This here is an analog video camera. This here is also a camera but is placed inside
a screw shape so it could be used as a spy camera of your enemies, those who are stealing
your resistors for example. LOL. Anyway, these days we can still see these cameras on FPV
drones or CCTV systems for security. The signal out of these is something like this. Difficult
to understand but it looks like it has a repetitive pattern. Interesting, why would that be? Hmm.
In this video I will try to make the simplest analog video transmitter and send this signal
over the radio frequencies and make our homemade spy camera. This circuit is easy to make and
requires just a few components. I’ll do my best to explain you how analog video signal
works, more or less, and since I still have my analog black and white TV from the vintage
teardown video, let’s see if I’ll be able to receive the video signal and display that
on the analog TV. So guys, let’s get started.
What’s up my friends, welcome back. Here’s what I’m going to do. I will first show
you and explain the analog video signal with the help of my oscilloscope. Then we will
take a look over the simplest analog video transmitter circuit and I’ll mount that
circuit on a prototyping PCB. Then we connect the signal from these cameras to that circuit
and test if we are able to receive anything so stick around.
So, a few months ago I’ve ordered these analog cameras from AliExpress for just a
few dollars. This one is a bit bigger and is mostly for FPV drones so you can see in
real time what the drone is seeing on this kind of googles.
These other two are smaller and could be used as spy cams. I’m not recommending spy cams
and I’m against the idea of placing these in public places but I still want to learn
how this works, that’s why I’m making this video.
These cameras work at 12V but be careful, sometimes they require only 5V or below that
value. I guess these ones have a voltage regulator of some sort, but that’s good for us because
in that way we can supply both the camera and the transmitter with the same voltage,
let’s say 12V. Red wire, is VCC, black is ground and the
yellow is the video signal. If the camera also has a white cable, that’s means it
also has a microphone and audio output. I connect the yellow cable to my oscilloscope
and we get this signal. This is the analog video signal that was used with analog TVs
back in the days. Each of these repeating signals represents one frame or one “picture”.
The frame starts with low pulse called thew “sync tip”. This pulse is used to synchronize
the frame rate of the signal with the framerate of the TV. So, each time the TV detects this
low pulse it will know that a new line for a new frame is coming in.
The next part of the signal is the so-called color burst and that’s for color TVs and
I’ll explain it in a moment. The rest are the actual “pixels” of the picture. I
put emphasis on “pixels” because this is analog so we have continuing lines of light
so this part of the signal represents the luminance values. The higher the signal is,
the more will the light shine on the TV.
So the electron beam from the TV ray-gun will start from the top left corner and depending
on this received signal it will change the amount of light, where low signal represents
a dark pixel and high signal represents a white pixel and we can get some sort of grey
color with in between values. But at the same time, this electrons beam is moving line by
line over the screen so those luminance values are now translated to dots of light from the
final picture. Do this fast enough and we get the real picture.
As you can see if I cover the camera, so we have a dark picture, the entire signal is
a low value. And if I place a flashlight in front of the camera so the entire picture
is white, we get a straight line of high values. Remember that small burst signal at the beginning
of each frame. These few oscillations will give the TV the oscillator of the color modulation.
If the TV is black and white will only work with the luminance signal. But if is color,
it also needs RGB information. So, if we make a zoom, you can see that the luminance signal
has another signal overlapped which is at a way higher frequency, and that has information
about the color. So, using this color sync burst, the TV locks on that frequency and
can demodulate the color information as well. Now we need to send this signal and for that
I will use this schematic which is very common on the internet, just google analog video
transmitter and you will get a lot of circuits like this. Since we are only sending video,
we can get rid of the audio part but if you also want to send audio, you can use the full
schematic. As you can see, we need some resistors, capacitors,
a coil, a small NPN transistor, a potentiometer, a diode and a wire for the antenna. I get
a prototyping PCB and I start soldering all the components, but first, what is each block
doing inside the circuit. Well, the coil and the capacitor is creating a so called LC tank.
This, as we have seen in so many previous tutorials, will resonate at a specific frequency.
That frequency will be our carrier and it must be high frequency since the very high
band of the analog TV works between 174MHz and 216 Mhz. Then we take the video signal
and we make the convolution with this carrier, so now the high frequency signal will carry
our video signal and since we have the antenna connected, this will create an electro-magnetic
wave which are basically radio waves and now the TV can read that signal and make the demodulation
process and show the pictures on the screen. If you want to know how this analog TV works,
watch my previous vintage teardown video. Instead of the LC tank to create the carrier
frequency, some circuits are using a crystal oscillator with a specific frequency. You
could also try that if you want. To make the coil I get some copper wire and make 3 loops
and 8mm diameter. Peal the enamel from the tips and add some solder. I first mounted
the circuit on the breadboard and instead of a 30pF capacitor I’ve used a variable
capacitor. So, in that way I was able to test the circuit for best results and then measured
the capacitor and it was 30pF so I’ve used that value for the final circuit.
I solder the components. I solder the voltage divider and then the two capacitors. Then
I solder the coil with the capacitor for the LC tank and also the BJT transistor and the
rest of the components. I have the PCB and I cut it to size and also find a place for
the camera as well and solder the wires to VCC and the video input. For the antenna I’ve
just used a copper wire. Now we can supply this to a 12V battery and test it out.
Start the TV and put it in VHF range of frequencies. I start rotating the knob and after a few
seconds of tunning, there we have it. I receive the video from the small transmitter. Isn’t
this amazing? The circuit is simple but this technology is still amazing knowing is so
old. Now you might need to tune a bit the circuit with the potentiometer or with a variable
capacitor. Also, if the frames are moving up and down, usually, the TVs have a synchronizing
dial so rotate that till you get steady frames.
So guys, that’s how analog video works, more or less,
and that’s how you can make a video transmitter. Check all the schematic
below on electronoobs.com and also the different cameras I had in this video and start testing
around different configurations. You can find small analog TV receivers for very cheap and
with that create your own FPV system. I don’t know for sure the range of this circuit, but
maybe you could mount it, test it and share your results. I hope that you have learned
something new, if so, comment below or give me a like. Thanks again and see you later guys.