[TenTec] Antenna Tuners...questions

[Dr. Gerald N. Johnson]

On Mon, 2008-05-05 at 18:22 -0700, Stuart Rohre wrote:
> Ken, you hit the downsides right on.  Dielectric loss in the coax pair, 
> and the voltage and current limits.
> 
> -Stuart Rohre
> K5KVH
> 
> 
To which I would add the low impedance section may lead to lower
impedance at the shack that may be harder to tune, but the 150 ohm line
is certainly better with a 1000 ohm load than a 50 ohm line.

I tested Belden 8290 with a 200 watt amplifier a couple decades ago.
First I set up a heavy duty tuner for series tuning and connected a
shorted length of 8290. I tuned for maximum current and ran it for a
while absorbing 200 watts somewhere. The line didn't heat excessively.
Then I reconnected the tuner for parallel tuning and cut the short of my
test line section. I had great corona streamers from the cut ends but
the line didn't flash over (nor the 1/8" spaced tuning capacitors). So I
extended the conductors and installed corona balls and cured the visible
corona and had no flash overs. This was probably at 75 meters with that
amplifier. Belden 8290 was a shielded 300 ohm oval twin lead. Probably
18 or 20 gauge conductors.

73, Jerry, K0CQ