Posted by
Jim Brown-10 on
Mar 14, 2019; 6:51am
URL: http://elecraft.85.s1.nabble.com/KPA-1500-tuner-questions-tp7649648p7649721.html
On 3/13/2019 10:45 PM, Peter Dougherty wrote:
> Well that's just it, the SWR is very, very high in the phone portions of
> both 40 and 80.
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.pdf73, Jim K9YC
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