On 10/15/99 7:34, Dave Earnest at k7jj@home.com wrote:
>To make a long story longer, I am having no luck getting in touch with a
>human who cares at Cushcraft. Anybody out there that knows the secret of
>unlocking that door?
Well, I've been doing some research myself. First thing I did was to
download all the .PDF manuals from Cushcraft's site and read everything I
could.
Second thing I did was to ask questions. I got a response from
<techsup@cushcraft.com>. The first response seemed canned, but I found
that if I persisted with questions, I could get more information. My
replies to that address are usually answered within a day or two.
>I am having the same problems others are having: poor bandwidth on 20,
>15 and dubious operation on 17.
My problems are not meeting bandwidth specs on all bands but 10m, plus
40m, 30m, 17m and 12m resonances are 2.0 or above.
Have you tried "adjusting" your R7000? I wouldn't suggest going far from
the book dimensions. My opinion is that this design is influenced by trap
resonances. If a trap is off, changing antenna dimensions won't work as
you might think. If adjustments don't seem to bring the changes you think
they should (ie lengthing the bottom segment doesn't move the 10m
resonance), then you may have trap problems.
>Any help or suggestions would be appreciated. Oh, my antenna is about 4
>months old.
You're in luck! Yours is still under warranty.
First, you need to determine which "version" of the R7000 you have. If it
is only four months old, it should be the August 1998 later version. You
can tell by the BD tube. Earlier antennas had two or three 12" BD tubes.
The later version has one 5" BD tube. The later version has slightly
redesigned traps at CT2 and CT3 which improve manufacturability. If you
have the early version, you may be able to get the R7000TFK (Trap Field
Kit) to convert yours to the later version.
Second, the antenna is greatly influenced by the installation. Cushcraft
recommends mounting it in the clear with no objects within 25 feet.
Heights of eight to 25 feet are recommended. (The antenna was designed
for mounting at 18 feet) If your installation can't meet these criteria,
you may experience problems. Describe your installation to Cushcraft
Technical Support.
Third, make some measurements. Cushcraft Technical Support recommended I
return my antenna to its original manual dimensions and take
measurements. I did this with an MFJ 259 antenna analyser. I recommend
you do the same. Buy or borrow an AEA, MFJ or other antenna analyser and
take measurements with a short length of coax. (Long runs of coax will
"improve" the SWR bandwidth due to losses) Measure the resonance
frequencies, the SWR present at those frequences, and the frequencies of
the 2:1 bandwidth points. Send all this information to Cushcraft
Technical Support.
Hopefully, they will be able to get your antenna operating. Act quickly,
since yours is under warranty.
Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr@radio.org
Quote: "Boot, you transistorized tormentor! Boot!"
-- Archibald Asparagus, VeggieTales
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