RF Signal Generator

[canthai55]

Can not find one online which meets my spec requirements.

Maybe someone here has an idea - or the skill to build one.

Good remuneration if possible.

 

25 Khz - 40 Khz - able to driver 3 or 4 tweeters at this frequency.

 

Probably Piezo style as these are available online

 

Any info appreciated - reply or PM is fine

 

Thanks

 

[simon43]

That's outside the human range of hearing. You might need to check that your tweeters are actually capable of vibrating at this ultrasonic frequency.  What kind of waveform do you need - sinewave, squarewave?  You can easily build an ultrasonic oscillator with adjustable frequency range using a 555 timer chip and then a small amplifier to boost the output. Aliexpress sells these chips, or why not buy the complete function generator for $15?

 

DDS 1HZ 500KHZ Functional Signal Generator Sine Triangle Square Frequency Sawtooth Wave Waveform 3.0 4.9 Inches audio generator|Signal Generators| - AliExpress

[captainjackS]

OP says "RF" and you got my attention. but then say that you want a few tens of kHz?  Can you share more about the application and what kind of waveforms you require?  The architecture (and price) really depends on the type of waveforms you want to generate.  As @simon43mentioned, you could build or buy one for a few dollars, but you will be limited to the basic config.  If you want something more flexible that uses a DAC, you could generate any arbitrary waveform including multiple tones,  noise, modulated tones, the list goes on...

[canthai55]

Thanks for the replies.

Found some tweeters which - they state - go to 50 Khz

Want to output an RF frequency between 25 Khz and 40 Khz, adjustable so I can find the freq that works best.

As I am a novice at this stuff, I do not know if I need pure sinewave, or modified (stepped), etc. A continuous tone will - I think - give me the output I desire. It does not have to be clean sound or anything - just adjustable RF output at the desired Freq.

I can not be more precise because - as said - I do not know what I want beside what I posted above.

[captainjackS]

"clean" sound is subjective -- especially since we humans are unlikely to hear the sound above 20kHz.  Most likely, follow simon's link and job done.   A sine wave is a single frequency.  All of the other listed waveforms can be mathematically decomposed into the sum of many sinewaves at different frequencies -- each of which has a magnitude and phase (Fourier Analysis).  If you want to use this to deter dogs, square wave probably sounds annoying enough. Or 2 square waves with frequency difference of 3-4 Hz added together to make a beat would be more annoying.  If you want to build proximity sensor / sonar, going to need more carefully designed modulation.

[canthai55]

Thanks

I read online that roosters hear at the 32 - 34 Khz freq

What I want to do is build something that can output that freq range - hence my asking for a broad 25-40 Khz range

Place a couple 3 or 4 Piezo tweeters aiming directly at them, and fire away.

Thanks for your explanation - I am trying to get my head around it !!!

Can the generator that simon kindly linked do the 2 square waves 3-4 Khz apart ?

All I really want is some peace and quiet in the morning so I can sit in my garden and enjoy coffee before beginning my day.

 

Appreciate It !

[sometimewoodworker]

4 hours ago, canthai55 said:

Thanks

I read online that roosters hear at the 32 - 34 Khz freq

What I want to do is build something that can output that freq range - hence my asking for a broad 25-40 Khz range

Place a couple 3 or 4 Piezo tweeters aiming directly at them, and fire away.

Thanks for your explanation - I am trying to get my head around it !!!

Can the generator that simon kindly linked do the 2 square waves 3-4 Khz apart ?

All I really want is some peace and quiet in the morning so I can sit in my garden and enjoy coffee before beginning my day.

 

Appreciate It !

Now your intention is clear. The anti dog bark devices probably do exactly what you want though the trigger sound and level may need to be adjusted. Also continually broadcasts are likely to be uncomfortable to the local children since they can probably hear those (25Khz to about 28Khz) as well an intermittent, sound triggered, blast isn’t likely to be so bad.

[canthai55]

Thanks - thought dogs were at a lower frequency

[sometimewoodworker]

8 minutes ago, canthai55 said:

Thanks - thought dogs were at a lower frequency

They maybe, but they have almost everything you need and can be modified.

[seedy]

On 9/16/2021 at 4:29 PM, sometimewoodworker said:

They maybe, but they have almost everything you need and can be modified.

My problem is I do not have a clue how to or what needs to be modified.

Hence the topic asking for assistance.

[sometimewoodworker]

3 hours ago, seedy said:

My problem is I do not have a clue how to or what needs to be modified.

Hence the topic asking for assistance.

Well you have a starting point now, don’t you?

[Sophon]

On 9/16/2021 at 4:20 PM, canthai55 said:

Thanks - thought dogs were at a lower frequency

Dogs can easily hear sounds at those frequencies (and higher). However, before you go too far with building your device I would do some more research. From all I can find, chickens (like most birds) can't hear sounds at higher frequencies, not surprising as they don't have any outer ears. E,g, this quote from https://www.audiology.org/

 

Quote

Birds, with the exception of the Barn Owl, do not hear well at high frequencies. Chicken (hen or rooster), for example, have very sensitive hearing in the low frequencies but are limited to hearing sounds below 10 kHz.