Yes indeed - the way it was described to me was "choke balun". I'm not
a purist in such matters - if it works, I'll go with the name it was
given.
I was sceptical when it was suggested, but since I was having trouble
matching the doublet, I decided there was little to lose. In fact, it
works well.
In contrast, a carefully-built balun with two expensive toroids (they
are expensive here) failed catastrophically the first time I tried it on
80m. It was "supposed" to be able to handle 2KW, but I think that must
have been in perfect conditions.
If Eddy is having trouble between a transmatch and a ribbon-fed antenna,
one of these (or a pair, as I have) may be a viable solution.
I'm restricted in what antennas I can have - the house was built in the
15th Century and is "listed" (ie covered by historical preservation
regulations). A doublet between two trees is invisible enough...
Keith
On 28/08/2012 23:11, Bill Aycock wrote:
> Keith--
> Pardon me, but, isn't what you describe really a choke, not a Balun?
> Bill--W4BSG
>
> -----Original Message----- From: Keith Jillings (G3OIT)
> Sent: Tuesday, August 28, 2012 1:36 PM
> To: Eddy Swynar
> Cc: topband@contesting.com
> Subject: Re: Topband: Wideband Balun...?
>
> 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
>
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
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