Fw: Re: Fw: [Antennas] Tuner Inductor Q

2003年1月05日 17:58:34 -0800

At 05:54 PM 1/5/2003 -0600, you wrote:
>Any on a completely different tuner subject, the "Balanced, Balanced
>Antenna Tuner" by AG6K is gaining in popularity at the local club, I
>may build one. Looks like a great tuner but I would add a switchable
>choke balun on the frontend ....30-33ft of coax for 160m through 40m
>and around 12 ft of coax for 20m through 10m. Using the 30-33ft length
>at 10-20m is too much loss and not required.

Hi Kees,
I built one of those tuners and it seems to work okay, but on closer 
analysis you'll find that it still has a problem with common mode 
(voltage/current) stress on the balun. In fact, under some conditions it 
*may* add to the problem rather than reduce it. While that design does 
address the differential impedance the balun sees it doesn't do the same 
for the common mode impedance. If your antenna is well balanced and the 
feed line it routed so as to reduce induced common mode current I think 
you'll be happy with it.
BTW: I used a W2DU bead balun (90 beads - almost double the recommended 50) 
as it is a lot less bulky than a big roll of coax.
73
Danny
K6MHE
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