TopBand: Feedline Thread

[W8JITom@aol.com]

In a message dated 96-10-23 12:04:57 EDT, you write:

>
>The RG-59 thread has been interesting...and leads me to a further
>question...why not use cheap 300-ohm TV twin-lead? 

Hi Ward,

The unbalanced antenna and load (the receiver is the load) would give you
common mode problems, but if you handle them properly the line will work
well. You will need a choke type balun at the antenna, as well as a properly
designed transformer balun at the transition to the unbalanced line.

With either coax or twinlead the ONLY thing that prevents ingress or
radiation problems are equal and opposite net currents in the line's
conductors, coax is just easier to handle. If either line is installed
incorrectly, it can have "leakage" problems.

But as others point out, CATV companies throw away lot's of good coax. Some
pretty good reel ends have even been known to bounce off the back of a truck
in exchange for a six pack of beer, or sometimes hundreds of feet of cable
are changed for something as simple as a bad fitting.

The nice thing about CATV coax is plenty of hardware is available for the
RG59, RG6 and RG11 they might toss, including grounding blocks and fittings.
But even so, I also use 450 balanced lines and plan on adding some antennas
with 300 ohm line.

73 Tom

--
FAQ on WWW:               http://www.contesting.com/topband.html
Submissions:              topband@contesting.com
Administrative requests:  topband-REQUEST@contesting.com
Sponsored by Akorn Access, Inc & KM9P