[TowerTalk] Base insulators for verticals

[K8RI on TT]

On 7/4/2011 11:32 PM, Stan Stockton wrote:
> 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.

Those bolts should have been a lot stronger than the thin wall of the 
25G tower legs, or am I missing something?

73

Roger (K8RI)
>   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 at 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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