Here's the model from the 1990s that I've used in YO for the 204BA, with
the tip dimensions for CW:
Hy-Gain 204BA
14.000 14.175 14.350 MHz
4 elements, inches
2.1448 1.2500 1.1250 0.8750 0.6250 0.4375
0.0000 3.1250 41.8750 46.0000 50.5000 24.0000 53.0000
122.8750 0.0000 30.5000 46.0000 50.5000 24.0000 53.0000
211.6250 3.1250 18.3750 46.0000 50.5000 24.0000 53.0000
307.2500 3.1250 14.1250 46.0000 50.5000 24.0000 53.0000
Match: 2 0.2500 8.0000 18.0000 4.0000 26.5 50.0
Bracket: 1 3.2500 7.2500 2.0000 0.2500
I used a modified set of tip dimensions that improved the SWR bandwidth
over the whole band without much gain or F/B penalty:
Phone CW Mod.
Refl 50" 53" 53"
Driven 50" 53" 50.75"
Dir 1 51" 53" 49.5"
Dir 2 51" 53" 49.5"
Other dimensions including Beta match are as standard per the manual.
The gain, F/B and SWR comparison YO calculation is as follows:
MHz 14.0 14.175 14.35
204BA Gain 8.18 8.33 8.49
F/B 23.6 22.3 16.8
SWR 1.3 1.3 2.2
204BA Mod Gain 7.98 8.08 8.20
F/B 19.7 26.0 21.0
SWR 1.5 1.0 1.5
As part of design efforts for my home setup, our former HC8 M/M station
and others, I've played around with many modifications of the basic
204BA elements, including direct feed with closer first director for
wide SWR bandwidth. For construction convenience, I've tried to change
only the first director location, leaving the rest of the elements in
the original positions. Modern modeling software can produce useful designs.
One last thing I've looked into more recently is the tip adjustment
necessary to account for the effect of wire lead length from a balun to
the driven element. In the case of direct feed, I've found that the tip
dimension as calculated needs to be reduced by a factor of 1.5-1.7x the
lead length, rather than the 1:1 I had expected. I use a wider frequency
range to help with the broadbanding calculations.
Here's an example of that process, using 1/2" tips:
Hy-Gain 204BA 50 Ohm
13.950 14.175 14.400 MHz
4 elements, inches
0.0510 2.1450 1.2500 1.1250 0.8750 0.6250 0.5000
0.0000 0.0000 3.1250 41.8750 46.0000 50.5000 21.5000 56.5000
122.8750 5.0000 0.0000 30.5000 46.0000 50.5000 21.5000 58.5000
162.5000 0.0000 3.1250 24.8750 46.0000 50.5000 21.5000 58.0000
307.2500 0.0000 3.1250 18.3750 46.0000 50.5000 21.5000 54.1250
Match: 1 0.0000 0.0000 0.0000 0.0000 26.5 50.0
Bracket: 1 3.2500 7.2500 2.0000 0.2500
MHz 14.0 14.175 14.35
204BA 50 Gain 8.15 8.29 8.41
F/B 25.5 21.0 17.5
SWR 1.04 1.03 1.03
The Hy-Gain 204BA seems still to be the standard of comparison in short
monobanders for 20m. Some folks have suggested extending the boom, but
making the 204BA longer runs you into the weird behavior of antennas
that are near 1/2 wave boom length (you either get gain or F/B, but not
both). This happens for 20m boom lengths from 30-36 feet. It takes a 40'
boom to begin to get clear of the near-half-wave boom area, and 42' to
45' to have real design freedom.
For my location here on a ridge, our high winds dictate strengthening
elements per the techniques outlined in my Yagi book. One caution is not
to allow any holes near the inner end of reinforcing tubes, as this can
be a site of eventual fatigue failures. Caribbean experience supports
the HyGain technique of ropes inside element tips.
Hope this is useful. As my grandkids always note, "Grampa, TMI!"
Dave, W6NL/HC8L
On 11/5/25 5:19 AM, Stan Stockton wrote:
Thanks, Dave! I had forgotten all about the great book you wrote 30+
years ago. Also, my wife and I are watching a series on TV that we
watched 10 years ago and it's almost like we had never watched
it.😀
So in the chart it shows the equivalent diameter as 2.14" and the
length as 2.925". I am assuming from what I read that the half
length of the clam shell clamp that extends out from the edge of the
boom is 2-5/8" with an overall length of 7.25" (5.25" + 2") and that
the length of 2.925 is derived by adding .3" for half the electrical
length of the boom diameter? Hope that makes sense and is correct?
Thank you so much for reminding me of the book. A lot of it is way
over my head but it's full of practical information as well.
73...Stan, K5GO/ZF9CW
On Wed, Nov 5, 2025 at 12:52 AM Leeson <leeson@earthlink.net
<mailto:leeson@earthlink.net>> wrote:
Modeling of the HyGain element clamp is derived in Chapter 9 of my
1992 book, "Physical Design of Yagi Antennas,"
https://www.dropbox.com/s/hmhkeofz0igrg1e/Physical%20Design%20Of%20Yagi%20Antennas%20D%20B%20Leeson%20V2.pdf?dl=0
<https://www.dropbox.com/s/hmhkeofz0igrg1e/Physical%20Design%20Of%20Yagi%20Antennas%20D%20B%20Leeson%20V2.pdf?dl=0>
From page 9.3, the equivalent diameter of the HG204BA clamp is 2.14
inches. This clamp model is used in K6STI's YO and other Yagi
software.
Dave, W6NL/HC8L
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