Re: KPA-1500 tuner questions

Posted by Peter W2IRT on Mar 15, 2019; 3:59am
URL: http://elecraft.85.s1.nabble.com/KPA-1500-tuner-questions-tp7649648p7649741.html

I love this idea, but there's one problem, though. I only have one coax line
leading out of the shack. It runs from the Palstar (or it could run from the
KPA-1500) to the input of my antenna switch. I have 5 antennas connected off
that--three Yagis, and the 80m vee off the tower, and a 160 inverted-L in
the back-40.

Antenna-2 on the K3s is my 6m antenna, and if I take the Palstar out of
line, how do I feed the vee separately? My 80m vee is also at about a 120
degree angle, about 65' at the apex, and it plays REALLY well to Europe, the
Pacific and North America. It doesn't do squat to Asia, unfortunately.

 - pjd

-----Original Message-----
From: [hidden email] <[hidden email]> On
Behalf Of Don Wilhelm
Sent: Thursday, March 14, 2019 10:59 AM
To: [hidden email]
Subject: Re: [Elecraft] KPA-1500 tuner questions

That is the antenna I use on 80 meters.  It has a double-humped SWR response
and stays below 2:1 between 3500 and 3900kHz.  Up at 4000kHz it is a little
higher than 3:1.  The 1/4 wave 75 ohm section is a transmission line
transformer.  The 1/2 wave 50 ohm line repeats the impedance at the antenna
feedpoint.

Mine is an inverted Vee with a 120 degree angle at the apex.

Since the 75 ohm section is 1/2 wavelength on 40 meters, the same feedline
can be used on 40.  So I also have two radiator wires for at right angles to
the 80 meter radiator.  Being at right angles, there is no interaction.

73,
Don W3FPR

On 3/14/2019 2:51 AM, Jim Brown wrote:

>
> Here's a VERY old solution that W6NL has taught to his EE classes.
> When I asked him about it, he says it's not his original idea, far
> older than him.
>
> Tune your 80M dipole to 3675 kHz, feed it with a half-wave of 50 ohm
> coax starting at the antenna, then a quarter wave of 75 ohm line. Line
> lengths are at 3675 kHz. Add 50 ohm coax as needed to reach the shack,
> or coil up the excess if those two lengths are too long. The result
> will be SWR below 2:1 from 3500 kHz to 3900 kHz. With good RG213 and
> RG11, Line loss is about 0.5 dB at the resonant point and about 0.7 dB
> at the limits.
>
> If you want to do some engineering, you can probably tame that 40M
> antenna too. Here's a tutorial applications note.
> http://k9yc.com/PacificonSmithChart.pdf
>
> 73, Jim K9YC

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