On 9/29/2012 11:26 AM, Robert G. Strickland wrote: > Is there anything to be gained in putting a 1:1 "balanced isolator" at the > feed point > of an antenna that is fed by a "parallel wire" feed line? Does such an > arrangement > achieve feed line isolation while preserving the ability of such an antenna > to be > driven on various bands other than its resonant frequency? Thanks for your > input.
Phrases and words like "balanced isolator" and "balun" are not only confusing, they are used to separate people from their money. The chokes described in my RFI tutorial can be built for the price of a single #31 core, a few yards of THHN wire, and a couple of connectors. You can put it in a box if you like, but it's only cosmetic. These chokes will handle legal power IF the antennas are not badly unbalanced. Off-center feed creates massive imbalance, and will fry even the best of chokes. The relatively small imbalances created by surrounding objects will not -- they simply couple noise. #31 cores cost about $4.50 in 1,000 lots, about $7 if you buy 100, and $15 from the rip-off vendors who advertise in QST. It's become fairly common for ham clubs to get together and make a group purchase. Over a period of about 8 years, I've been part of several at the 1,000-piece level. There are guidelines in Appendix One of the tutorial about how and where to buy. It's worth buying in quantity, because these 2.4-in diameter cores are almost universally useful for RFI suppression. 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
