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Author Topic: AEA Isoloop 10/30 repair  (Read 2383 times)
KC8GPD
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Posts: 49




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« on: July 30, 2009, 07:52:18 AM »

are there any parts available to repair these.

the big plastic gear for the air variable cap is trashed.

has anyone done a home brew solution to this problem?

also has anyone home brewed a stepper motor controller for these?

mine has no controller either. i hate to just see it have to be trashed.
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N3OX
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Posts: 8847


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« Reply #1 on: July 30, 2009, 03:52:15 PM »

Oh definitely don't trash it.

I haven't built a stepper controller for my magloop yet but I probably will at some point.  Right now I just use a simple DC motor drive with limit switches:
http://n3ox.net/files/magloopnew_lg.jpg

It's pretty easy to use band noise to get the tuning "about right" this way.  

If you want to get started building a stepper controller with "memorized" or "commanded" capacitor positions, you can look at what I did build a stepper controller for:

http://n3ox.net/projects/stepperswitch/

What you need is probably closer to another project I built, this one for the lab.  It's a little "antenna rotator" designed to point an ultrasound transducer for flow measurements in different directions:

http://n3ox.net/files/US_rotator.jpg

This uses a normal four coil unipolar stepper and a (really expensive) worm gear drive.  The controller is also an Arduino with exactly the same MOSFET circuits as my other switch.
rotator is available here:

http://n3ox.net/files/US_rotator_v_1_3.pde

This one is probably more up the alley of a variable capacitor drive.  It has a serial interface that can be accessed using Hyperterminal and accepts inputs in the form of 0-290 degrees in 1 degree steps (could be much smaller actually) and moves the switch accordingly.  It uses a 35:1 worm gear reduction ... but I had to machine the housing for it, so it's not a very good home project.  But spur gears are a bit easier to use (you'll see that careful drilling was good enough on my antenna switch to engage those gears sufficiently).

So those might be some starting points for a controller for your loop.  If you want it to tune to low SWR, that can be done too but is harder.  I've seen at least one full-autotune ham loop homebrew project but can't find it right now.

Gears are available from places like Small Parts:

http://www.smallparts.com

and Stock Drive Products

https://sdp-si.com/eStore/

And probably more.   You'll have to do some research to figure out the right pitch and size to get a drop in replacement but acetal ones are pretty cheap.  

I've had good luck using Lego for medium torque loads, too.


73,
Dan
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
N3OX
Member

Posts: 8847


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« Reply #2 on: July 30, 2009, 03:52:58 PM »

whoops, shoulda been "code is available here" in front of the .pde file ;-)
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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
WA3MJY
Member

Posts: 3




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« Reply #3 on: August 02, 2009, 05:16:53 PM »

I had the similar problem a couple of years ago. My antenna stopped working and when I opend it up to look inside I found that the plastic gear was broken.  My solution was to glue the pieces together with JB Weld. I then carefully dressed up the gear teeth with a small file. The antenna works perfectly now.
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