I had several requests to share direct resonses to my inquiry about shunt
feeding crank-up towers. I have included the responses below with out the
responder's call or name.
Thank you to all who took time to respnd.
Pat, K8PC
****************************
I've shunt-fed my 72' US Tower crank-up on 160 meters for the past six
years without doing anything special. The sections are always in contact
at two points in addition to the lifting cables. I also have not had any
problems, at my 100 watt power level, with the coax and control cables
which hang from arms off the tower. The cables all go to ground level and
then into a conduit which takes them underground to the shack. The shunt
feed is 120 degrees from the coax/control wire bundle. This system seems
to work OK: so far 72 countries on 160 with 100 watts.
I'd say light it up and go!
******************************
Pat, I recently shunt fed a US TX472 tower, still working out the bugs, but
it works. The cable and the other hardware provide adequate conductivity.
The thought of jury-rigging something to "electrically attach" each section
is ugly.
*****************************
Mine has been used for over 18 years without any special provisions other
than the cables in it.
Have worked over 180 countries on top band and used it in two locations.
*******************************
My very recent experience with a crank up tower involved "slopers" ... two
multi-band models opposing each other. For several years, I had "intermittent"
contact of the sections touching each other ... and of course, that threw off
the SWR and efficiency.
I had a very l-o-n-g discussion with the Alpha Delta people ... the makers of
the slopers and it was first suggested I bond the sections together. I got half
inch wire braid and used Stainless Steel hose clamps to connect the sections
and the results were like night & day.
So ... for your question about shunt feeding a crank up ... I would strongly
say in my opinion, "yes ... the individual sections should be bonded to one
another."
Also, I have read it is strongly suggested you run all control cables and Coax
down the center of the tower itself.
If you are using something like a Gamma or Omega Match and can't ... or don't
want to run the cables down the center ... then place all cables on the
opposite side of the feed point side as a minimal precaution.
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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