[TowerTalk] 80/40 Top Load Sleeve

[Ford Peterson]

Many have asked for dimensions.  Here goes.

THE TOWER
The model (NEC4WIN95VM) is based on Mininec 3 at this point.  I am trying to
avoid the need for messing with a full sized 25G tower when simple
components can be used.  I haven't built it yet (maybe this weekend) but I
harvested about 16 - 21' planks of 1.315" chain link fence top rail--the
stuff with swaged ends.  I can place two end-to-end in the air (41') in
about 1 minute by hand.  I intend to run 3 tiers of guys 90 degrees apart
(20' 40' 60').  The top will be 62.5'.  The mast support is very
light--possibly too light.  It is easy to work with and it is very very
cheap.  I figure I could make the center support out of garden hose with
enough guy supports.  One every 20' should be overkill with this stuff.

ADD 40 METERS
According to Gary Breed's (K9AY) patent on coupled resonators, the proper
spacing for the 40 meter sleeve (34') is 1.333' off the tower.  I intend to
use 2 pair of 14 awg bare wire, spaced 1.333' off the tower.  Each pair of
wires will be about 6" apart and placed on each side of the tower.  The
feedpoint on 80 and 40 (when resonant) models to 38 ohms with a decent
ground system.  A simple 1.4:1 transformer and I have a perfect match on
both bands (75 and 40).  Extending the center radiator to 80 meters will
either require tuning at the base or tuning at the top.  Because of the
small diameter of the elements, the bandwidth suffers somewhat (on 40 I use
a pair of wires spaced 6" - 8" apart on each side to extend the bandwidth to
the whole band).

ADD 80 METERS
When using small diameter elements, the match would have to be variable if
done at the base--making it mechanically more complex.  If done at the top,
the hat (2 - 4' long 1/2" copper shaped as an "X") will provide all the
bandwidth I need simply placing it on and off the tower.  A 3 position
switch (I'll be lucky to figure out a 2 position) will allow me to make the
hat in two pieces--selecting 3.6, 3.75, and 4 mHz.

DUMPSTER DIVING
I think I will take a trip to the Cadillac bone yard this weekend and snatch
me a door lock mechanism or a pneumatic heater control switch (nifty idea).
At this point the knife switch is winning in popularity here.  Perhaps
cable, perhaps rod, perhaps compressed air, I haven't decided yet.  When I
see it at the bone yard, I'll know.....

Thanks for the input guys.  This design is unconventional.  So what!  It's a
lot more fun this way than trying to simply copy everybody else's work.  If
I pull it off, the cost will be <$100 using new components.  If it doesn't
work, 88% of you guys that responded will be able to puff out your chests,
hold your heads high, and bark "I told you so...."  I'm going to build it
anyway....

Ford-N0FP
ford@cmgate.com




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