PSN-L Email List Message

Subject: update on radio interference
From: "John Tacinelli" John.Tacinelli@........
Date: Tue, 08 Aug 2000 15:17:14 -0500

A little more progress has been made on my radio problem.  I have =
discovered that the radio tower is less than 2 miles from here.  Also I =
hooked up a small speaker to the amplifier and I can hear the radio =
station on the seismograph.  I tried unplugging the coil and I could still =
hear it although it was much reduced.  When the pre-amp was unplugged I =
couldn't hear it at all.  So it looks like the coil is acting as an =
antenna for the pre-amp.  The cable from pre-amp to amp may also be doing =
so but to a lesser degree (it is shielded).  I tried several other coils I =
have around the lab and they all worked fine as antennae.  So I doubt that =
another coil would help.  A different pre-amp might do it if I could get =
one.  Do your seismographs have pre-amps? Is there a diagram?

I called the electronics company and they are working on it.  They seemed =
to doubt that shielding it would work since AM is long wavelength.  The =
guy at Wards is on vacation so I can't get any parts from him for a while. =

While I was listening to it, I made some observations.  When I touched the =
intrument the magnet would move and the radio signal would go out.  I =
guess the instrument signal overpowers the radio signal when it is moving. =
 Also, my touching the coil or preamp seemed to affect it too.  With the =
coil unplugged, I could hear better if I touched the pre-amp.  However =
with the coil plugged in touching it would often stop the signal.  It =
seemed very touchy. =20

Anyway, If this gives anyone some ideas, I would love to hear about it.

John Tacinelli
Earth Science Instructor
Rochester Community and Technical College


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Larry Cochrane <cochrane@..............>