[Elecraft] KAT500 Tuning issue

[Anthony Scandurra K4QE]

You don't need to add 8 foot wires for 10 meters.  The 80 meter dipole will
load up there with a little help from the tuner.

73, Tony K4QE

On Sat, Dec 8, 2012 at 7:27 PM, Ron D'Eau Claire <ron at cobi.biz> wrote:

>
> If you want to use your 40 meter dipole on 20 meters, one way is to add two
> 16 foot wires at the center feed point, putting a 20 meter dipole in
> parallel with the 40 meter dipole. On 40 the extra 16 foot wires will
> simply
> make the radiator look a bit "fatter" to the RF. On 20, the 40 meter dipole
> exhibits a very high impedance at the feed point (which is what is causing
> your problem now) while the 20 meter dipole will present a decent match.
>
> Your 40 meter dipole already makes a decent 15 meter antenna because it's 3
> half waves long, with a relatively decent match at the feed point.
>
> In the extreme you could add a 120 foot wire paralleled wire so the system
> will cover 80, 40, 20 and 15 meters and a pair of 8 foot wires to cover 10
> meters to make it an 80/40/20/15/10 meter system.
>
> That was a common multi-band antenna before the WARC bands were opened. The
> mismatch is much greater on the WARC bands because they are not
> harmonically-related to the others. Even though your tuner may produce a
> good load to the transmitter, feed line losses can get rather high.
>
> Ideally you want to fan the wires to the ends are as far apart as possible,
> but even several inches or a foot or so will work.
>
> Understand that a 2:1 or worse SWR is common even though the wires are cut
> to 1/2 wavelength due to interaction between them, but the losses should
> not
> be serious over a typical run of good quality coax.
>
> 73, Ron AC7AC
>
>
> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Jerry Weisskohl
> Sent: Saturday, December 08, 2012 2:59 PM
> To: Mark Bayern
> Cc: Elecraft Reflector
> Subject: Re: [Elecraft] KAT500 Tuning issue
>
> Mark,
> Thanks for the reply. I received quite a few replies pointing out exactly
> what you said. Because it wouldn't load on 20 meters I was using my other
> antenna, which works fine with the KAT500 (80 meter vertical). However, I
> was trying to understand why the 40 meter dipole wasn't working well on 20
> and I thank all those that replied. This reflector is a wealth of
> knowledge!
> Now I realize my KAT500 is working as it should. Having two antennas comes
> in handy!
>
> Thanks,
>
> Jerry - AC4BT
>
>
> On Sat, Dec 8, 2012 at 5:49 PM, Mark Bayern <plcmark at gmail.com> wrote:
>
> > Just to make sure we're all on the same page ...
> >
> > When the tuner (at the radio) gets an acceptable match, that just
> > means the transmitter will _think_ there is a good antenna system out
> > there. The feedline between the antenna and the tuner will know
> > otherwise and can have points of very high voltage that could cause
> > insulation breakdown, and points of very high current that can cause
> > overheating and will be a source of power loss. This isn't really a
> > problem in QRP operations, but when you head into the QRO world it can
> > make a difference. The antenna also has issues. In an earlier post
> > K3KO had the calculated feedpoint impedance, and it was very far from
> > the 'nominal' 50 ohms of your feedline or the ~75 ohms of a dipole at
> > altitude. W6GF also gave this info in terms of SWR to show how bad it
> > was. All in all a resonant 40M dipole makes an unhappy antenna system
> > on 20 meters.
> >
> > I understand that if that is all you have you're stuck with it, but it
> > is really time to consider something else. Maybe a fan dipole, or trap
> > dipole?
> >
> > Mark AD5SS
> >
> >
> >
> > On Sat, Dec 8, 2012 at 3:30 PM, Jerry Weisskohl <jweisskohl at gmail.com>
> > wrote:
> > > Right now, I have the coax from the antenna directly connected to
> > > the KAT500. I could try using my Delta-4 switch, have the coax go to
> > > that and then a small run to the KAT500 to see if that makes a
> > > difference. The
> > high
> > > swr is an issue on 40 and 10 meters, however, ten is manageable,
> > > it's
> > about
> > > 1.9 - 1 and I am working around the issue but using my 80 meter
> > > vertical
> > on
> > > 20 meters. So this is not a "show-stopper" but just wanted to
> > > understand  why it was happening.
> > >
> > > Jerry - AC4BT
> > >
> >
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