46
votes
Accepted
Optical audio transmitter can't handle speech
It seems to me that you are probably using a music source that is stereo and, instead of it delivering a mono signal as you expected (L plus R), the connection of the transformer to L and R channels ...
- 443k
38
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,...
- 162k
31
votes
Why are color difference signals transmitted rather than R,G,B signals?
Since color transformations are a linear 3x3 matrix, so is converting RGB to YUV and back. Y is needed anyway for compatibility with B/W TVs, and Y signal consists mostly of G component, then mostly ...
- 137k
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 ...
- 33.4k
20
votes
Best practice in transmitting sensor analog signal over longer distances (approx. 100') -- in cost sensitive products for microcontrollers
"Best practice" and "inexpensive" are both subject to opinion.
In all cases, I'd put a really inexpensive little processor at the sensor, and have it talk digital. The 1950-1975 way to do it would ...
- 45.4k
19
votes
Why are color difference signals transmitted rather than R,G,B signals?
I'll address a couple of points briefly here. A full discussion of the analog color TV signal and the decisions that went into its design would fill a book.
When color TV was introduced, the broadcast ...
- 170k
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 ...
- 72.8k
14
votes
Accepted
Best practice in transmitting sensor analog signal over longer distances (approx. 100') -- in cost sensitive products for microcontrollers
The other solution can be I2C — there are extenders, allowing to create buses up to 100m (300ft). One of them is NXP P82B96. It is very useful in amateur constructions, because it is not expensive and ...
- 1,578
13
votes
Will a spark gap transmit a signal an FM receiver can "hear?"
A spark-gap (without a tuning circuit) will generate a broad band array of radio interference and it's likely to produce some crackles in the FM radio's speaker at any unused tuning position. You ...
- 443k
11
votes
Accepted
What's the purpose of the band-pass filter in an RF transmitter?
The output of an AM (Amplitude Modulating) mixer contains a number of frequency components. These components are 1) the modulating signal. This signal is typically audio frequency, and in the diagram ...
- 20.7k
11
votes
What's the purpose of the band-pass filter in an RF transmitter?
Every mixer produces quite a deal of unwanted frequencies.
These include:
frequencies contained in both input signals
the above frequencies multiplied by various integer numbers
all of the above ...
- 8,746
11
votes
Accepted
Will a spark gap transmit a signal an FM receiver can "hear?"
Yes, but not as loud as in an AM receiver. This is why:
Broadcast FM uses a wider bandwidth than broadcast AM. That reduces its susceptibility to electrical noise
Broadcast FM works at a higher ...
- 18.7k
10
votes
How does this FM transmitter work?
Q1 amplifies audio with a gain of approximately R4/R5. This audio feeds Q2 (an oscillator) and modulates its base-collector miller capacitance thus producing a varying output frequency. Q3 is an RF ...
- 443k
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. ...
- 5,751
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.
- 39.4k
8
votes
Accepted
Can I use a DAC to tune a VCO?
Can I replace R1 with the DAC output from an AVR microcontroller?
Yes you can but be aware of noise on the output of the DAC especially when changing DAC values - you get a bit of capacitive coupling ...
- 443k
8
votes
Accepted
My FM transmitter never works, Why?
Forget building this on a breadboard. The oscillator can't work on a breadboard.
Breadboards have capacitance between the pin rows that's about the size of the capacitors in the oscillator.
...
- 69.1k
8
votes
How does someone design a low frequency FM radio transmitter?
I've been told that using VCO circuits to simply generate a low
frequency signal and modulate it with an input signal would be
unstable and unreliable
There's no evidence to suggest that what you say ...
- 443k
8
votes
What is this circuit diagram found on an FM transmitter?
As noted, this is not a "schematic", its more of a functional block diagram.
The triangles are power amplifiers. The arrow means they are adjustable.
The Sigma symbol means the amplifiers ...
- 7,373
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" ...
- 171k
7
votes
Best practice in transmitting sensor analog signal over longer distances (approx. 100') -- in cost sensitive products for microcontrollers
I've had excellent results transmitting sensor data using the Controller Area Network (CAN). I have a 16-bit microcontroller with a built-in CAN that interfaces through SPI to a 24-bit A/D converter. ...
- 71
7
votes
Can anyone explain how this 433MHz RF transmitter module works?
That's the simplest RF transmitter at 433.92 MHz that one can design.
That's the lowest cost RF transmitter ever.
That's an on-off RF transmitter.
T1, R1, C1, C3 and the SAW filter are the oscillator....
- 4,181
7
votes
Accepted
Why are pull-up inductors biasing the power amplifier output of radio transmitters chips needed?
Applying DC supply straight to the output pin would cause a dead short when the amplifier attempts to sink current to drive the output in an open-drain fashion, as documented in the datasheet:
This ...
- 18.8k
7
votes
NPN transistor with no resistance at collector?
What's the point of the capacitor between Vcc and ground?
It is a decoupling capacitor. It provides short term stabilization of the voltage across the op-amp. The current drawn by the op-amp will ...
- 20.7k
7
votes
Please verify tube AM radio transmitter
No, it will not work.
There are about five major issues, nevermind the absent part numbers and component values. There also isn't any modulation going on; if we are to assume the input (if that's ...
- 27k
7
votes
Will a spark gap transmit a signal an FM receiver can "hear?"
FM radios aren't made to receive AM or pulsed RF. They are generally immune to the kind of interference that a spark gap transmitter would produce.
You might be able to gimmick up a spark gap ...
- 69.1k
6
votes
Building an fm transmitter broadcasting simultaneously to all fm frequencies
In days long ago, this was done by transmitting a strong signal at the IF frequency of 10.7 MHz. Most radios in that era did not have sufficient shielding in the IF section and this signal was ...
- 23.6k
Only top scored, non community-wiki answers of a minimum length are eligible