Re: Using an FM-Carrier for the Y [Luminance] Signal -- how to relieve the bandwidth issue?

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3 total messages Started by Green Xenon [Radium] Mon, 24 Sep 2007 04:50

#166

Author: Green Xenon [Radium]
Date: Mon, 24 Sep 2007 04:50

57 lines
3874 bytes

On Sep 23, 3:02 pm, Brendan Gillatt 
<brendanREMOVET...@brendanREMOVETHISgillatt.co.uk> wrote in 
http://groups.google.com/group/uk.tech.digital-tv/msg/4c903b0a453a39fa :

 > Okay now you're actualy irritating me quite a LOT.

How so? I am just asking extremely interesting questions about video 
technology.

 > Please, do yourself a favour: buy an Amazon book voucher and shut up.

I�ve tried painfully hard to answer my questions doing my own research 
-- including reading information from books. I still haven�t found 
answers to my questions. That is why I am turning to NGs for assistance.

Is Quadrature Frequency Modulation used? What for?

AFAIK, Quadrature Amplitude Modulation uses a combo of AM and 
Phase-Shift-Keying.

So QFM would use a combination of FM and PSK. Would this decrease the 
bandwidth required for broadcasting FM luminance video signals?

I did a Google Search for �Quadrature Frequency Modulation� on 
http://www.google.com/search?hl=en&lr=&q=%22Quadrature+Frequency+Modulation+%22&btnG=Search

None of those pages made any sense to me.

One major reason the luminance signals of television are broadcasted on 
an AM-carrier instead of an FM-carrier is because FM requires large 
amounts of bandwidth. Is there a way to use FM video without hogging so 
much bandwidth using QFM?

Quotes from 
http://groups.google.com/group/sci.electronics.basics/msg/0c013cf5371da8dc?hl=en& 
:

 > Multiple-level quadrature modulation,
 > "constellation modulation",
 > is most common for packing
 > lots of bits per Hz of bandwidth.
 > The more you pack,
 > the better the s/n ratio has to be.
 > http://en.wikipedia.org/wiki/Quadrature_amplitude_modulation
 >
 > http://en.wikipedia.org/wiki/Constellation_diagram

Does this mean that the FM-equivalents-of-QAM and Constellation 
Modulation can -- at least in theory -- be applied to FM video so that 
excessive bandwidth is not needed? If so, then what would be the minimum 
radio-frequency required to transmit the video signal? Is a 150 kHz 
radio-frequency sufficient to be an FM carrier for this video signal?

Constellation modulation is a type of AM. What�s the FM-equivalent of 
constellation modulation?

Has multiple-level QFM ever been used for video before?

Re: Using an FM-Carrier for the Y [Luminance] Signal -- how to relieve the bandwidth issue?

#168

Author: Brendan Gillatt
Date: Mon, 24 Sep 2007 15:36

33 lines
3185 bytes

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Green Xenon [Radium] wrote:
> On Sep 23, 3:02 pm, Brendan Gillatt
> <brendanREMOVET...@brendanREMOVETHISgillatt.co.uk> wrote in
> http://groups.google.com/group/uk.tech.digital-tv/msg/4c903b0a453a39fa :
> 
>> Okay now you're actualy irritating me quite a LOT.
> 
> How so? I am just asking extremely interesting questions about video
> technology.
> 
>> Please, do yourself a favour: buy an Amazon book voucher and shut up.
> 
> I�ve tried painfully hard to answer my questions doing my own research
> -- including reading information from books. I still haven�t found
> answers to my questions. That is why I am turning to NGs for assistance.

AGGGHHHHH.... plonk

- --
Brendan Gillatt
brendan {at} brendangillatt {dot} co {dot} uk
http://www.brendangillatt.co.uk
PGP Key: http://pgp.mit.edu:11371/pks/lookup?op=get&search=0xBACD7433
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Re: Using an FM-Carrier for the Y [Luminance] Signal -- how to relieve the bandwidth issue?

#170

Author: Brian Gregory [UK]
Date: Mon, 24 Sep 2007 18:08

37 lines
3446 bytes

"Green Xenon [Radium]" <glucegen1@excite.com> wrote in message 
news:46f73fc6$0$32520$4c368faf@roadrunner.com...
> On Sep 23, 3:02 pm, Brendan Gillatt 
> <brendanREMOVET...@brendanREMOVETHISgillatt.co.uk> wrote in 
> http://groups.google.com/group/uk.tech.digital-tv/msg/4c903b0a453a39fa :
>
> I�ve tried painfully hard to answer my questions doing my own research --  
> including reading information from books. I still haven�t found answers to 
> my questions. That is why I am turning to NGs for assistance.
>
> Is Quadrature Frequency Modulation used? What for?
>
> AFAIK, Quadrature Amplitude Modulation uses a combo of AM and 
> Phase-Shift-Keying.
>
> So QFM would use a combination of FM and PSK. Would this decrease the 
> bandwidth required for broadcasting FM luminance video signals?
>
> I did a Google Search for �Quadrature Frequency Modulation� on 
> http://www.google.com/search?hl=en&lr=&q=%22Quadrature+Frequency+Modulation+%22&btnG=Search
>
> None of those pages made any sense to me.

I had a quick look at a few of them.

Some guy seems to be trying to patent something he calls Quadrature 
Frequency Modulation. I see this as similar to the many perpetual motion 
machines that get patented.

If it works at all I can't see it offering anything different from QPSK (aka 
QAM4) in performance or bandwidth requirements.

-- 

Brian Gregory. (In the UK)
ng@bgdsv.co.uk
To email me remove the letter vee.

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