[Elecraft] Balun for K-1

Sat Jul 20 23:34:00 2002

I would imagine (haven't tried it yet, by the way!) that a choke balun
wound on a very high permability ferrite toroid (a small one say 1"" in diameter)
with RG-174 coaxial cable would do a fine job from 7-21 Mhz. for the
4 band card K1.  I plan on trying this and making some measurements
to see what happens with a G-R R.F. Bridge.  Will report on the
findings soonest.
73,
Sandy W5TVW
----- Original Message -----
From: "Tom Hammond N�SS" <[email protected]>
To: "James R. Duffey" <[email protected]>
Cc: <[email protected]>
Sent: Saturday, July 20, 2002 4:07 PM
Subject: Re: [Elecraft] Balun for K-1

| Hi Jim:
|
| >I think it is unecessarily complicated for the task at hand. For the use
| >over the short frequency span of interest to a K-1 4 band module user, 7 MHz
| >to 21 MHz,  a simple coiled coax choke balun, 6 or 7 turns should provide
| >adequate choking reactance. It is simple, can be made in minutes, and is
| >effective. With it you can be on the air in minutes. The numbers you quote
| >indicate the effectiveness of the simple coiled balun, the balun in column
| >5, 8 turns sceamble wound into a 6 5/8 in coil, has a peak choking reactance
| >of 8530 ohms and a 200 Ohm choking reactance bandwidth (recommended by
| >deMaw) from 2 MHz to 16 MHz (an 8:1 bandwidth. There are those who think a
| >200 Ohm reactance bandwidth is inadequate, so the 500 Ohm choking reactance
| >bandwidth is from 3.5 MHz to 10.5 MHz, still a respectable 3:1 ratio.
| >Winding a coiled coax choke balun as I suggested should be adequate for the
| >4 band K-1, which was the application I was addressing. Other applications
| >may require more care and a better balun. When improvements are made to the
| >antenna system at a later time, the balun can be upgraded. But to get on the
| >air quickly with a minimum of fuss and acceptable performance, the coiled
| >coax balun is hard to beat.
|
| I agree completely with your response!
|
| I was mainly posting the article for the benefit of all of us on the
| reflector, rather than directing it at anyone is particular.
|
| Of course, MANY (thousands, I'm sure) scramble-wound baluns have been made
| over the years (my tribander sported one for probably 15-18 years itself).
| And we never knew the difference between the way it worked and the way it
| might have performed had it been wound in a solenoidal fashion. Heck... we
| STILL don't now... <G>
|
| But, thanks to the article, I now know that if I want to obtain PEAK
| performance from my coaxial-cable baluns, I should probably wind them in a
| single-layer coil, rather than in the manner I'd been using for many years.
| As you state, in many instances a single-layer coil is not required to
| obtain more than adequate performance.
|
| >The posting was in keeping with my QRP KISS (Keep it simple stupid) policy.
| >I find the KISS policy keeps me out of trouble and on the air more than
| >pursuing optimum (and oftem more complicated) solutions. Don't get offended,
| >the stupid in KISS is not meant to apply to anybody but me.
|
| I'm not offended in the least... and I do appreciate your further
| discussion (above) of the subject. Thanks for taking the time to respond.
| And, don't worry, MOST CERTAINLY applies to me very well...!!
|
| 73,
|
| Tom Hammond   N0SS
|
|
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