Jim,
Thank you for your suggestions. Others have sent me emails agreeing with
you.
Within what distance would you suggest to measure field strength? What
protocol? I would think cranking down the rig to minimal power and taking a
reading at relative distance of a few hundred feet. Is there a field meter
out
their that will accurately read field strength. I remember Radio Shack had
one
in the 70's and 80's during the CB craze. It had a dopey 4 inch antenna on
top of it but operated as good as a cereal box decoder ring-
I've learned several things from experimenting and this question/answer
round regarding impedance, radials, and SWR on the Cushcraft 4080V multiband
vertical.
First, my radial system added to the Cushcraft 4080V significantly lowers
the resonant frequency anywhere from +-85KHz on 80M and +-314Khz on 40M. So
it
doing something considering it is not much with again, 20 buried radials.
The impedance almost doubles to a higher value on both bands with the
radials detached.
But again, the SWR readings are not that effected at resonance.
The general conclusion of the antenna masters was not to worry about the
impedance issues but to concentrate on field strength measurements. Obviously,
the radial system, if graded, is working. But how well?
To know, I'll start my field testing by disconnecting the radials, measuring
the signal, the connecting the radials and taking another measurement to see
just what difference is. Then add 10 or more radials and see what happens.
Of interest to me, and my backyard turf, I am now going to join a radial
wire from my west antenna which is now in place, to a radial wire of the new
antenna on the east side. This way, I will use the existing radial system for
a
big part of the planned array. Of course I will add new radials to the
system but with a small backyard, I think sharing is a good idea.
And I thought impedance mattered- It sure did on my 160M wire Inv L with 120
1/4 radials. Thank God for UNUN's
With enough radials, it would on the 4080V too. The manual states that:
More than the prescribed number of radials may be installed on the MA8040V
at your option in order to optimize radiation efficiency. However, not that
as radials are added, SWR may eventually increase to an unacceptable level as
driving resistance drops progressively further below 50 ohms. Use the best
compromise for your operating system."
I have never seen a manual state this. I wish I had the room for too many
radials!!!! Well, this is my last posting on things. Thanks for the help.
Once I get the array up, I'll have my field strength meter and let you know
how
it is going. I'll be sneaking in various backyards at 3 A.M. to take test
with my beacon on-
73
Paul N0AH
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