dimension of a NAv antenna balun?

[Dave]

Hey jim,

I've read it in here, but I've slept since then.
What are the dimensions of the balun of a nav antenna?

Cheers

Dave

[RST Engineering]

Are you talking about a coax cable balun or a ferrite balun?

Jim



"Dave" > wrote in message
...
> Hey jim,
>
> I've read it in here, but I've slept since then.
> What are the dimensions of the balun of a nav antenna?
>
> Cheers
>
> Dave

[FlyWithTwo]

Dave wrote:
> Hey jim,
>
> I've read it in here, but I've slept since then.
> What are the dimensions of the balun of a nav antenna?
>
> Cheers
>
> Dave

Hi Dave,
If you're making a folded coax balun, the matching section should be
a quarter wave at the center of the nav band, or 113 MHz. That's
26.13" in air. Divide that by the square root of the dielectric
constant of the material in the coax. I think the dielectric constant
is about 2.1. That would make the quarter wave section right at 18
inches. At the dipole end, connect the two center conductors together
and connect each of the shields to a half of the dipole. At the other
end of the balun, connect the center and sheild of the balun to the
shield of the coax line. The rest of the coax is the unbalunced 50 ohm
cable. There are lots of variants on this. I can recommend several
books on it. One is "The ARRL Antenna Book" published by the Amateur
Radio Relay League. The other is McGraw Hill's "Antenna Engineering
Handbook", edited by Johnson and Jasik.

Good luck
Brian