Topband: Wideband Balun...?

[Keith Jillings (G3OIT)]

On 28/08/2012 19:29, Eddy Swynar wrote:

> I am thinking of incorporating a homebrewed 4:1 balun as part of a transmatch that I have here, which was designed to feed coaxial cable-fed antennas only...
>
> Is there really & truly such a thing as an air core 4:1 balun that will cover the entire spectrum from 1.8- to 29.7-MHz...? I've looked & I've repeatedly searched on the internet, but can not quite come up with such an animal. Maybe the frequency range of such a beast is far too great for any practical design...
>
> Anyone have any leads in this regard...?

I've not come across anything that would cover that much spectrum in one 
unit that didn't have ferrite in it.

I needed something very similar to match a doublet.   I ended up with a 
pair of coax baluns (in series - don't tell me!) and I get 1:1 indicated 
on the input to the transmatch on all bands 80 to 10.   The doublet is 
too short for 160m, so is fed as a T on that band, and loaded quite 
differently.

The main balun is 14 turns of good quality RG213 on a 4 inch plastic 
drainpipe former.   The smaller one is 6 turns.

73

Keith
G3OIT