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[TowerTalk] Ham-M rotator mod web sites?

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Subject: [TowerTalk] Ham-M rotator mod web sites?
From: (Bill Coleman)
Date: Mon, 8 Oct 2001 07:56:10 -0400
On 10/7/01 8:01 PM, Ed Pugh (VA3PU) at wrote:

>I just bought a used Ham-M rotator last week.  This is the "old
>version" with the brown bakelite control box with the single
>lever switch.  I am concerned that there is no brake delay for
>this controller (not even a manual one).

I bought one like this last fall. Wouldn't turn. Turns out the motor 
capacitor had gone west. I replaced it with one in a small box mounted 
just outside the rotator.

>Is there a web site somewhere that details how to build (from
>scratch) and install a brake delay circuit for this rotator?

There's a couple of sites that offer kits. Look in the TowerTalk 
archives. There's also some articles in back issues of QST and 73 

In my case, I designed my own. I happened to have a DPDT relay with a 
winding resistance of about 1 K ohm. What I did was to make a crude DC 
supply by taking one diode from each of the switch terminals for the 
motor windings to an electrolytic capacitor (100 mF). This way, no matter 
which way you turn the rotator, you'll get a DC voltage on the cap. The 
relay winding is placed across the cap, with a shunt resistor ( I think 
it was 2 K ).

The cap has more than enough charge the hold the relay closed for 11 
seconds. I thought that was too long, so I put a 1 K resistor across the 
relay. Now it's about 6 seconds. Still long, but good enough.

>Would putting in a brake delay make it unnecessary to add the
>"torsion bar" recommended in the Ham-M rotator manual?

Depending on the type of tower used, you probably don't need a "torsion 
bar" anyway. A brake delay would certainly remove any cause in the 
rotator for one.

>Also, is there a web site anywhere that shows how to construct
>and install a PC interface?
>In general, are there any other web sites which detail home-brew
>mods to the Ham-M rotator?

I did a search, and somewhere I found a PDF of the Ham-M and Ham-II 
rotator manuals. Oh, here they are:


Make sure your Ham-M is updated to the Series-5 circuitry. You might also 
consider adding the regulated instrumentation supply from the Ham-II. The 
big different that makes is the meter circuit doesn't change indication 
when you start or stop turning the rotator. (due to voltage fluctuations, 
not the rotator turning) I did not do this, but have considered it since.

Another idea is to build your own Ham-II rotator box. The Ham-M and 
Ham-II are identical, except for the control box. 

>If I were to add a switch into primary of the motor/brake
>transformer, or switches into the motor and/or brake circuits on
>the secondary side, what should be the contact ratings for such

It ain't much current. Any standard AC switch should be sufficient.

>Note that I am interested in completely home-brewing my own mods
>to the rotator control; not purchasing a commercially available

Me too. I'm really cheap, too.

Bill Coleman, AA4LR, PP-ASEL        Mail:
Quote: "Not within a thousand years will man ever fly!"
            -- Wilbur Wright, 1901

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