On 31 Dec 2005 16:51:02 -0800, "
wrote:

I wonder if u could help me, i have a tri-band beam erected and am
considering using 450 ohm feeder due to the less amount of loss on the
line (as opposed to RG58)

The radio i am using is an IC-756PROII, with inbuilt ATU, will i be
able to connect the feeder direct to the beam and run it straight into
the back of my 756 (using 259 connector) ??

Or will i requrie a balun at either the beam or radio end???

hope you can shed some light on this, have got a bit confused with it

It would have helped if you disclosed the feedline length, it has
bearing on selection of solutions.

On the one hand, one respondent has told you 200m of RG8 is ok (that
is about 6dB of loss at 28MHz), and another has told you that the VSWR
on 450 ohm line will make it unattractive... you can only make these
calls if the length of the feedline is known (and the 450 ohm line
need not operate at high VSWR).

Do you rotate this beam? Will you need a coax tail at the rotator, or
have you some scheme in mind for using open wire line at this point?

There is probably already a balun at the beam feedpoint... but you
will probably continue need to use coax right close to the beam (the
rotator issue).

Owen
--

"Owen Duffy" wrote in message
...
On 31 Dec 2005 16:51:02 -0800, "
wrote:

I wonder if u could help me, i have a tri-band beam erected and am
considering using 450 ohm feeder due to the less amount of loss on the
line (as opposed to RG58)

The radio i am using is an IC-756PROII, with inbuilt ATU, will i be
able to connect the feeder direct to the beam and run it straight into
the back of my 756 (using 259 connector) ??

Or will i requrie a balun at either the beam or radio end???

hope you can shed some light on this, have got a bit confused with it

It would have helped if you disclosed the feedline length, it has
bearing on selection of solutions.

On the one hand, one respondent has told you 200m of RG8 is ok (that
is about 6dB of loss at 28MHz), and another has told you that the VSWR
on 450 ohm line will make it unattractive... you can only make these
calls if the length of the feedline is known (and the 450 ohm line
need not operate at high VSWR).


Got to admitt I ment 200 feet instead of 200 meters. That is less than 2 db
for rg8. Even the rg8x is only about 3.5 db for 200 feet at 30 mhz. By the
time you factor in the loss due to the swr and probably a couple of baluns
and the trouble to run open wire up a tower and in the shack you do not gain
much over a good grade of rg8 with open line up to 200 feet or more.

Owen Duffy wrote:
... another has told you that the VSWR
on 450 ohm line will make it unattractive...

Not unattractive, just less attractive than if
it was a matched line case. I feed my 20m rotatable
dipole with 300 ohm ladder-line and put up with the
SWR loss in order to gain 20m/17m/15m/12m/10m
operation.
--
73, Cecil http://www.qsl.net/w5dxp