[time-nuts] "Vanguard Ultra precision Golden Oscillator"
t_list_1_only at braw.co.uk
Mon Aug 24 05:02:40 EDT 2015
Hi, I've got bitter experience from about 17 years ago of a high end
Vectron SAW 'vcxo' in a ceramic package which despite internally having
a metal plated 'well' could not be made sufficiently immune to emi
problems on a high density PCA, on the other hand I have a bag somewhere
of Fordhal high spec VCXO in the traditional 1inch square metal
packages that suffered similar problems with all glass seals on the
leads. All of these expensive parts had good phase noise on the bench in
isolation, the grief came when integrated into the complex PCA, the
solution was a different Vectron osc of similar data sheet spec mounted
on a daughter board off the main one. These items were on jitter/wander
measurement products, the intrinsics were critical as was the PLL
response, injection locking rewrote the PLL response and would have
trashed the LF jitter measurement response of the instrument which was
calibrated and adaptive according to measurement.
The final instrument went very well commercially and technically,
measuring perturbations (jitter/wander) continuously 1uHz to 20MHz on
carriers of of 1.5MHz to 2.5GHz. The 1uHz (1week) part was wanted as
some large (continental) SDH loops apparently showed tidal effects when
their clocks were free running.
On 23/08/2015 22:02, Bob Camp wrote:
> If all the spec’s on it are lies, then of course they don’t help much at all. I have
> not contacted the seller with any questions. I have no idea if there is more data
> on the parts or not. Some parts from other sellers with very similar markings have
> quite good paper specs associated with them.
> There are technologies that have been used on similar products over the years that result
> in parts that do not meet that phase noise spec at any point in the frequency range from
> 6 to 100 MHz. Those are the parts that you probably don’t want to use on
> your DDS clock.
> The spec he states is quite do-able over that range without a lot of effort on an XO.
> Who knows if he meets it or not. I certainly know of no reason why he could not do so.
> He might exceed the spec by quite a bit at one end …
> The header production process is a fraction of a cent cheaper if you use all glass seals
> than if you weld one of the leads. In that case, you simply hand weld a ground onto the
> base. A bit ugly, but they save money. Inductance wise, not much difference. It’s miles ahead
> of any of the modern ceramic packages in terms of shielding either way.
>> On Aug 23, 2015, at 2:55 PM, David <t_list_1_only at braw.co.uk> wrote:
>>> The most encouraging thing is that there *is* a phase noise spec on it.
>> BUT its seems to be the same spec on all irrespective of carrier frequency which goes from to 6MHz to 100MHz, with similar design the time jitter may be somewhat similar but I'd be astonished if the phase noise was common to all (implying grossly different time jitter). In addition, the package would worry me, 4 pins all with a glass seal, I want the ground pin to be directly connected to the case to minimise ground inductance leading to issues like injection locking. I'd assume these are cheap and cheerful clock oscillators, similar can be bought with a known brand label and spec from Digikey etc for less $.
>> Message: 14
>> Date: Sun, 23 Aug 2015 08:33:59 -0400
>> From: Bob Camp <kb8tq at n1k.org>
>> To: GandalfG8 at aol.com, Discussion of precise time and frequency
>> measurement <time-nuts at febo.com>
>> Subject: Re: [time-nuts] "Vanguard Ultra precision Golden Oscillator"
>> Message-ID: <86ABCF10-FC65-4713-B286-BDC3E33FEB8E at n1k.org>
>> Content-Type: text/plain; charset=utf-8
>> A few things I would wonder about:
>> 1) Is it 0.1 ppm over 0 to 50C (or some other range)? If not, what is the temperature stability?
>> 2) Does it run at 3.3V -or- at 5V (pick one) or do they run equally well at either voltage?
>> 3) Since there is no EFC, is 0.1 ppm the set tolerance? If it’s not, what is the initial accuracy?
>> Lots of questions, there’s not much information there. That may be due to the seller not
>> having the information. It also may just be because nobody ever asked. The term TCXO can
>> mean a variety of things to a different people ….
>> The most encouraging thing is that there *is* a phase noise spec on it.
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