3 ms·
BTW, this is article is not actually correct[1]. The technique is however. The measurement used an HP pulse generator to send a pulse down a piece of coax and t
by ChuckMcM 6y ago
BTW, this is article is not actually correct[1]. The technique is however. The measurement used an HP pulse generator to send a pulse down a piece of coax and that pulse, and the "echo" or return were both attached to Ch1 and Ch2 of an oscilloscope in the measurement trailer.
When a pulse was fired a Polaroid picture was taken of the screen at the same time. By measuring the difference between the leading edge of the initial pulse and the returning pulse the length of the cable could be computed. With a lot of pulse generators and oscilloscopes you could synchronize them to each fire slightly later than the next and get a number of solid data points on the cable being vaporized.
The Polaroids all included on the picture the rack and rack slot where they were located, and the sequencing was known, so you could digitize the pictures and extract the data.
[1] I actually worked in one of these trailers as part of a summer job during college writing code on said PDP 11/34.
- kps 6y agoThis paper lists the gear used (at some point) for the measurements, on p16: https://www.osti.gov/biblio/7352892 https://www.osti.gov/biblio/7352892 2 - 1.5 MHz tape recorders 2 - Oscilloscopes with cameras (HP-180 w/1805A and 1821A) 2 - Digital freq. and time interval counters/dig. volt meters HP5326B 2 - Sandia SLIFER chassis, shop made 2 - Pulse generators, HP214A 2 - Engine generators, 25 kW 1 - Trailer or shelter, portable, with utilities 2 - Time code generator 2 - WWV receivers 4 - Radios for local communication 2 - Countdown receivers 2 - Hi potters, HP4329A 1 - Time mark generator (Cal scopes) HP226A 2 - Variable oscillators, HP3312A 2 - Time delay generators, Rutherford 3 - Counter (HP5345A) 2 - Program timer, shop made
- ChuckMcM 6y agoWow, that is awesome. I wish they had a picture from inside the trailer. Basically a Decwriter + PDP-11/34 at one end, and two back to back rows of 19" "telco" racks with scopes, pulse generators, and cameras.