Offhand, I would suspect undersampling or mistriggering.... I picked up a Hameg scope with 200 megasamples/sec a few years ago. It saved quite a bit of time when I was putting together a parallel interface between Linux and a Tek storage tube terminal. Push a button and a hard copy pops out of my Laserjet - definitely beats a Polaroid for what I was doing.
On 06/06/2011 10:40 AM, J. Forster wrote:
As some of you know, I've been working on restoring a WW II LORAN-A system. To test it, I've been using a Tektronix TDS1002 Digital 'Scope and a Military TS-251 Test Set. First a bit about the LORAN-A signal. It is a precisely timed Master pulse of roughly 2 MHz RF. The spacing of the Master Pulse is precisely crystal controlled, but the RF is just gated... the carrier is not locked to the Master Pulse. It looks sort of like this: |||||....................................|||||................. ^ | Master Pulse start. Anyway, I was triggering on the Master Pulse and looking at several succeeding ones, all generated by a TS-251 Test Set. For the longest time, I could not figure out why the successive Master Pulses envelopes were bouncing around all over the place by perhaps a factor of 5. Eventually, I worked out that most of the samples taken by the digital scope were being taken during the quiet time, and the actual LORAN pulse was being badly undersampled. This resulted in displayed waveform that had almost nothing to do with what the system was really doing. Also, because of slight trigger uncertainties, the LORAN pulse was being "smeared" in time. IMO, the lesson is that digital scopes do not always accurately depict what a circuit is doing. Even a $50 analog 'scope would never have this issue. FWIW, -John =================== _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
-- Chuck Forsberg WA7KGX N2469R c...@omen.com www.omen.com Developer of Industrial ZMODEM(Tm) for Embedded Applications Omen Technology Inc "The High Reliability Software" 10255 NW Old Cornelius Pass Portland OR 97231 503-614-0430 _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
