I have a 40M3L vintage 2005. It is at 80 ft with a 10M 6 el underneath by
10 ft. The nearest tower is 140 ft away.
I found the measurements to be "in the ball park" but not exact. However I
got reasonable resonance points by raising it up 35 ft to the first guy
point of the tower - just don't worry about the SWR, look for the resonance
X=0 line. It went uo in frequency by about 20khz at 80 ft. Mine is tuned
to 7080 and I have 1.6 SWR at 7.000 and 2.0 SWR at 7.210. Like most 40 M
shortened beams, it climbs pretty quickly after that and is about 3.1 at the
top of the band. Plus the gain is dropping off. But for contesting and
DXing CW + SSB, this is a good spot for tuning.
It is a very potent antenna on the bands and a very solidly built antenna
with one exception (if they haven't fixed it). The connection of the cross
bar of the tuning wire to the post on the boom. The method breaks after a
few years. I redesigned mine to eliminate the pinch point that eventually
snapped. Not a fun repair in the air.
73
Ed N1UR
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|