Where can I buy a BC TX antenna

[Tom W2ILA]

Who is still making the monopole antennas that use Rohn 25 or 45 style guyed tower sections standing on a little cone insulator at the base?

Tom

[Bill, KD0HG]

Do you need a whole tower, or just a base insulator?

Here's the base insulators, if you provide the tower itself.

http://www.comteksystems.com/tower-insulators.html

[Jim, W5JO]

Those guys are pretty expensive.  Wonder if Hygain would sell theirs for less?

[k4kyv]

You might look for a used tower insulator.  I picked up one at a BC station in Alabama in 1980 for $100.  At the time, Rohn was selling the base insulators new for a little over $500 (1980 dollars) each.  I had to make an adaptor plate to make mine fit the base section of the Rohn tower.  Later on I picked up a spare insulator, made just for the 25G, for $25 at a local hamfest - cheap insurance in case anything ever happens to the one on my tower.

These insulators are designed to fit the special tapered base section made by Rohn.  When I put up mine in 1980, the base section cost about double that of a regular 10' section.  I checked a few years ago, and the price of the  regular section was about twice what I paid, but the tapered base section was over 5 times as much!

It shouldn't be too difficult to have a base plate custom made.  The base plate that Rohn sells won't work because it was designed to sit flat on a concrete slab, and the metal is too thin.  The plate needs to be about 5/8" thick, with holes drilled to match the mounting holes in the insulator.

The best bet might be to find a small AM station that has gone dark, that used a lightweight tower like the 25G.

My hamfest find came from a ham club that had dismantled a 4-tower array, each tower using 25G material.  They took down all 4 towers and divided up the sections amongst members.  They all wanted to put up the typical hammy hambone 45' tower with the bottom section buried directly in the concrete, so no-one was interested in the base insulators or had any use for the tapered base sections, except that a couple of the club members had already buried the bottom ends of the special base sections in concrete, hammy hambone style.   At the time, the seller said one of the base insulators got broken so they still had two left after I bought mine, along with two base sections.  As I recall, it all went cheap.  I posted the info on the web, and before long the rest of the stuff was sold.  Hopefully some of the base insulators and base sections fell into the hands of someone who could use them for their intended purpose.

[k4kyv]

Here are pix of the base of my tower and a close-up of the insulator.

The black tubes are pieces of automotive heater hose, to divert rainwater dripping down the copperweld feeders away from the tower, to prevent corrosion of the zinc galvanising by copper leached off the feeders.

[N3DRB The Derb]

i did a google on the subject earlier today at my dad's place - there's a company out there
that is selling a ball and socket base so the tower can move side to side in any direction. it has a huge ball lightning  spark gap about big around as a basket ball and 4  2" wide solid copper strap wrapped around  a massive concrete block above ground. it looks like a gift wrapped package.

I had a bad seizure today down at my dad's house, over it now, have to keep quiet tonight.
Tomorrow I'll start back up.   

[WBear2GCR]

I may be confused - oh wait a second... I am - but I seem to recall being told that some folks used one of those quart sized Coke bottles for bottom insulators?

They had really thick glass...

Anyone confirm or deny?

         _-_-bear

[Jim, W5JO]

I have an inverted L up 44 ft. vertical and it took me longer to empty the wine bottle for the base insulator than it did to put up the antenna.

[k4kyv]

It wouldn't take me that long to empty the wine bottle.  Usually one meal is enough to do the trick.

I wouldn't trust a quart size coke bottle.  The glass is too thin.  And the  non-returnable bottles are not made of very durable glass, since they are designed for single use.  More likely one of the old fashioned 6 oz. returnables would work.  I have heard of people using those things to drive nails without breaking them.

The coke bottle would probably work OK for 50 or 60 ft. of lightweight mast, but I wouldn't try it with a tower.  Make sure water can't collect inside it to freeze and crack the glass in the winter. 

For years, I used 65 ft. of TV push-up mast, and the main insulator (about the same size as a 6 oz coke bottle) taken from a pole pig.  The mast fit right over the top part of the insulator where the wire lead was supposed to attach, and the bottom end of the ceramic, the part that extended down into the transformer case, was buried in concrete.  When I quit using that antenna, it was one hell of a job to remove the concrete base pier from the ground, and the insulator didn't break in the process, even though I made no effort at all to avoid breaking it.

[c. mac neill w8znx]

as Don sayed
most quart bottles will not hold up
even 30 year old quart beer bottles
often will not take the load

old smaller bottles
such as old 8 oz coke
and old style 12 oz beer bottles are darn sturdy
( be wary of modern 12 glass beer bottles
  often they are designed for one time use
  and are not very sturdy )

want a realy heavy duty bottle for insulator
for real deal
use a sparkling wine / champagne bottle

remember to plug the top of the bottle

[Bill, KD0HG]

What about old glass telephone, railroad or ceramic power line insulators?
They seem to be at every flea market that I've ever been to.

[N3DRB The Derb]

i wonder what type of glass that is. some of those come in wild colors. I think I would want to make a knob type support for the inside so that all the weight was not on the skirt.

maybe a thrust bearing of some kind of take the load to the concrete and let the insulator sit there without a load force on it and just be a happy insulator. gotz me thinkin now. look out. get back.

[k4kyv]

The ceramic base insulators used on commercial towers are relatively thin walled and hollow on the inside.  The only time I ever heard of one breaking is when the weep hole gets plugged and it fills up with water, and freezes in the winter.

The curved cone shape of the ceramic insulator is mathematically designed for maximum compressive strength.  I'm not so sure about the unique shape of the coke bottle.  I would suspect it might tend to expand at the middle under load and break.  But I am sure that one of the original 6 (or was it oz. coke bottles would take a lot of punishment.  You could probably use it as a jack stand to hold up a full size classic American-made car.

[N3DRB The Derb]

ifn you gotz lots a $$$, just go buy this and have fun.

http://www.kintronic.com/Systems/UnipoleSkirtKitGroundedTower.aspx

[WB3LEQ]

I bought some Delrin round solid plastic from www.Mcmaster.com The plan was to use them as base insulators.  The only draw back to using it is to prevent exposure to UV sunlight.  The plan was to use PVC as shielding to prevent this.  I still haven't started this project so I can't report any results. Also since I bought this the black looks like the electrical characteristics might have changed. See the full text at their website - search delrin.

Delrin Performance Characteristic
High Tensile Strength
Superior ability to resist being torn apart. Generally withstands a pulling force greater than 10,000 psi.

Wear- and Water-Resistant Delrin:
    * Color: Opaque white or black
    * Temp. Range: -20° to +180° F,  unless noted
    * Softening Temp.: Not rated
    * Tensile Strength: Good
    * Impact Strength: Good
    * Low friction
    * Good electrical insulator, unless noted
    * Use indoors
    * Machine with high-speed steel tooling;  cut adhesive-backed strips with scissors
    * Hardness: Rockwell M89-M94