Question LSB + USB + Carrier (AM Signal Reconstruction)

Welcome to the forum. This is a good technical question. My opinion, in the USA you are allowed to have more than one transmitter so if each transmitter is operating by rules there's no problem but as for your question about the sidebands, are you saying that 2 transmitters would be transmitting slightly off carrier where the 100mW would be in the sidebands? And one transmitter right on carrier thinking this is a way to go farther(get more range) using 3 transmitters instead of one....just so I am understanding right?
This is where we need Rich who was the expert in all this technical stuff but my opinion only, I don't think it would work...I see what you are saying but there would be interference between the transmitters as the sidebands are only 5klz above and below the carrier and I'm sure there would be interaction between the carrier and 2 sidebands with the transmitters in close proximity. Is there anything in the rules about transmitting on sidebands?  That's another subject that could be brought up here. 

This is a new one that has never been discussed here. And it's hard to find new things that haven't been talked about.

Here is a link to a discussion surrounding synchronizing multiple (in this case 2) Part 15 transmitters.

As discussed, there will be technical issues.

And I thought I had seen somewhere that the FCC frowns upon what they call coordinated systems, i.e., multiple transmitters for a single purpose operating above the levels of a single Part 15 transmitter. 

What Chard is saying is each transmitter will be operating in a different frequency. One in the upper side band, one in the lower side band and one in the middle(carrier) not as the post Artisan linked where two transmitters would be operating at the same carrier. But I think still there would be interaction between the three. And then besides how do you do that, there's the question of the legality of doing that. Isn't there separate broadcasts on the sidebands as some radios have SSB reception? 

I know we all look for loopholes to try to get more range. And the big question here is can you broadcast specifically with part 15 on the sidebands? And can transmitters be modified to do that? You need a carrier reference in the sidebands.

Here's some info on sidebands, and why this may not work.....

Thanks for the responses!

As Mark pointed out, I don't think synchronized transmitters and what I'm proposing is the same at all. That thread seemed to be about using multiple transmitters to essentially boost a single signal, acting like one intentional radiator, but over powered.

What I'm picturing here is three completely separate, independent transmissions that don't interact or overlap with each other.

For example, on 1610 kHz, imagine this:
Transmitter 1: A lower sideband signal, running from 1605.0 kHz to 1609.7 kHz at 100 mW.
Transmitter 2: A super-narrow carrier signal at 1610.0 kHz, also at 100 mW.
Transmitter 3: An upper sideband signal, running from 1610.3 kHz to 1615 kHz, again at 100 mW.

I got this idea while poking around the FCC rules for HF/Shortwave broadcasting. Normally, SSB transmissions (the kind used for amateur and two-way radio) suppress the carrier completely. But the FCC's rules actually require shortwave broadcasters to include a small carrier, as a hack for AM receivers.

Specifically, 47 CFR 73.757(b)(6) says the carrier needs to be there "...to allow SSB (USB) emissions to be received by conventional DSB receivers with envelope detection without significant deterioration of the reception quality."

That got me thinking: if they want a carrier to help with reception, and we have one sideband, what's to stop a Part 15 broadcaster (in the AM band) from transmitting the other sideband separately, with the full 100 mW (instead of 16.5 mW)?

Each of the two sideband signals could be picked up on its own by an LSB or USB receiver. And the carrier could be picked up on its own with a CW receiver I think. They don't overlap, and they're all distinct, separate signals.

Mark, I get what you're saying about interference. This is an unknown to me. But from what I've read in reviews, some of the newer SDRs are said to produce incredibly clean SSB signals. Thanks for the video, I'm going to check it out in a bit!

So after watching that video and doing a bit more digging, I think I've learned a bit more. It looks like having separate antennas might cause the signals to arrive out of phase at the receiver, which could totally mess up the sound or even make it unlistenable on a car radio. I probably need to think this part through a bit more!

The reason I included the entire thread in the link I provided was mainly the discussion around the FCC and coordinated installations.

Regardless of whether you're synchronizing transmitters, or using multiple transmitters to increase signal strength, if the FCC considers what you're doing with these transmitters is coordinated, you could be in trouble.  You're not allowed a coordinated installation that gives you greater range than a single, Part 15 legal, transmitter.

Whether what you want to do is technically feasible, I'm not sure.  Why not do what the shortwave stations do, leave a small carrier, and increase the strength of the sidebands with a single transmitter.  This should be possible using an SDR/SDT(ransmitter).

I'm a radio amateur, and own several Quansheng UV-K5's, which  have the ability to hack the firmware.  An amateur somewhere has given this FM transmitter the ability to transmit in DSB (without the carrier), but I'm sure it would be possible to use this technique to add in a small carrier.  So it is technically feasible in this fashion.  It doesn't have to be done with hardware.

I believe the HackRF SDR/SDT has the ability to transmit down on the AM band.  All the software for it is open source.

Something like this couldn't be done in Canada, as everything we use here has to be certified by ISED.  That's one good thing about the FCC U.S. rules - as long as you're compliant, you'd be OK.

Thank you! Yeah, let me wrap my mind around using a small carrier and boosting the sideband(s) with a single SDR, just like you suggested. Thanks for the tip!