[time-nuts] How I got my FE-5680A to lock in Sydney, Australia

Jamieson (Jim) Rowe jimrowe at optusnet.com.au
Sun Feb 9 19:39:56 EST 2014


Hi again Magnus, Mark, Tom Harris, Ed Palmer et al,

Well, before performing any surgery on my tricky little beasty, I decided to 
check its frequency swing limits when starting up in the 'inverted' 
position, and then when starting up in the right-side-up position. Here's 
what I found, as before looking at the frequency with my counter (GPSDXO 
1pps timebase):

Inverted position:  swings between 9,999,798Hz and 10,000,001Hz, before 
locking.
Normal position:   swings between 9,999,756Hz and 10,000,057Hz, a few times.

But wait for it -- it then locked up, reliably, in the right-side-up 
position!

So now I'm really confused. It looks as if whatever was wrong with it before 
has somehow fixed itself, after running it for a couple of days locked in 
the inverted position...

Anyway, I think I'll leave opening it up for a while (at least) -- since 
it's now running locked fine in the right-side-up position. I don't want to 
tempt fate, while its OK.  What's that old adage?  If it ain't broke, don't 
try to fix it.

Cheers all,

Jim Rowe


-----Original Message----- 
From: Jamieson (Jim) Rowe
Sent: Monday, February 10, 2014 8:05 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia

Hi Magnus,

Thanks for your further comments. As you probably saw in my reply to Mark
Sims, I am proposing
to check the swing limits 'before and after' inverting the unit, to check
out the theory before I open it up and try tweaking C217.

Cheers,

Jim


-----Original Message----- 
From: Magnus Danielson
Sent: Sunday, February 09, 2014 7:34 PM
To: time-nuts at febo.com
Subject: Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia

On 09/02/14 02:57, Jamieson (Jim) Rowe wrote:
> Hi Magnus,
>
> Thanks again for those further suggestions. I do have a GPSDO, and I had
> been able to use it with a counter to check that the FE-5680A was
> swinging either side of 10MHz. But I didn't make sure that it was
> swinging evenly each side of 10MHz . According to my notes it was
> swinging between  9.999770 and 10.000036MHz -- i.e., about 230Hz low and
> about 36Hz high. But it was spending more of the time below 10MHz than
> above -- does this suggest to you that I should tweak C217 until it
> swings by about the same amount either way?

Yes, that is exactly what I would do.

Cheers,
Magnus

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