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?
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