[TowerTalk] 40 Meter MOXON Yagi

[Lee]

Some time ago I decided I wanted to build a full size 40 meter Moxon 
Yagi beam.  It never happened.   Right now I've gotten Cold Feet to the 
project.  I'm beginning to think the beam would be just too heavy for my 
situation.  I'm now considering building a 40 meter Mini MOXON beam as 
built by W7XA.  This rendition uses fiberglass tubing instead of 
aluminum tubing and is inductively loaded making it close to a 26 foot x 
16 foot rectangle.  Has anyone on here built one?  I'd like to hear from 
you if you indeed have one up and running.  Since fiberglass tubing is 
shipped in 8 foot lengths, the two elements would be made up of 4 eight 
foot lengths.  The design has an element length of 26 feet.  That means 
I'd have to discard 3 foot off two pieces.  I looked at the MOXGEN 
UTILITY Software and for 7.1 Mhz, the program shows you all the other 
beam dimensions. They were as W7XA described except for he shortened the 
two elements and made up for it with loading coils.  What I don't know 
is if I make the two elements longer to make use of the full fiberglass 
tubing and then if I reduce the size of the inductors to maintain 
resonance, will I upset the feed point impedance?  I'm thinking this 
will be the case.  But, by altering the length will I be able to find a 
1:1 SWR at 7.1 Mhz ?  The bottom line to all this is, will I screw up 
the feed point impedance by  making the elements longer and have smaller 
loading coils?  Then too, I'm not sure W7XA actually saw 50 ohms at his 
feed point with his design in the first place. Looking at the MOXGEN 
software, it does not appear you can alter element spacing with it's 
program.  It just gives you all the dimensions without loading coils for 
a specific frequency.  (The only thing I see you can do with the program 
is put in the desired frequency and you give the element diameter.  
Also, what happens to the impedance if I use a longer boom like 20 foot 
instead of 16 foot?  I think the impedance would then change too.  The 
MOXGEN software doesn't allow you to pick different length booms.   
Anyone on here brighter then me on this subject?  Is there a better 
software program for designing a Moxon Yagi beam then MOXGEN UTILITY?

Lee, w0vt