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I've seen what this is a counter proposal to on a wed-based SDR, and there were ten carriers within a 5 kHz space. The 10 carriers were switching on and off. It

I've seen what this is a counter proposal to on a wed-based SDR, and there were ten carriers within a 5 kHz space. The 10 carriers were switching on and off. It seemed to me like it was using a much more basic definition of digital, meaning off was "0" and on was "1". This would/could be a zero latency system, if the extended information was sent by legacy IP/internet, but the commands that require zero latency (i.e., "buy", "sell") were sent as a carrier on/off signal. This proposal is for a 50 kHz system, so if they used bandwidth in the same way, that would be 100 carriers sending on/off commands and/or combinations. This is for a Part 90 (of the FCC rules) operation, so I would guess they'd install a Part 90 UHF transmitter at the place business is being conducted to control or retransmit to the Part 90 shortwave transmitter, which would take up too much physical space in most buiness environments.

mlyle 3y ago
> This would/could be a zero latency system No, this is just discrete multitone. Leaving aside the issue of errors, it still takes you time to know the carrier is gone. You'd have much better choices about how to do this that are more spectrally efficient and equivalent in latency. Reductio ad absurdum: if it were zero latency, you could turn on and off the signal infinitely fast, and then send an infinite amount of information across a narrow channel. > This proposal is for a 50 kHz system, so if they used bandwidth in the same way, that would be 100 carriers sending on/off commands and/or combinations. Yah, or broadly: it's like OFDM. You don't have to constrain yourself to one bit per carrier, and you can use error coding across multiple carriers, etc. Also important to consider authentication...
- RF_Enthusiast 3y ago
  Yes, those are both good points. Also, a bad actor could straight up jam the signal. If you want to check out the signal of the competing system, it's just above or just below 15.735 MHz, using the sidebands of a shortwave broadcaster operating in Digital Radio Mondiale. 5 kHz is usually the DRMondiale signal, and 5 kHz is the sideband transmission.
  - cycomanic 3y ago
    Microwave links for HF are already ubiquitous. I find it surprising that nobody jams the signals, but it isn't happening to large extend AFAIK

mlyle 3y ago

> This would/could be a zero latency system No, this is just discrete multitone. Leaving aside the issue of errors, it still takes you time to know the carrier is gone. You'd have much better choices about how to do this that are more spectrally efficient and equivalent in latency. Reductio ad absurdum: if it were zero latency, you could turn on and off the signal infinitely fast, and then send an infinite amount of information across a narrow channel. > This proposal is for a 50 kHz system, so if they used bandwidth in the same way, that would be 100 carriers sending on/off commands and/or combinations. Yah, or broadly: it's like OFDM. You don't have to constrain yourself to one bit per carrier, and you can use error coding across multiple carriers, etc. Also important to consider authentication...

RF_Enthusiast 3y ago
Yes, those are both good points. Also, a bad actor could straight up jam the signal. If you want to check out the signal of the competing system, it's just above or just below 15.735 MHz, using the sidebands of a shortwave broadcaster operating in Digital Radio Mondiale. 5 kHz is usually the DRMondiale signal, and 5 kHz is the sideband transmission.
- cycomanic 3y ago
  Microwave links for HF are already ubiquitous. I find it surprising that nobody jams the signals, but it isn't happening to large extend AFAIK