FM generation by PIC

[c36041254]

Well,

Why don't you ask in any radio club near you? At least to know what are the bands where, without license, you could experiment?

I would point you towards getting your hands on a copy of the latest A.R.R.L handbook and start reading...
It might already be in your local library, if not ask them to get it for you...

thanks for all this, but the place where I live it is very difficult to find such things still, I'll try that, I was wondering if it will be better if I try first with AM, just for switching purpose, I'm thinking of making this (see the attachment )
Will this work ?, How far 100k carrier can go ? I just want to switch something in the next room (even the same room will do), BTW : Can any one provide a link that shows the calculation (derivation) of RC phase shift network's attenuation to be 1/29.

 

[atferrari]

You have access to Internet thus Google. I am sure you can find out.

Let me tell you: try to find the way to get that no the reason why you eventually couldn't. Be positive. Been there, done that.

 

[audioguru]

The antenna for 100kHz must be very long.

Most ordinary opamps don't work at 100khz. The 741 opamp has trouble above 9kHz.

 

[binzer]

Well,



thanks for all this, but the place where I live it is very difficult to find such things still, I'll try that, I was wondering if it will be better if I try first with AM, just for switching purpose, I'm thinking of making this (see the attachment )
Will this work ?, How far 100k carrier can go ? I just want to switch something in the next room (even the same room will do), BTW : Can any one provide a link that shows the calculation (derivation) of RC phase shift network's attenuation to be 1/29.

If you are going to make a remote control of sorts, FM is easier, and Holtek (I think) makes some chips that make it coded, so with some switches or keypad, the Holtek chip and an FM Rx / Tx pair yopu have most of it done. If you need a pic in the mix use it to similate the Holtek chip.

Mike

 

[philba]

If you are going to make a remote control of sorts, FM is easier, and Holtek (I think) makes some chips that make it coded, so with some switches or keypad, the Holtek chip and an FM Rx / Tx pair yopu have most of it done. If you need a pic in the mix use it to similate the Holtek chip.

Mike

We certainly took a round about route to get to the actual application. I agree with the use of encoder/decoders using simple transmitter/receiver pair.

Check out reynolds electronics - they have all the parts (including holtek) plus tutorial pages as well. https://www.rentron.com/PicBasic/RemoteControl.htm even if you can't order from them, they have lots of good info.

 

[c36041254]

Hmm...I forgot about antenna length, what I don't get (have tried google) is that how they make the carrier frequency very in AM, is it done by giving the amplified lower frequency (audio or any switching freq.) voltage output as the SUPPLY, to the carrier oscillator the way I shown in the pdf ? I am not sure that's the way, just show me what is the basic behind this and I'll find a way, I talked about op amp in a hurry but, I just want to understand the AM concept (not that simple "overlapping" block diagram theory),HOW A CIRCUIT SUPERIMPOSE LOW FREQUENCY ON HIGH FREQUENCY?, i.e. How the amplitude of high (carrier) frequency follows the amplitude of low frequency? Please help me with that and I'm sure I'll find some way to do that, either from Google or myself or what ever.I searched for AM in many way and all end up in a fine working ckt schematics but, I don't want that, not at least now.

EDIT:
In short, I need a circuit explanation for AM

 

[binzer]

Hmm...I forgot about antenna length, what I don't get (have tried google) is that how they make the carrier frequency very in AM, is it done by giving the amplified lower frequency (audio or any switching freq.) voltage output as the SUPPLY, to the carrier oscillator the way I shown in the pdf ? I am not sure that's the way, just show me what is the basic behind this and I'll find a way, I talked about op amp in a hurry but, I just want to understand the AM concept (not that simple "overlapping" block diagram theory),HOW A CIRCUIT SUPERIMPOSE LOW FREQUENCY ON HIGH FREQUENCY?, i.e. How the amplitude of high (carrier) frequency follows the amplitude of low frequency? Please help me with that and I'm sure I'll find some way to do that, either from Google or myself or what ever.I searched for AM in many way and all end up in a fine working ckt schematics but, I don't want that, not at least now.

EDIT:
In short, I need a circuit explanation for AM

You are now mixing wording between AM and FM.

Check this out. https://en.wikipedia.org/wiki/Amplitude_modulation


AM MODULATES a fixed amplitude carrier with a lower frequency, in most cases it can be voice, but in some cases it's just another fixed frequency which can change (remote controls). This adds and subtracts from the fixed carrier.

FM is frequency modulation, it adds and subtracts the modulation frequency to the carrier frequency.

Both types have circuits to extract the modulation for whatever purpose you desire.

I don't think you can do AM with a pic.

Mike

 

[c36041254]

Thanks for replies ! I finally found what I needed from a book, there can be many way to do AM which I found the easiest is COUPLING MODULATING SIGNAL TO THE COLLECTOR OF THE CARRIER OSCILLATOR. (That is what I was looking for, see ?!!), during high cycle of modulating signal the current of osciilator's collector increases and hence the output voltage and during low cycle of modulating signal current decreases and so does the output voltage, Thus we have AM at the output. Thank you all for your efforts and answers especially for the Op amp - frequency relation.

EDIT: It is going Radio side in MCU section so I'll start new thread, I think I got confused between PIC,AM and FM but now first I should concentrate on AM and then the PIC for switching and all that job.