Right, I reckon that makes sense nowadays. I've had a little to do with spectrum management in the past, in fact I was once on several different committees making recommendations for WRC (aka WARC).

That said, I'm not currently fully up to date nor do
I have inside info on NATO's comms or spectrum use. Reading other info that initially led me to the report, I gathered that back then NATO's use of HF was already in decline and that HF was mainly a fallback option in the event of a calamity - a major failure, nuclear war etc.

In many ways that makes sense as it's a low tech option that needs few resources and usually works subject to ionospheric fluctuations.

Although I had expected the EMR/RFI noise floor to have increased on all bands from ELF through to at least UHF, I was very alarmed at the 17dB figure on HF when I heard about it (I'd not have anticipated that it would have been quite that high).

Even before I'd heard that figure I'd been watching the increase which I put down to the following reasons:

1. The obvious one is the large and increasing use of electrical and electronic technology.

2. A more significant reasons is that in the 1980s many countries downsized and or outsourced their spectrum management departments. Lisensing spectrum was often then separated from the engineering - i.e.: EMR noise suppression, reduced protection ratios in band planning, reduced physical separation for same-channel and adjacent-channel transmitters, etc. In essence, commercial pressures were deemed more important than engineering niceties such as ensuring all non-message producing equipment, motors etc. incorporated adequate RFI noise suppression.

(Previously, engineering often took precedence. Whilst it can be argued that in the past that this policy was too restrictive, there's little doubt that both deregulation and the economic imperative have driven down engineering standards too far - witness the evidence - increased interference and noise (especially so from digital switching).

3. With the enormous increase in digital electronics in recent decades there has been less emphasis on radio engineering in university electronics courses (50-plus years ago analog radio and television engineering almost dominated electronics). The outcome is that nowadays many electronic engineers no longer get the solid grounding in RFI and noise reduction techniques that they one did. (Remember Henry W. Ott's Noise Reduction Techniques in Electronic Systems.) Yes, I know that's a sweeping statement and there are many exceptions but in general it's true.

This has resulted in not only reduced RFI standards but also we've seen the introduction of some outrageously bad engeering. For example, BPL/PLT (Broadband over Power Lines/Power Line Transmission). Putting what is effectively broadband noise into the world's largest antenna - the power line grids - has to be as about as diabolical as it gets. Before deregulation, such outrageously bad engineering would have been unthinkable.

(Here's an example of the problem. I recall some years back a rather bright young engineer who was working with me coming to me wondering why he couldn't get a rather complicated circuit board full of CMOS and TTL logic working and that I may be able to help. He explained that he had double checked his circuit and board layout and could find no fault. With only a split second look at the board I saw the problem, I explained to him that he'd omitted to put 0.1 uF bypass capacitors across the IC's power supply rails. Little wonder the circuit didn't work.)

That all said, I don't expect the spectrum's noise floor to come down the foreseeable future.