What is minimum frequency that can transmit live video?

Thread Starter

Man10

Joined Jul 31, 2018
163
If I want to transmit live video via radio waves, what is the lowest frequency that has enough bandwidth to transmit live video?
 

ronsimpson

Joined Oct 7, 2019
3,131
The radio waves are shared by all of us. It is not good for one person to transmit on just any frequency. You could be at the police band or fire truck frequencies.

How fare do you want to transmit?
I am using WiFi at 2.4ghz and 5ghz to transmit video from cameras.

The old TV standard has channel 2 at 54 to 60 mhz. It takes 6mhz width to transmit video without compression.
 

MrSalts

Joined Apr 2, 2020
2,767
The radio waves are shared by all of us. It is not good for one person to transmit on just any frequency. You could be at the police band or fire truck frequencies.
Let's assume he is asking,
1) what is the lowest legal frequency, or,
2) what is the lowest theoretical frequency
 

Thread Starter

Man10

Joined Jul 31, 2018
163
What is the lowest frequency, that can theoritically transmit live video( that is black and white and has a resolution of 40,000 pixels) over a distance of 100 miles, without a repeater?
 

MrChips

Joined Oct 2, 2009
30,931
There are way too many parameters involved to give you a definite answer.
Hams transmit SSTV (slow scan TV) at low frequencies, 2-10MHz.
Analog TV broadcast channels start at 40MHz.
 

Thread Starter

Man10

Joined Jul 31, 2018
163
There are way too many parameters involved to give you a definite answer.
Hams transmit SSTV (slow scan TV) at low frequencies, 2-10MHz.
Analog TV broadcast channels start at 40MHz.
I really want you to list the parameters.
 

MrSalts

Joined Apr 2, 2020
2,767
What is the lowest frequency, that can theoritically transmit live video( that is black and white and has a resolution of 40,000 pixels) over a distance of 100 miles, without a repeater?
Assuming a 200 x 200 pixel screen and 15 frames per second, that's 15 * 40k pixels and 1-bit "color", you'll need 2MHz plus some more for timing if your data signal is your carrier signal and you use some type of amplitude modulation to achieve this. However, transmitting such a signal becomes difficult - especially as range increases because of significant distortion of the encoded signal.

if you wish to encode the 2M bits of data needed for 15 frames per second - you'll need a carrier frequency that is somewhat (5x to 10x) higher as a minimum for ASK or much higher if you want FM. If you want more gray scale depth, then you'll need to transmit 4x the number of bits for 16 shades of gray per pixel.

which class is thus for?
 

WBahn

Joined Mar 31, 2012
30,239
What is the lowest frequency, that can theoritically transmit live video( that is black and white and has a resolution of 40,000 pixels) over a distance of 100 miles, without a repeater?
What frame rate? What kind of compression? If you are really looking to transmit at a low carrier frequency, you want to use the minimum frame rate that is acceptable and use as much compression as you can.

Then there's the matter of what encoding you are going to use and what modulation technique.

How much power are you going to use? The higher the signal to noise ratio, the more bits you can cram into one symbol and the further away it can be picked up by a distant receiver.

Which brings up the question of how sensitive is the receiver?

Is the transmitter using a directional antenna, or an omni?

What about the receiver?
 

Thread Starter

Man10

Joined Jul 31, 2018
163
Assuming a 200 x 200 pixel screen and 15 frames per second, that's 15 * 40k pixels and 1-bit "color", you'll need 2MHz plus some more for timing if your data signal is your carrier signal and you use some type of amplitude modulation to achieve this. However, transmitting such a signal becomes difficult - especially as range increases because of significant distortion of the encoded signal.

if you wish to encode the 2M bits of data needed for 15 frames per second - you'll need a carrier frequency that is somewhat (5x to 10x) higher as a minimum for ASK or much higher if you want FM. If you want more gray scale depth, then you'll need to transmit 4x the number of bits for 16 shades of gray per pixel.

which class is thus for?
Just trying to make sure I understand the response, so if I transmit a 200 x 200 image, that is a black and white image at 15 frames per second, I will need a 2 megahertz bandwidth signal, not including timing information?
 

MrSalts

Joined Apr 2, 2020
2,767
Just trying to make sure I understand the response, so if I transmit a 200 x 200 image, that is a black and white image at 15 frames per second, I will need a 2 megahertz bandwidth signal, not including timing information?
It depends. What encoding will you use? And, as I said, that method with no carrier frequency will not reach your 100 mile target with reasonable transmitter efficiency. .
 

Thread Starter

Man10

Joined Jul 31, 2018
163
What frame rate? What kind of compression? If you are really looking to transmit at a low carrier frequency, you want to use the minimum frame rate that is acceptable and use as much compression as you can.

Then there's the matter of what encoding you are going to use and what modulation technique.

How much power are you going to use? The higher the signal to noise ratio, the more bits you can cram into one symbol and the further away it can be picked up by a distant receiver.

Which brings up the question of how sensitive is the receiver?

Is the transmitter using a directional antenna, or an omni?

What about the receiver?
You asked what kind of compression. Can you give me a list of the compression techniques, that I could use to transmit video information via radio waves?
 

DickCappels

Joined Aug 21, 2008
10,226
Just trying to make sure I understand the response, so if I transmit a 200 x 200 image, that is a black and white image at 15 frames per second, I will need a 2 megahertz bandwidth signal, not including timing information?
You can probably do it with 1 MHz given your frame rate, and that would include timing pulses
 

WBahn

Joined Mar 31, 2012
30,239
I don't see any indication that this is about actually transmitting anything. It looks more like a hypothetical question (particularly in light of an earlier thread). There's a lot that would have to happen between this discussion and an actual implementation.
 

Ya’akov

Joined Jan 27, 2019
9,230
There is an additional problem that has not been addressed: the specified propagation.

You will not be able to transmit “100 miles without a repeater” reliably on any terrestrial band without outrageous power. If you choose in or just above the MW (Medium Wave) band, you’d need kilowatts of power to achieve any sort of reliability and there would still be issues with fading and other troubles. This means you’d need error correction which would increase the required band width and higher frequencies would change the propagation.

The mode of propagation has an effect of the distance and, ironically, you would start to be able to transmit farther but not “close” to you (in this case 100 miles). If you could deal with spotty coverage and crappy video, you could probably manage it with a ~2MHz signal at, say 10kW (to achieve at least some consistency) but day-to-day you would not know just how well it would work and at might, when the D layer goes away, you‘d be transmitting maybe 1000 miles instead of 100.

This is all a long way to saying that your parameters fail to take into account reality. The question of minimum frequency in theory is a simple math problem. If you add in propagation, it becomes a practical problem whose parameters make a solution unworkable.

This brings me to ask, what problem are we imagining being able to do this would solve? Without knowing why you are trying to figure this out, there is no way to actually help answer in a meaningful way since you are including implementation specific parameters along side theoretical questions.

The right way to ask something like this is, “If I wanted to be able to transmit video of (specific type) directly over a distance of 100 miles while limiting the frequency of the transmission as much as possible in order to accomplish (some goal), what what frequency and other parameters would work?”

But, since you don’t know some things that make such a question possible, the question would be something like “I want to do X and I have constraints Y, how do I do it?” Where X is the problem to be solved (not transmitting video, but the problem the video transmission solves) and Y is anything that you know you can’t or must do as part of that (not minimum frequency but the problem minimum frequency answers).
 

Thread Starter

Man10

Joined Jul 31, 2018
163
I am trying to learn how to design radio communications systems.
I think this exercise is helping a lot. let's say hypothetically I build a 1 megawatt transmitter and the receiver can detect a 1 milliwatt signal. I use mpeg compression and an amplitude modulated signal. The radio signal will transmit a 200 x 200 picture( that is black and white ) at 15 frames per second. What is the lowest frequency that has enough bandwidth to transmit live video over a distance of 100 miles without a repeater?
 
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