300 ohm TV Twinlead
 

I am considering making an HF antenna out of 300 ohm TV twinlead. I
am thinking of making an OCF or CF dipole and using an MFJ-941 tuner
to tune it to the various ham bands. I will be using an IC-706 MKII
which transmits from 5 to 100 watts output.

Here are a few questions:

How much power can the twin-lead handle?
Radio shack has both the old thin twin-lead as well as the low-loss
foam version. I realize that the low-loss will be better for the feed
line portion, does it make a difference in the antenna portion?

Since the antenna tuner has a balun in it, I won't be using a balun.
The purpose of the antenna will be to keep it in the car and to set it
up for portable operations on occasions. When practical to do so, I
may leave one of these antennas in locations where I visit frequently
and wish to operate.

Thank you for your comments.


--
73 for now
Buck
N4PGW

Buck wrote:
I am considering making an HF antenna out of 300 ohm TV twinlead. I
am thinking of making an OCF or CF dipole and using an MFJ-941 tuner
to tune it to the various ham bands. I will be using an IC-706 MKII
which transmits from 5 to 100 watts output.

Here are a few questions:

How much power can the twin-lead handle?
Radio shack has both the old thin twin-lead as well as the low-loss
foam version. I realize that the low-loss will be better for the
feed
line portion, does it make a difference in the antenna portion?

Hi Buck, this brings back memories, when I was a Novice, the first
antenna I ever put up was made of 300 ohm TV line. It was a dipole
made up of two 50' lengths of twin lead. The ends were shorted
together, and a 1' length of 1 conductor was removed 16' from the far
end of each section. I fed it with ~70 ohm twin lead (lamp cord).
What you wound up with was a sort of fan dipole, that was resonant on
80, 40 and 15m. The 80m part was 50' + 16' folded back for a 132' 80m
dipole. The other conductor was 33', for a 66' dipole which is 1/2
wave on 40m and 3/2 on 15m. I chose this design and materials because
I was 14 at the time and this was all I could get my hands on. I
worked stations all over the country on 80 and 40 with 15 watts cw.
Only had 2 crystals.
I never checked the swr because I had no way to do so, but all the
transmitters I used had pi network outputs, that would load most
anything. When I got my General I ran 100 watts AM with this antenna
with no problems.
I would go with the least expensive RS twin lead, should handle the
power, and do fine as the radiator and transmission line.
73 Gary N4AST

Buck wrote:

I am considering making an HF antenna out of 300 ohm TV twinlead. I
am thinking of making an OCF or CF dipole and using an MFJ-941 tuner
to tune it to the various ham bands. I will be using an IC-706 MKII
which transmits from 5 to 100 watts output.

Here are a few questions:

How much power can the twin-lead handle?
Radio shack has both the old thin twin-lead as well as the low-loss
foam version. I realize that the low-loss will be better for the feed
line portion, does it make a difference in the antenna portion?

Since the antenna tuner has a balun in it, I won't be using a balun.
The purpose of the antenna will be to keep it in the car and to set it
up for portable operations on occasions. When practical to do so, I
may leave one of these antennas in locations where I visit frequently
and wish to operate.

Thank you for your comments.


If you make a folded dipole to match your 300 ohm feedline impedance
then you should use the low-loss. If you're just going to short the
wires together and treat it as one fat wire then use any old thing.

--
-------------------------------------------
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com