Re: HP11729C 640 MHz magic cable?
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Hi Robin,
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Phase is a very strong function of the frequency (for a good reason). I re-measured the phase this time checking the frequency of the signal generator with a counter, it was few kHz off. With exactly 640MHz now I measure 0.95ns. This is with a 2467B, a 400MHz scope measuring 640MHz so accuracy is not great. Total delay has to be multiples of 1/640MHz, cable needs to add to 0.95ns. Shortest cable delay is:1/640MHz-0.95ns=0.61ns, about 13cm with vf=0.7. HP cable still looks shorter than that. Perhaps delay through the attenuator or my measurement inaccuracy explains the rest. My cable was around 13cm though. If anyone in the group has the cable it would be good to know the exact length.? I used series of BNC connectors, not locked, and experimented with various delays by sliding them. Picture of the connectors is attached. Ozan On Tue, Nov 14, 2023 at 01:03 PM, Robin Szemeti wrote:
Ah, thanks for that!? I shall try messing with the cable length then until it takes off ...? 1.9nS is arounf 400mm of cable at vf=0.7 ... the one shown in the manuel is much shorter, so maybe it is a bit variable, but I shall try with 1.9nS andsee how it goes, thanks again! |
