Piezo-Electric Filters

[@andrewmcfarland57]

My first "Citizen Band" (27Mhz) radio from the 1970's had 40 channels. When i finally dismantled it out of curiosity, I discovered it had 40 replaceable " tin can" piezo crystals! 🙂

[@dean5263]

I thought to myself when I first saw the case, “That's a delay line from a 1970s TV”. Yep, I'm old.

[@FesZElectronics]

It took me quite some time to figure out what it was... I remember seeing these in old TV sets in the past, but I never knew what they did.

[@trcwm]

PAL, SECAM or NTSC? 🤣

[@xDR1TeK]

Hello fellow old person.

[@pietpaaltjes7419]

Me 2. Also old person 😂

[@joeteejoetee]

@0:08 it's a video scan-line delay-line. It contains 1 scan-line (63.5uS long) and its analog contents are used to repeat/replace a scan-line that has a "Drop-Out" in it. The piezo-electrodes are on the corners of the glass, and the Piezo transmit beam enters @ a 45 degree and bounces around diagonally off of all of the edges inside until the signal finally hits the Receiver Piezo. The Seven black-spots on the glass are between the reflection grid to reduce beam path cross-talk and total crystal resonance.

[@brianharper9798]

If that was a Philips delay line, I used to make those at the Philips plant in Blackburn UK probably around 30 years ago. I operated the screen printing machines that put the diamonds of damping compound on the glass. I remember a display in the entrance that had with one of all the different generations of the delay line they had made. The very early ones were huge.

[@FesZElectronics]

Indeed it is a "Philips, DL700, 84701; kh 08010" these are all the markings present on the top side. I think it would be really special if this was one of the components you worked on in the past;

[@brianharper9798]

It would think that it would be rather unlikely to be one that I helped produce. We would probably have produced many thousands per week. I think I left in around 1996 but production was ramping down by that point. Didn't think about it when I worked there but looking back it was really quite an interesting process. Thanks for showing it. It's brought back some great memories.

[@ciprianpopa1503]

So is that glass or quartz?

[@brianharper9798]

Was definitely glass, although if I remember correctly I think some special formula (it's a long time ago).

[@ats89117]

The crystal model used is called the Butterworth Van Dyke (BVD) model. The model can be extended by adding multiple RLC circuits along with a single parallel capacitor to model the primary and secondary resonant and anti-resonant frequencies. For sonar usage, widening the band between the resonant and anti-resonant frequencies by addition of series and parallel inductance is an underutilized method for achieving better performance...

[@dimitrioskalfakis]

comprehensive presentation.

[@AdityaMehendale]

Now waiting for Andreas, and my Sunday shall be whole :)

[@MegaCadr]

Who?

[@AdityaMehendale]

@@MegaCadr Spiess.. Andreas Spiess.

[@MegaCadr]

@@AdityaMehendale Oh, right. I'm subscribed to him, too. :)

[@ahooper99]

@4:55 how did you get the equivalent component values?

[@ahooper99]

Sorry, I now see it in the Measuring video linked in the description

[@johnwest7993]

Thank you.

[@RensePosthumus]

Top video, Thanks!

[@MegaCadr]

This is fantastic! Any chance you are going to do one on mechanical filters?

[@FesZElectronics]

What sort of filters do you have in mind?

[@MegaCadr]

@@FesZElectronics The ones that they used to use as IF filters on radios, like the Collins 455khz filters. Very similar in a lot of ways to what you have here. It just find how they model the physical parts in between interesting.

[@FesZElectronics]

I'm not really sure if the operating principle is different, its just a different material - ceramics vs crystals.

[@MegaCadr]

@@FesZElectronics no, same principle, I just find it super cool. I wanted to experiment making my own bad ones by hand and just seeing what I end up with :)

[@Stefanev]

Thank you! 🙏

[@tonychristoph1063]

👍

[@killcar5nbike2]

Anyone else get audio issues? Last couple of vids and this one I get lots of glitch artifacts from my DAC. Make it unwatchable unfortunately

[@killcar5nbike2]

@@joel_mckay It's optical out to a DAC from TV. My Yamaha RN301 also does the same thing using the internal DAC. No other videos do it's an odd one, skipping CD type noise