20 votes

Why is 30MHz Clock signal distorted on oscilloscope?

There are two issues here: Bandwidth and Measurement technique. Bandwidth: Your measured signal is bandwidth limited. A 30MHz square wave has lots of harmonic content and your scope has a relatively ...
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  • 1,029
10 votes
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High pitch audio frequency measuring

Most common audio equipment is set to match human hearing, 20Hz to 20kHz is their operating range. So you want to measure ultrasound, If you want only to measure high frequencies, you can use a bat ...
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  • 968
9 votes

How to test a crystal resonator in board?

As I see, no answer was accepted. Let me offer another answer. Most modern ICs use so-called Pierce Oscillator to generate stable clocks using crystals. Here is the main circuit configuration: As ...
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  • 37.4k
8 votes

High pitch audio frequency measuring

By definition of the audio range for humans, beyond 20kHz is beyond audio. There are audio equipment designers such as Rupert Neve who believe the range could be wider, but this is not necessarily ...
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7 votes
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Differential Amplifier's Unusual Behavior

The first thing I noted when I saw your circuit is that the VAS (Voltage Amplification Stage, as you call it) is directly connected to the feedback network and this implies that its gain and its ...
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6 votes
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Signal power and spectrum analyzer

The actual measurement of Spectrum Analyzers is "power / filter bandwidth". Your spectrum analyzer has a filter bandwidth that you can typically configure. For example, if your filter bandwidth is 10 ...
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6 votes

How are high-speed circuits tested if test equipment doesnt exist?

For some perspective, consider that optical signals are still too high frequency for the instantaneous electric field to be sampled and measured, but there are still lots of different kinds of ...
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6 votes

Is it possible to measure frequency upto 500Mhz with 50Mhz oscilloscope?

Not really. 500MHz is too far above the nominal bandwidth for any aliasing frequencies to get through to the digitiser within it. You can use your scope as a 'back end' for two different types of ...
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6 votes

How to find the frequency of any device?

Yes, such devices exists and are called spectrum analyzers. You will also need to buy an near field probe kit, if you want to work with lower frequencies. They do not propagate well through air, so ...
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5 votes
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Are old frequency counters good deals or a waste of money?

You need to look at the datasheet and the specific products in hand to make any valid judgment. A badly damaged HP anything probably isn't going to perform better than even a cheap-o new frequency ...
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5 votes
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Questions about sound card scope software?

What is x-y graph? What does each axis represent? XY mode is used when you have two inputs (channel 1 and channel 2) and you want to represent the phase relationship between them differently: - ...
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5 votes
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Direct frequency measurement with two hw timers

EDIT: Because of the low precision of the HSI - 0.1%, the clock needs to be switched to HSE. I'm doing all of this in cubeMX so I won't be writing out the bits, you can find them in the reference ...
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5 votes

How to measure antenna S21?

In a two-port network, S21 is the complex number that describes the linear power gain of the network. (it's kinda backward - S2 is output, S1 is input). It's a complex number because it is used to ...
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  • 1,810
5 votes
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NE555P Frequency Drop to 0 after a couple of minutes?

It is very difficult to see, but as far as I can tell it looks like you have the wrong pinout for the 555 timer. The pins on the right-hand side should be numbered 5-8 from the bottom up, not from the ...
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5 votes

How are high-speed circuits tested if test equipment doesnt exist?

Long ago they relied of the speed of Gunn diodes for sampling the input signal waveform with a control pulse duration so that the difference frequency could be displayed on a slow timebase ...
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4 votes
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filter whose gain increases from minimum to maximum for frequency 400Hz to 1kHz

The steep response you want will require a multistage filter. The most commonly used active filter configuration is Sallen–Key topology, which provides two stages per amp using just 2 resistors and 2 ...
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4 votes

Frequency DC voltage

The question here is what is meant by DC and what is meant by AC. There are two contexts, where DC and AC mean completely different things. One perspective is that DC is any static voltage that ...
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  • 55.4k
4 votes

Frequency Counting on a Raspberry PI

The Pi is not really the best tool for the job. You have an entire operating system vying for processing time, with many processes running at the same time as yours. The only way you would be able to ...
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  • 55.4k
4 votes

How to detect a number of frequencies with minimal circuitry?

If you know what frequencies you're looking for, run a Goertzel for each of those frequencies. https://en.wikipedia.org/wiki/Goertzel_algorithm This is much more efficient than an FFT. This algorithm ...
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4 votes
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Counting signal frequency with binary counter

Am only going to address your question about reading the count output from a '393 counter. You have two problems to overcome. This counter is asynchronous, which means that a clock input ripples ...
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4 votes

Overtones Produced From Speaker Load on Asymmetric Square Wave

First, you can easily make a nice square wave from any duty cycle pulse train by running it thru a toggle flip-flop. That's basically using it as a 1-bit counter. That divides the frequency by 2, so ...
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4 votes
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an/prm-10 grid dip question - how the voltage can be negative at the grid?

I was studying tube designs as a child, long before I had any clue how a grounded cathode amplifier might be designed. Which means I don't remember that much. But one thing I do recall, which had ...
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4 votes
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How can i convert an AC output from an outlet to a digital signal?

This is best done with a opto-isolator. That not only handles the level conversion, but also isolates the digital signal from the AC line. All you really need is a single opto-isolator. However, if ...
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4 votes

Unit conversion: dBμV to dBm, including measured frequency

The "dBm" is a unit of power where 0 dBm = 1 milliwatt. The dB\$\mu\$V is a unit of voltage where 0 dB\$\mu\$V is 1 microvolt. If you know the resistance of the circuit (often called the impedance) ...
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  • 384k
4 votes

Simple high frequency (GHz) RF radiation detector

The ISS86 diode has a capacitance of 0.85 pF and, at 5 GHz this is an impedance magnitude of 37.45 Ω making it pretty unsuitable as a diode detector because, in the forward direction, it will rectify (...
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4 votes
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IC for measuring frequency

At 500 MHz what's usually done is to use a lower frequency counter with a prescaler. You should be able to get up to around 50 MHz with a PIC micro, adding a divide by 10 prescaler would get you to ...
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  • 4,460
3 votes
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Usefulness of VBW in spectrum analyzer

Do you have any hands-on experience with a spectrum analyzer ? If not then maybe you should as it will give you a better understanding of the effect of changing the RBW and VBW. Ad 1) Indeed the VBW ...
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3 votes

Frequency of TL084-based oscillator producing a triangular wave

The equation you have should be correct. I derive it this way: Note that the only assumption I'm making here is that the output swing of the first opamp is symmetrical about zero, ±\$V_{O1}\$. ...
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3 votes
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Cyclical output counts from a D Flip Flop, what is this effect called?

The effect is basically Aliasing. Your clock makes a digital sampling system, whenever the data signal is less than half the clock your data signal will determine the number of edges in a window ...
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