Jim,
Your comment about hams not being limited, " Huh? We're hams --
we're not limited to products we can buy! And we can build far better
than we can buy.". you may be correct, but from what I see, the majority
of hams, at least around here, buy what they need. Even of our more
serious hams buy baluns and chokes from sources like DX Engineering and
Balun Designs; few are really building these easy to make devices. There
are exceptions to what I just said, but in the main, more hams are
buying rather than building. Sorry, but that's what it looks like to me.
I do like your paper and have it. I also wish that you continue to
get more hams to actually build more things.
73,
Barry
K3NDM
------ Original Message ------
From: "Jim Brown" <j...@audiosystemsgroup.com>
To: elecraft@mailman.qth.net
Sent: 1/14/2019 2:21:30 PM
Subject: Re: [Elecraft] Slightly Unbalanced dipole?
On 1/14/2019 9:02 AM, Barry wrote:
The simple answer is that the common mode chokes available to hams are of the
unbalanced type.
Huh? We're hams -- we're not limited to products we can buy! And we can build
far better than we can buy. In 2010, I published the design for a common mode
choke to cover the HF bands using a pair of #12 THHN wound on a 2.4-in o.d. #31
toroid. k9yc.com/2018Cookbook.pdf has dozens of designs using THHN, teflon
pairs, and RG400. These chokes are fairly easy to wind, and all can be built
for less than about $35, including connectors.
A member of our contest club is building a serious contest station, and asked me to
measure a "balun" from a well-known manufacturer. It came in a nice
weatherproof non-metallic enclosure, and was nicely made. But it looked NOTHING like the
data sheet that WAS on the website at the time (and which has been removed since I showed
my data to a few engineering colleagues, one of whom obviously asked the mfr about it.)
The problem with choking a two-wire feedline is NOT one of balance -- if it's a good
choke, the choke takes "balance" out of the equation. What matters is
dissipation in the choke due to excessive voltage or current that is present because the
antenna is not matched to the line.
73, Jim K9YC
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