Long bursts of digital "noise" on 145.4125 MHz.

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Long bursts of digital "noise" on 145.4125 MHz.

Postby db13 » Tue Dec 13, 2016 11:47 pm

What are they?
How do they get away with never transmitting a call sign?
I am located near Reading in Berkshire.
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Re: Long bursts of digital "noise" on 145.4125 MHz.

Postby m0lsx » Wed Dec 14, 2016 11:02 am

The licence requirement is given in Section 13 of the following link.
https://www.ofcom.org.uk/__data/assets/pdf_file/0027/62991/amateur-terms.pdf

13 (1) (C) states.
"The Callsign is given in voice or other appropriate format consistent with the mode of operation."


So from that it would be sensible to conclude in the mode of operation. As a minimum.


In April of this year Ofcom issued the following guidance paper.
https://www.ofcom.org.uk/__data/assets/pdf_file/0026/82637/amateur_radio_licence_guidance_for_licensees.pdf

2.93 states..
It is for individual operators or licensees to determine how often a call sign or other identification is transmitted, to comply with the requirement in Clause 13(1)(a) that the station be clearly identifiable at all times. This includes digital transmissions, where, again, licensees must determine how to comply with the overall requirement.
One solution might be to embed the call sign into the signal . It is unclear how a station would be clearly identified if it did not, as an absolute minimum identify itself at the beginning and end of transmissions.


Note the use of callsign or identification in the first line. Clearly Ofcom views the embedding of a callsign identification in a digital signal to be sufficient to meet our legal requirement.
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Re: Long bursts of digital "noise" on 145.4125 MHz.

Postby G4RMT » Wed Dec 14, 2016 12:32 pm

When stations identified with CW, nobody who couldn't read it got too bothered - as when FM only ops hear sub - rarely can they detect the callsign. Then we had amateur TV - again, only those with the right equipment could get the callsigns, then into digital.

I's always assumed that since OFCOM can probably decode most generic analogue and data formats, then that is enough. Anything encrypted would defeat it - hence why that's not allowed. It's absolutely annoying, but legit.
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Re: Long bursts of digital "noise" on 145.4125 MHz.

Postby db13 » Thu Dec 15, 2016 7:54 pm

Okay so probably nothing wrong with me not hearing a morse callsign.

There were two, or possibly more, transmitters alternating like they were exchanging a lot of data. The stronger one seemed to make the longer transmissions, I would guess a couple of minutes long, with a very short buzz at the end. But the weaker transmissions seemed longer than just an acknowledgement of a block received okay. It sounded like a high data rate, like something more advanced than FSK. Any ideas what it was?
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Re: Long bursts of digital "noise" on 145.4125 MHz.

Postby db13 » Fri Dec 16, 2016 11:27 pm

Solved, well probably anyway.
I think it was a conversation in C4FM digital mode.
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