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: [email protected] > 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 > _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK
