Fellas---
We at HG5C are stumped. Building 3 el 40m yagi from WA7RAI design and it
resonates at about 7.4 mHz! We lengthened the elements in hopes of bringing
it down to the design freq of 7.050 but now it is extremely hard to get the
gamma match properly adjusted and the bandwidth is ridiculously narrow (under
2:1), about 50 kc!!! We built other yagis from this design and they played
right off the bat, but this is a mess. K4VX software shows very little
difference in el lengths, etc. We can't be THAT far off!
Here is the dope --- ANYBODY GOT ANY SUGGESTIONS AS TO WHAT IS WRONG AND WHAT
TO DO ABOUT IT?
40 Meter Yagi - HG5C Budapest, Hungary
Dimension Meters
Boom Length 15.59 51.14 feet
DE to DIR 6.69 21.94 feet
DE to REF 8,.95 29.36 feet
Dir Length 19..65 64.46 feet
DE Length 20.58 67.53 feet
REF Length 20.94 68.71 feet
Gamma Rod spcng 0.32 12.7 inches
gamma diameter 0.02 .63 inches
gamma length 3.41 11.17 feet
computed Gamma c 255.3 pf
Boom Diameter 0.05 2.17 inches
Design Freq 7.050 mHz
Height above ground 66 feet
Please give us any suggestions.
(Note: We believe there is no interaction from the guys and trusses since
"Philllystran"-type line is used for element guy's, etc. No difference in
VSWR when turning ant.)
Mike
HA/W0YR
Budapest
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