> >Any thoughts on a 600' or 700' run of open wire feeder.
> >Anything special I need to be aware of?
>
> The tuning adjustment at the matching device will be more cricical, since
> you will be running over a full wavelength of tuned feedline.
Don made a very good point. The longer the low-loss feedline (and higher the
SWR) the more rapidly peaks and valleys in impedance occur.
I had a 1500-foot open wire line of number 8 solid copper spaced just over 2
inches, and I impedance matched the line at both ends through broadband
transformers. I measured a power loss of 2% on 4 MHz, including the
transformers.
You can purchase transformers from DX Engineering, or build you own. The DXE
balun transformers are exceptionally good, essentially flat from below
300kHz to above 100MHz. I'd match through a good broadband balun. A modest
bit of unbalance on several hundred feet of line can be a lot of wasted
power.
73 Tom
|