[AMRadio] open wire line (update)

Larry Szendrei ne1s at neandertech.com
Tue Nov 20 16:37:44 EST 2007

Geoff/W5OMR wrote:
> Yeah... I screwed up and connected the SWR bridge output to an antenna 
> connection on the tuner, instead of the RF input connector (DOH!)
> (me and my dumb-ass!  I wish hard living didn't come so easy to me!)
I told you about my latest blonde moment (with apologies to all blonds!) 
privately. Unlike you, I'm not going to disclose it to the list ;>)

> Still mysterious as to why the feed line (disconnected from the tuner) 
> and loop showed to be 'open', instead of closed, like it did this 
> morning.  (*shrug*)
Either another brain-fart, or an intermittent connection. If it were me, 
I'd hope it was the former.

> So, I'll continue with plans to build the open wire feed-line.. I'm just 
> not as pressed for time now as I was, prior to reviving the antenna system.
> I'm gonna go with either 1/8" or 1/16" plexi-glass, drill holes 1/4" in 
> from the 4 1/2 plexi strips and 'v' a notch with a triangle-shaped small 
> wood file.
I'd use at 1/8", or maybe even 1/4", Geoff. For the work you're going to 
put into it, you want it to last. I don't think 1/6" would hold up well 
to the elements and stresses involved.

> The wire I'll be using is 14ga stranded, insulated copper clad steel.
Great! The feedlines for both my wire antennas are the W7FG stuff others 
have mentioned. I like it; it's worked well, but if I had the time to 
roll my own I'd make something more robust, as you are doing.

> Due to the size of the coax hole (through the wall, near the ceiling of 
> the shack) that the 450 ohm ladder line barely fits through now, I'll 
> leave about 5' feet of that on the tuner, and connect the 4" wide 
> feed-line outside.  There'll be a slight impedance bump, but nothing 
> drastic or critical below 30Mc (I never get above 7.3Mc, anyway)
The feedline for my cellar shack does exactly that - "window line" to 
the cellar window, and the aforementioned W7FG line from the cellar 
window up to the feedpoint. The tuner sucks up any difference. There is 
no -practical- reason not to do it.

> Thanks to everyone for the suggestions.
> I'd like to extend an invitation to all AM'ers;  look for activity on 
> the bands late Wednesday evening.  I'll be either at the bottom of 3700 
> (up to 3.725 - wherever there's a clear hole) or up around 3.880~90 
> operating while my traditional turkey smoking process is taking place, 
> over night.  If there's too many in any one particular round table, find 
> a clear frequency and call CQ AM!   With a cold front draping across the 
> nation and dropping the temperatures in Texas (at least) down some 30+ 
> degrees, long distance conditions -should- be favorable.
See you tonite (Tuesday) hopefully - just got the rig tuned up on 3716 
(There was an AM QSO on 3710). Also will try to get on tomorrow 
(Wednesday) nite as well.


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