I have both HP and Tektronix pulse generators. Neither are expensive and both have been very reliable. Since I need some really slow rep rates for receiver testing, I use my Tek 115 triggered with an HP 8904A synthesizer. Rob, NC0B
Sent from my iPad > On Apr 12, 2016, at 5:05 PM, "Logan Cummings" <logan.cummi...@gmail.com> > wrote: > > > > Hi Bill, > > Lots of resources out there on EEVblog forums and elsewhere. One nice > alternative to the avalanche pulser is a very fast comparator like the > ADCMP580 from Analog Devices. Generate a pulse of whatever width you want > with slower gear, and have the comparator sharpen the edges. > > See here: > http://www.eevblog.com/forum/testgear/inexpensive-diy-50ps-ultra-fast-pulse-generator/ > and > http://www.starlino.com/build-a-really-fast-pulse-generator-50ps-rise-time-using-an-ultra-fast-sige-comparator.html > > For a couple of examples. The EEVblog thread also has a link to info on an > avalanche pulser using a transistor that avalanches at 30V rather than 70+. > > -Logan > > On Tue, Apr 12, 2016 at 2:28 PM, Alan Melia <alan.me...@btinternet.com> > wrote: > >> Bill, Avalanche pulse gens only require high voltage because of the high >> VBRcbo and the gain of normal NPN transistors. I cant find the reference >> now it might have been a 1970s Ham Radio but if you use the same circuit as >> Jim but put an NPN "upside down" that is emitter where the collector is in >> Jim's circuit you can fire off fast pulses from a 12v supply, instead of >> requiring 70 to 100v. I do wish I could locate the source as I have had >> several arguments about it :-))....in the nicest possible way of course. >> >> Alan >> G3NYK >> >> ----- Original Message ----- From: "BIll Ezell" <w...@quackers.net> >> To: <time-nuts@febo.com> >> Sent: Tuesday, April 12, 2016 9:30 PM >> Subject: [time-nuts] Fast risetime pulse generator >> >> >> >> (cross-posted to volt-nuts) >>> After paying only limited attention to this topic, I suddenly have a need >>> for a pulse generator that has <150 ps risetime and a pulse width of at >>> least 2 ns. 100mv amplitude or more is fine. I've looked at the classic Jim >>> Williams avalanche generator, but I don't want to have to deal with the >>> (relatively) high voltage source needed. >>> >>> I've done microwave design using Gunn diodes, so I'm drawn to using a >>> step-recovery diode. The topology seems very straightforward, and I can >>> build it right onto a BNC connector, no PCB. >>> >>> I'm thinking using an SMD835 diode, biased at ~1ma. The (sketchy) >>> datasheet claims a T of 20 nsecs and a Tr of 85 ps, Cj of 0.4 to 0.8 pf. >>> >>> Questions: >>> >>> The obvious, is it reasonable? >>> >>> Is the bias current reasonable? I'm assuming the bias current is actually >>> dependent on the repetition rate, you need enough current to replenish the >>> charge within one pulse cycle. I suppose I could compute it from the stated >>> junction capacitance, but I'm not sure that's the only factor. >>> >>> Will the stored charge actually give me the desired transition rate into >>> 50 ohms? Hmm, again I should be able to compute this, but any other factors >>> ignoring the non-diode ones like cap inductance? >>> >>> How should I compute the coupling cap from the diode to the load? Use the >>> impedance at the pulse rep rate? Seems reasonable. BTW, I don't care about >>> droop in the pulse, just the risetime. (measuring overshoot in an HF >>> amp). Again, just want to verify that the obvious answer is the correct >>> one. I clearly need to be very careful about the inductance. >>> >>> Thanks, Bill >>> >>> -- >>> Bill Ezell >>> ---------- >>> The day Microsoft makes something that doesn't suck >>> will be the day they make vacuum cleaners. >>> Or maybe Windows 10. >>> >>> _______________________________________________ >>> 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. >> >> _______________________________________________ >> 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. > _______________________________________________ > 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. > > > > -- > If this email is spam, report it to > https://support.onlymyemail.com/view/report_spam/ODExMjI6MTg3MTg0ODczMjpyb2JAbmMwYi5jb206ZGVsaXZlcmVk > _______________________________________________ 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.