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ATV theory
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? On a side note, what's the lowest carrier frequency ATV can operate on before the video signal degrades or begins aliasing? Thanks in advance for any information! Dave |
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http://ac6v.com/opmodes.htm#A -- Lamont Cranston The Shadow Knows "David Harper" wrote in message om... 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? On a side note, what's the lowest carrier frequency ATV can operate on before the video signal degrades or begins aliasing? Thanks in advance for any information! Dave |
TRY SEVERAL LINKS AT URL:
http://ac6v.com/opmodes.htm#A -- Lamont Cranston The Shadow Knows "David Harper" wrote in message om... 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? On a side note, what's the lowest carrier frequency ATV can operate on before the video signal degrades or begins aliasing? Thanks in advance for any information! Dave |
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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. Gotcha...thanks for the response! However, based on what you've said, "what if" I were to do what I described on AM? Technically, assuming you were using a high enough frequency to prevent aliasing, you "could" transmit a video signal with a simple AM transmitter and receiver...or am I mistaken? Thanks in advance! Dave |
David Harper wrote in message om... wrote in message . .. On 21 Jun 2004 10:06:11 -0700, (David Harper) wrote: I have a question in regards to the theory of ATV. snip Gotcha...thanks for the response! However, based on what you've said, "what if" I were to do what I described on AM? Technically, assuming you were using a high enough frequency to prevent aliasing, you "could" transmit a video signal with a simple AM transmitter and receiver...or am I mistaken? Thanks in advance! Dave Most (all?) ATV activity on 70cm is AM. You still have the video bandwidth requirements in your modulation circuits and getting the modulation linearity needed for a good picture isn't trivial. |
David Harper wrote in message om... wrote in message . .. On 21 Jun 2004 10:06:11 -0700, (David Harper) wrote: I have a question in regards to the theory of ATV. snip Gotcha...thanks for the response! However, based on what you've said, "what if" I were to do what I described on AM? Technically, assuming you were using a high enough frequency to prevent aliasing, you "could" transmit a video signal with a simple AM transmitter and receiver...or am I mistaken? Thanks in advance! Dave Most (all?) ATV activity on 70cm is AM. You still have the video bandwidth requirements in your modulation circuits and getting the modulation linearity needed for a good picture isn't trivial. |
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