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Author Topic: balanced tuner help  (Read 436 times)
KD5FOY
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Posts: 39




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« on: October 15, 2006, 03:21:03 PM »

don't know if this is the right forum but what the heck.
i have always wanted to build a step motor driven
balanced tuner.
i have acquired an excellent tx air capacitor and 2 matched
28 uh roller inductors.  next step is to acquire 2 step motors with
some kind of positioning indicator, either optical or a pot.

anyone have any recommendations for a company site, or for
anything else related, pulleys, belts, encoders etc

larry
kd5foy
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KE4XJ
Member

Posts: 31




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« Reply #1 on: October 15, 2006, 11:35:41 PM »

Larry, I , too, have thought about the same thing. I got a kit from Parallax, Inc (www.parallax.com) to explore the usage of step motors for just such an application. My approach is to use a step motor for each individual incuctor and include a routine for calibrating and zeroing the stepper motors on the inductors so that they are synchronized and a separate stepper motor for the capacitor. Using two separate stepper motors for the inductors does increase cost and complexity but a Basic Stamp controller can easily drive both motors. At the same time, such an arrangement  reduces the torque requirement for each stepper motor and eliminates the mechanical compexity in the pulleys, belts and/or gear drives required if you use only one stepper motor to turn the indutcors. It also allow you to mount the inductors at right angles to each other so that you get negligible mutual inductance/coupling between them.

A simple software counter is all that is needed to keep track of position and can run off a register that counts (accumulates) the stepper motor pulses given by the Basic stamp controller. Parallax sells LCD output displays for such a purpose. The memory (RAM) and (ROM)  allow one to bandswitch easily to a preset inductor and capacitor setting and would even allow one to  automatically switch in a fixed capacitance in parallel or series with the variable capacitor if the range of capacitance is not enoungh. The stepper motors would be driven to mid band on my set-up. Another approach would be to just write down the desired settings and have your program go to them. This would allow antenna set up changes. Another approach would be to allow the controller to store settings that can be input to non-volatile storage and changed as desired. The settings could have alphanumeric labels that would show up on the display by scrolling through them and when the correct setting shows, then push a button to go to them. As long as you keep the state of the present setting save in non-volatile memory of some sort, this is easy. In the internal porgram, the presets would be  encoded as pulses.

I have thought a lot about this and I have decided to go with a Basic Stamp controller, as you can (possibly) guess. Right now I am learning how to use the controller. In addition such a controller offers all sorts of possibilities of allowing one to remotely control a narrow bandwidth antenna from the shack. Steppir antennas by Fluid Motion did it first, but I don't think they will be the last to use this sort of device. A simple variable iductor or capacitor at the antenna would allow remote tuning of a highly efficient radiator such as a vertical antenna. You could even use homemade inductors or capacitors.


73,

Brad

Brad A. Steffler
KE4XJ
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KD5FOY
Member

Posts: 39




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« Reply #2 on: October 16, 2006, 04:33:01 AM »

brad, tnx for a very helpful post!!!!

larry
kd5foy
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K8AC
Member

Posts: 1466




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« Reply #3 on: October 16, 2006, 12:59:39 PM »

When I built my remote balanced tuner, I decided that using stepper motors was an unnecessary complication.  Here's a link to info on my tuner: http://k8ac.us/BalancedTuner.html

I've included info on the source of drive parts.  It's been in operation for about 5 years now, and have recently replaced the controller shown with one with digital meters.  That allows me to reposition the caps and inductors with great accuracy.  
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KD5FOY
Member

Posts: 39




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« Reply #4 on: October 17, 2006, 05:23:49 AM »

K8AC

Wow!!! very, very impressive indeed. many tnx
for the url.

larry
kd5foy
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AE6WA
Member

Posts: 59




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« Reply #5 on: November 30, 2006, 07:20:17 AM »

I went to your site to see your remote tuner and the website went to someplace else. It appears that your Domain has expired.
Is there another place you tuner is hiding now on the Web?

....Mike
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