Fortunate? Good fortune, or bad? Heh! Cortland
(I didn't write a thing that speaks For my employer at all; If anything I say is wrong, I'm the one to take the fall!) "Pettit, Ghery" wrote: > David, > > Ideally an OATS should have no ambient signals within 6 dB of the lowest > limit that you intend to use. Now, after everyone has had their laugh and > picked themselves up off the floor, let's look at the practical aspects. > > There are very few OATS facilities in the world that meet the requirement > from DC to daylight (well, maybe we don't have to go that far, but you get > the idea). I recall one that was built in an underground salt mine in > England and there have been some in very remote locations in the US, but > that's about it. Every other OATS that I know of has a few or more signals > over the limit, some way over the limit. > > Factors to consider in making your decision would be - > > 1. How much of the spectrum of interest is occupied by ambient signals? In > the past, we've been able to live with television transmitters as the only > real serious signals were the video and audio carriers. The actual picture > information was much lower in amplitude and the carriers seldom shared a > frequency with an emission from a computer. This will (and is) change with > the advent of digital TV. Spectrum utilization is much more efficient. > Good for the spectrum planners. Bad for neighboring EMC labs. > > 2. How strong are the ambient signals? Are they strong enough to drive > your pre-amplifier into gain compression or worse? You'll need filters to > fix this. > > 3. Do ambient signals sit at frequencies you expect to measure on a routine > basis? > > This should give you a general idea of things to worry about. Also, keep in > mind that typically VHF/UHF ambient signals are stronger higher off the > ground. Roof top OATS facilities will likely see higher ambient signal > amplitudes than ground level facilities in the same area. > > Ambient signals in a metropolitan area are one of the strongest arguments > for RF semi-anechoic chambers that I can think of. You might price out a > chamber as part of the study. I've heard that the chamber vendors are > hungry for business and have really sharpened their pencils as of late. > > Good luck with whatever you build and have fun. I've enjoyed the process of > building labs each time I've been fortunate enough to do it. > > Ghery Pettit, NCE > Intel > > -----Original Message----- > From: Gelfand, David [mailto:[email protected]] > Sent: Thursday, January 24, 2002 8:14 AM > To: [email protected] > Subject: Ambient noise limits for OATS? > > Hello all, > > We are being asked to evaluate ambient noise for a possible rooftop OATS. > Are there any published limits to ambient noise for an OATS location? > > Thank you, > > David. > > David Gelfand > Regulatory Approvals > Kontron Canada > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Michael Garretson: [email protected] > Dave Heald [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > Jim Bacher: [email protected] > > All emc-pstc postings are archived and searchable on the web at: > No longer online until our new server is brought online and the old > messages are imported into the new server. > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Michael Garretson: [email protected] > Dave Heald [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > Jim Bacher: [email protected] > > All emc-pstc postings are archived and searchable on the web at: > No longer online until our new server is brought online and the old > messages are imported into the new server. ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: [email protected] Dave Heald [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
