[Fwd: Fw: [Fwd: Re: [Antennas] U-110, rotatable dipole]]

Tue Sep 13 00:09:11 EDT 2005

From: "k3hx at juno.com" <k3hx at juno.com>
Date: Mon Sep 12 22:55:14 CDT 2005
To: k3hx at verizon.net
Subject: Fw: [Fwd: Re: [Antennas] U-110, rotatable dipole]

---------- Forwarded Message ----------
From: Joe <nss at mwt.net>
Date: Mon Sep 12 15:11:01 CDT 2005
To: k3hx at verizon.net
Cc: antennas at mailman.qth.net
Subject: Re: [Antennas] U-110, rotatable dipole

k3hx at verizon.net wrote:

>I'd stay away from the U-110.  Had a TV antenna business 
>
>'82-'98 in a rural area 
>
Same Here,  Put up Hundreds of towers, before the days of the dishes, 
then migrated to the Big Dishes, and finally no one ever would want a 
tower now with the small dishes.

>>>>Never did the big dishes, too many fly-by-night "operators" in

that racket.  Did a booming business in the beginning days of DirecTv,

C/M had a dandy portable self-powered test rig which made pointing a

30 minute job.

Installed exactly one tower, a Riverside.  Got scared off by

liability concerns.  Climbed a fair number of 'em, however.

Which brings us to a "war story."  I affirm on my honor the following 

is true:

Guy calls me up saying a nearby lightning hit has detonated his preamp.

Says he has a 50' tower.  I show up to find a twisted, bowed, rusted

Riverside tower.  When I shook it, it rained rust!  "Guyed" to some

nasty little shrubs with cotton clothes line!  When I told him I would

not climb it, he got somewhat hostile and said: "What-sa-matta, you

chicken?" To which I replied: "Yes."  Got back in the truck and went

home. 

>  Aside
>
>from their tendency to get out of sych and the annoying
>
>"ka-chunka, chunka, chunka" racket the controller makes,
>
>the U-110 lacks the braking ability to handle the torque moment should the wind catch the dipole.
>  
>
This one I beg to differ,,  The U-110  OLD version, had a worm gear 
final drive,,  The newer ones a had a spur gear final.

The worm here NEVER EVER turned by the wind EVER. Been up there for 20 
Years! Still Chunkaing away happily.

And again this is with a Mosley TA-33   the BIG one NOT the Junior,,  14 
foot boom,, 3 elements about 33 feet long,,  a 5.7 sq ft surface area.  
and at 10 feet or so above that was a cross arm  with a pair od 8 
element 2 meter beams stacked.

All that has been up there for man at least 15  years now. And other 
than the sync problem  I've NEVER have had a problem. with it.. and it 
was USED too bought it from a guy after we installed a BIG dish..

>>>>I was unaware of the older worm-drive model, do we know if the

guy who posted the note has a worm-drive or spur drive model?  My

experience was with whatever unit was on the jobber's shelf in '84.

Stopped using them as they would not hold up as well and I could 

instruct the customer to re-synch the Channel Master rotator over the 

phone.

>The dead weight of the antenna is not the problem as
>
>you can either buy or find a mast support bearing
>
>so that the weight is transferred to the mast or
>
>tower leg.
>
AS suggested,

>  
>
>I suspect the fellow using one with good results on 
>
>his tribander has led a righteous life and is being 
>
>rewarded for staying on the straight and narrow.
>  
>
Far from it,, I grew up in the 60's  Need I add More?

>>>I grew up in the '60s as well and expected to be sainted shortly 

after my demise.....NOT!!!  HI HI!

>
>As for the rotating dipole, you might try to find a 

>used tribander at a hamfest and use one of the 
>
>elements.  I'm using the reflector from a Hy-Gain TH3
>
>with a homebrew fiberglas angle stock center mount-
>
>insulator.  I chose the reflector as I'm a CW guy and 
>
>it was just easier to tune the antenna for the lower
>
>part of the bands using the reflector.
>
>Using a HAM-M to turn it and a 6m and 2m beam.
>  
>
I'm surprised you got it to resonate properly all by itself,  The dipole 
in all alone has a much higher impedance than when with the other elements.

>>>>> No trouble to get it to fly.  Just loosened the trap clamps.

set to work with the MFJ-259B and it took off after about an hour and

a half.  Impedance in the beam situation much lower than the 50 ohms

we have come to know and love.  Once outside the influence of the

reflector and director and properly tuned, it operates just like

any other trap dipole.

>I find very little difference when rotating the 
>
>antenna.  Were I to do it again, I'd just put up a 
>
>"fan" dipole for 10-15-20 and spare myself the trouble
>
>and expense.
>  
>
Then I think there must have been something wrong with that dipole,,,  
Before I had the TA-33  I had a home made 20 meter dipole up there,,  
and it was also at 60 feet or so.  The nulls off the ends were 
incredible.  Just like textbook almost,,

I could take the dipole and swing it sideways to an interfering station 
and he'd just disappear compared to the station I wanted to hear,, (as 
long as they weren't in the same direction.)  But the nulls were 
incredible!  Take someone 20 DB over and put then in the noise.  But it 
was very narrow,,  sometimes One Kerclunk was too wide, and the deep 
null was between each clunk.

>>>>>I envy your 60' height, nearly a full  wavelentgh above ground

for 20 meters.  I should have mentioned that my rotating dipole is

a pittiful 25' high and only 7 or 8 feet off the roof.  House wiring,

electric lines on 2 sides (corner lot) no doubt conspire to make it

stink.  A fan dipole would be at about 40' and likely be somewhat

less awful.

Joe WB9SBD

>73,
>
>Tim Colbert  K3HX
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>
>  
>

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