[TowerTalk] Base insulators for verticals

w7xu at iw.net w7xu at iw.net
Mon Jul 4 19:05:46 PDT 2011


I'm looking for some suggestions on how to insulate the base of  Rohn 25 tower so
it can be series fed.  This is for a 4-square on 80 meters.  I already have the tower
on hand, so I'm not really looking for alternatives to using tower as the radiating
elements.  I've looked through the archives of TowerTalk and Top Band, but I'm
wondering if anyone has some other ideas.

The options I've found are:

1)  Base insulators carried by DX Engineering, with one insulator in each leg of the
tower.   They go for about $450 pertower.  I've seen the arguments that having 
an insulator in each leg is less than ideal, due to torque, etc.,  but each tower will
only be 60 some feet tall.  This is the lowest cost commercial alternative I've found.

2)  Commercial AM tower insulator.  I did some investigating and was quoted about
$1100 per insulator, with of course just one insulator per tower.  I've been looking
locally for several years and can't come up with 4 used ones, so the used route
hasn't proven to be a viable option.

3) Power line insulators.   I checked with my power company and they won't sell
these.

4) Rohn insulated tower section --  These cost about $2000 each now, plus shipping.
Ouch.

5)  Home made insulator?  I'm willing to go this route if it doesn't involve finding some
one-of-a-kind items that I probably won't be able to locate locally.   Also, for those that
have made insulators with Teflon sheet, etc., I also wonder how the shunt capacitance
introduced into the system affects performance.

Thanks in advance,

Arliss, W7XU
  





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