[Elecraft] KAT2 without balun - which doublet length is better?

[Dave Van Wallaghen]

Hi Oleg,

Well, I wish I could take credit for implementing this configuration, but it
was at the urging of Ron, AC7AC and Don, W3FPR who stated that if the
doublet was fairly well balanced, that connecting it directly to the KAT2
should work well and eliminate any losses due to the balun. There was a
pretty good discussion of this about a year ago I think.

The doublet I used was 66' across with about a 33' feeder. I was able to get
a good match 80m - 10m. The only bands I had some trouble tuning were 17m
and 12m. Again, at the suggestion of Ron, I added a 6 foot stub feeder and
got it to tune up pretty well on those bands.

I wish I could tell you that I modeled this setup and designed it to work
properly, but alas I did not. I simply built it up with convenient lengths
and stuck it up in a tree and had a ball with it all summer long. As I learn
more about antennas, I will surely come back and revisit it and try to
figure out why it seemed to work very well for me. 

One thing I did notice toward the end of summer and beginning of fall, is
that I started to have a harder time getting a match on 20m. My guess is
that as time and weather took some toll on the antenna that it became
somewhat unbalanced. It eventually succumbed to a branch knocking down one
leg after a nasty storm here and I took it down for the season. Looking
forward to putting it back up when the weather gets nice here. In fact, I'm
looking to use my K3 out there this summer as well. I just bought a solar
controller from Don Brown, KD5NDB, and may try to run the K3 (and K2) QRP
from a solar power configuration. Sounds like fun anyway.

If I can answer (unscientifically) any more questions, let me know.

Take care & 73,
Dave W8FGU

> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net [mailto:elecraft-
> bounces at mailman.qth.net] On Behalf Of ub5_073_oleg
> Sent: Monday, March 17, 2008 5:22 PM
> To: elecraft at mailman.qth.net
> Subject: [Elecraft] KAT2 without balun - which doublet length is better?
> 
> Hi,
> 
> I'm going to use my K2 with KAT2 internal ATU to operate a
> doublet from 80m to 10m including WARC bands without a
> balun. Among others, Dave's W8FGU home page inspired me to
> try this.
> 
> I hope this is not a problem, especially when battery-fed
> during portable operation, as there is [almost] no
> HF-connection to the ground (the whole system is 'floating')
> 
> Quick modelling of 2x20m + 13.5m feeder antenna shows that
> KAT2 should be able to do the job, as its 20uH and 2400pF
> are enough on all bands.
> 
> My question is: can/should I make it easier for KAT2, e.g.
> choosing other antenna or feeder lentgh or maybe
> adding/removing a piece of feeder on some bands? Are there
> some proven length to use?
> 
> 73  Oleg
> 
> 
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