Jeff,
Someone has misinformed you a little. See below:
At 03:31 PM 11/3/2004, you wrote:
I have read a lot about baluns, and still cannot decide what to get. I have
a KAT100 and, want to experiment with several antennas fed with open wire
line.
>From all the discussions of baluns I have a formed a few impressions.
1. For QRP operation the balun is probably not needed.
Depends on the feed line. I guess you can run the KAT2 on the K2 into a
balanced line by grounding one side. Works. Probably works better with a
balun.
2. Use a 1:1 balun unless you know your antenna system has high
impedance on all bands of operation.
A 1:1 balun actually works as well feeding an open wire line as the more
common 4:1 current balun. Take a G5RV for example. The bands where the
impedance is closer to 50 ohms and those where it is closer to 200 ohms are
about the same. The current baluns works better for this application. A
1:1 balun is a current balun. You have to be careful that the balun or kit
you buy is a current balun. Most will say, but some don't.
3. For multi-band operation make the balun really big to handle any
waste heat.
This is wrong. First of all, if you are going to waste power, a big balun
or a small balun will waste the same. You just won't notice it on a large
balun. I have used a 2 core balun using F-114-43 cores on 100 watts with a
reactive load with a SWR of 5:1 without the balun getting hot. Measured
efficiency on the balun under these conditions was about 93%. Losses at100
watts were 7 watts, well under 1 dB. Efficiency into a 200 ohm load was 97%.
With these ideas in mind I am tempted to get a super heavy duty balun like
the ones form DX Engineering. The $100 plus price tag on these big baluns is
encouraging me to take a look at cheaper alternatives.
One alternative is to make a heavy duty balun form a kit. Any comments on
the various kits available? Two sources I have located are:
http://www.amidoncorp.com/aai_cost_experimenter.htm and
http://thewireman.com/index.shtml
With the idea that you don't need a KW balun for 100 watts, try the
Elecraft BL1. LDG has a kit, in an enclosure. It works ok, but it is a
voltage balun and not a current balun. Also, NJQRP offered a low power
(read 100 watts) balun kit in 2002. Details are at www.njqrp.org under
retired projects. You can buy the parts yourself. They will run $15 to
$20 at most.
Another alternative is Elecraft's BL1. Is this little balun really up to
100W service for multi-band antennas?
Yes. I never measured its efficiency, but it should be about the same as
the NJQRP kit. It covers 160 to 6 meters, where the NJQRP kit covered 160
to 10 meters.
Has anyone found a good enclosure for
the BL1? Can a switch be used to switch from 1:1 to 1:4 configurations?
Possible, but not a good idea. Really not needed.
I use Bud plastic enclosures which you can buy from a distributor or a
similar one from Radio Shack. I have a nice two core balun ala NJQRP built
into a Sucrets box.
Thanks for taking one more look at this old topic.
Anytime.
73, Chas
Jeff Burns
AD9T
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