I have solid fiberglass rod in each leg plus a sheet of G10 plate
across each insulated joint held with a couple of muffler clamps above
and below the joint. The sheet can be about 4 inches wide and 12-18
inches long and about 1/4-3/8 inches thick. Total cost will probably
be less than 50 bucks per tower. There was enough stretch in the
small diameter ropes I had guying the towers that the bolts in the
legs through the fiberglass kept breaking. The sheets of G10 across
the joints took care of it.
Stan, K5GO
Sent from Stan's IPhone
On Jul 4, 2011, at 9:05 PM, w7xu@iw.net wrote:
> 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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