Feature for automatic transmission of HAM callsign

[alexis-nicole]

Hi,
I've added a feature to automatically transmit my HAM callsign when using the Sik Telemetry Radio v3. I decided to share it with you and ask if you are interested in adding my changes to your code base. Please find below more details about my changes.

Rationale

Licensed amateur radio operators are required by the Federal Communications Commission (FCC) to identify their station using their assigned callsign at regular intervals during transmissions. This requirement is outlined in Part 97 of the FCC rules (§97.119) and exists to ensure accountability and traceability within the amateur radio service.

The callsign serves as a unique identifier that links their transmissions to their license, helping to prevent misuse of the airwaves and to facilitate enforcement in case of interference, unauthorized operation, or other violations.
According to the regulation, the callsign must be transmitted at the end of a communication and at least every 10 minutes during ongoing transmissions. This applies whether the licensed amateur is transmitting voice, Morse code, or digital data.

Even in cases where communication is automated (such as telemetry link) the station must still identify itself appropriately, typically by including the callsign in the data stream.

I personally found out that I am supposed to transmit my callsign since, although I am transmitting at 915 MHz, my radio does not comply with Part 15 certification. Instead, it is operating under FCC Part 97 (Amateur Radio Service).

Disclaimer: I am not a lawyer, and this is based on my understanding of the FCC regulations. I am not providing any legal advice.

How this feature is implemented

I have created custom AT commands that allow the user to set their callsign and the interval for the transmission of their callsign. It is important to note that this feature is disabled by default, but the user can enable it with the appropriate AT command.

Following is the list of AT commands:

• AT&CE: Enables the transmission of the HAM callsign. If the user does not set their callsign before enabling the transmission, the system will send the default "NOSIGN" callsign.
• AT&CD: Disables the transmission of the HAM callsign
• AT&CS=xxxxx: Sets the user's callsign. This option assumes that the operator is using a standard callsign length (6). However, some regions might use 7 characters (some special events as well as some regions outside the US might use 7 characters). The maximum length is set to 7.
• AT&CI=yyy: Sets the interval (in seconds) for the transmission of the callsign.

Default values:

• AT&CE=0
• AT&CS=NOSIGN
• AT&CI=600

I have tested it on my Holybro Sik telemetry radio v3 (915 Mhz @ 500 mW) and it seems to be working fine for my needs. Of course, I am more than happy to implement any improvement or bug fixing that other contributors migght suggest.

Thanks,
Alexis

www.alexisbenini.com