[R-390] Antenna question

[Thomas W Leiper]

On Thu, 18 Jul 2002 20:32:45 -0500 blw <ba.williams@charter.net> writes:
> Tom,
> 
> Are you saying that CAT-5 ethernet cable is better than coax?

It depends upon what you want. If you are only receiving or
transmitting at QRP levels, using a receiver with a balanced input
available, want to effortlessly null out any currents that are not
induced in the antenna elements, want to use several antennas
without having an antenna switch or relay outside and up high,
don't want to care if lightening zorches your expensive feedline,
and have boxes of the stuff laying around...yes, CAT 5 is better.

> I wonder why coiling CAT-5 will slow things down so much.

Because "coiling" can allow induced peaks and nulls to develop
in the line. Remember, those signals have very high bandwidth
so many resonances can develop along with imbalances. If you
had instead simply stuffed the cable into a milk jug in a random
fashion you would not have had a problem. I've run into this
problem all the time with network installers who are too tidy
and like to leave extra cable coiled up in the ceiling. I just undo
the tie-wraps and scramble it into a nice ugly ball.

> I would have to feed 2 dipoles. I guess the extra twisted pairs 
> would be good for additional antennas this fall.

Yup. And you can just make a plexi disk with eight posts around
and wire up your four dipoles in a radial or fan array.

> Okay, here is another problem. ...The new TV in the den is
> causing light RFI every 15 kc up and down the bands.
> The TV is 3 rooms away!!! 

The question is how close it is to the antenna. Your receiver may
be doing it's job and the TV is simply a piece of shit. I would
first stick a wire in the unbalanced connector and see if I could
get that TV marker generator directly, and, if so, work on cleaning
up the TV. How do you do that (I hear you cry)? First make sure
the HV anode connection (in the piece of shit) is good and there isn't
a leak somewhere, next put an RFI filter on the power cord of the
TV, and finally, trade it in for a couple of good books. The kids need
to read more anyway.

Otto Von Helseng