[TowerTalk] Shortening an M2 6M5-X

[W7CE]

I have an EZNEC model for the 6M5X, which I copied from a YO model.  With 
all 5 elements the freespace gain is 11.6 dBi and F/R is 22 dB.  Removing 
the 3 director changes the gain to 10.5 dBi and the F/R to 10 dB.  The feed 
point impedance is also cut in half, so you may have trouble adjusting the 
T-Match for good SWR.

I played around with the placement of director 2 to see if I could get a 
better match.  If you remove the 3rd director and move the 2nd director 16" 
closer to the first director (no change in element length), the gain is 10.2 
dBi, the F/R is 19 dBi and, according to the model, the feedpoint impedance 
is very close to the original 5 element design.  To do this you will only 
have to drill one extra hole in the boom to relocate director 2.  When field 
day is over you can move director 2 back to it's original mounting hole and 
the beam will be as good as new.

Hope this helps and have fun on Field Day.

73,
Clay  W7CE

----- Original Message ----- 
From: "Dennis W0JX" <w0jx at yahoo.com>
To: <towertalk at contesting.com>
Sent: Thursday, June 05, 2008 6:35 PM
Subject: [TowerTalk] Shortening an M2 6M5-X


> Tower Talkians:
>  Our club is preparing for Field Day. I have a 6M5-X ( 6 meter, 5 elements 
> on an 18 ft boom). It is a bit too much for our 20 to 30 foot mast so I am 
> considering taking off the last boom section with the shortest director 
> which would make it a four element beam on a 12 foot boom. This is very 
> easy since the boom comes in four sections. No changes in element spacing 
> or length would be done.
>
>  Will we still have a reasonable amount of gain, directivity and F/B if we 
> do this?
>
>  73, Dennis W0JX/8
>
>
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