A suggestion on shielding the coil with foil: Make sure the foil doesn't make a shorted turn around the coil. This would cause serious problems and poor sensitivity. _______________________________ Al Allworth On the Beautiful Southern Oregon Coast ________________________________ ----- Original Message ----- From: "Bob Smith"
To: Sent: Tuesday, July 25, 2000 2:11 PM Subject: Re: those strange jumps > John -- > > One additional thought, The time that a radio station "signs > off" does not necessarily coincide with the time that they > drop carrier (shut down the transmitter), same on start up > in the morning. These periods just after and just before > the broadcast day are often used for tranmitter adjustments > and testing. I suggest a portable A.M. radio to listen for > carrier outage while you are monitoring. A strong, > unmodulated carrier will have a marked "quieting" effect on > what you hear. > > Best wishes, Bob Smith > > > > John Tacinelli wrote: > > > > HI again, > > > > I am overwhelmed with good ideas! Thank you all so much. I will try do deal with each. First of all the line voltage. I have not checked this, however since the UPS showed the same problem, I don't think it is the line voltage. I called the utility company and they said there were no shifts related to capacitors at that time. They said there was a shift in usage around that time but they couldn't be very specific. I'm pretty sure its not a joke, our students are not that bright.... I thought about streetlights but each is on its own photo cell and so they come on irregularly. I did not have the seismograph running during the time change so I don't know if it tracks. We are decidedly not in the desert here in Minnesota so I doubt it is the building heating and cooling, besides, this is too regular for something like that. > > > > I like the idea put forward by Charles and Bob about AM radio interference. I called around and there are two radio stations that have restricted licences. One goes off the air at 8:45 and back on at 5:45. Very interesting. The other station changes power level from 5000 to 1000 watts at about that time. They couldn't be more specific. The station that goes off air says that I could shield the coil with grounded aluminum foil. So I took the box that I use as an air cover and taped aluminum foil all over it. I attached a wire to it with electrical tape and modified a regular AC 3-prong plug so that only the ground plug was there. I attached the wire and plugged it into the power strip for the computer. The trace that had been going more or less down the middle, shifted to the left side of the screen. So it seems to be doing something. Tonight I will watch the thing again, this time with the shield in place and two radios going. If it happens again I'll see if it > > coincides with the radio sign-off ( or signal decrease). Also , the radio station changes its on-off times monthly so I can also see if it changes at the end of the month. I am hopeful and will keep you all informed. Thanks again for the help. > > > > John Tacinelli > > Earth Science Instructor > > Rochester Community and Technical College > > > > __________________________________________________________ > > > > Public Seismic Network Mailing List (PSN-L) > > > > To leave this list email PSN-L-REQUEST@.............. with > > the body of the message (first line only): unsubscribe > > See http://www.seismicnet.com/maillist.html for more information. > > -- > > --------- Avoid computer viruses -- Practice safe hex > ------------- > * * Specializing in small, cost effective embedded control > systems * * > Robert L. (Bob) Smith Smith Machine Works, Inc. > internet bobsmith5@........ 9900 Lumlay Road > landline 804/745-1065 Richmond, Virginia > 23236+1004 > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. __________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>