[time-nuts] Frequency divider PCB: Current status on "pre-ord ers", and pointers to documentation.

Reeves Paul Paul.Reeves at uk.thalesgroup.com
Thu Mar 18 09:28:47 UTC 2010


Hello David,

Could you add me to the list for one board please?

regards
Paul Reeves     G8GJA

-----Original Message-----
From: David C. Partridge [mailto:david.partridge at dsl.pipex.com]
Sent: 17 March 2010 18:28
To: TekScopes at yahoogroups.com; TekScopes2 at yahoogroups.com;
hp_agilent_equipment at yahoogroups.com; TestEquipTrader at yahoogroups.com;
'Discussion of precise time and frequency measurement'
Subject: [time-nuts] Frequency divider PCB: Current status on
"pre-orders", and pointers to documentation.


The current situation is that I have almost enough statements of intent to
get to the magic 50 which will allow a price of GBP14.50 per board plus
delivery.   For the avoidance of doubt, this is the price for a bare PCB,
not for a kit, and definitely not for a made up board.

I intend to "keep the book open" until 18:00 Zulu (UTC or GMT) on Sunday
21st March, I will then count up what I have and order that many boards (and
maybe a few over to get a nice round number).

I've received numerous reqeusts for the design documentation, schematic, and
a bill of materials

They can all be downloaded from my website, but there's no way (yet) to
navigate to them (a round tuit problem).

Write up:

<http://www.perdrix.co.uk/FrequencyDivider/Frequency%20Divider%202.pdf>

Schematic:

<http://www.perdrix.co.uk/FrequencyDivider/Frequency%20Divider%202%20Schemat
ic.pdf> 

and BOM:

<http://www.perdrix.co.uk/FrequencyDivider/Frequency%20Divider%202%20Bill%20
of%20Materials.pdf>

The schematic and write up have both been updated today, and the BOM is new
today.

For those who worry about SMT soldering, you don't need a reflow oven, it
can all be done with tweezers, a small tipped iron, fine solder wire, and
liquid flux (or a flux pen).  A good pair of strong reading glasses helps
too!   See:

<http://www.curiousinventor.com/guides/Surface_Mount_Soldering/101>

I've also had questions on part pricing:  Back in 2008, the cost to populate
one PCB using a MAX999, thick film resistors, and standard (X7R) chip
capacitors was about GBP28 including Molex headers and SMB sockets.   I
don't expect it to be massively different now.   I'm afraid I don't have
full parts kits, and the necessary up front costs to do so is more than my
finances allow at present.

FWIW, the ADCMP600 is a bit pricier than the MAX999, and is supposed to be
"better", though I'm not sure in what respects it is better.

If you want the lowest possible level of phase noise, you would follow the
bill of materials recommendations and use thin film resistors and C0G
capacitors in the clock shaper part of the circuit at the very least, but
this adds considerably to the cost (for example 100nF C0G 1206 capacitors
are about 1 pound each, while an X7R part is only a few pence).

Regards,
David Partridge


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