Moxon for 11 meters

[91IR109]

Here we go again, after the project dropped almost 3 months.
I finish my Moxon to satisfy my curiousity about the dimensions.
Ok here :
Freq designed : 28.555mhz
SWR :
1 : 4 @ 26mhz
1 : 2.5 @ 27mhz
1 : 2 @ 28mhz
1 : 1.5 @ 29mhz
So the temporary conclusion is the Moxgen is match 1mhz BELOW the freq design.
Then I tried to put the center on 26.555mhz.
Here what I got on SWR :
1 : 2.5 @ 26mhz
1 : 1.8 @ 27mhz
under 1 : 1.1 @ 28mhz
and 1 : 1.4 on 29mhz.
Look like I have to put the center freq on 25mhz & re-adjust all the tubing ya?

 

[vkrules]

NOT AGAIN>>>> NO...Forget the Vswr for now ! where is it resonate? Do you still have the analyzer ? If not try just making the driven element only a little longer and also test to see if you have a good front to back ratio.If you do, don't change the reflector length.

 

[91IR109]

Vkrules,
So the driven element is a bit longer than the reflector?

 

[vkrules]

NO.I'm talking about increasing the driven by a few inches ,the reflector will still be 15 or so inches longer. The moxon is fairly broadband and yours is most likely close enough to work well. The trouble is the match to 50 ohms is complex and dependent on critical spacings "c and 'e' as well as element length, height above ground .surrounding objects etc.You are close ,changing all the dimensions will have you chasing your tail, change one thing at a time.Low swr alone is not an indication of resonance It is possible to get a low swr and have the antenna nowhere near resonate and wont perform well, it is also possible to have a high swr with a resonate antenna that performs well.

 

[SMILEX2692002]

My MFJ Moxon was built for 10 meter phone. See below for what I find on my MFJ 259B.
I found the specs in the MFJ installation manual were way off in my particular location.
I could fine tune the antenna to bring the point of resonance to 28.400.
Since I'm a one man installation team I figure its not worth the effort of climbing on/off the roof to adjust my antenna then come back in the shack to check the analyzer ect.
So far my Moxon works great. I'm also using a NTE U-105 rotor.

28.300 R=38, X=9, SWR of 1.3.1
28.400 R=42, X=8, SWR of 1.2.1
28.500 R=46, X=6, SWR of 1.1.1
28.600 R=47, X=6, SWR of 1.1.1
28.700 R=47, X=6, SWR of 1.1.1
28.800 R=46, X=8, SWR of 1.2.1

Just for fun I swept through CB on the Moxon.
26.965 R=35, X=64, SWR of 5.0.1
27.205 R=25, X=40, SWR of 4.4.1
27.405 R=22, X=25, SWR of 3.6.1