Hi Raymond,
Tried a tunnel diode based 7B92 in a 7904A/7A29, with input from a TG501 and internal triggering. At 2 ns and 1 ns the TG501 "pulse" stream is nearly a sine wave. At 2 ns (500 MHz) the 7B92 triggers well in Norm mode with signal less than 0.5 div. At 1 ns (1 GHz) it fails in Norm mode but syncs in HF Sync mode (and signal far below 0.5 div). But a 7B15 performed far better with a much sharper trace, so with much less jitter. Even at 1 GHz the 7B15 would trigger in Norm mode.
Checking TB performance this way in a 7904(A) is somewhat undefined since it's not clear what trigger amplitude arrives at the TB. Testing in a 7104 would give better information.
The 7B92 was "as is", so other units might perform better.
Albert
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Tried my newly acquired SG504 (with leveling head) and saw this 7B92A triggering happily at around 1.05 GHz on my 7904 + 7A19... Of course, amplitude isn't shown anywhere near correctly. 7B92A is specified to trigger "above 500MHz".
Raymond
