[time-nuts] Question concerning failure and value of HP 5371A

Magnus Danielson cfmd at bredband.net
Sat Oct 15 20:24:32 EDT 2005

From: "Arnold Tibus" <Arnold.Tibus at gmx.de>
Subject: Re: [time-nuts] Question concerning failure and value of HP 5371A
Date: Sun, 16 Oct 2005 01:36:51 +0200
Message-ID: <E1EQvbQ-0005o2-J8 at febo.com>

Hi Arnold,

> Hi Hal, thanks for your hints!
> On Sat, 15 Oct 2005 12:38:56 -0700, Hal Murray wrote:
> >> The point is, I do not find gates capable to work well beyond 30, 40
> >> MHz. I there somebody having a helpful idea how this could be solved? 
> >How fast do you want to go?  Modern FPGAs are loafing at 100 MHz.
> I would like to experiment with 1 ns or 2 ns pulses and gates capable to count 
> such pulses, meaning with bin. counters able to work with 250 MHz or 
> up to 500 MHz clock in  signal. That speed just for that 2 primary elements 
> of a (high speed) counter. Am I dreaming? I like it.
> I thought that this should be possible in times with GHz PCs...?

Are you aquanted with the term analog interpolators? Basically they try to
measure the time-difference between the counting-clock edges and the start/stop
trigger edge.

However, I have yeat to understand what you are really after. There is many
ways to skin a cat, but maybe if I knew what type of cat you are looking to
skin I might give some more ideas on what to do...

> >A major problem at high speeds is signal integrity.  You can't toss something 
> >together with proto-board technology.  You need a good ground plane and power 
> >supply decoupling.  (and they generally require several power supplies)
> That is  v e r y  clear, I am preaching since decades of years to all the 
> 'digitals', that as well for digital circuit design you have to know and respect 
> all the physics for RF, as it is even worse: digital signal transmission even on CBs 
> is not just switching dc on and off (combined with mathematics), but it is 
>  w i d e b a n d  RF, not so easy to match the lines and stages properly as 
> for 'normal' RF circuits with small bw.! 
> We are arriving the moment that one need to be both experts, analog RF and digital.
> Impedance matching everywhere, excelent returns (gnd), good rf-shielding and 
> blocking together with stiff and rf-resistant pwr-supplies are stringent, a must.

Living the life, I can tell it took some learning, but it is getting easier to
handle. Actually, some of the old RF knowledge you can just toss over the
shoulder, since it really applies to narrowband high dynamics. Here we have
wideband with low dynamics. However, the physics is the same, but you have to
use the knowledge in a slightly different way.

If you care to get some reading tips, please let me know. There are some good
books which will maybe not be earth-moving but certainly help getting things
straigthened out.


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