"ringing" noise on HP54602A scope

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Hello,

When I have a pulse generator into channel 1 thru a 50-ohm feedthru I
see a damped ringing on channel 2 (1/delta-t ~190 MHz) even though I
don't have anything hooked up on channel 2. When I hook up a PMT to
channel 2 thru a 50-ohm feedthru any response from the PMT is obscured
by the ringing. Actually, with just a 1.5 ft SMA to BNC cable
(DC-3GHz, 30pF/ft) connected to channel 2, the amplitude of the ringing
about doubles. Is something wrong with my scope or is it something
else?

Thanks,
Tony

 

[John McMillan]

Hello,

When I have a pulse generator into channel 1 thru a 50-ohm feedthru I
see a damped ringing on channel 2 (1/delta-t ~190 MHz) even though I
don't have anything hooked up on channel 2. When I hook up a PMT to
channel 2 thru a 50-ohm feedthru any response from the PMT is obscured
by the ringing. Actually, with just a 1.5 ft SMA to BNC cable
(DC-3GHz, 30pF/ft) connected to channel 2, the amplitude of the ringing
about doubles. Is something wrong with my scope or is it something
else?

Sounds broken to me. You say "amplitude". You don't actually say
how big any of these signals are - but I suppose if you can see them,
than they're too big.