Question about transmitter

[ljp2706]

Hello,

I have designed something that uses an RF power detector on the input of the design and I need to set up a transmitter so I can test if it is working. I have a hc-12 module in my possession but I am not very familiar with using it. I was wondering if there would be an easy way to just transmit the carrier frequency without sending data since I really only care about RF power level, not the data itself. I don't have an Arduino, but I do have an MSP430 if I need to use that. Also, can I just forgo the use of the MSP430 and just apply a voltage to the TX input of the hc-12 module to enable the transmitter?


Thanks.

 

[BradtheRad]

If your rf detector can pick up a wide range of frequencies then you can try a transmitter in a garage door remote, or a car's remote, or wireless headphones, etc.

Electrical noise emanates from many appliances, which your detector may pick up. However it's hard to be sure what reaches your device, whether it's really (a) electromagnetic waves (photons), or (b) electrical activity borne by nearby inductive (or capacitive) coupling.

 

[c_mitra]

if there would be an easy way to just transmit the carrier frequency without sending data since I really only care about RF power level, not the data itself...

That is not how it works! You need to pass on information and they must recognize each other. Of course you need not bother all these factors for a power level detector but for a proper communication you need to worry about data and security.

 

[ljp2706]

I hadn’t thought about using stuff I already had, I took a quick look at some of the electronics I have and nothing seems like it’ll work unfortunately.

I have an antenna on my pcb with a 433MHz band pass filter. Goes to an RF power detector. LED lights up if the measured input dBm is greater than a certain threshold. I don’t need any security or communication between the board and the transmitter. I just want to verify that the antenna+bandpass+rf detector is working as expected before I proceed with the rest of the design.

I don’t have all the components I need yet, but once they come in, I’m planning on seeing if that hc-12 module will suffice. I’m just not sure if I can transmit by applying a dc signal to the transmit pin. It doesn’t make sense to me that this would work properly so ultimately, I might have to use the msp430.

 

[Nik_2213]

could you mcgyver something using an existing attic or outdoor aerial to feed a scratch-wound 'search coil' to tickle your sensor ?

( Ducks those Hams and RF folk throwing rotten tomatoes due gross impedance and tuning mismatch... )

IIRC, when early transistor radios only had low sensitivity and a small ferrite rod for its internal antenna, this trick was often used to adapt the long, long room or attic loop that had fed the family's radiogram...

 

[kripacharya]

You could try with a off-the-shelf 433Mhz transmitter. They are easily available and cheap. It works on ASK, which means if input pin is high, it transmits a carrier, if low then no carrier. Only other thing is power.
Here is typical product https://www.electronicscomp.com/433...FJnhTmYVajD3A9XF6uTS-O9kgtM-wH5hoCinAQAvD_BwE

Just make sure your BPF allows the exact frequency transmitted.

 

[ljp2706]

Okay, that’s what I’m planning on doing. The hc-12 is GFSK based. Would the carrier frequency be present when the TX is enabled there too, or should I just look for an ASK module?

 

[kripacharya]

Forget the hc-12. Its too complicated for your purpose. Stick with 433 tx module. Much simpler.