One of the definitive documents on Radio Noise is the ITU-R Recommendation on Radio Noise, version P.373-12. This (latest) version is dated 07/2015, so it’s only a year old. You can download it [as a PDF] here. It has a lot of info on natural and man-made radio noise.
My favorite graph from the document is shown below:
It shows the level of radio noise vs. frequency for good and poor conditions. It can be rather surprising how noise, even under the best conditions, can be quite excessive on shortwave frequencies. For example, the best case noise level for 10 MHz is about 30dB above the Johnson Noise level. (That’s the noise level from just a resistor at room temperature.) That’s why the noise level in your shortwave receiver’s speaker gets so much higher when you attach the antenna!
That is fascinating, Steve! It’s no wonder we struggle with noise issues–even in the best of times, it appears.
Many thanks to SWLing Post reader, Bill, who shares this public notice from the FCC:
Comment Deadline: August 11, 2016
The FCC’s Technological Advisory Council (TAC), an advisory group to the FCC operating under the Federal Advisory Committee Act, is investigating changes and trends to the radio spectrum noise floor to determine if there is an increasing noise problem, and if so, the scope and quantitative evidence of such problem(s), and how a noise study should be performed. In this public notice, the Office of Engineering and Technology (OET) announces the TAC’s public inquiry, seeking comments and answers to questions below for the TAC about radio spectrum noise.
The Society of Broadcast Engineers (SBE) has told the FCC that the regulatory agency needs to take another tack in its efforts to tackle AM revitalization. If the FCC takes the SBE’s advice, the result could be less noise in the MF and HF Amateur Radio bands. In comments the SBE filed in response to an FCC Further Notice of Proposed Rulemaking and Notice of Inquiry (MB 13-249) proposing ways to enhance the viability of the AM broadcast service, the SBE said the Commission must “commit to a regulatory plan which, over time, will reduce the levels of man-made noise in the MF bands, and more broadly in the bands below 30 MHz.” In comments it filed earlier in the proceeding, the SBE pointed out that “AM radio in particular is susceptible to interference from electronic devices of all types,” and that ambient noise on the AM band is only bound to get worse with further proliferation of noise-generating electronic devices, including certain lighting devices regulated under FCC Part 15 and Part 18 rules.[…]
Released: 03/01/2016. FCC ENFORCEMENT ADVISORY: PERSONS OR BUSINESSES OPERATING “PIRATE” BROADCAST STATIONS ARE SUBJECT TO ENFORCEMENT ACTION. (DA No. 16-159) This Enforcement Advisory discusses the rules that prohibit “pirate” radio, explains to the public at large what broadcast actions are illegal, why such activities may harm the public, and what do to in case someone suspects “pirate” broadcasts. EB . News Media Contact: Will Wiquist at (202) 418-0509, email: Will.Wiquist@fcc.gov
While the FCC is busy sabre-rattling, they should also think about ways to diversify the broadcast airwaves legally. There is a significant entry barrier for any would-be broadcaster on the FM and AM bands.