[Towertalk] RE: Force 12

[K6RB]

I sent this email to Dink, privately, but with the ensuing Force 12 issues
being raised, I thought I'd make it public. I'd also like to add that I can
now operate 20, 15, and 10 - end-to-end - with the SWR below 1.8:1. In
addition, with the MAG 240N just 10 feet above the XR, there has been no
apparent degradation in patterns, gain or SWR. The two antennas are
parallel; not 90 degrees to one another, too.

Rob K6RB

----- Original Message -----
From: "K6RB" <k6rb@baymoon.com>
To: <mwdink@eskimo.com>
Sent: Wednesday, May 08, 2002 11:48 AM
Subject: Re: [Towertalk] 15M on C31XR


> Dink,
>
> I have a C31XR at 55 feet and a MAG 240N at 65 feet. I feed all three
bands
> with one line on the XR and I'm very happy with its performance on all
three
> bands. I had a KLM KT34XA in exactly the same position for 18 years and
> replaced it with the C31 last August. Though the XR has only 3 active
> elements on 20 and 4 on 15 compared with 5 for the XA, it seems to be more
> effective on all three bands - especially on 10 (where it has 7 elements
> compared with 6 for the XA).
>
> When I was setting it up, we had to prune the driven element about 3/4
inch
> to get the minimum SWR at 21.2. That was at a height of only 5 feet off
the
> ground. When it was raised to 55 feet, there was little noticeable change,
> and it is still well below 2:1 from end-to-end on 15 meters.
>
> The only thing I can think of that might cause the problem you're seeing
is
> that when you raise it from 20 feet to full height, it's coupling with
> something on your tower. Have you emailed Natan at Force 12 about it? He's
> always been real knowledgable about weird stuff on the XR models.
>
> Rob K6RB
>
> ----- Original Message -----
> From: <mwdink@eskimo.com>
> To: <towertalk@contesting.com>
> Sent: Wednesday, May 08, 2002 11:31 AM
> 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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> >
> >
>