Bob, I've been mulling over the question of a case, and I was thinking of getting a 2M brick amp and putting it inside, bolted upside down to the heat sink.  Good idea?  Anybody got a busted one?

Bob

Hi

There are lots of case solutions. A busted piece of HP gear is a nice way to come up with a case. Heatsink material is available from several web sites cut to order quite cheap. A simple computer fan is way more air than you will ever need. The obvious missing link is the controller. I'd run something up with a micro talking to a 4 wire fan header. That way you have tach feedback on the fan and all the PWM stuff is driven on the fan end. More or less a weekend project on a piece of pert board. Maybe a bit more than that if you do a pc board.

(yes I realize this heading horribly close to talking about building things …. alarm bells are ringing somewhere…..)

Bob

On Sep 18, 2013, at 8:32 PM, Bob Stewart bob@evoria.net wrote:

Hi

Some numbers:

Your Rb should hold <10 ppt per month. It's 1 second ADEV should be about 10 ppt as well. (makes it interesting to measure).

Your Rb should hold  < 1 ppt per degree C on average. It will have a nasty glitch (around 1 ppt as it steps over a temperature boundary). Best to keep it stable to < 0.5 C.

For long(er) averaging times the Rb should have an ADEV that goes as the square root of tau. It'll be 10X better at 100 seconds than at 1 second. It could be 100X better at 10,000 seconds except for that glitch. It's not going to get beyond 0.2 ppt ADEV without some major help.

All that said, with simple temperature stabilization, it should let you check out your GPSDO for drift. Within the ADEV imposed limits it'll tell you if things are holding together on a day to day / week to week basis.

Bob

On Sep 18, 2013, at 8:32 PM, Bob Stewart bob@evoria.net wrote:

Bob,

Does your Rb send the serial out on the DB-9, or did you solder in a connection?  I'm looking at mine and it looks like pin 8 is connected to something and pin 9 seems to come in to an empty SMT slot for a cap or resistor.  I was thinking of bringing a ribbon cable out between the covers above the DB-9, but maybe I should just take over 2 pins on the DB-9?  Any ideas what the pins 8 and 9 would have been hooked up to if they don't go to the serial input?

Bob

Hi

All of my FE Rb's have serial out of a 9 pin D connector. They bring power (+15 and +5) in on that connector, and put 1 pps and 10 MHz out on the same 9 pin D.

There are (apparently) dozens of variations of the FE 5680. There is no single standard for what is hooked up where. I'd be very careful about playing with wires I had not either traced out or had data from the seller on. It's very easy to blow one of these beasts up.

On mine serial is normal RS-232 levels on pins 8(rx) and 9(tx). 15 V power is on pin 1, ground on pins  2 and 5, +5 power is on pin 4.

Outputs are on 6 (pps), 7 (10 Mhz), 3 (lock).

Again - I'd be very careful with information that may or may not apply to your specific Rb.

Bob

On Sep 20, 2013, at 5:25 PM, Bob Stewart bob@evoria.net wrote:

Understood.  If I do anything, it will probably be to cut pins 8 and 9 at the board side of the connector and route the serial connections there.  I dislike opening this thing up any more often than I have to.  Thanks for all the info.

Bob

If the lock output comes from the micro or a logic port with a maximum
output of 3.3 or 5V, a LED connected to it from +15 will be always ON.

On Sat, Sep 21, 2013 at 4:55 PM, Bob Stewart bob@evoria.net wrote:

There is a problem introduced if you sink too much current off the lock pin.
An LED draws enough current to cause the issue, I think to do with not going into lock or PPS output.
If I could just remember what the issue is...

Anyway, this guy has it nailed:  http://www.ka7oei.com/10_MHz_Rubidium_FE-5680A.html

Except, the ones that I have that need a +5V supply are programmable. Go figure..

--marki

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf Of Azelio Boriani
Sent: Sunday, 22 September 2013 1:25 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] FE-5680A Loop Lock Indicator

If the lock output comes from the micro or a logic port with a maximum output of 3.3 or 5V, a LED connected to it from +15 will be always ON.

On Sat, Sep 21, 2013 at 4:55 PM, Bob Stewart bob@evoria.net wrote:

time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Hi

As far as I know the lock output is a CMOS output that will drive a couple of ma. There are so many variations that yours may indeed be an open collector and good to +15 volts.

Bob

On Sep 21, 2013, at 10:55 AM, Bob Stewart bob@evoria.net wrote: