crystal oscillator module generating radio waves without an antenna?

[dl09]

i installed a crystal oscillator module on a breadboard and connected the breadboard to a battery and there was no antenna, i saw 2 spikes on my spectrum analyser.
why is the crystal oscillator module generating radio waves, there is no antenna?

 

[d123]

Photos.

 

[KlausST]

Hi,

Every piece of conductive material is an antenna. Maybe no good antenna.
So even the pad/pin of the oscillator and the piece of copper of the breadboard acts as an antenna.

Don't think black and white think as bad and good.

Klaus

 

[dl09]

but if i install an antenna and a filter to remove the harmonics, i will still remove the harmonics?

 

[danadakk]

If osc is to be used with an antenna then you can design a filter
at output of osc to remove harmonics, which if you remove all
but the fundamental will give you a sine wave.

But you must also make sure osc part is bypassed adequately on supply pins
to make sure harmonics are not radiated from its switching noise and oscillation
circuit power. Ceramic caps for high freq desired

No where do you indicate your goals, osc freq, harmonic suppression specs, distortion....

RF Tools | LC Filter Design Tool

Regards, Dana.

 

[KlausST]

Hi,

As I already said: don't think in black and white.

You can not completely "remove" them, you will attenuate them.

Klaus

 

[betwixt]

This is your underlying problem:

i installed a crystal oscillator module on a breadboard

A breadboard is not a suitable construction for an oscillator unless the frequency is very low (less than about 1 MHz). You need to think in terms of RF, things like ground planes and close decoupling are needed or the breadboard wiring/tracks will all act as antennas.

Brian.

 

[andre_luis]

Just to complement Brian's observation, try to lift the oscillator terminal output out of the breadboard and much likely you'll see decreased the artifact on the spectrum analyzer.

 

[dl09]

This is your underlying problem:
A breadboard is not a suitable construction for an oscillator unless the frequency is very low (less than about 1 MHz). You need to think in terms of RF, things like ground planes and close decoupling are needed or the breadboard wiring/tracks will all act as antennas.

Brian.

so i use groundplanes to connect the crystal oscillator module to the battery and the antenna? i don't know what groundplanes are.

 

[BradtheRad]

My home-brew waveform generator is in a steel enclosure. (Circuitry is unshielded.) Sometimes for fun I set the frequency to hundreds of kHz, and turn on an AM radio nearby. It produces noises, a buzzing to either side of a silent spot. I'm certain that's evidence a radio broadcast is coming from my waveform generator, even though it has no antenna

 

[betwixt]

Think of a ground plane as the lowest possible impedance you can possibly achieve between ground connections in a circuit. Typically it will be an expanse of copper on one or both sides of a PCB covering as much of the area as possible. The worst case scenario to look at it the other way around is to connect the ground points together through thin wires or tracks. Even short tracks and wires have inductance, that means they also have reactance (XL = 2 * pi * frequency * inductance) and that allows signals to develop from one part of the track to another, in other words it looks like an antenna. Even ground planes are not perfect but if well designed they can be pretty good at providing a 'zero signal' zone.

Brian.

 

[dl09]

Think of a ground plane as the lowest possible impedance you can possibly achieve between ground connections in a circuit. Typically it will be an expanse of copper on one or both sides of a PCB covering as much of the area as possible. The worst case scenario to look at it the other way around is to connect the ground points together through thin wires or tracks. Even short tracks and wires have inductance, that means they also have reactance (XL = 2 * pi * frequency * inductance) and that allows signals to develop from one part of the track to another, in other words it looks like an antenna. Even ground planes are not perfect but if well designed they can be pretty good at providing a 'zero signal' zone.

Brian.

so how do i design a groundplane so the crystal oscillator module, generates no radio signals?

 

[betwixt]

What do you want the oscillator module to produce?

Brian.

 

[dl09]

Just trying to make sure it won't generate radio waves without an antenna and will generate radio waves with an antenna.

 

[schmitt trigger]

D109:

what you are discussing is Electro Magnetic Interference, perhaps one of the most difficult aspects of high speed electronics.

 

[dl09]

so is there a way to do it, so it won't produce radio waves without an antenna and will produce radio waves with an antenna?

 

[FvM]

A radio transmitter doesn't need to have zero spurious emissions, just emissions below the limit values of the applicable standards, e.g. FCC 47cfr15 in the U.S. or ETSI regulations in Europe. This is always achievable by using shielded enclosures and filters.

 

[dl09]

This is your underlying problem:
A breadboard is not a suitable construction for an oscillator unless the frequency is very low (less than about 1 MHz). You need to think in terms of RF, things like ground planes and close decoupling are needed or the breadboard wiring/tracks will all act as antennas.

Brian.

What would be a suitable construction for a breadboard?

 

[volker@muehlhaus]

As FvM wrote: put it in a metal box.

 

[dl09]

Would a perfboard be a more suitable construction than a breadboard, for radio frequency work?