[R-390] Antenna question

[Thomas W Leiper]

On Thu, 18 Jul 2002 13:25:17 -0500 "Scott, Barry (Clyde B)"
<cbscott@ingr.com> writes:
> 1.  Isn't the impedence of a plain-old dipole somewhere near 50 - 75 

In free space or a wavelength above ground, yes. 75 Ohm.

> 2.  Not familiar with CAT5.

Cheap network cable. You can go to a scrap yard and
get all you want for pennies. It has four twisted pairs and
is just fine for receiving. As to UV exposure, you can
rplace it every year for ten years and it will be cheaper than
using a good 50 ohm cable like RG-55 or RG-9. I use
a run of CAT 5 to hook up to four dipoles that are oriented
in two directions and on two bands. A simple 2P4T wafer
switch is at the receiver end to select between the antennas.

> Is it possible to take some good, insulated wire...and twist
> my own twisted pair?

I wouldn't waste that fine wire or your precious time on that.
The 100 Mhz CAT 5 has twisted pairs that are actually bonded
together and the twists are very consistent. You might find
some nice old thermostat or doorbell wire that is twisted, and
also of heavier gauge...about 16 to 18, just in case you want
to transmit as well. If nothing else, ordinary "zip" type lampcord
makes a dandy balanced line...and the neatest thing is that all you
have to do is put a tie-wrap one quarter wavelength from one end
and "unzip" it back...instant dipole with no connections in the weather.
But like ladder line, you have to be more cautious about where you
run the zip cord...best is straight out the window. It's great for
portable outdoor operation, however.

> Thanks for the suggestion.  I would like to have a separate 
> receiving antenna so I can run my xcvr without changing the antenna 
> everytime.

All the above will work for you.

Professor Irwin Cory