39
votes
Accepted
Can I break a radio tranceiving device by operating it with no antenna connected?
You could potentially break some radio transmitters by operating them without the antenna connected.
Several things combine to make this possible.
First, it's difficult to make power at RF frequencies,...
- 171k
28
votes
Accepted
Why would a time signal receiving watch have an airplane mode?
Most useful radio receiver designs utilize some form of the superheterodyne architecture, where one or more radio-frequency local oscillator signals are used to shift the frequency of the received ...
- 33.6k
26
votes
Accepted
How do two UARTS know which baud rate to use?
Ordinary UARTs have to be pre-configured with the desired baud rate (as well as word length, stop bits, parity, etc) traditionally by a human.
For several decades now though there have been ...
- 33.6k
18
votes
Is there a limit to how much power could be transmitted wirelessly?
Using directional antennas, hundreds of watts have been transmitted to drones. Further, a bit higher in the EM spectrum, lasers have been used to remotely power unmanned aerial vehicles (UAV's).
In ...
- 4,957
16
votes
Accepted
How can a low efficiency antenna be used for receiving but not for transmitting?
The reciprocity theorem is about the gain of the antenna. Let's say we have an antenna with 50% power efficiency, so 3dB more loss than a perfect antenna.
If used for reception, it will lose half the ...
- 171k
15
votes
Can I break a radio tranceiving device by operating it with no antenna connected?
Just to complement the excellent answer of Neil_UK and stress the fact that at RF frequencies voltages and currents don't really behave as those nice entities you know from KCL and KVL.
You must ...
14
votes
Accepted
How to end sending data over I2C by Slave or Master?
But I wonder how does this handshaking takes place between a Master and Slave when the Slave is sender and the Master is receiver and only the Slave (sender) knows when there is no more data to send ...
- 73.3k
11
votes
Can an LED be used as a receiver and as an emitter?
Ordinary LEDs can also be used to detect incident light, because they work as photodiodes too.
You will need to amplify the incoming signal.
Take a look at this projects (Jeff Han is the first one ...
- 4,767
10
votes
Diode in opposite direction?
At the point just before the first amp, the radio waves have been filtered to a particular frequency by L1, C1 & C2. That first amplifier is not an op-amp, it is an RF gain amplifier. It amplifies ...
- 181
9
votes
How to design a 10GHz PCB antenna
First of all is it possible to create 10 GHz wave on a PCB? Any clue
on how to do something like, regarding the circuitry?
If by "creating" you mean propagating and/or radiating, the answer is yes. ...
- 5,811
9
votes
How can a low efficiency antenna be used for receiving but not for transmitting?
There is a bigger picture to consider...
For the reciprocity theorem, if an antenna has a low efficiency in
transmission, it has the same efficiency when receiving.
Just to be absolutely clear ...
- 466k
8
votes
Why would a time signal receiving watch have an airplane mode?
I think that there is a very simple answer to this question that has nothing to do with electronics. A number of airlines prohibit the use of GPS receivers in flight. Their rationale does not actually ...
- 29.4k
8
votes
How do two UARTS know which baud rate to use?
Two UARTS "agree" on baud rate by means of documentation and by operator/user setting the baud rate by hands, including handshake protocol, stop bit size, etc.
- 41.8k
8
votes
How does this circuit work? (AM receiver)
First, I do not understand how the LC filter selects the frequency. I know that it's impedance is 'infinity' at the resonant frequency, but I don't understand how it rejects the other frequencies: no ...
- 98.2k
8
votes
Can an LED be used as a receiver and as an emitter?
Yes, certainly is possible.
For further info, I suggest finding a copy of a MERL reseach report by Dietz et al from 2003 how they did it.
It does not in fact produce enough voltage to detect it with ...
- 164k
8
votes
How is our voice tone transmitted and received without the change of our own voice?
Your voice creates vibrations (sound pressure waves) in the air.
A microphone generates an electrical signal whose voltage changes with the air pressure. The electrical signal is an "analog" ...
- 178k
7
votes
Accepted
Datasheet/screw function on XY-MK-5V 433 MHz receiver?
The component in question is called a variable or tunable inductor. The screw slot is in a ferrite material that cams in or out of the coil form as it is turned. The inductance varies according to the ...
- 5,604
7
votes
Accepted
Diode in opposite direction?
In this particular circuit application, the demodulation of amplitude modulated RF, no, the polarity of the diode does not matter. If you reverse the diode, you simply track the positive part of the ...
- 171k
7
votes
Why does the regenerative circuit not saturate?
Mostly because there's a knob on the receiver that adjusts the feedback, and the user has carefully adjusted it to the point where the gain is just below the point of saturation (at least, for a ...
- 7,948
6
votes
Accepted
Incorrect Output of RF Mixer
Your 100 MHz preamp is a common emitter amp stage. It's not popular, because the capacitive feedback from the collector to the base knocks the gain down even at 100 MHz except in case it's compensated ...
- 113
6
votes
Is there a limit to how much power could be transmitted wirelessly?
Much of the work on power transmission takes place in the near field. When the transmitting and receiving antennas are coils, this system is better modeled by thinking of it as a weakly coupled ...
- 1,011
6
votes
Is there a limit to how much power could be transmitted wirelessly?
The proponents of space-based solar power stations believe that GW can be transmitted and received by microwave RF. From what I've seen it's more likely that it is possible than it being economical. ...
5
votes
Accepted
Will this AM radio receiver work?
It wont work .C4 stops the detector diode from working .Remove C4 by shorting it .R2 is way way to low and will load the tuned circuit meaning no selectivity.Use a high impedence buffer like say a ...
- 15.5k
5
votes
Accepted
Can a standard computer function as a radio receiver without additional hardware, and how?
Short answer: No. You can often however get it to transmit radio, even if you don't want it to.
Long answer: This is going to depend on your definition of standard. Just as every bit of wire is ...
- 46.9k
5
votes
How to end sending data over I2C by Slave or Master?
Let us say a Slave or Master is sending multiple bytes to the receiver
on I2C bus and the number of bytes is not defined before hand. So then
how will the sender tell the receiver that it has no ...
- 11k
Only top scored, non community-wiki answers of a minimum length are eligible