To me, covering almost the entire
40 meter band at the 2:1 points says you have considerable losses involved.
This may sound backwards but it's not. I just checked the manual on-line
and there is no matching device/ mechanism for the feedline so the best VSWR
should be on the order of 1/4:1 like you have on 80. I would try adding
more radials and see if the VSWR on 40 gets "worse". You may find that the
80 meter adjustments need to be redone.
Good luck,
Bob, W5AH
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com]On Behalf Of Dinsterdog@aol.com
Sent: Thursday, May 12, 2005 1:48 PM
To: towertalk@contesting.com
Subject: [TowerTalk] Impedance difference on 4080V from Cushcraft?
I am going to phase a pair of 4080V verticals by Cushcraft using the W9AD
multiband phase system sold by WX0B.
But before I install the phased system, I am trying to figure something out
about the single antenna I have up.
My impedance at resonance on 40 meters is 50 ohms with an SWR of 1:1.
My impedance at resonance on 80 meters is 40 ohms with an SWR of 1.4:1.
I have 20 buried radials averaging 30 feet, some as small as 10 feet, some
as long as 90 feet crossed over, spreading out in a 40 degree pattern going
east away from the antenna which is next to my fence. I have a real estate
problem.......
If you visit the website at Cushcraft, you can download the manual.
I am trying to lower the SWR on 80M without effecting 40M.
Since I can no longer lower the resonant point by adjusting the top element
length, per the manual, I began adjusting the length of the capacitance
rods
on the 80M hat. I have spent a lot of time already working with them. I
had success lowering the initial resonant SWR from 2:1 to 1.4:1. But I'm
stuck
there.
Should I just be satisfied with the performance or can I do more to improve
things? I don't really need anymore bandwidth on 80M. I have around 80KHz
at
2:1 SWR and I only work the SSB DX window. If this was only for 80M, I'd
use an UNUN to get flat. But since this is a multiband
vertical...................................
My question is more about theory with the 80M issue than anything else.
I'm
just picky-It is just interesting to see the impedance difference between
40M and 80M.
Just for FYI, on 40M, I have 280KHz of bandwidth at 2:1 SWR and I am flat
at resonance. This antenna plays well on an analyzer, hi.
In the rain, I get a 70KHz resonant point drop on both bands- You are
warned
in the manual but not the sale's brochure- So far, I have had fun with this
thing- Can't wait to phase them-
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.
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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.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
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