[Towertalk] 15M on C31XR

[Mike Fatchett]

Is there anything else on the tower other than the c31?  This sounds like an
interaction problem.  What kind of guys are on the tower.  Are there other
antennas close by?  Does the SWR change as you rotate the antenna?

Just a few questions.

Mike W0MU

-----Original Message-----
From: towertalk-admin@contesting.com
[mailto:towertalk-admin@contesting.com]On Behalf Of mwdink@eskimo.com
Sent: Wednesday, May 08, 2002 12:31 PM
To: towertalk@contesting.com
Subject: [Towertalk] 15M on C31XR


Hello All

Since the talk about antennas and towers seems
far and few between lately, I'm gonna throw
something out for reflection. I've tried
asking this on the Force12 reflector a
couple years ago before but didn't get
much response. Since this antenna is even
more wide spread now, Steve suggested I
try it over here.  (I also figure
ALL of them are over here plus more.)

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~`

I have a C31XR. I'm quite happy with it but I
get the "feeling" 15M isn't playing as well as it
could. Yes!, that's a really hard thing to quantify.

1) The antenna's SWR on 15M reaches it's minimum
between 20.0MHz and  20.3MHz. I just use a tuner
to make the rig happy. I know that SWR is not the
be all and end all but I know the expected minimum
SWR for the antenna design is higher up the band.

2) After several years of competition, I just keep
getting the heck beat out of me on 15M. (I feel
competitive 10M and 20M.) When others in the area
have high Q totals on 15, mine are always mediocre.
I do accept the possibility that I may just be a lousy
contester too.

No, this is not a case of adjusting the infamous
parallel wires, this antenna is feed with 3 separate
feedlines (though I am tempted to go to one feedline
just to see if things improve). I am well versed in
all the ONE feedline techniques but it's not the
same beast.

Yes, I have made all the changes in the
instruction book (moved driven element back, different
hairpin coil, shortened and lengthned specified elements,
etc). I have rechecked the measurements until I am blue
in the face. I have made sure the tubing is going the
right direction (an easy mistake if not careful).

Last summer, I had it down and played with the driven element
length just to see if I could raise the frequency at
which the SWR bottom out. (I realize I may have messed up
my gain and f/b but it was an experiment). I got it
where I wanted it at ground level (about 20') but as
soon as it went back up the tower - same result, back
into lower 20MHz region.

So, I am looking for someone else with the same antenna,
feed with 3 feedlines, who may have experienced a similar
situation and solved it. It's not intolerable, the antenna
(at 100') works and it beats a C3S I have at 40' - it just
doesn't seem up to par with the other bands.

I thought I would throw it out and see what floats up.
Give us something to think about beside viruses and
insurance. :>) (NO criticism intended on ANYBODY)

73
dink, n7wa








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