Topband: New Top Band antenna

[Tom Rauch]

> California (W6JL), we modeled and put up a inverted L 
> which when fed
> direct with RG8-U, no tuner, has a SWR near 1:1 at 1.830. 
> We modeled it
> first using G4FGQ's DOS program found at this web site:
> http://www.btinternet.com/~g4fgq.regp/page3.html#S301
> The neat thing was that I also envisioned 100 foot radials 
> of at least 20
> each strung all through my yard and flower garden.  How to 
> bury them and
> not tear up the yard was the biggest issue which kept me 
> from action for
> some time. When Don, W6JL suggested this modeling program 
> I was skeptical
> but the results were great. Turns out, in my case, the 
> vertical section
> could only make it up 62 feet with the horizontal being 
> the remainder of
> 137'.  The radials ended up at 25 feet and only needed 12. 
> More radials
> or longer radials were better but the improvement was 
> almost
> insignificant.  We're at 45% efficiency over average soil. 
> 100 radials at
> 150 feet each would have given us maybe 55% efficiency.

You really have to be careful using these oversimplified 
BASIC programs to model complex interactions. The very fact 
antennas themselves don't model well with simple programs is 
the reason behind method of moments based programs. When we 
consider there is some question about accuracy of the more 
complicated programs with soil, I'd be VERY skeptical about 
accepting programs that consider even less of what is really 
going on.

>From actual measurements, I know some of the other DOS 
programs depart from reality quite a bit.

I'd rely on something using a NEC engine, if anything at 
all.

73 Tom