Buck wrote:
Ok, just to reiterate so I know I understand (and you can see if I
don't), If I feed a 20 meter dipole cut for my favorite frequency, I
can feed the radio with exactly 1/2 wave of 450 ohm feedline and it
will match the radio?

Actually, any integer multiple of 1/2 wavelengths will work

Of course, coax will make a better match (with
less loss?)

Amazingly, not necessarily true. Better match? Yes. Less loss?
Not necessarily. Ladder-line with an SWR of 9:1 may actually
have less loss than coax with an SWR of 1:1.

Depends upon the type of coax and the type of ladder-line.

For instance, at 10 MHz, RG174 has a matched line loss of 4 dB
per 100 ft. while 600 ohm open-wire line has a matched line loss
of about 0.075 dB, so small I have trouble reading it on the chart.
Even adding the additional losses due to SWR, the open-wire line
is far, far below the RG174 matched line losses.

Now, if I understand, the principle of the 130 foot dipole matching
the rig is based on the length of 450 ohm twin-lead. The twin lead is
always 1/2 WL long.

Nope. The twin lead is whatever length it takes to resonate
the antenna system plus an integer multiple of 1/2WL. Correct
this concept first before drawing additional conclusions.
--
73, Cecil http://www.qsl.net/w5dxp


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