Hi.
Somewhere, perhaps this forum, decades ago, someone put an antenna to the output of a channel 3 TV RF modulator gadget and received the signal short range over-the-air within dwelling televisions.
What is the RF output level supposed to be ?

 

Google AI states:
"For a standard NTSC analog TV RF input, the ideal signal level at the tuner ranges between 0 dBmV and +15 dBmV (roughly 60 to 75 dBμV) into a 75-ohm impedance, with +3 dBmV to +10 dBmV being the operational sweet spot for a clear, snow-free picture."
so I would expect the modulator output to be within that range.

Since you want to abolish the deciBel, I'll translate:
10dBmv is approximately 3.1mV.

You do realize that it outputs an NTSC analog standard definition signal, not the ATSC digital high-def format, so you have to check if your TVs can accept that.

If you want a high-def ATSC modulator, those appear to be at least an order of magnitude more expensive.
Alternately you can buy HDMI wireless transmitters with more than one receiver.

 

The amplitude of the RF output of one of those RF adapters (they are not really "modulators") is quite low. .
It does not bear any relation to the standard amplitude of an analog composite video signal, which I have measured on a scope to be about one volt. (several years ago) The FCC regulation used to have the limits at 100 MILLIWATTS.

 

they are not really "modulators"

Don't understand why you say that(?).
They modulate the output RF with the video and audio inputs to the NTSC standard.

 

A "modulator" is the portion of a circuit that usually modulates an RF signal. So those are "RF Interface " devices, or "micro-transmitters".
Certainly they may deliver a modulated RF signal, but to call them a"modulator" is not corect, technically. Modulator without a signal source to be modulated is certainly an incomplete system. YES, it is a commonly used term among those unwilling to provide a complete description.

 

A "modulator" is the portion of a circuit that usually modulates an RF signal

That's exactly what that modulator circuit does.
Why do you think it doesn't?

Modulator without a signal source to be modulated is certainly an incomplete system

That makes little sense.
The signal source (the video and audio) is not what's modulated.
The RF generated by the modulator's internal oscillator is being modulated by the signal source.

 

Referencing post #1, calling a video link transmitter a "modulator" does not make it a modulator. It is still a video signal RF generator.
Socially acccepted shortcuts in terminology can certainly lead to confusion among those used to being precise in device descriptions. Like calling a motorcycle a "MOTOR" can be confusing to the folks who are more used to electric motors as the devices to convert electrical energy into rotary motion, rather than 2-wheeled transportation devices.
I looked on my shelf today and I did see two of them clearly marked as "modulators". And just as obviously they contain much more that the modulator part of the circuit. They also onclude mains powered DC power supplies, and the stable carrier frequency oscillators.
So those are "RF Interface " devices that have been marked as "modulators" because many people have seen them called that.
So the word now is a slang term for an RF interface module with an included mains powerd DC supply.

 

calling a video link transmitter a "modulator" does not make it a modulator. It is still a video signal RF generator.

You still haven't clearly explained why you think that device is not a modulator, as it clearly is modulating the RF carrier with the video and audio inputs.
What is your definition of "modulator" that does not fit the function that unit performs?
Arm-waving and saying it isn't, does not make that statement true.

 

Referencing post #1, calling a video link transmitter a "modulator" does not make it a modulator.

Referencing post #1, the device in post #1 is not a video link transmitter. It is cable in, cable out, and has no intentional radiated fields of any nature. The TS is asking about using it as a transmitter, but that does not change what the device is. It modulates video and audio onto an RF carrier. Hence, it is a modulator.

ak

 

Referencing post #1, the device in post #1 is not a video link transmitter. It is cable in, cable out, and has no intentional radiated fields of any nature. The TS is asking about using it as a transmitter, but that does not change what the device is. It modulates video and audio onto an RF carrier. Hence, it is a modulator.

ak

The second view of that device, in the same post #1, clearly shows video and audio inputs as well as a power supply input. OF COURSE, it ALSO includes an "F" connector loop-thru connection just like many cable boxes do, for another RF input, either antenna or??? MOST older VCR devices also included that pair of "F" connectors, one tagged "TV" and theother tagged "CABLE".
The device first must include an RF source to be modulated. That is why they usually include a channel 3/4 switch. To provide the modulated RF on either channel.
Once again: calling an item by an incorrect name does not alter what it actually is. Certainly the device includes a modulator, but it also includes the RF signal source that is modulated. So really it is much more than just a modulator.
Colloquial use does not alter reality. BUT it can certainly obscure it.

 

So really it is much more than just a modulator.

Yes the active a modulator with a built-in RF source.
The rest of the functions are just passive.
So if we call it a modulator with a built-in RF source, that would satisfy your pedantic concerns???

 

Yes the active a modulator with a built-in RF source.
The rest of the functions are just passive.
So if we call it a modulator with a built-in RF source, that would satisfy your pedantic concerns???

Since a big part of my career required getting descriptions correct, including those pesky details, it is still a part of my nature to prefer correct descriptions of stuff.
That may not be a big deal to a lot of folks until they order something that does not arrive including what was assumed to be included.
In block diagrams of radio transmitters, the modulator is separate from the signal source string, in a separate block. Of course, in many video players, both tape and disk, the entire RF output system is one small block. AND that does typically get called "the modulator", so it is no wonder that the name use has been confused.

 

A more correct term is "transmitter", since it includes both the carrier generation section as well as the modulation section.
Certainly it is a challenge to attempt to correct misuse of words by those who see no need at all to use the correct term when providing a name for something, because often the discussion is only among a small group.

An interesting project would be to use one of those devices as strictly acarrier signal generator, with FM audio, to feed an actual power amplifier stage, or two, and then modulate the carrier to finally deliver several watts of amplitude modulated video and audio. That could provide a neighborhood TV station, is suitable program material was available.

 

A more correct term is "transmitter", since it includes both the carrier generation section as well as the modulation section.

Not in my book.

I also think the same, that the common meaning of transmitter is something that generates a signal to be broadcast wirelessly.
The "Modulator" in question here is not designed for that purpose (although that's what the TS wants to use it for).

 

Certainly that little module WILL TRANSMIT if it gets connected to an antenna. Connecting a VCR incorrectly, to an outside antenna, will provide a signal that the folks nearby can view. But mostly folks do not tune to channel three. I have not experimented to see how far it could be viewed using an indoor set of "Rabbit Ears" for the antenna. My guess is a few hundred feet, if the receive antenna was good. That would be an interesting experiment!

 

So here, again, we have a confusing use of a word because previously a technically illiterate writer used it incorrectly. That is often how terms become confusing: some widely read unknowing individual misuses some term and other folks are mislead, not seeing that the word or words are incorrect for what is actually meant. And, often, anyone attempting to effect a correction is accused of being picky or pedantic, or obsessive. And others just think that it does not matter, since the inaccuracy in the meaning is lost on them.
Consider the incorrect performance of some electronc system if some portion of the circuit is omitted, and the effect on some electronic system if some portion is not included.