A good review of the kit, including the added header for an input signal from an external in-circuit source to the frequency counter.
https://medium.com/@rxseger/crystal-oscillator-tester-frequency-counter-kit-review-586ea0bac2f9

Note: copy and paste this link, doesn't work otherwise...
Also: When building these cheap china DIY kits, ALWAYS test measure the components. In particular, the capacitors as they can be significantly off-spec by more than 20%. I have been refunded for several after reporting the discrepancy and told that a return was not necessary. In other words, A Free Kit for the price of a few minor components. YMMV

 

Mr.Chips, In step number 4 of your suggestions, the two units will be isolated from each other and I would expect an infinite resistance in that case. Am I wrong?

 

Thanks for the link SamR.

 

Mr.Chips, In step number 4 of your suggestions, the two units will be isolated from each other and I would expect an infinite resistance in that case. Am I wrong?

Correct. Both scope and MCU board are isolated. If either is isolated then there should be no electrical connection between the two units.

If your scope bandwidth is 20MHz then you will have difficulty reading 40MHz.

 

I also coiled a wire and connected it to my oscilloscope probe with the micro controller powered and held it near the crystal and got nothing.

If you already had a scope, why didn't it occur to you to use it? Why aren't you trying to probe the oscillator directly (with a 10X probe)?

 

I have but got nothing and needed to make sure I was doing it correctly. I was not sure if the probe was altering and truncating the crystal operation. I was also not sure what level of voltage I should expect to see. And yes I was using the 10X probe.

 

If you want to build a narrow band amplifier from scratch for 40 Mhz or 8 Meter.
It may require a little help getting started on a successful LC section.
one possibility is to use 10pF any smaller than that is usually touchy.
https://goodcalculators.com/resonant-frequency-calculator/
I got 1.58uH
this is easy and it should be taught along with the math maybe, anyway most of you can play with it.
It is nice when Xc=Xl in proximity to 40 Mhz crystal oscillator this resonant subcircuit will ring.
That is why I began loving math because it works nicely on the bench.
Most of the simple narrow band meters output to a few diodes it will pin a meter needle or register on a multimeter
it's a very small coil on a stick with a 10pF cap or attached to scope probe. The high impedance of jfet transistor amplifies and
the signal is sampled. Magnetically coupled isolation is preferred over point contact and there is no need of an expensive probe.

 

I have but got nothing and needed to make sure I was doing it correctly. I was not sure if the probe was altering and truncating the crystal operation. I was also not sure what level of voltage I should expect to see. And yes I was using the 10X probe.

A scope is the best tool for troubleshooting your problem. Standard procedure is to put the vertical sensitivity on a range that's higher than the highest voltage you expect to see. Then you increase sensitivity until you get a waveform. Your scope won't trigger unless it has a minimum amount of vertical deflection, so seeing nothing or not triggering correctly isn't unusual until you get the vertical sensitivity in the ball park.

 

Use the X10 probe. Apart from having a wider bandwidth it also means that the probe adds less capacitance to your circuit. Using a X1 probe may add enough capacitance to stop the oscillator. You should see perhaps 1V p-p on one or other of the crystal pins.

 

Thanks Sparky, Dl and Alpert.

 

Finally got results. Using the Hantek6022be system and placing the probe on one leg of the xtal I got a roughly 4 volt peak to peak signal at the crystal frequency. Somewhere along the line, I printed the frequency to be 40 mhz. Turns out to be 4 mhz. I originally was placing the ground lead and probe on either side of the crystal and got nothing. Still do not understand why that did not work. Placing the ground lead at a point of circuit ground, I found the signal on only one side of the crystal. Just for information, nothing was tied to house ground.

 

Thanks to all for all the input I received!

 

The crystal oscillator relies on the capacitance on each of the crystal pins to function correctly. As I said earlier even the capacitance added by a X1 probe can be enough to stop the oscillator. When you connect the ground clip to a crystal leg you add the capacitance of the probe cable and the whole body of the 'scope to that pin so it is no surprise that it stops the oscillator.

 

Finally got results. Using the Hantek6022be system and placing the probe on one leg of the xtal I got a roughly 4 volt peak to peak signal at the crystal frequency. Somewhere along the line, I printed the frequency to be 40 mhz. Turns out to be 4 mhz. I originally was placing the ground lead and probe on either side of the crystal and got nothing. Still do not understand why that did not work. Placing the ground lead at a point of circuit ground, I found the signal on only one side of the crystal. Just for information, nothing was tied to house ground.

This is a typical circuit. Grounding either side of the crystal kills it. There is also the load for the scope probe.

 

Thanks again for the insight.

 

I originally was placing the ground lead and probe on either side of the crystal and got nothing. Still do not understand why that did not work.

Unless you "float" your scope, the ground clip is connected to earth ground. If you don't know what you're doing, you should never float a scope.

Battery operated won't have this problem because they're isolated from earth ground.

 

It should also be brought to your attention that 40mhz is not 40mHz is not 40MHz.
Mistaking m for M is a huge mistake, nine orders of magnitude difference.

1 mHz = 0.001 Hz
1 MHz = 1 000 000 Hz

 

Unless you "float" your scope, the ground clip is connected to earth ground. If you don't know what you're doing, you should never float a scope.

Battery operated won't have this problem because they're isolated from earth ground.

Even if the 'scope is not earthed, connecting the ground clip to either crystal pin will add a very large stray capacitance and stop the oscillator.

 

https://www.aliexpress.com/item/4000632385465.html?

Easy kit and cheap, works well!

https://www.aliexpress.com/item/4000632385465.html?

Easy kit nd cheap, works well!

SamR I just finally got the frequency/counter you suggested. There is some confusion as to where the three hole socket for component measurement goes. Is your located as shown in the attached picture?

 

There is some confusion as to where the three hole socket for component measurement goes. Is your located as shown in the attached picture?

The picture shows 4 holes for a connector. The two on the right would be connected to whatever you're measuring if G is circuit ground:


One that I'm thinking about buying has a place for a 3 pin connector: