[time-nuts] Wenzel VHF PLO Oscillators Off Frequency

[Bob Camp]

Hi

I guess my point was more that there is not a VCO / PLL combo in an OCXO. 

If dropping the supply gets you on frequency, then you have moved things a lot
with that voltage change. 50 PPM is a lot of delta T on any normal OCXO crystal. 
That strongly suggests there is something wrong in the control circuit. 

Bob

> On Nov 12, 2017, at 2:52 PM, Mark Goldberg <marklgoldberg at gmail.com> wrote:
> 
> The standard oscillator, 501-14057 (
> www.wenzel.com/wp-content/parts/501-14057.pdf) will lock to an external 10
> MHz reference and this one is marked "80 MHz" and "15V on the label. Maybe
> someone swapped the labels. I did try lowering the supply voltage. It got
> to 80 MHz at about 11V and still did not lock to the reference. This
> oscillator is specified at 1e-6/year aging. That is way less than it is off
> now.
> 
> Mark
> 
> On Sun, Nov 12, 2017 at 12:34 PM, Bob Camp <kb8tq at n1k.org> wrote:
> 
>> Hi
>> 
>> It’s pretty certain that there is no PLL inside an 80 MHz low phase noise
>> OCXO.
>> If it is 4 KHz off frequency at 80 MHz, that gets you into the 50 ppm
>> range. Either
>> it is running on a really odd crystal spur or it’s not at the right
>> temperature. Drifting
>> around by 100’s of Hz ( = ppm’s at 80 MHz) is also a good indication that
>> the oven
>> is not doing it’s job correctly.
>> 
>> If multiple units do the same thing, either they all got busted being
>> puled from gear
>> (unfortunately that’s common) or you are running it at the wrong supply
>> voltage.
>> 
>> Bob
>> 
>> 
>> 
>>> On Nov 12, 2017, at 1:19 PM, Mark Goldberg <marklgoldberg at gmail.com>
>> wrote:
>>> 
>>> The seller has replaced it with one that does the exact same thing, which
>>> is weird to have two fail in the same way. They are getting hot and the
>>> frequency varies with the input voltage, so I tended to guess not the
>>> heater as I don't think it could pull that far over temp, and it always
>> is
>>> high. If it has an unlocked PLL on the output, with no control, would it
>> go
>>> to the max frequency? Since the seller seems to be reasonable, I was
>> trying
>>> to figure out best not to waste both of our's time, and me get a good
>> unit
>>> and them getting a sale.
>>> 
>>> Mark
>>> 
>>> 
>>> On Sun, Nov 12, 2017 at 9:22 AM, Bob Camp <kb8tq at n1k.org> wrote:
>>> 
>>>> Hi
>>>> 
>>>> As a guess - the oven circuit has stopped working. Next step
>>>> would be to tear it open and trace out the schematic. After that
>>>> make reasonable guesses for any parts that are poorly labeled.
>>>> 
>>>> Much of what shows up on eBay has been through the ringer in
>>>> China. A high percentage the OCXO's I get on eBay show up with
>>>> issues as a result. There is no way to be sure this or that part was
>>>> ok before it came out of the gear it was in. It’s always a gamble.
>>>> 
>>>> Bob
>>>> 
>>>>> On Nov 12, 2017, at 10:41 AM, Mark Goldberg <marklgoldberg at gmail.com>
>>>> wrote:
>>>>> 
>>>>> I have obtained a couple 80 MHz Wenzel Oscillators P/N 500-16423A. They
>>>> are
>>>>> proprietary but similar to the VHF PLO and 501-14057 Oscillators. I
>> want
>>>> to
>>>>> use this to replace the internal oscillator in my Perseus SDR, for
>> better
>>>>> accuracy and maybe better phase noise. Both of these are way off in
>>>>> frequency, about 4-5 kHz high from the ideal 80 MHz, and drift around
>>>>> hundreds of Hz. I believe they are broken in some way. The PLL lock
>>>> signal
>>>>> toggles when I put an input into the 10 MHz reference, but the output
>>>>> frequency is not affected.
>>>>> 
>>>>> Wenzel has answered some of my questions, but can't get specific as
>> these
>>>>> are proprietary to a customer.
>>>>> 
>>>>> Any experts on these oscillators out there?
>>>>> 
>>>>> Thanks,
>>>>> 
>>>>> Mark
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