[AMRadio] Re: new antenna and matchbox a bust.


ne1s ne1s at neandertech.com
Tue Jan 30 11:51:33 EST 2007


Brett gazdzinski writes:
> There is a difference when running high power though,
> many here seem to be running moderate power, which will
> work with mfj antenna tuners and various baluns and feedlines,
> traps, etc, but some of that stuff may not work with 
> higher powers and high swr's. 
> I would worry about setting fire to the trees
> running the wire right on them, depending on the voltage/
> current points, insulation rubbing through, wet or dry
> wood, etc....

Brett, 

I've run my non-insulated 160M dipole through the trees, and used it on 
160M, 80M, 40M (tuned feeders/ladder line) without any catastrophes running 
the pre-1990 legal AM power limit. YMMV. 

The only time I set a branch on fire (that I'm aware of) was when I was 
forcing an 80M dipole to tune on 160M, and the branch shunted the FEEDLINE 
at a hi-Z point. Quite impressive display, and this was at moderate power 
(only 80W out from a Viking I). The part of the branch shunting the feedline 
turned to carbon, that part of the branch fell to the ground, and after that 
all was OK FINE. 

Later on, that tree (a willow) came down in a hurricane - no more worries. 
(Luckily, it fell such that it only scraped a few shingles off the house 
roof - coulda been a LOT worse.) 

Get rid of the coax and run your open-wire line directly to the tuner - I 
think you'll be happier with the results. Running both coax lines greatly 
increases your capacitance to ground for that portion of the feedline, which 
is important of that's a moderately hi-Z section of line (which it probably 
will be on some frequency you care about). 

 -Larry/NE1S



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