" wrote in message
...

"Caryl Duncan" wrote in message
...
Anyone know about this type of setup? My understanding is I must use 75
ohm coax from the ground up to the "T" then to each antenna. Is this
true? Anyone have a formula?

Use 75 ohm cable if your antennas are 50 ohm. Getting your antennas to be
50 ohms is nearly impossible. usually the actual impeadance of the antenna
is around 30 ohms so you can use 50 ohm cable instead of the 75. When you
use 1/4 wavelength of 75 ohm cable on a 50 ohm antenna the the radio end
of the cable will look like 100 ohms. put the 2 100 ohms loads in paralell
and now they are 50 again. Use 75 ohm cable this with 30 ohm oantenna and
you get 30 ohms at the radio one they are cophased. Use 50 cable and
instead of doubling the impedance of the antenna its now qradrupled so a
single antenna is seen as 120 ohms and the cophased set is seen as 60, a
beeter match for the 50 ohm radio.

Sorry, got to thinking you were cophasing antennas on a truck Shouldnt do
post when Im this tired.

Thats ok, I really can use this info too. I just found out the roofs onmost
of the newer Big Rigs aren't metal but fiberglass!

I got a long way to go.
" wrote in message
.. .

" wrote in message
...

"Caryl Duncan" wrote in message
...
Anyone know about this type of setup? My understanding is I must use 75
ohm coax from the ground up to the "T" then to each antenna. Is this
true? Anyone have a formula?

Use 75 ohm cable if your antennas are 50 ohm. Getting your antennas to be
50 ohms is nearly impossible. usually the actual impeadance of the
antenna is around 30 ohms so you can use 50 ohm cable instead of the 75.
When you use 1/4 wavelength of 75 ohm cable on a 50 ohm antenna the the
radio end of the cable will look like 100 ohms. put the 2 100 ohms loads
in paralell and now they are 50 again. Use 75 ohm cable this with 30 ohm
oantenna and you get 30 ohms at the radio one they are cophased. Use 50
cable and instead of doubling the impedance of the antenna its now
qradrupled so a single antenna is seen as 120 ohms and the cophased set
is seen as 60, a beeter match for the 50 ohm radio.

Sorry, got to thinking you were cophasing antennas on a truck Shouldnt do
post when Im this tired.

"Miles Davis" wrote in message
...
Thats ok, I really can use this info too. I just found out the roofs
onmost of the newer Big Rigs aren't metal but fiberglass!

You can take down the headliner and line it with aluminum foil. This also
keeps the government from stealing your thoughts. LOL