[time-nuts] fast edge, rise time.

[bownes]

There are some good alternatives to krytrons. Just don't expect to be able to afford or export them. ;)


> On Dec 26, 2013, at 21:26, Bob Camp <lists at rtty.us> wrote:
> 
> Hi
> 
> Unless you want run for < 1 second, that rules out a Krytron. 
> 
> Length of operation also impacts some of the other implementations. 
> 
> Bob
> 
>> On Dec 26, 2013, at 9:16 PM, ct1dmk <ct1dmk at gmail.com> wrote:
>> 
>> Many thanks to all for the nice tips.
>> 
>> I may narrow down by saying a few more specs as suggested.
>> The pulse would see a somehow unknown load but for a start I
>> was suggested to have my source with 50ohm impedance so worst
>> case would be a short circuit and therefore the pulse would be a current pulse
>> and would have some 10Amp. Pulse length about 100ns so only some 0.5mJ energy that would die inside the pulse source( this would be the worst case).
>> The 100us repetition rate make a a very small duty cycle of 1/1000 so average power
>> maximum 5W.
>> 
>> Since the amplitude and timing parameters are to be controlled (pulse timing come from an FPGA) I really need a solution using that trivial switching element fet or bipolar (and can't really do a more exotic scheme if I cant electronically control the parameters) also I must use a transformer because these short pulse are to be superimposed to another voltage and a transformer becomes very handy to do that. I interrupt the wire and insert the secondary there to add the pulses.
>> 
>> The challenge I'm facing is on the device either RF FET or Biplolar tr etc. and
>> surrounding circuits, transformer, etc. this to achieve the 4ns (or 5ns).
>> (the transformer I have in mind is something very similar to those transformers
>> on the final stages of HF/VHF ham radio amps, coax cables and ferrite cores)
>> any suggestion regarding devices etc ?...
>> 
>> Thanks for all comments.
>> 
>> Luis Cupido.
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