|[AMRadio] open wire line|
w4bws at comcast.net
Mon Nov 19 18:32:39 EST 2007
The older ARRL handbooks had a table of wire size and spacing vs. impedance.
600 usually was about 6 inches. I made some from 6 inch pieces of 1/2 inch
plastic pipe. Drilled holes 1/2 inch in from ends and fed wire thru. After
stretching it out and positioning the spreaders, I secured them with RTV.
Works well. Your tuner doesn't care about spacing since the impedance varies
band to band anyway.
----- Original Message -----
From: "Geoff/W5OMR" <ars.w5omr at gmail.com>
To: "Discussion of AM Radio in the Amateur Service"
<amradio at mailman.qth.net>
Sent: Monday, November 19, 2007 4:52 PM
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,
> Our Main Website: http://www.amfone.net
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