[Elecraft] KPA-1500 tuner questions

[Don Wilhelm]

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