[time-nuts] FE-5680A help/identification (again!)
Ed Palmer
ed_palmer at sasktel.net
Sat Apr 20 02:33:45 UTC 2013
Hi Skip,
You might have seen my reference to the small board in the 'variation 2'
FE-5680. I looked at the signal on the orange lead and found only about
2.02 Vdc. The orange lead goes to the output of a D-A converter on the
small board. So, on a hunch, I used a 10-turn pot to put 0-5V into the
main board at the point where the orange lead connected. My hunch was
good. It's the analog tuning input. Range on my unit is about 3e-9 for
0-5 volts input. Higher voltage = higher frequency.
So I know *what* the board is doing, but I can't imagine *why*. Is it
nothing more than temperature compensation? Is it just a factory
calibration adjustment? Are they attempting to compensate for the Rb
aging by following some model and gradually changing the frequency of
the DDS or the C-field? Maybe a model, even an inexact one, helped them
to meet a more stringent aging spec. No clue. You'd have to watch the
output voltage of the small board and track it over time to see how or
if it changes.
I didn't attempt to talk to the board so I can't help you there.
Ed
On 4/19/2013 3:46 PM, Skip Withrow wrote:
> Hello Nuts,
> I know the FE-5680 (and FE-5650) have been discussed at length here.
> However, I'm trying to figure one out and need a bit of help.
>
> Yes, there are MANY variations - but I have found the telecom units to
> generally fall into three classes.
>
> 1. The "10MHz and 1pps" units. These need +15V on DB9-1 and +5V on DB9-4
> and have both 10MHz (DB9-7) and 1pps (DB9-6) outputs. RS-232 is on DB9-8 &
> 9. These units have two labels on the top of the unit - one large and one
> smaller. These units are programmable over a small range using the RS-232
> interface.
>
> 2. The "1pps only units". These need only +15V on pin 1 and only have the
> 1pps output on pin6. These units have only the smaller label on the top of
> the unit. FLL runs at 50.xx MHz, DDS outputs 8.3xx MHz. The DDS is
> presumably programmable over a wide range, but the RF signal and RS-232
> lines must be brought out of the box. A photo is attached of the inside of
> this unit.
>
> 3. The "new(est) FE-5680A". I have not had one to examine, but pictures
> are on Diders website. These units have only the single board inside (and
> not the stacked configuration). I don't know the I/O configuration. FLL
> runs at 60MHz.
>
> I have several questions:
>
> 1. How do the older units with both 10MHz and 1pps (#1) get both outputs?
> (perhaps they had decade dividers, as opposed to the 2E23 division of
> variation '2'?
>
> 2. In the photo of variation '2', What is the function of the small board
> at the left? I know it has been mentioned before, but can't find the
> reference. It only seems to have three connections - power (red), ground
> (black), and analog voltage out (orange). The orange wire is connected to
> one side of an optional component, the other side of which goes to DB9-9
> (Are there options of the 5680 that use pin 9 for EFC or C-field
> adjustment? - the optional component being a resistor). This board has its
> own microprocessor and lots of associated circuitry, but does not seem to
> have any input unless it is the device that is thermally bonded to the
> center support/heatsink (a LOT of harware for temperature compensation).
> This small board also has an RS-232 converter, the signals come out to two
> pins on the small 5-pin connector on the bottom of the board. Anybody have
> a clue as to protocol?
>
> Any help would be appreciated. Thanks in advance.
> Regards,
> Skip Withrow
>
>
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