[time-nuts] ACAM GP22 Chip

Thomas Allgeier th.allgeier at gmail.com
Wed Nov 25 09:23:40 EST 2015


Hello Hal,

The book has been sourced and is on its way to me - a good pointer, thanks. 
With it and the comments I have had from you guys I expect I will get pretty 
much what I want, given a little time which thankfully I have.

I will report back any outcome that looks plausible / presentable.

Kind regards,
Thomas.
----- Original Message ----- 
From: "Hal Murray" <hmurray at megapathdsl.net>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
Cc: <hmurray at megapathdsl.net>
Sent: Tuesday, November 24, 2015 7:44 PM
Subject: Re: [time-nuts] ACAM GP22 Chip


>
> th.allgeier at gmail.com said:
>> I should say from the start that I am new to time and frequency 
>> measurements
>> and not even an electronics engineer – but then I have been exposed to
>> high-precision electronics for the last 25 years hence have picked up 
>> some
>> dangerous degree of half-knowledge.
>
> Do you have a copy of Art of Electronics by Horowitz and Hill?
>
>
>> In order to evaluate the chip I was planning to replicate John A’s
>> experiment with the coaxial delay line from the HP5370b – but as my 
>> interest
>> is in “measuring range 2” of the GP22 I need a delay of 500 ns or 
>> more
>> (actually 1 µs sounds a better start). This is the equivalent of a 200 m
>> length of cable. I fear trouble with this: Am I not getting unwanted
>> inductivities if I use a coil of that size?
>
> The trick is that your coil has 2 wires.  It's a transmission line.
>
> Here is the handwaving explanation: The current on the return path is 
> going
> in the other direction and cancels out the inductance.
>
> Twisted pair will work almost as well as coax, maybe better than cheap 
> coax.
>
> AoE has an appendix on transmission lines.  You can find lots of info on 
> the
> web.  You need to terminate it.  You will want a scope to check the
> termination.
>
>
>
> -- 
> These are my opinions.  I hate spam.
>
>
>
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