[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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