how to transmit video am
bkrdr
If I am not wrong you mentioned FM and AM .
The TV band begins from 40-50 MHz .
Video signal band is about 5.5 - 6.5 MHz(used in TV video in/out, PAL SECAM , NTSC standards ),so you can use modulated signals to transfer video over the radio freq , under assumption that used bandwith is big
enough . But AM freq is not as suitable as FM, due to AM freq propagation behavior ....
Normally , Video signal is transmitted by AM at the frequency above 40MHz . With AM modulation, bandwith is around 4.5-6.5Mhz depend on system( PAL, NTSC, SECAM) . If you want to transmit by FM , the bandwith much bigger.
Hi bkrdr
I think you want to transmit an analog video-signal. As written above you need approximatively 5.5MHz for AM (inkl. mono sound carrier) or about 25MHz for FM.
Video broadcasting is specified in several bands (VHF, UHF) in cable systems there are also other frequencies. But it's normally not allowed to use this frequencies for 'private' video broadcasting. Depending on the country there are some frequency bands which allows a small band transmission over some 100 meters.
Bye
yes it is posibale.
about the bandth , remember that u can comprase your signal !
Transmitting is possible but not allowed for everyone. Ferquency spectrum is devided into bands where legal services operates. Check rules and law for your country. Technically speaking it is not a problem.
If you mean using a standard broadcast receiver, you cannot use full speed video because of the audio bandwidth limit. If you mean sending a still picture, you can if you have enough time.
For several decades hams have been sending still pictures with their voice equipment.
Transmitting is possible by compressing the video signal first using DCT (Discrete Cosine Transform) + DWT (Discrete Wave Transform) and Motion Estimation Detection. By using these techniques we can tranmsmit the video signal as low as 10 Kpb/s.
The above post has a good point. It depends upon the picture quality and the amount of complexity at each end. A DVD output averages 5 Mb/s. At the other extreme is the 40- 50 year old US PicturePhone system which put sort of video on a telephone instrument. Id did not catch on with the customers. There was a camera and display on the telephone instrument so that the talkers could see each other. The signals were sent on the same wires as the audio. The resolution and frame rate were low.
Transmitting is possible by compressing the video signal first using DCT (Discrete Cosine Transform) + DWT (Discrete Wave Transform) and Motion Estimation Detection. By using these techniques we can tranmsmit the video signal as low as 10 Kpb/s. :(
you are all wrong
TV signals are a transition of k3F mode or phastidual sideband
not therefore AM
and only a form of modualted sideband so it a far different mode
it is ment for soaking a wide area while not suffering too much from relections and diverse interferance's
however if it was am the carrier would be modulated
instead of symetricaly recified and used as an injected signal to a double balanced modulator
all that is needed to send video signals across a carrier is a double balanced modulator and 50 to 100mw injected local oscilator
like the contence of a video modulator
however the freq bandwith of forinstance a pal signal is fairly large requiring also 75mhz passband
as said above this is split into various blocks for different signals
this mode is kind of a sideband amplitude modulated and bandwidth modulated transmition mode
with am only a small factor
the real term should be
bandspred interaxial phastidual am suppressed carrier
or a bipas carrier for short
however fm and am will both carry video
when it is digitised easily
am does have propigations problems when used for freq less than 50 mhz
above this only speradic e is a problem so this is seasonal to a vast propotion
for digital vide you need to make a frame store and a frame buffer
and also use a digital camera and capture from it
in digital modes
for fm digital signals work best
but narrow band fm posseses for nice properties for a clean signal from digital equipment
you simply use a ddc to genorate the carrier adding in the data as modulation to the ddc lower order bytes to add the modulation
this way witha very stable transmiter design you can get 64 bits into less then 1 khz bandwidth
infact you can reliably get 1024 signals into a 1.2khz bandwidth
and these methods are used today for digital phones and tv coms
even some security systems use multi modulated secure systems running in less than 1khz
@ 500mhz having 40 cameras
then add this to a carrier thru a modulated vco or local injection oscilator for further amplification
Monkey, do not be overly restrictive in interpreting the question. Taken in the most general way the answers are yes. The US 1kW limited coverage stations use pure AM without the VSB filters. Cross country microwave relay systems in the early days used FM. Television video signals were included in the FDM stack up.
Within pure TV signal dependent on encoding system , audio is modulated on 5.5 or 6.5 Mhz via FM . Video signal are placed below that freq. But what is the lowest TV signal freq .Does it goes down to 0 Hz ? If it isf TV signal - how the double balanced modulator will be applicable ?
Side band is filtered just as it is not needed - carries redundant information and waste bandwith .
At PAL B/G the lowest frequency of picture signal is 25Hz. Double balanced mixer can be used for modulation process but carrier signal with proper amplitude must be added. Maximum modulation depth is 90%. Modulation is negative. After modulation, vestigial side band filter must be used and all necessary corrections must be implemented. That is group delay, differential gain and phase, modulation depth sync amplitude and many others if you want to make decent picture TV transmitter. Sound transmitter cam be made separately or sound signal can be multiplexed with picture signal. And so on.
i think you all missed the
actual asked question
and if you read what i types - my spelling errors
you will see i fully answered it
am and fm tv is highly used
in the us
but digital tv systems are sole invented and patented by the uk...tv industry
therefore only licenced to countrys to use
much like any analogue system
am and fm dosnt support digital tv signals as such
and requires a digital dds or ddc to do the modulations of the bytes for carrier encoding
as i pointed out
and i thought was what the guy asked
maybe i am wrong
im only human and never watch tv signals
only on a scope for 20 years or so
so realy i know nothing
but you pointed out all the things i said anyway were fact ..... not fiction
Double balanced mixer can be used for modulation process but carrier signal with proper amplitude must be added.
you never add a carrier
you add to a carrier
or intermodulate a carrier
so Borber sorry your terms are way wrong
Within pure TV signal dependent on encoding system
?artem pure signal?
this is a contradiction
there is no such thing as a pure !
it is like 0 it dosnt exist and is only convinient
flatulent
i see you interprited what i said
i didnt have all night to write a good text and had planned to edit it later anyway
to add some more info
however
The US 1kW limited coverage stations hahahahahahahahahahahahahaah
ANY us radio ham has a trilawatt amp and a very loud mike
i cant beleve any tv station just has 1k input
unless they transmit down the street 100 yards
so i guess with a good slot
thats what 220,000 watts erp ? or more on a hot sunny day .....
i know this already other than adding the word america {these guys think they are so cleaver
so cleaver we in the uk had to show them how to build a computer and supply them tv and make a standard for them
they do use a pathetic ntsct system
never the same colour twice
america is a long way away and i dont like american goverment policies anyway......
i rest my case....! :P
Hi Monkey,
I was talking about using double-ballanced mixer as modulator and you know that TV AM is not DSBSC. To be more precise: DC ofset is added to if port to get DSB AM.
Well if you are talking about commercial FM or AM, here in the USA and Canada, no and yes.
You can not transmit Fast Scan TV as in commercial TV, because its bandwidth is tooooo wide at 6 MHz
A FM station's bandwidth is much smaller at 200 KHz and an AM station's bandwidth is even much much smaller at only 10 to 15 KHz wide.
Now there is slow scan TV, who's bandwidth is only 3 KHz wide and is able to broadcast along side voice communication over HAM radio such as W7FEN, also an AM Stereo radio station called the RAVEN is transmitting stereo on the AM band along with color slow scan pictures, check out the webb site videoamstereo.com also a video FM station is in the works with a video SCA FM2 station between the stations.
CHOW
---------- Post added at 01:52 ---------- Previous post was at 01:32 ----------
Well if you are talking about commercial FM or AM, here in the USA and Canada, no and yes.
You can not transmit Fast Scan TV as in commercial TV, because its bandwidth is tooooo wide at 6 MHz
A FM station's bandwidth is much smaller at 200 KHz and an AM station's bandwidth is even much much small at only 10 to 15 KHz wide.
Now there is slow scan TV, who bandwidth is only 3 KHz wide and is able to be broadcast along with voice communication over HAM radio such as W7FEN, also a radio AM Stereo station call the RAVEN is transmitting stereo on the AM band along with color slow scan picture, check out the webb site videoamstereo.com also a video FM station is in the works with a video SCA FM2 station between the stations.
CHOW
far out guys
what a random and convoluted bunch of wild answers for such an easy question
Us amateur radio operators have for many many years been transmitting full frame speed video and audio over many different bands using FM. Its dead easy with all the modules that are available on the market these days ... eg the units available to amateurs at ATV Special Offers, Pakage Deals and Offers Amateur Televsion
ATV (Amateur TV) has a bandwidth of ~ 8.5 MHz
We rarely use AM TV these days its just so much more difficult and messy to use vesidual sideband that to use FM. I have used Gunn Diode oscillators to
produce FM tv transmissions on 10GHz and 24GHz see down the page at ....
Amateur TV for some of my activities
some guys are also using digital transmissions following the format of terresterial digital tv transmissions so that we can use standard set top boxes as receivers
cheers
Dave
VK2TDN