Back in the 1950s we used to install TV antennas on 30 and 40 foot steel
masts to get a 100 uvolt signal on channel 2 with a 10 or 12 element yagi.
We used regular 300 ohm twim lead and twisted it before putting it into the
slot of the standoff. the standoff were about 4" long. The twisting did
two things: minimized leadin pickup and equalize any stresses from wind.
What happens when you transmit with high SWR is out of my league.

--

73
Hank WD5JFR
"KC1DI" wrote in message
...
ml wrote:
I wonder exactly what happens when you run ladder line say next to a 1''
metal pipe spaced about 1" apprt

is it just that the ohms that change would it be a bit or does it swing
waaaay off?? tnx
Hi ML

Keep the Ladder Line 3X it's width away from the metal for 300 ohm twin
lead that would be about 2 " For 450 ohm Ladder line it would be about 5
" a twist in the portion of the line near the metal object about every 18"
or so will also help. Remeber though that the portion of the line near
the metal object must not be allowed to sway in the the wind if it does it
will cause the impedence to very sometimes widly as the line moves closer
then further away..

I've found the above to be very accurate and have not had problems in many
installations over the years.

73 Dave