You've had more progress than I did, I don't get anything out of pin 6. I
did see the levels toggle, but that was about it. On various websites I
read to get exactly 1pps, you need a programmable 5680 because it needs to
be set to something like 8.388MHz (2^23) to divide down properly. I suspect
you may not be able to get both; 10MHz and 1pps.
Bob
----- Original Message -----
From: "beale" <[email protected]>
To: "Discussion of precise time and frequency measurement"
<[email protected]>
Sent: Thursday, January 05, 2012 12:46 PM
Subject: Re: [time-nuts]FE-5680A performance - 1 PPS output issue
I think there is something funny about the 1 PPS output on pin 6 from the
currently available cheap FE-5680A units. I have three of these units. On
one unit, on one occasion, I did observe a logic-level 1 PPS pulse, exactly
1 microsecond wide. But after a power cycle it never came back, although
the unit indicates a locked condition, and is apparently working. The other
two units also seem to work (10 MHz output OK, lock OK) but I have never
seen a 1 PPS signal on pin 6 from them. My Tek TDS-210 is easily capable of
triggering on and displaying a 1 usec pulse. Is it possible the pulse
appears only after a RS-232 command, or after some other special condition?
-------Original Message-------
From: David <[email protected]>
To: Discussion of precise time and frequency measurement
<[email protected]>
Subject: Re: [time-nuts] FE-5680A performance
Sent: 05 Jan '12 07:49
On Thu, 05 Jan 2012 01:44:13 -0800, Hal Murray
<[email protected]> wrote:
>[email protected] said:
>>
>> Have an older Tek 465 scope that is in only "fair" shape and I see
nothing
>> on that pin but milivolt level sine wave of about 60MHz. I can't set
the
>> scope to show any hint of a PPS ...
>
>I do have a 465. You should be able to see a 1 uSec PPS.
60MHz is about a 6nS rise time and is easily fast enough to see it.
>Now turn up the Intensity until you can see the pulse. It might help to
turn
>down the room lights.
This is the problem. With a 1 second repetition rate, the brightness
is going to be very low.
The old ways of viewing such a low repetition rate signal include
using a hood or dark room, special CRT phosphors, photographic film,
MCP (micro channel plate) intensified CRTs, and of course analog
storage and later digital storage.
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