[TowerTalk] XM240 element spacing
Tony Brock-Fisher
barockteer at aol.com
Sat Jan 8 08:02:19 EST 2022
To answer Dave N3AC's questions:
I built a version of the W6NL Moxon from scratch. Because the max length
of readily available tubing was 6', I had to modify the taper schedule
from the original W6NL design, which was a modification to the
40-2CD/XM-240. I modeled it in 4Nec2 (therefore limited to the NEC2
engine) and results came out low in frequency. Minimum SWR was right at
7.0 MHz; max gain was around 6.8 MHz. On the advice of K3LR and K1GU, I
used the same lengths as in the original design and it came out spot-on.
Dave: What do you mean by 'wingspan'? Boom length or element length?
This would likely have a significant effect.
Modeling curves and details were presented at Dayton Antenna Forum 2012,
available in pdf from K3LR's website:
https://www.kkn.net/dayton2012/DaytonAntennaPaper05102012.pdf
My design 'package' available on request - email me directly off-list.
Let me add my kudos to W6NL for this amazing design! The bandwidth of
the original CC design(s) is partially due to loading coil losses. The
W6NL design achieves wider bandwidth without loading coils, which
implies much higher efficiency.
-Tony, K1KP
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