Re: [time-nuts] Measurement of frequency of HP 8720D option 1D5 oscillator after switch on

2014-10-04 Thread Bob Camp
Hi I’m not sure *what* goes wrong with the SR-620’s. I do know that I have a couple of them that have problems. Maybe I’m just very good at killing test gear …. One day I’ll sit down and dig through the pile. Bob On Oct 4, 2014, at 8:39 PM, John Miles wrote: >> Out of curiosity, what's the

Re: [time-nuts] Measurement of frequency of HP 8720D option 1D5 oscillator after switch on

2014-10-04 Thread John Miles
> Out of curiosity, what's the difference between the two first traces? > One looks more jump than the other. These are all factory new OCXOs (in this case, they're TimePod spare parts undergoing incoming test before I put them on the shelf). The 1303-series parts both exhibited a small jump a

Re: [time-nuts] Measurement of frequency of HP 8720D option 1D5 oscillator after switch on

2014-10-04 Thread Bob Camp
Hi Both the 5370 and the 620 are getting a bit old. They both run (relatively) hot. Each has their own reliability issues. The 5370 was the more common of the two. Finding parts for it will be easier long term than a 620. Keeping either one fully up to spec long term is likely to be a bit invol

Re: [time-nuts] Measurement of frequency of HP 8720D option 1D5 oscillator after switch on

2014-10-04 Thread Magnus Danielson
Dave, On 10/05/2014 12:13 AM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote: On 4 October 2014 23:03, John Miles wrote: I just stuck an offer on a SRS 620, which is sold as seen. I'll take a chance it works if my offer is accepted. The 5370B is still the only high-performance counter that I

Re: [time-nuts] Measurement of frequency of HP 8720D option 1D5 oscillator after switch on

2014-10-04 Thread Dr. David Kirkby (Kirkby Microwave Ltd)
On 4 October 2014 23:03, John Miles wrote: >> I just stuck an offer on a SRS 620, which is sold as seen. I'll take a >> chance it works if my offer is accepted. > > The 5370B is still the only high-performance counter that I own, personally. > SR620s are fine as far as they go, Is it me, or do

Re: [time-nuts] Measurement of frequency of HP 8720D option 1D5 oscillator after switch on

2014-10-04 Thread Magnus Danielson
Out of curiosity, what's the difference between the two first traces? One looks more jump than the other. Cheers, Magnus On 10/05/2014 12:03 AM, John Miles wrote: -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Dr. David Kirkby (Kirkby Microwave Lt

Re: [time-nuts] Measurement of frequency of HP 8720D option 1D5 oscillator after switch on

2014-10-04 Thread John Miles
> -Original Message- > From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Dr. David > Kirkby (Kirkby Microwave Ltd) >... > If I recall correctly, when I did look some time ago at getting > another TI counter, the Agilent 53230A seemed to have some > specifications *worst* th

Re: [time-nuts] Measurement of frequency of HP 8720D option 1D5 oscillator after switch on

2014-10-04 Thread Dr. David Kirkby (Kirkby Microwave Ltd)
On 4 October 2014 13:24, Tom Van Baak wrote: > Dave, Hi Tom > Thanks for the raw data. Attached is my plot. Your data looks ok to me. Great > If you're interested here are some random comments about your > 8720D-1D5-oscillator-frequency.csv file: Sure > - Thanks for including the descriptio

Re: [time-nuts] Measurement of frequency of HP 8720D option 1D5 oscillator after switch on

2014-10-04 Thread Tom Van Baak
urday, October 04, 2014 3:38 AM Subject: Re: [time-nuts] Measurement of frequency of HP 8720D option 1D5 oscillator after switch on > On 4 October 2014 08:01, Magnus Danielson wrote: >> Tim, >> >> The shape does not look exactly what I would expect from a less than >> crit

Re: [time-nuts] Measurement of frequency of HP 8720D option 1D5 oscillator after switch on

2014-10-04 Thread Dr. David Kirkby (Kirkby Microwave Ltd)
On 4 October 2014 07:57, Magnus Danielson wrote: >> This answers my original curiosity now - did I have an OCXO or TCXO. > > > With that curve it is definitely an OCXO, and my guess is that it is an > SC-cut, which matches starting +40 ppm high (if I recall things correctly). > It is also typical

Re: [time-nuts] Measurement of frequency of HP 8720D option 1D5 oscillator after switch on

2014-10-04 Thread Magnus Danielson
Tim, The shape does not look exactly what I would expect from a less than critical damped oven, it looks a little to peaky, but maybe it is the resolution of the graph that fools my eye. Agree that you end up in critical damped oven with fast warmup requirement. Cheers, Magnus On 10/02/2014

Re: [time-nuts] Measurement of frequency of HP 8720D option 1D5 oscillator after switch on

2014-10-03 Thread Magnus Danielson
On 10/02/2014 09:21 AM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote: On 2 Oct 2014 07:10, "Magnus Danielson" wrote: David, The character of starting high/low and then stabilize some 5-30 min later is typical of oven oscillators. Underdamped ovens have been seen before, I have even seen o

Re: [time-nuts] Measurement of frequency of HP 8720D option 1D5 oscillator after switch on

2014-10-02 Thread Tim Shoppa
As to "oscillation": most older octal style crystal ovens have no proportional control at all, they are simply a bimetallic click-on-click-off thermostatic switch that is on or off, and after initial warmup they cycle up and down every few minutes. A tiny fraction of the better octal crystal ovens

Re: [time-nuts] Measurement of frequency of HP 8720D option 1D5 oscillator after switch on

2014-10-02 Thread Tim Shoppa
The overshoot behavior from 150 to 220 seconds is exactly what you expect for slightly less than critical damping which is where many closed loops end up when rapid lock or warmup is a criteria. Most rapid warmup is almost always the design point of an OCXO oven. Tim N3QE On Thu, Oct 2, 2014 at 3

Re: [time-nuts] Measurement of frequency of HP 8720D option 1D5 oscillator after switch on

2014-10-02 Thread Dr. David Kirkby (Kirkby Microwave Ltd)
On 2 Oct 2014 07:10, "Magnus Danielson" wrote: > > David, > > The character of starting high/low and then stabilize some 5-30 min later is typical of oven oscillators. Underdamped ovens have been seen before, I have even seen one on the brink of oscillation. Thank you. Do you know the likely caus

Re: [time-nuts] Measurement of frequency of HP 8720D option 1D5 oscillator after switch on

2014-10-01 Thread Magnus Danielson
David, The character of starting high/low and then stabilize some 5-30 min later is typical of oven oscillators. Underdamped ovens have been seen before, I have even seen one on the brink of oscillation. TCXO will not have the same wide range, as it compensate for the temperature. Cheers,

[time-nuts] Measurement of frequency of HP 8720D option 1D5 oscillator after switch on

2014-10-01 Thread Dr. David Kirkby (Kirkby Microwave Ltd)
Further to my question the other day about what type of oscillator was used in the HP 8720D VNA, fitted with the high stability oscillator option (1D5), here is the frequency as the instrument is switched on, after being powered off for 2-3 hours. The oscillator appears to start too high in freque