RadioBanter - View Single Post

June 22nd 04, 12:28 AM

On 21 Jun 2004 10:06:11 -0700, (David Harper)
wrote:

I have a question in regards to the theory of ATV.

If I were to run a video signal straight into, say, a 70cm transmitter
(staying within the linear range of the transmitter's input, i.e. not
clipping) and had a receiver that had a video out / TV connected to
the reciever's output (and could adjust the amplitude of the output
signal), would that work?

Or do most "standard" (audio) transmitters/receivers have limitations
about the maximum frequency they can modulate/de-modulate? It seems
to me that the latter would be the only reason that ATV equipment
would be nessesary. Or is there some other reason this scenario would
not work?

That's it: The video signal has a bandwidth of a few MHz and needs
frequency response down to DC. It's way beyond what the average
transceiver is capable of.

The average radio has frequency response from 100 Hz to 3.5 KHz or so.
Using direct discriminator/varactor connections gives wider response,
but not wide enough. Dedicated ATV equipment is needed.

On a side note, what's the lowest carrier frequency ATV can operate on
before the video signal degrades or begins aliasing?

440 is the lowest band ATV is allowed on.

Thanks in advance for any information!
Dave

ATV is a neat mode. Have fun!