Monday, October 19, 2026

Using AI to Design Crystal Filters -- Please comment, especially on the use of AI

 
Earlier, AI told me that for 17 meters with a VFO in the 5.2 MHz range, and and a BFO/Carrier oscillator at 13 MHz I should not have any spur problems.  So I ordered 10 crystals from Mouser.  I hope to use it with the VFO from the Kenwood TS-820s. 

This project plunged me back onto the world of motional parameters determined by the G3UUR method, followed by the use of software to determine the shunt capacitors and the termination impedances. I have used Dishal, AADE software, and Wes Hayward's GPLA. 

Using this software can be a pain in the neck.  There are a lot of exponents.  Capacitance often has to be expressed in femto farads.  Frankly, there is a lot of potential for error. 

There is no way (as far as I know!) to skip the G3UUR measurement stuff.  You just can't tell AI to determine the motional parameters.  But after that, AI should be able to handle the calculations.  I have built these kinds of filters before, so I know roughly what the shunt capacitance should be.  Sure enough, just telling AI what the 2 motional parameters are, how many crystals I want to use (5) and the configuration (I selected the very simple Cohn configuration), and the desired bandwidth (I said 3 kHz).  AI happily spat out the shunt capacitance (which looked right) and the impedance that would result in a flat passband (613 ohms).  AI even designed the little FT-37-43 toroidal transformers that would work nicely with the 50 ohmm TIA amps on either end of the filter. 

I think this is a good example of one of the uses that can be made of AI.  It made the design of this filter a lot easier.  

Both Images Produced by AI Gemini (FLASH HIGH)

I have built the filter (in the real world) and it is mostly working.  I will perform some more tests on it and will report on this here.  

What do you folks think of all this? 

4 comments:

  1. The more a man uses his own mind and
    hands, the less time he will waste standing
    on street corners!
    Due to AI, I predict that being old-fashioned
    will soon become a very celebrated virtue.
    --Walter KA4KXX

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    1. Hey Walter: Would you use a calculator when plugging the numbers into the formula? That sounds like cheating, right? And BTW, did you develop the formula for motional parameters by yourself? Did you write the AADE, Dishal, or GLPA programs? I was thinking that perhaps you should use your own mind and stop wasting time standing on street corners! 73 Bill

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  2. Using AI as an assistant to someone who is already knowledgeable about a subject is a perfect use-case. You knew enough to understand that the AI wasn't wildly hallucinating and you could recognize a useful response from a likely poor is or inaccurate one. This is exactly the way I have been using it. But, for someone who doesn't share our experience, They will be taking a leap of faith that the AI is correct.

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  3. better get used to it. I know of a few firms that are already using AI to write software. Aside for a few programmers to guide and troubleshoot the end product produced by AI, programmers will go the way of the linotype operator at a newspaper printing firm. It is sad, but this is the future.

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