[AMRadio] open wire line


Craig C. Heaton wd8kdg at worldnet.att.net
Mon Nov 19 19:48:04 EST 2007


As already mentioned, find the chart in some of the old books, then use what
is available. The local hardware store had some 1/4 inch diameter fiberglass
rod in 5 or 6 foot lengths at a reasonable price. I went for #14 solid
copper wire with 5 inch spacing, it handles a Johnson Desk on 75 and 40
meters, no strain or pain. 

Cut the rod into 5-1/4 inch lengths. Drill holes parallel to each other 1/8
inch from the ends. Then use a dremel tool with a cut off wheel to notch the
ends about 1/16 inch deep parallel to the holes. Attach two runs of wire to
a support, feed the rods onto the wire, use a short length of wire maybe an
inch or so long to wrap around each side of the rod thru the notch and then
solder in place. I found a spacing of 2 feet between the fiberglass kept the
two runs separated. 

Some have used plastic coat hanger, PVC pipe, etc. I'll add that the
fiberglass can take the heat from a small torch for the solder job without
scorching. 

Wd8kdg,
craig

-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of Geoff/W5OMR
Sent: Monday, November 19, 2007 2:53 PM
To: Discussion of AM Radio in the Amateur Service
Subject: [AMRadio] open wire line

I tried to get on the air a few days ago, and noticed the SWR was 
extremely high on my loop, fed with ladder line.

After much futzing it finally dawned on me to check the loop for 
continuity.  There was none.

The 450-ohm ladder line I've been using for two and a half years, before 
it broke, is 14ga solid copper-clad steel wire. 
Not conducive for windy (read: outdoor) applications.

So, my solution is going to be to home-brew an open wire feed line, 
using insulated 12ga stranded copper wire.
I will still be using the same SA-2060A tuner that's carried me for years.

I'll probably go down to the local hardware store and get either some 
wooden dowel rod, and chop it up to equal length pieces and cut a slot 
at the end of each, spray 'em with urethane (for weather protection) and 
then 'hot-glue' the wire/dowel in place.  Or, get some plexiglass rod 
and do the same thing, minus the urethane spray paint.

My question is:
how far apart should the two wires be kept?
I've seen as little as 4" and as many as 6", and both claim to be ~600ohm.

The 450-ohm ladder line is only about 2" wide.

-- 
Driving your AM Rig without a scope, 
is like driving your car at night, without headlights. (K4KYV)

--
73 = Best Regards,
-Geoff/W5OMR

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