How to transmit a signal (530 - 550 Khz) to a point

[nlopwer]

TL;DR Summary

Transmitting a signal to a point

Hi everyone,

I'm pretty new to electromagnetism and have no experiences in this topic.

I have a signal generator (Digital Dual Channel Funktion Signal Generator) and want to generate two signals (530 and 550 Khz signal) and want to transmit these generated signals to the points on a table (see picture bellow) one by one.

I don't know, how a signal generator works. I think, when i generate a signal it transmits the signals to everywhere. But i want to send the signal only to certain points on table.

The distance between the points on table and signal generator is one meter.

Is that possible? if yes, how?

 

[davenn]

Hi there
welcome to PF

Summary: Transmitting a signal to a point

Is that possible? if yes, how?

No, because the signal will spread out to all the points.
Even at microwave frequencies say ~ 2GHz or more, with a directional antenna
the spreading out of the signal will still cover all points.

The only thing you could do would be to have coding. The transmitter transmits a certain code that only the receiver at one of those points responds to and the others don't.
So a different transmit code for each of the 6 received positions

This is commonly done with SELCAL or CTCSS ... google those terms Dave

 

[nlopwer]

What if i want to send the signal directly from under the table? Will it be possible?

 

[RPinPA]

Is there a reason why you need to transmit it through the air rather than perhaps over wire to those points?

Or perhaps you could control the receivers so that only one at a time is listening?

What happens if you are intending to listen to point #1 but energy is being received at #2-6 at the same time? What problems will that cause in your experiment?

 

[Baluncore]

What if i want to send the signal directly from under the table? Will it be possible?

You could use coaxial cable to distribute the signals.
If the table top is plastic then it will be transparent to RF EM signals.
If the table legs are steel they may influence any antennas used.

But i want to send the signal only to certain points on table.

Why do you want to do that?

 

[nlopwer]

Is there a reason why you need to transmit it through the air rather than perhaps over wire to those points?

Or perhaps you could control the receivers so that only one at a time is listening?

What happens if you are intending to listen to point #1 but energy is being received at #2-6 at the same time? What problems will that cause in your experiment?

My supervisor want that i have to send signal only to send that points. When the points receive the signal then they are moving. That's mean i only should send the signal to point which i want to move. They have a embedded chip which only listens 530 and 550 khz frequency. So i have no chance to transmit the signal via a cable.

I thought i can send the signal from under the table, but do i then need a antenna?

You could use coaxial cable to distribute the signals.
If the table top is plastic then it will be transparent to RF EM signals.
If the table legs are steel they may influence any antennas used.Why do you want to do that?

I can choose the material of the table. Plastic, metal no problem. But i have to send the signal vertically. I can chose the thickness of table. The problem is here when i send the signal from above, the chips which receive the signal is embedded in above in chips.

I think it's very hard to send to signal on air directly. That's why, maybe from under the table. But I'm not sure how can i send the signal vertically to the points. I have a signal generator (https://www.amazon.com/gp/product/B07593GDB7/?tag=pfamazon01-20).

 

[Marco Aquino]

To transmit creates more variables than to receive. You have to show the Chosen points receiving the signal at the same time. (If I understand your chosen purpose correctly).

Maybe adding an element to eliminate the variables floating around the signals. Some greater than, or cancels out... adding elements to what exists in order for a designated point to receive signal not to send.

 

[DaveE]

The wavelength of radio waves is λ = c/f. f = frequency (Hz), c = 3e8 m/sec. So 550KHz will have a wavelength of 545 meters. Your table is much smaller than that, like 200 times smaller. Imagine you are standing on a beach with waves coming in with a wavelength of 50 feet, could you make those waves hit a rock on the shore but not hit another rock 3 inches away? That is a rough idea of the problem you will have. It's as close to impossible as any engineering problem I've heard of.
As others have said, you can let the signals go to all locations, and then have "smart receiver circuitry to measure the frequency and ignore the ones you don't want. This is possible but not a problem for beginners in circuit design. This is what your typical AM radio receiver does.

 

[hutchphd]

Summary: Transmitting a signal to a point

Hi everyone,

I'm pretty new to electromagnetism and have no experiences in this topic.

I have a signal generator (Digital Dual Channel Funktion Signal Generator) and want to generate two signals (530 and 550 Khz signal) and want to transmit these generated signals to the points on a table (see picture bellow) one by one.

I don't know, how a signal generator works. I think, when i generate a signal it transmits the signals to everywhere. But i want to send the signal only to certain points on table.

View attachment 244804

The distance between the points on table and signal generator is one meter.

Is that possible? if yes, how?

It is not clear to me what your constraints are.
For instance it is easy to modulate LEDs to tens of MHz . This light is then easily directed to particular locations. Can this be made to work? Then you would need a photodiode on the receiver end to reconvert.

 

[davenn]

What if i want to send the signal directly from under the table? Will it be possible?

no, the signal will still spread out to all points

 

[davenn]

This light is then easily directed to particular locations. Can this be made to work?

then when that receiver moves, it will be uncontactable again because the beam of light will no longer be pointing at the receiver

The BEST way is still to use selective calling codes. This can be as simple as transmitting DTMF codes along with the carrier and any other data. This is used on amateur radio and commercial radio repeaters etc

 

[RPinPA]

then when that receiver moves, it will be uncontactable again because the beam of light will no longer be pointing at the receiver

The BEST way is still to use selective calling codes. This can be as simple as transmitting DTMF codes along with the carrier and any other data. This is used on amateur radio and commercial radio repeaters etc

I agree with this solution. It means that you need the receiving devices to have an embedded processor which can recognize their own code and ignore instructions addressed to other devices. Is that feasible?

 

[Baluncore]

Maybe you could make a single wire loop that runs once around the table, under the edge of the table. When you drive that loop with close to 540 kHz you will get a vertical magnetic RF field passing through the table top. Use thin wire for the loop and put a capacitor in parallel with the loop to tune it to the signal.

Because the loop is small in terms of the carrier wavelength of 560 metres, the field inside the loop will be strong while the field outside the table top will tend to cancel and not interfere with other equipment. Broadcast transmitters have electrically vertical radiating fields so they will not interfere with your magnetic vertical system, and your system will not interfere with broadcast receivers.

Each of the objects on the table top will have a many turn coil with a vertical axis, that is tuned to the carrier frequency band. The geographical orientation of an object will not be important because the magnetic axis is always vertical for transmit and receive.

Each object placed on the table will detect that same signal and depending on the carrier frequency, or the modulation of the signal, will be programmed to respond to your control signal transmitted by the loop. How are the embedded controller chips in the objects programmed to receive and identify the command signals?
Where has that been specified?

 

[davenn]

I agree with this solution. It means that you need the receiving devices to have an embedded processor which can recognize their own code and ignore instructions addressed to other devices. Is that feasible?

No, it doesn't need a processor, just a simple tone decoder