Walkie-talkies into vidoe transmitters - Electronic Circuits Projects Diagrams Free

Imnewtothis · 29th January 2007, 01:12 AM

Hey, i have 5 cheap walkie-talkies from places like walmart and target that are all on the same frequency. And I'm wonderin' if it is possible to turn them into video transmitters and receivers. Ive tried to hook video straight into the mic input, but all i get on the receiving end are lines across the tv screen.
I would greatly appreciate any help that u can give.

audioguru · 29th January 2007, 01:27 AM

The walkie talkie has an audio bandwidth of only 3kHz. Video needs a bandwidth of at least 6MHz, two thousand times more.

Russlk · 29th January 2007, 01:43 AM

Do a Google search for slow scan TV. Radio Amateurs use it in an audio bandwidth.

Imnewtothis · 29th January 2007, 02:13 AM

Thanks, ok. so is there any way to cheaply build a video transmitter? And please don refer me to searching the old posts. Ive sped-read through the stuff lots of times, but if it aint gibberish its that i cant do it, or it wont work.
But thanks for takin the time to answer my questions!

Imnewtothis · 29th January 2007, 02:17 AM

Dude!!!!!! I def cant spell. the headline should be "Walkie-talkies into video transmitters " sorry people.

RadioRon · 29th January 2007, 02:56 AM

http://www.epanorama.net/links/video...ml#transmitter

scroll down to Video Transmitters

ericgibbs · 29th January 2007, 09:58 AM

hi audioguru,
Its possible that you already know, but just in case.
Others maybe interested.

Baird transmitted tv video from the UK to USA in 1928 using shortwave radio.

EricG

**Nigel Goodwin** · 29th January 2007, 11:24 AM

Quote:

Originally Posted by ericgibbs

hi audioguru,
Its possible that you already know, but just in case.
Others maybe interested.

Baird transmitted tv video from the UK to USA in 1928 using shortwave radio.

Was it colour and HD?

The original Baird TV system was very low resolution, and only used fairly low frequencies for transmission - although they weren't that low for the time of course!.

stevez · 29th January 2007, 12:18 PM

A small but important point is that those devices are legal if used as directed by the manufacturer. Modification or use for another purpose is likely to be illegal. My warning has less to do with points of law and more to do with interfering with other services - some of these could be critical. Stuffing a video signal into your W-T could generate a lot of RF garbage. It certainly won't be powerful but even a few milliwatts in the wrong spot can create a problem.

**Nigel Goodwin** · 29th January 2007, 12:29 PM

It wouldn't really do any harm, unless you're overdriving it, as the audio and modulation circuits will limit it to the speech bandwidth it's designed for. It won't work at all, but it shouldn't cause any problems.

stevez · 29th January 2007, 12:41 PM

I'm not sure that in this case the experimenter would know whether or not he was overdriving it.

audioguru · 29th January 2007, 01:02 PM

The experimenter already tried cramming a line-level video signal into a microphone input (without the proper attenuation?). If he wants good resolution then his video bandwidth most likely will exceed the carrier frequency (27MHz) of his cheap walkie talkies.

In the '90's I was doing audio teleconferencing and video teleconferencing. Some video systems used only two phone lines to transmit and receive highly compressed "jerky vision". The companies who could afford wide bandwidth had pretty good video.

stevez · 29th January 2007, 03:34 PM

I suppose that if you had all day you could send enough information and put it together to make a nice picture - one at a time. That's probably what they did and still do with spacecraft. You really couldn't send live video - that's the bottom line.

G8RPI · 29th January 2007, 03:41 PM

Quote:

Originally Posted by Nigel Goodwin

It wouldn't really do any harm, unless you're overdriving it, as the audio and modulation circuits will limit it to the speech bandwidth it's designed for. It won't work at all, but it shouldn't cause any problems.

As these transmitters are built to a cost they generally don't have input ALC, but rely on the microphone chacteristics. Stuffing 1V of video will almost certainly overdrive them. This can be a serious problem as in the USA these radios operate on frequencies between commercial two-way radio channels. Overdriving them can disrupt repeaters causing lots of problems!

It is illegal to modify them in any way.

You can buy 2.4GHz video senders cheaply, I'd go that way.

Robert.

**Nigel Goodwin** · 29th January 2007, 03:43 PM

Quote:

Originally Posted by G8RPI

You can buy 2.4GHz video senders cheaply, I'd go that way.

Bit tough if you've got wireless broadband though! - or if anyone nearby has!.

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29th January 2007, 01:12 AM	(permalink)
Imnewtothis	Walkie-talkies into vidoe transmitters Hey, i have 5 cheap walkie-talkies from places like walmart and target that are all on the same frequency. And I'm wonderin' if it is possible to turn them into video transmitters and receivers. Ive tried to hook video straight into the mic input, but all i get on the receiving end are lines across the tv screen. I would greatly appreciate any help that u can give.

29th January 2007, 01:27 AM	(permalink)
audioguru	The walkie talkie has an audio bandwidth of only 3kHz. Video needs a bandwidth of at least 6MHz, two thousand times more. __________________ Uncle $crooge

29th January 2007, 01:43 AM	(permalink)
Russlk	Do a Google search for slow scan TV. Radio Amateurs use it in an audio bandwidth. __________________ see my website: www.geocities.com/russlk

29th January 2007, 02:13 AM	(permalink)
Imnewtothis	Thanks, ok. so is there any way to cheaply build a video transmitter? And please don refer me to searching the old posts. Ive sped-read through the stuff lots of times, but if it aint gibberish its that i cant do it, or it wont work. But thanks for takin the time to answer my questions!

29th January 2007, 02:17 AM	(permalink)
Imnewtothis	Dude!!!!!! I def cant spell. the headline should be "Walkie-talkies into video transmitters " sorry people.

29th January 2007, 02:56 AM	(permalink)
RadioRon	http://www.epanorama.net/links/video...ml#transmitter scroll down to Video Transmitters __________________ RadioRon

29th January 2007, 09:58 AM	(permalink)
ericgibbs	hi audioguru, Its possible that you already know, but just in case. Others maybe interested. Baird transmitted tv video from the UK to USA in 1928 using shortwave radio. EricG

29th January 2007, 12:18 PM	(permalink)
stevez	A small but important point is that those devices are legal if used as directed by the manufacturer. Modification or use for another purpose is likely to be illegal. My warning has less to do with points of law and more to do with interfering with other services - some of these could be critical. Stuffing a video signal into your W-T could generate a lot of RF garbage. It certainly won't be powerful but even a few milliwatts in the wrong spot can create a problem. __________________ stevez

29th January 2007, 12:29 PM	(permalink)
Nigel Goodwin	It wouldn't really do any harm, unless you're overdriving it, as the audio and modulation circuits will limit it to the speech bandwidth it's designed for. It won't work at all, but it shouldn't cause any problems. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

29th January 2007, 12:41 PM	(permalink)
stevez	I'm not sure that in this case the experimenter would know whether or not he was overdriving it. __________________ stevez

29th January 2007, 01:02 PM	(permalink)
audioguru	The experimenter already tried cramming a line-level video signal into a microphone input (without the proper attenuation?). If he wants good resolution then his video bandwidth most likely will exceed the carrier frequency (27MHz) of his cheap walkie talkies. In the '90's I was doing audio teleconferencing and video teleconferencing. Some video systems used only two phone lines to transmit and receive highly compressed "jerky vision". The companies who could afford wide bandwidth had pretty good video. __________________ Uncle $crooge

29th January 2007, 03:34 PM	(permalink)
stevez	I suppose that if you had all day you could send enough information and put it together to make a nice picture - one at a time. That's probably what they did and still do with spacecraft. You really couldn't send live video - that's the bottom line. __________________ stevez