RadioBanter - View Single Post

April 25th 06, 02:54 PM posted to rec.radio.amateur.antenna

wrote:
An important correction: I DO NOT get a lower-than-50ohm *impedance* on
any band.

I may be taxing the limits of my '259B but this is what I measure as
far as ballpark magnitude of impedance.

80M 225 ohms
60m 600 ohms
40m 630 ohms
30m 330 ohms
20m 420 ohms
17m 206 ohms
15m 216 ohms
12m 216 ohms
10m 180 ohms

Nowhere is this resistive.

So, maybe the 4:1 current balun is the more appropriate one. How does
the impedance transformation work with reactive loads?

Here are the impedances if anyone needs:
80m 41-j220
60m 500-j320
40m 500+j370 when paralleled with a 1k resistor (300+j1000ish?)
30m 39-j325
20m 300+j255
17m 50-j200
15m 190+j104
12m 70-j205
10m 170+j60

Will a 4:1 current balun transform a random impedance Z1 to Z2 where
|Z2|=|Z1|/4? I know Roy pointed out that this won't work for a voltage
balun...

To the extent that the balun is working, it will work with complex
impedances as well as with a purely resistive ones.

The Trask paper has several designs for 2 core 4:1 current baluns that
should work. They need two cores. If you want really wide band
performance, you can stack a low frequency and higher frequency
ferrite toroid for each of those cores. With this approach you can
achieve a 1000 to 1 frequency range. The long tube bead ferrites make
good baluns in a small space.