[amsat-bb] Re: UHF QRM from HAM stations!!

Glen Zook gzook at yahoo.com
Sun Dec 20 18:33:42 PST 2009

Technically all 47 CFR Part 15 devices must accept any interference and not cause any interference.  However, in a practical sense, there are so many 433 MHz Part 15 devices around that it would be VERY difficult, if not practically impossible, to eliminate all of them.

For example:  There are hundreds of thousands (and probably millions) of remote temperature sensors used by homeowners that operate in the 433 MHz segment.  Not that long ago my wife was in the process of purchasing one of those "atomic clocks" (actually the ones that sync to WWVB) and most of them have a remote temperature sensor included.  I noticed that, depending on the manufacturer/model, that these remote sensors might operate on the 433 MHz segment, on the 960 MHz segment, and some on the 1.2 GHz segment.  Although I don't operate on the 23 cm band I do operate on 432 MHz.  Therefore, I made sure that she got a clock with the 960 MHz remote sensor so that there was no chance of it causing problems to my operations.

However, there are definitely quite a few 433 MHz sensors operating in my neighborhood, I can hear several as I rotate my 432 MHz yagi.  Although I have lived in this particular house for well over 37 years, I don't believe that I would be very popular if I even tried to locate all of these 433 MHz devices and then press the FCC to shut them down.  Besides, I don't think that the FCC would put a very high priority on this particular problem.

As for ISM:  47 CFR Part 18 Section 18.111(c) gives priority to ISM operations when the operations are within specific frequency segments which are listed in 47 CFR Part 18 Section 18.301.  There are 12 frequency segments listed in this section.  Fortunately, the 70 cm amateur radio band is not one of these segments.

Glen, K9STH

Website:  http://k9sth.com

--- On Sun, 12/20/09, Art McBride <kc6uqh at cox.net> wrote:

In the USA, US Military has priority over all users on the 420-450 MHz band. Amateur Operators are secondary (cannot cause harmful interference to US Military. Under the terms of Part 15 all users under Part 15 must accept harmful interferences and must no cause harmful interference to other users.

BTW: ISM refers to services that do not intentionally radiate and do not use radiation for communication purposes. A Microwave is ISM. A WiFi is not.


More information about the AMSAT-BB mailing list