"Ken Bessler" wrote in message
...
Take a dipole, cut for 3.922. Put it up as an inverted V
with the apex at 30' and the ends at 10'. Feedline is 100'
of 450 ohm ladder line/12t 5-1/4" coax balun/30' rg58.

Antenna works nice, esp at night.

Now take the same setup and feed it with an L network
autotuner, say an LDG AT100 pro and run it on 1.825
mhz. Feeding the antenna as a marconi is not an option
due to lack of ground area for radials.

Where does my 100w go? is it lost as heat in the tuner?
(my guess) Is it lost in the feedline due to high SWR at
the apex?

73'd de Ken KG0WX



Hi Ken:

On 1.824MHz, 4.5 db of your power (3db equals 1/2 of the power) is lost in
the feedline. I know that 450 ohm line is supposed to be so low loss that it
doesn't matter, but a 80m dipole on 160m presents such a very bad match that
even open wire line has loss. I would make your antenna as showing a load
of about 10J -1250Ohms. Don't feel bad if you were feeding this with coax
the excess loss due the miss-match would be over 20db. The 4.5db doesn't
include the loss in the coax balun, and the tuner. According to the ARRL
review of tuners on 160 with a SWR like that 25% of the power is lost in the
tuner. These numbers were derived from modeling the antenna with EZNEC and
the TL program that comes with the ARRL handbook. Other people with slightly
different models will get slightly different numbers but the bottom line is
a 80m dipole is a very bad antenna on 160m. You could be losing 1/4 of your
power in the tuner and well over 1/2 of what's left in the feed line. But if
its all you have the use it.


--
John Passaneau, W3JXP
Penn State University