[Amps] Maximum RF output in practical application: 4-250A

[Peter Chadwick]

Wynand - and this applies generally, I think - 

>WE are already in ZS in a grey area of owning equipment capable of
more than 400W so the last think we need is the regulator having to enforce
the regulations<
We need to bear in mind the spurious emission requirements enshrined in Radio Regulations by ITU-R Rec. SM329. Interestingly, the FCC managed in their last update of Part 97 to implement the requirements incorrectly - they have it as requiring harmonics and spurious as -43dB, when it should be -43 plus 10log P, where P is the PEP, and for HF, not needing to exceed 50dB. Even then, they didn't make as much of a mess of things as the UK! The requirements for commercial equipment in the EU are less than the Radio Regs, but the UK licence says we have to abide by the RR! So you can legally buy a piece of kit that in theory you can't use. Fortunately, the enforcement in the UK is so minimal it doesn't have any effect........
However, we should aim for all harmonics to be at least 50dB down - not exactly too difficult - but high order IMPs might be. To meet the RR, emissions separated by 250% or more of the necessary bandwidth (say 2.5 times 2.7kHz)  should be down 43+10log P, not exceeding 50dB for an HF tx. Nobody is sure whether the number for harmonics above 30MHz from a tx operating below 30MHz need to meet the 43+10logP not exceeding 70dB that applies to transmitters above 30MHz, or 43+10logP not exceeding 50dB. That applied to the Chairman of ITU Task Group TG1/5 where some of these numbers came from, too! On the other hand, if  in a 10kHz wide band starting 6.75kHz away, you aren't down 50dB, then you're  somewhat antisocial anyway.
Personally, I think that SM329 isn't very good: unfortunately, I wasn't at ITU-R TG1/3 where a lot of this started. Incidentally, that edition of  SM329 was the first time there had ever been any limits on amateur transmitters, and because nobody thought about the effects of phase noise on narrow band transmitters, the limits at microwaves are ridiculous. This has been changed somewhat after the satellite people realised their tracking beacons are narrowband and thus have the same phase noise problems as amateurs! Ironically, the whole thing on spurious came about because of radio astronomy complaining about the spurious emissions from Iridium satellites in radio astronomy bands, and like Topsy, it 'just growed'. But an Administration enforcing the rules and complaining to other Administrations about their amateurs could cause us problems if we don't at least meet the RR spurious emission limits. The use of HF isn't going away, and there are a lot of people would like our ban
 ds....
Hopefully this isn't considered too far off the amps topic....
73
Peter, this week SM5/G3RZP