Gene Heskett wrote: > On Sunday 23 December 2018 20:27:37 rhkra...@gmail.com wrote: > > > On Sunday, December 23, 2018 07:33:38 PM Doug wrote: > > > RE: Time Domain Reflectometer: > > > > > > Theoretically, you can build your own with a fast pulse generator > > > and an oscilloscope. The trick is, you need a REALLY FAST > > > oscilloscope! The pulse generator is easy, just a couple of > > > transistors, maybe a diode. The circuit is probably in every > > > edition of the Radio Amateur's Handbook. The scope is expensive. If > > > you don't have at least a 1GHz digital sampling scope, don't bother! > > > > > > --doug, WA2SAY, retired RF engineer > > > > Hmm, with CPU clocks hitting 4 GHz, I wonder how expensive an ADC > > converter to work at corresponding speeds would be? (Just an idle > > question ;-) > > If you have to ask, you can't afford it. Bring outrageous sums of money > This is typically done by every trick tek knows about fast analogue > circuitry, in the best units with long vertical deflection plates in a > custom made crt with teeny delay lines between the sections of the > plates so the signal is virtually traveling toward the screen at the > same speed as the electron beam is traveling. And its moving fast enough > at 22,000 volts, relativity can and does get in the way. Such scopes put > the plates so close to the beam that the beam is intercepted by striking > the plates at just a hair over 4 cm high, 2cm from the horizontal center > line. The only one of those I ever saw was in the early 1980's or so at > the NAB show in Vegas, and it was well into a 5 digit asking price then.
We're almost in 2019, which means: https://www.mouser.com/ProductDetail/Analog-Devices/HMCAD1511?qs=sGAEpiMZZMvTvDTV69d2Qnrp4UY3MFmsfo%252bIC8KWhPQ%3d Analog Devices HMCAD1511 1 GS/s, 8 bits, 1 channel: quantity 1 from Mouser: $64.76. That's the cheapest GHz+ ADC they have; you can still go up to much heftier prices for more channels, more bit depth, even higher sampling rates. -dsr-
