Cecil Moore wrote in news:cIZSf.57484$Jd.33257
@newssvr25.news.prodigy.net:

Basil Burgess wrote:
It apparently tunes the antenna down to an SWR of 1.5, ...

An antenna tuner doesn't change the SWR between the tuner
and the antenna. If it's 100:1 before the tuner does its
thing, it is still 100:1 after the tuner does its thing.
The extra feedline losses are caused by that unchanging SWR.

Yep, though feedline losses are not usually so large as to preclude at
least SOME QSO's on 80 and 40 unless that SWR is AT LEAST 50 (especially on
80m). Of course poor quality coax and twinlead that is touching metal can
really increase those losses, even though they actually REDUCE the SWR that
the tuner is seeing.

A slinky is such a poor antenna to begin with (basically a coil of iron),
it's probably best to just feed it in the center with good quality 450 ohm
line (which you then dress properly all the way to the tuner's balanced
output--if the tuner has one or a balun located AT the tuner if it
doesn't). Next best would be to feed it with decent COAX like LMR400 or
better.

For example, my balcony whip gives an SWR of almost 6 on CW at 3652. I
could lower this by adding a capacity rig at the stinger end of the
hamstick, but I'm a bit too lazy to keep going out and taking it off and
the thing is resonant on 3729 where our phone net meets. But it's still 88
percent as efficient as it is at resonance when tuned up on 3652 with my
tuner, which can tune that SWR flat. (We won't talk about how inefficient
an 8ft antenna actually is on these frequencies, but you get the point).

And that's using RG8X (Belden 9258). Better coax would improve that some.
If the slinky actually has an SWR of 100, then 450 ohm ladder line would
introduce additional loss, due to SWR of 2.04 db per 100 feet.

Moral of the story, when using inefficient antennas with weird impedances,
then make sure you use good, low-loss feedline and keep it short as you
can.


--
Dave Oldridge+
ICQ 1800667