[NLRS] Elevation rotators for small stuff

[Dr. Gerald N. Johnson]

On 9/5/2013 1:22 PM, Doug Reed wrote:
> I don't remember the QST article about U100 vs CDR bell rotors. I'm
> not too surprised about bending strength or turning torque. I liked to
> use a second empty rotor housing as a thrust bearing and mast support
> to improve handling of large antennas. For many years I had.a VHF-UHF
> antenna stack on my chimney using a U100 rotor. It performed quite
> well. My dad still has a large TV antenna at his house on a pole with
> a similar dual rotor mount. If the wind blows the rotor, a touch on
> the control forces it to turn and balance the bridge circuit again.
> This is using the 5-wire electronic control box from the U100.

I had to hunt a bit at arrl.org. The QST articles were in April and May 
1967.

Looking at Amazon yesterday the showed an available mast bearing for the 
offset rotors.
>
> I had almost managed to forget the U110 "clacker" version of the
> rotor. The motor assembly is the same except for using a SPDT switch
> instead of a pot for position control. The SPDT switch caused a small
> motor to rotate a pointer in the 4-wire control head while the rotor
> was turning. It was kind of like the old CDR-22 rotor control except
> it goes "swish-swish" rather than "clack-clack." If you find one of
> these, you can use the rotor, but I'd put the control head in the
> trash. That control box was a serious POS. A lousy SPDT leaf switch in
> the rotor, more lousy leaf springs in the control head, and a
> miniature DC motor for the pointer that didn't always run if the wire
> was long or voltage drop was high.

There was a true clacker version before the silent version. Where the 
indicator moved in chunks. I had one of those pairs on the work bench 
with short wires and it didn't work because the current was so high the 
clacker armature stuck to the pole of the coil. I added a shim of brass 
to keep the clapper from touching the coil pole piece and it went back 
to working and wasn't bothered by long wires apparently.
>
> I think there was also a 3-wire version but I was long gone from Radio
> Shack before those came out. I think those lacked the thru-hole rotor
> design. The 5-wire rotor was Radio Shack 15-1220, I think the 4-wire
> version was 15-1221. I expect you can find both service manuals as PDF
> downloads from the radioshack.com web site. I used to have manuals for
> both models, and some of the CDR series, but I haven't seen them for
> over 10 years.....

Last year I found real Alliance manuals on line somewhere. MFJ's HyGain 
division has manuals on the contemporary Ham-M versions on line these 
days and sells individual parts for rotors and controls.
>
> As I remember, the direction lights were a 24v bulb, but an odd
> physical size. You'd probably have trouble finding an exact match.
> These days I'd probably use a 10mm high-intensity red LED and one or
> more diodes to change the 24V AC bulb voltage to DC.
>
> If you have the 5-wire head and the rotor only turns one direction and
> doesn't shut off, replace the two bridge balance transistors. I think
> the originals were germanium, which made them hard to find, so I
> always replaced them with NPN silicon transistors at least 60 volt
> breakdown so they had a chance to withstand the relay kickback
> voltage. The difference in base voltage wasn't an issue since the
> bridge was driven by the 24v motor supply. I believe I finally started
> seeing silicon transistors from the factory after 1980.
>
> I like the U100 for VHF-UHF antennas. For anything large or for HF,
> I'd go back to a Ham-M or later rotor. The U100 would work for
> Azimuth, but you'd have to do something to slow it down since it will
> otherwise slide right past your peak. A conversion to use a
> pancake-type stepper motor would be idea for our purposes.

I was using a Ham-M with a full bearing set for my 2m 5WL M2. That 
antenna shook the rotor apart and the brake steps were bigger than the 3 
dB beam width. I sold that antenna at CSVHF and plan to finish building 
a pair of FO-9 to stack for practically the same gain (plots in my 
artcle: www.geraldj.networkiowa.com/papers/CSVHF2011/HowCloseB.pdf
that was first shown at Aurora in 2011.

Last year during my tour of the Iron Range before heading to the UP I 
stumbled upon a meter indication Alliance rotor control for a few bucks 
in  thrift shop. I brought it home but haven't fired it up yet. Probably 
should plan on new electrolytics for the motor phasing and for the meter 
power supply, presuming its DC.

Found a nice warm Faribault Woollen Mills wool blanket there too that 
was useful some fo those nights in the north woods. I think I paid $12 
for it, would have been over $100 at the mill. It came in handy early 
mornings in SW Minnesota this year.

>
> Good luck finding one. As I remember the 1970's price was around $60- $70.


Searching antenna rotators in the QST on line search at arrl.org, I 
noticed a number of articles on elevation rotors, primarily for 
satellite tracking which with a short beam at 2m and 432 is much easier 
than aiming a 31 dBi dish.
>
> 73, Doug Reed, N0NAS.
>
A catalog received this morning from Marlin P. Jones and Associates
shows two pages of stepping motors and several stepping motor drivers,
not all cheap, and their shipping charges tend to be on the high side to 
compensate for low sales prices. They tend to have more on line than in 
the printed catalog. Some of the stepping and conventional motors 
include screws and nuts of various lengths and pitches. The index shows 
linear actuators, but there are no complete linear actuators, just 
motors with lead screws and matching nuts. Prices vary considerably. 
www.mpha.com

Rotors that don't turn often need the motor run capacitor, typically 90 
mfd at 24 volts AC. I have found a common motor start capacitor that 
used to cost maybe $2.99 from W.W. Grainger, same capacitance range but 
rated at 120 volts lasts very well, is larger but is easily purchased.

73, Jerry, K0CQ