[time-nuts] DIY Frequency extension for HP Agilent 53181A, 53131A or 53181A

[RFSPACE]

Samuel,

The prescaler option is detected by pin 9 and 10 of the 10 pin header. If 
you look at the page3 of 4 of the 53132A, you see a pair of pins called 
CH3CODE1 and CH3CODE0. Those tell the processor that the board is plugged 
in. If you go to the page for the 12.4 GHz prescaler, you can see that the 
pins 5 and 10 can be pulled high or low to tell the counter what board it 
is. The pinout on the main board and the prescaler board is different to 
confuse the hacker. The pinout on the prescaler board is:

6-1
7-2
8-3
9-4
10-5

the pinout on the main board is:

2-1
4-3
6-5
8-7
10-9

This is why the pins 10 and 5 that are used to ID the board, match the 
schematic pins 9 and 10. It looks really simple to build this board. I would 
like to add 3GHz to my HP53131A. Currently I use a programmable divider from 
Hittite. I have it set to /10 and do the math in my head.

Pieter, N4IP


----- Original Message ----- 
From: "Rick Karlquist" <richard at karlquist.com>
To: <mccorkle at ptialaska.net>; "Discussion of precise time and frequency 
measurement" <time-nuts at febo.com>
Sent: Sunday, February 15, 2009 2:53 PM
Subject: Re: [time-nuts] DIY Frequency extension for HP Agilent 53181A, 
53131A or 53181A


> Richard H McCorkle wrote:
>> Hi Samuel,
>>
>> I suggest starting by downloading the component level information for
>> the 53131A and 53132A from tha Agilent site at the following links.
>>
>> http://cp.literature.agilent.com/litweb/pdf/5989-6308EN.pdf
>> http://cp.literature.agilent.com/litweb/pdf/5989-6307EN.pdf
>>
>> The 53132A document includes a schematic of the channel C board with
>> parts list and may assist in getting you started.
>
> I see that they have a factory select resistor that unbalances
> the input slightly to keep the prescaler from oscillating with
> no input.  This a simple, obvious "solution" to this problem.
> It is also non-optimum, for three reasons.  It desensitizes the
> prescaler, it uses a factory select part that may not work
> consistently over temperature, and it still results in a range
> of input power where the counter displays garbage.
>
> In the 5334B C channel, I used a diode detector that turned on
> the counter at a repeatable input power.  Thus you never got garbage
> on the display due to low input power.  The detector used the
> well known circuit where you bias the diode on with a few 100
> microamps of DC and have a compensating diode that is not excited
> by RF.  A difference amp subtracts the compensating diode voltage.
> Simple, but effective.
>
> It is also interesting to note that in 1987 I used the MB506 prescaler.
> Here they have simply upgraded to the MB510.  Not likely to be
> any better on noisy sources.
>
> Rick Karlquist N6RK
>
>
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