Wednesday, May 24, 2006
I was at IWCE last week to give a talk entitled "Managing Interference in the Unlicensed Spectrum". While talking to a guy in one of the booths, he asked what talk I was going to present. When I told him, he just laughed. His opinion was that nothing could be done about interference at 2.4 and 5.8 GHz because there aren't laws governing who can put up a transmitter on those bands. In some places it is like the Wild West - the guy with the biggest signal and antenna wins.
In the talk I proposed that heavily populated areas could do well to establish coordination committees that could help mitigate interference issues. While these bodies wouldn't have the force of law, if there is enough membership they could have the force of peer pressure.
By the way, the talk went well and the questions at the end went far afield from the unlicensed spectrum to things such as how to locate the source of a third order intermoduation source.
One question asked how someone could become a good interference troubleshooter. As a result of that question, I intend to develop a course to teach either as a teleclass or by e-mail on how to find and mitigate interference. In the long-term plan for RFIwizard I intend to also have live events where experts in different RFI and EMC areas would teach their methods and we could have hands-on classes. Sounds like fun to me!
Steve
In the talk I proposed that heavily populated areas could do well to establish coordination committees that could help mitigate interference issues. While these bodies wouldn't have the force of law, if there is enough membership they could have the force of peer pressure.
By the way, the talk went well and the questions at the end went far afield from the unlicensed spectrum to things such as how to locate the source of a third order intermoduation source.
One question asked how someone could become a good interference troubleshooter. As a result of that question, I intend to develop a course to teach either as a teleclass or by e-mail on how to find and mitigate interference. In the long-term plan for RFIwizard I intend to also have live events where experts in different RFI and EMC areas would teach their methods and we could have hands-on classes. Sounds like fun to me!
Steve
Saturday, May 06, 2006
Interference in the unlicensed spectrum hit home last night as I started heating something in the microwave oven while my wife Melissa was talking on a cordless phone in the same room. All of a sudden she couldn't hear the other end of the conversation due to high noise. As soon as I turned off the microwave oven the noise went away.
I was very surprised since I'd previously measured the leakage from the microwave oven - which measured -40 dBm right at one of the horizontal door cracks. The cordless telephone measured -20 dBm at the same position.
I was very surprised since I'd previously measured the leakage from the microwave oven - which measured -40 dBm right at one of the horizontal door cracks. The cordless telephone measured -20 dBm at the same position.
Tuesday, May 02, 2006
RFI and EMC Rants
Steve Thomas here. The RFI level at the NAB show last week in Las Vegas was incredible. Just in the North Hall there were over a dozen active 802.11(b) and 802.11(g) signals, plus another 4 or 5 802.11(a) signals. The NAB had several access points themselves. I used one of the 802.11(g) access points when I could. Sometimes I just couldn't stay connected so I had to resort to using my Verizon Wireless 1XEVDO card.
Several transmitter vendors had FM IBOC transmitters on display. IBOC stands for "In-Band On-Channel" which is really somewhat of a misnomer since the signal covers the two adjacent channels. AM IBOC is currently allowed daytime operation only because of the potential of serious interference to adjacent channels hundreds or thousands of miles away due to night time ionospheric propagation.
Several transmitter vendors had FM IBOC transmitters on display. IBOC stands for "In-Band On-Channel" which is really somewhat of a misnomer since the signal covers the two adjacent channels. AM IBOC is currently allowed daytime operation only because of the potential of serious interference to adjacent channels hundreds or thousands of miles away due to night time ionospheric propagation.
