Testing crystal filters with a Nano VNA
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- Опубликовано: 5 фев 2025
- Grab a few same frequency crystals and some disc ceramic capacitors and what can you make? A ladder-type crystal filter. Watch how it's done and see tests using a Nano VNA.
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Thanks for picking this idea up. Gotta get one of these.
Watched this and bought one :)
Nice bit of kit! Useful for antenna measurements too.
You might get better results if you adjust the termination values. Right now you're at 50 ohms (VNA), but most filters need something in the 100-500 ohm range.
It's a really useful piece of kit!
Superb demo!
Excellent!! Thanks that was a great help…!
Any way to use crytals for a notch filter instead of a band pass?
Yes. Look up old (1940s-50s) communication receiver circuits for the use of single crystal filters with a deep (though uneven) notch.
@@vk3yeThe goal would be to make a narrow notch on 136.7 MHz VDL2 blips because they overload the SDR interfering with APT/LRPT signals from 137.1 to 137.9, but 136.7 is too close to 137.1 so I have no idea how I would solve this. A normal notch has a rather wide drop curve so no way of eliminating or deeply attenuating the interference without affecting the wanted signal
@@t0nito That's too high for a crystal. You need to investigate cavity filters etc as used in VHF repeaters.
@@vk3ye I've tried a helical resonator filter, what some people suggest is to downconvert to a lower frequency
Another useful vid. Thx Paul. I wonder if it would be same with the NWT500 or so.
Waldemar Antonik
Sure it would. You don’t need phase information for such measurement. So not only VNA could do it, but scalar analyzer like NWT would do it with the same results.
Very useful video, but how do I test a filter requiring 800 Ohms termination, can I just add resistors or is the loss too great?
I would try some sort of broadband transformer.
ooookay. Why do so many of these videos show the results but NOT how to set the van for thru put and showing what each trace is set to?
1:57 -11dB Is your NanoVNA calibrated?
Now many peoples using it nano vna
🙂👍
I dont think these crystal filters are matched to 50 ohm. Therefore, this is not the correct method for measurement. You need matching
@@tcarney57 Most certainly, and a great demonstration of how to use a Nano VNA to display various crystal filter configurations, rather than taking precise measurements for designing an actual filter.
As a proof of concept it hits the mark! Kudos to Peter VK3YE
My NanoVNA-F v3.1 with 4.3" screen has just arrived in todays mail and I'm busting to use it to test my ladder filters (and many other things) as soon as I get up to speed with the Nano's controls. If you're a homebrewer you're lost without test equipment to design and troubleshoot.