[time-nuts] Adding prescaler to HP 5334B

[Bruce Griffiths]

Robert Berg wrote:
> Having seen it discussed, I was wondering whether anyone has actually added
> the Schottky diodes and prescaler chip to a 5334B to provide a C-channel
> input. The matched Schottky quads (5082-2831) are no longer available, and
> even the recommended replacements (5082-2303) seem scarce.  Was thinking of
> trying 1N5711s, which can be obtained as matched sets, although probably not
> on my budget. How critical is the need to use matched sets? The NEC
> UPB1507GV-ACT-ND looks promising for the prescaler, if the small form factor
> isn't too minute to handle.
>
> Bob
> WA7ZRX
>   
Not particularly critical as they are only used as clamps to limit the 
input signal to the 30dB gain preamplifier.
You may be able to use a single pair instead, albeit with a lower input 
damage level.
Using a quad allows the clamp current to be shared between a pair of 
diodes, however some matching is required to ensure effective current 
sharing.
Too much diode shunt capacitance will limit the bandwidth.

Bruce