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11-14 of 14 messages
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RE: Compact HF auto-tuner
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by N3OX on July 12, 2009
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PicATune as designed good for 200W, apparently:
http://homepages.tesco.net/~a.wadsworth/pictures.htm
One problem, I suspect, about relay-type autotuners is that it's hard to find cheap relays that will handle big enough voltages.
W8ZR's EZtuner is a good electromechanical design for a high power tuner, but it it doesn't find a match on its own. It's a memory tuner.
Depending on what your antenna situation is, this could be just fine. It certainly would be "automatic" enough for me on most bands, as long as the system could check for bad SWR at the memorized settings before "telling" the amp it was OK to transmit, or if the amp bit had its own good protection circuitry in case something went screwy.
I would absolutely use motor driven components like that for any auto-tuner.
In fact, I'm sitting among the bits of an almost finished project that's simpler but similar to what I'd do otherwise, a motorized, "automatic" six position high voltage/high current switch to switch among fixed-tuned matching networks on my 60 foot vertical.
It's got a rotary switch on the front. (It's actually a potentiometer with an indexing setup from a wafer switch, it saved a lot of microcontroller pins and switch wiring to read the pot voltage as a control with one of the six analog inputs on my controller rather than try to do it binary )
But it also plugs in to the parallel port on my computer. When the front panel switch is on "auto," it reads the parallel port bit pattern on its digital inputs, which is placed there by Ham Radio Deluxe depending on the band the radio is set to.
It then drives a stepper motor to run the big bandswitch to the desired position.
Since my load doesn't really change, fixed tuned networks work just great and all I need is to be able to select among them.
And since I don't have to measure the RF frequency to get band information from my radio, the "automatic-ness" is really easy. Just read from the computer which band the radio is on, and if the computer is out of commission or I just don't want to turn it on, I have the front panel switch instead.
You could do a similar thing with any rig that has a "band data" binary coded output (if I weren't using computer control, I could actually set the radio's back port to do this). Then you don't need any of W8ZR's frequency dividing and counting circuitry, because the *radio* tells the tuner what band it should tune to.
The computer control route is even better for me since I can ultimately tell the switch that I've tuned to some part of some band... so I can have a different setting for 80m CW vs. 75m SSB. You can't do that with band data; you can with Ham Radio Deluxe or DXLab Commander or some other other rig control software, but then you're tying yourself to a computer and CAT control... though I guess in principle you could program your tuner to talk to most radios to read the frequency using CAT :-)
Another thing that simplified my project is that I used an Arduino for my microcontroller:
www.arduino.cc
bought from
www.sparkfun.com
It's certainly more expensive that buying an ATMEGA168 controller and necessary external components, but it comes ready-to-run on a board with all necessary support components and can be programmed over USB. Plus a lot of hobbyists have embraced it, so it's easy to find all kinds of simple examples on how to do stuff.
If you already know some microcontroller programming, well, then you can go with what you know... but as someone who just started with it this year, I think the Arduino environment and board are a good way to get started.
I'm sure the PIC A Tune guy likes PIC ;-)
Anyway, I would definitely go with something like W8ZR's project if I were going to do this... stepper motor driven air variables and switched inductor.
In fact, if you've got a suitable manual tuner already it might save a *lot* of time and money to convert it!
It'd be the automatic equivalent of this:
http://n3ox.net/projects/servo/
That one is just remote, and while servo drive *could* be pressed into service for an autotuner, I think it's too sloppy without real PID control loops, and there's just no point when you could likely use steppers instead.
73
Dan
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RE: Compact HF auto-tuner
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by HFRF on July 13, 2009
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Why bother with all this u controller crap? Use a small low power auto tuner that you can usually get for less than $200 and let the relays flip much bigger relays like HC3 vacuum. The vacuum relays would switch in/out separate wound coils (1/8" copper tubing works good)and hi current mica or door knobs caps. The coils and caps would need to match those in the smaller tuner. I know of 4 such tuners and they easily work at 3kw with a matching range of 10 to 5000 ohm. These setups use splitters to send a small amount of RF through the sense circuitry to measure load Z.
I personally bought over 50 brand new vacuum relays off ebay for less than $20 each.
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RE: Compact HF auto-tuner
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by N3OX on July 13, 2009
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"Why bother with all this u controller crap? Use a small low power auto tuner that you can usually get for less than $200 and let the relays flip much bigger relays like HC3 vacuum"
Still uses "microcontroller crap," difference is you can't change it... :-)
"I know of 4 such tuners and they easily work at 3kw with a matching range of 10 to 5000 ohm. These setups use splitters to send a small amount of RF through the
sense circuitry to measure load Z. "
Pretty cool.
Certainly another way to go.
Personally, I'd still prefer to have control over the firmware just because it could simplify integration with the amp...
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RE: Compact HF auto-tuner
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by HFRF on July 13, 2009
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There is no reason not to make your own control circuitry and controller. But, designing the software isn't so easy, actually it is a real pain! I don't see the purpose in reinventing what MFJ already designed and their tuner algorithms are pretty decent.
At work we did something similar to MFJ's tuner software and it took 3 of us 4 months to get it to work right. We didn't work full time but it took about 3 times longer than we thought it would.
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