(Jason Hsu) wrote in message . com...

Hi Jason,
I tried to make a DCTL antenna for 80 m from a 300 ohm TV twinlead.
Unfortunately, after I made some measurements, a strom approached and
I put the antenna down. I have never continued the experiments since
then.

1. How seriously is it affected by nearby metal?
Sorry, no experience.

2. How do you insulate and reinforce the wires at the feedpoint?
I used several layers of adhesive tape only, as it was a temporary
experimental installation. A better construction seems to be necessary
for long-term usage. One proposal is at
http://www.radiohc.org/Distributions...l-antenna.html

3. Could the length of the open stub LC be adjustable to modify the
resonant frequency?
The antenna is "fine-tuned" by the open stub. The formula given in
http://www.n5nw.org/antennas.html works quite well.

4. How much feedpoint resistance can one expect from the DCTL? The
author suggests using a 6:1 balun. So it sounds like the DCTL Antenna
should be about 300 ohms. 300 ohms is about the characteristic
impedance of twin lead.
Despite that, the RF-1 bridge showed approx. 150 ohm impedance around
resonance. Maybe it is always one half of the characteristic impedance
of the twinlead used ? And remember, the input of the antenna is
balanced.

Some more links:
http://www.io.com/~n5fc/dctl_ant.htm
http://www.radiohc.org/Distributions...l-antenna.html

73 Ivan OK1SIP