Quote:
Originally Posted by Bert[_3_]
Considering a roof-mounted 3-el 6 meter beam and don't want to have to
spend more than the cost of the antenna just to turn it.
I see a number of apparently mechanically identical rotators intended for
turning TV antennas, ranging in price from about $50 to $120, which look
like they'd work under normal conditions.
We don't have much trouble with ice here, but long stretches of near-
zero or below-zero F temperatures are common, with occasional dips to -20F
or so.
Would these rotators work in those temperatures? Would they continue to
work for more than one winter?
--
Bert Hyman W0RSB St. Paul, MN |
Lets break your question down into smaller, more digestible parts.
A 3 element - SIX METERS beam has a wind loading of X.
Six Meters - Lets see - the FCC took 6 meters off the television broadcasters and gave it to the amateurs.. 6 meters is just below the frequency for channel 2. How many elements does a good UHF / VHF antenna have?
My answer is many, the Winegard 8200U I had up probably had 8 to each side. Then again, my rotors broke until I discovered how to build them so they wouldn't break.
The rotor in question was a RCA sold in Lowes with a rotor control - VH126N
The problem was three fold.
1. - there was three 1/4-20 bolts inside that were not Loctited and were not torqued.
2. - I did not use an antenna thrust bearing.
3. I did not use guy wires.
So how did I solve the problem?
I threw away the carbon steel components and replaced all of them with stainless steel. I used Green Loctite on all the threads, I put three guy wires directly to the rotor.
Only the very old rotors with bad gaskets has a problem with corrosion or water getting into the bearings. If you buy a new rotor, rob the gasket from the new rotor, take it back to Lowes, tell them there was something wrong with the rotor, get another rotor, then you will have two rotors in working condition.
The thrust bearing isn't expensive - under $100.00 and the rotor is only $80.00
The manufacturer tells us not to place any antenna more then 3 feet above the rotor. So all we have to do is make a plate, attach the plate to the tower, attach the rotor to the plate, center the rotor in the tower, put a thrust bearing near the top of the tower, put the antenna above the tower and we are golden.
If we are worried about corrosion - water getting into the rotor, we can cut a two liter bottle, slide it down the mast and put a hose clamp around the threaded portion of the bottle.
3 conductor - communications grade wire - 24 gauge will work for length up to 100'. No reason to spend $28.00 on Radio Shack rotor wire.
I think the last time I bought 3 conductor it was $.12 cents a foot.
The problem with using a television rotor for ham radio is that it was never designed to be started and stopped and there is no brake inside of the rotor and the rotor will turn in the wind and then you will have to re index it from time to time and eventually the parts inside of it will fail and then you will have to buy another rotor.
A CD 45 rotor can usually be had at a hamfest for about $150 in working condition and even less if someone is just giving it away. Not many of the parts goes wrong, and the parts that does go wrong can still be bought - for a price. Most times with the CDE product the capacitor goes bad.
Same is true with the old Tenna rotors probably laying around in most peoples basements and garages.
The CD 45 has a brake and a reluctor that tells you where the antenna is pointed. Why not use a CD 45?