It's worth mentioning that Jim's method needs the dipole to be at a
reasonable height - 40ft or more - to avoid having a low resonant
feedpoint resistance. Once you go much lower than 40ft, and the resonant
impedance falls below about 55 Ohms, the SWR will stay *above* 2:1 all
across the band.
Steve G3TXQ
On 21/10/2013 17:44, Jim Brown wrote:
On 10/21/2013 2:50 AM, Doug Scribner wrote:
I'd like to find a quick way to switch between the CW and Phone
portions of the band.
There's an easy method to obtain a broadband match using transmission
lines. Carefully tune the antenna for 3675 kHz. Feed it with a half
wave, or a full wave, of 50 ohm line beginning at the antenna, then a
quarter wave of 75 ohm cable, then as much 50 ohm cable as you need to
get to the shack. Measure those lengths carefully as a stub at 3675
using something like a MFJ 259. This will give you a match in the
shack below 2:1 from 3500 to 3900. Make that first 50 ohm length the
least number of half waves that will still reach the shack. This
method is shown in detail in a presentation I did last year at Pacificon.
http://k9yc.com/PacificonSmithChart.pdf
<http://audiosystemsgroup.com/PacificonSmithChart.pdf>
73, Jim K9YC
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