[time-nuts] Adding prescaler to HP 5334B

Robert Berg bob.b at pobox.com
Tue Apr 1 11:46:16 EDT 2008


Bruce,

Thanks for the ideas. The HSMS-2822 looks like it could serve in the
detector role, while a pair of HSMP-3822's might work for clamping--low
capacitance, matched pair in series, and in stock at Mouser. The 3822 is
actually a pair of PIN switch diodes, but couldn't it function as a clamper?
The 482x series looks better for clamping, but isn't available in a
series-pair configuration. There are other possibilities, but not many in
stock, and I couldn't find any suitable ring diode packages.

Bob
WA7ZRX

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Bruce Griffiths
Sent: Monday, March 31, 2008 6:37 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Adding prescaler to HP 5334B

Bruce Griffiths wrote:
...

> 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
>   
Quad CR303 acts as a clamp, Quad CR302 acts as a detector with 
temperature compensation.
Only 2 diodes in CR302 are used so CR302 can be replaced by a matched pair.

Try using low barrier microwave specified schottky diodes with lower 
capacitance than a 1N5711.

Bruce

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