[time-nuts] Inside a CTS 1960017 OCXO

Bob Camp kb8tq at n1k.org
Sat Feb 27 17:17:08 EST 2016


Hi

Ok, so that’s phase modulation and not frequency modulation. Simply put, it’s not a high level 
signal into the EFC. It’s also not anything inside the oscillator loop. Normally the best way to do
a broadband phase mod like that is to feed a signal into the input of the output buffer. I’d check it
with a couple of different loads and see if that chip sings when loaded this way vs that way.

Bob


> On Feb 27, 2016, at 4:18 PM, Rob Sherwood. <rob at nc0b.com> wrote:
> 
> Here is a look at the spectra.  6.3 kHz span, 7.6 kHz resolution bandwidth. 
> I have a 1.6 MB file with better resolution, but I assumed that would never make it through the reflector.
> Rob
> NC0B
> 
> -----Original Message-----
> From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Bob Camp
> Sent: Saturday, February 27, 2016 12:25 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Inside a CTS 1960017 OCXO
> 
> 
> 
> Hi
> 
> The controller shown on the PC board is not a chopper. The only reason you would be getting 60 Hz is that somebody did an “aw shucks” and left a part off the board. I suppose they could have left a part off (or put the wrong part on) on whole batch of them. I’d make sure it still does it with a big bypass (100 uF tantalum) on the supply right at the OCXO before I gave up on the parts. 
> 
> Given that it’s China, those parts may not have any relation at all to the CTS we think of over here (regardless of how they are labeled). Internal workmanship and design suggests that they did come from CTS.
> 
> Bob 
> 
>> On Feb 27, 2016, at 12:35 PM, Rob Sherwood. <rob at nc0b.com> wrote:
>> 
>> Hi Dan,
>> 
>> I purchased two of these, and VA7OJ one.  One of mine is defective, and the seller is going to replace it.  What was disappointing was all the spurious at 60 Hz intervals relatively close-in to the 10 MHz carrier.  I suppose if all one wants is a reasonably accurate 10 MHz, then they work OK.  My good one and Adam's unit were 1x10^7 low in frequency once warmed up, and there are pins for frequency adjustment and sync to another standard.  However if one wanted it for an oscillator with good close-in phase noise, the spurs ruin that hope.
>> 
>> Do you know if there is a chopper at 60 Hz that runs the proportional oven that is the source of all the spurious?
>> 
>> Rob
>> NC0B
>> 
>> -----Original Message-----
>> From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of 
>> Daniel Watson
>> Sent: Saturday, February 27, 2016 9:48 AM
>> To: time-nuts at febo.com
>> Subject: [time-nuts] Inside a CTS 1960017 OCXO
>> 
>> 
>> 
>> Hi,
>> 
>> I'm sure many of you are tracking the cheap CTS 10MHz OCXOs available on eBay right now. I purchased a case of them, and decided to crack one open.
>> I took pictures along the way, thinking that might be interesting to the list. Here is the blog post if you are interested:
>> 
>> http://syncchannel.blogspot.com/2016/02/10mhz-ocxo-teardown-cts-196001
>> 7.html
>> 
>> Comments on the internal construction of the OCXO are welcome. It seems pretty straightforward inside though.
>> 
>> 
>> Best regards,
>> 
>> Dan W.
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