EMRFD Message Archive 15213

Message Date From Subject
15213 2019-01-10 17:08:30 peepholenz NDK Osc

Looking for info on a 10Mhz osc : Suspect it is an OCXO

it is marked    NDK  9100Q7 10Mhz Feb'90 No.MF788.    Size about 40x40mm and about 35mm high.Pinout?Specification? Particularly the trim/control voltage characteristics.

Peter

 ZL2AYX

15214 2019-01-10 18:19:17 dave Re: NDK Osc
15215 2019-01-10 20:41:04 peepholenz Re: NDK Osc
Thanks Dave , already in touch with Glenn but still looking for control voltage data.
73
Peter
15216 2019-01-11 09:25:25 Andy Re: NDK Osc
Did you try asking NDK?

They have a "Contaact us" link at the bottom of their webpage.

Andy

15217 2019-01-11 11:14:50 ad7jt Re: NDK Osc
Peter,

Have you considered using a GPS module that you can program the PPS output to generate 10MHz directly?

I have a GPS "clock" with a 50-ohm driver on the PPS output that I can program for any frequency from 1 Hz to 10 MHz in steps of 1 Hz.  It uses the Ublox NEO-6M-0-001 GPS receiver available from many vendors on eBay for as little as $6.29 USD.



73,
Dave Collins - AD7JT
15222 2019-01-15 09:53:51 cctbcn Re: NDK Osc
I have a potload of these things (from scrapped VSAT gear) and here is what I can tell you:

- Nominal voltage:  10-12 volts for the heater:  An internal 7805 is used to regulate down for the oscillator portion.

- Tuning voltage:  0-10 volts seems fine, but like any varactor circuit voltage below about 1 volts would be used at one's own risk.

- Output:  TTL level, more or less.

* * *

Comments:

Several of these oscillators have been used in a local 2 meter synchronized repeater:  The system went online in 2009 and we set the transmitters 4 Hz apart on 2 meters - and they don't seem to budge from that, and really haven't in the 9+ years that it's been running, despite the fact that the units are in mountaintop locations without heat or air conditioning.

It is recommended that the main voltage be regulated as the stability does depend slightly on applied voltage - mostly because different voltage apply varying thermal ballistics to the oven and it will "walk" a bit otherwise - but that's true of practically any single-oven OCXO that I've ever seen.  On the repeater system, during "warmup" (as determined by the current consumption) the system bus voltage (which can be 12-15 volts) is applied to the TCXO to maximize heater power to speed warm-up, but once the oven current drops (e.g. it has warmed) the CPU drops the supply voltage to 10 volts where it has been determined that it can maintain the internal temperature - at least to -20F, which is as low as my freezer would go.

I have distributed several of these units to other local hams and at least one person used one with his 10 GHz transverter:  Given a 30 minute warm-up cycle, it did pretty well, holding frequency to within a few hundred Hz - but because he'd not regulated its input voltage there was a slight, slow frequency shift as his battery voltage (when he ran portable) would change between RX and TX.

* * *

If you are planning to use this for GPSDO purposes, I would make the following modification as the tuning voltage pin is WAY more sensitive than it needs to be:

- Open up the unit
- Power it up and find the regulated 5 volt DC bus.
- Place a 10k resistor between the 5 volt bus and the Tuning terminal.  Because the resistor itself is inside the oven, it need not be super-stable - but use a 1% metal film if you have one.
- Reassemble, let it warm up and stabilize and then, with nothing connected to the tuning terminal, adjust for precisely 10 MHz.

One would then drive the frequency tuning control with a metal-film 100k resistor (or higher) in series:  With 100k and a 0-10 volt tuning range (which would yield roughly 1 volt swing at the tuning terminal) there is plenty of range for this inherent stability of this oscillator.

Best of luck,

73,
Clint
KA7OEI

15226 2019-01-23 14:10:12 cctbcn Re: NDK Osc
I have a potload of these things (from scrapped VSAT gear) and here is what I can tell you:

- Nominal voltage:  10-12 volts for the heater:  An internal 7805 is used to regulate down for the oscillator portion.  I see that 'ZAZ has written 12-24 volts on the one in his picture and that may be OK, but I've not tried above 18 volts.

- Tuning voltage:  0-10 volts seems fine, but like any varactor circuit, a tuning voltage below about 1 volts would be used at one's own risk!

- Output:  TTL level, more or less.

* * *

Comments:

Several of these oscillators have been used in a local 2 meter synchronized repeater:  The system went online in 2009 and we set the transmitters 4 Hz apart on 2 meters - and they don't seem to budge from that, and really haven't in the 9+ years that it's been running, despite the fact that the units are in mountaintop locations without heat or air conditioning.

It is recommended that the main voltage be regulated as the stability does depend slightly on applied voltage - mostly because different voltage apply varying thermal ballistics to the oven and it will "walk" a bit otherwise - but that's true of practically any single-oven OCXO that I've ever seen.  On the repeater system, during "warmup" (as determined by the current consumption) the system bus voltage (which can be 12-15 volts) is applied to the TCXO to maximize heater power to speed warm-up, but once the oven current drops (e.g. it has warmed) the CPU drops the supply voltage to 10 volts where it has been determined that it can maintain the internal temperature - at least to -20F, which is as low as my freezer would go.

I have distributed several of these units to other local hams and at least one person used one with his 10 GHz transverter:  Given a 30 minute warm-up cycle, it did pretty well, holding frequency to within a few hundred Hz - but because he'd not regulated its input voltage there was a slight, slow frequency shift as his battery voltage (when he ran portable) would change between RX and TX.

* * *

If you are planning to use this for GPSDO purposes, I would make the following modification as the tuning voltage pin is WAY more sensitive than it needs to be:

- Open up the unit
- Power it up and find the regulated 5 volt DC bus.
- Place a 10k resistor between the 5 volt bus and the Tuning terminal.  Because the resistor itself is inside the oven, it need not be super-stable - but use a 1% metal film if you have one.
- Reassemble, let it warm up and stabilize and then, with nothing connected to the tuning terminal, adjust for precisely 10 MHz.

One would then drive the frequency tuning control with a metal-film 100k resistor (or higher) in series:  With 100k and a 0-10 volt tuning range (which would yield roughly 1 volt swing at the tuning terminal) there is plenty of range for this inherent stability of this oscillator.

Best of luck,

73,
Clint
KA7OEI

15227 2019-01-23 19:34:54 Jim Strohm Re: NDK Osc
$$$??

15229 2019-01-25 15:54:17 peepholenz Re: NDK Osc
Thanks for that info Clint.
NDK have not been able to find any info on it!
 Running it on 12v regulated with separate well regulated tuning voltage .Mechanical trimmer adjusted to give tune volts between 4 & 5 for about 1in 10^9.Can adjust tune volts with 10 turn pot . In alu box with a bit of foam insulation ,sitting in garage room with ~10 C variation day/night.Impressed with stability measured against Trimble Thunderbolt GPS 10Mhz (using HP53131 counter).Has sat within a few parts in 10^10 for the last fortnight.
Not really intending to use it "seriously" just playing to see what it's capable of. Turning all power off for a minute it takes a few minutes to return to same 10^10 reading as before .Have not yet tried letting it cool completely and see what thermal effect is.
Definitely an interesting little box.
Peter
ZL2AYX