[time-nuts] Chinese NTP Time server

Fri Dec 27 19:12:46 UTC 2019

On Fri, Dec 27, 2019 at 2:24 AM xaos <xaos at darksmile.net> wrote:

> Brian,
>
> I created a new web  page with some pics and a live output of the NTP
> server from "Lady Heather V5.0"
>

Nice. Did you interface LH using the serial output or through a network
connection? I haven't run LH in about 6-7 years so I don't know its current
feature set. I haven't made a cable for the HD-15 connector.

> https://www.maximaphysics.com/GPS.shtml
>
> You can clearly see the Missing OP-AMP on the bottom of the unit in the
> pic.
> You would think that these guys would add a penny part to this ...
>

Well, the parts came to around $10(us) from Mouser but I get your point.
They should be here today so I should be able to give you more info tonight.

>
> The guy I bought it from has already agreed to have me sent it back.
> However, If you get yours working I don't want to bother. Also, I wonder
> of my OCXO from a HP counter
> would fit in there. Prob needs lots of work.
>

The OCXO is powered by the +12V supply after passing through the input
filter. The wall-wart switcher they provide is quite noisy, as one would
expect of a cheap wall-wart switcher. (Ripple and noise measuring about
60mV p-p with ripple and switching transients clearly visible.) Measuring
the noise at the input to the OCXO the noise is down to about 15mV, mostly
just HF noise, around 50-60MHz my 'scope says. Switching transients and
ripple are gone. So it appears to me that they did spend some effort trying
to quiet down the noise at the power input.

And here I was worried what my next crazy project would be.
>

Heh.

> George, N2FGX
>
> On 12/22/2019 12:49, Brian Lloyd wrote:
> >
> > On 11/26/19 09:28, xaos at darksmile.net wrote:
> >> Hello everyone,
> >>
> >> Does anyone here know about this item:
> >>
> >>
> https://www.ebay.com/itm/Brand-New-NTP-Time-Server-GPSDO-GPS-Disciplined-Oscillator-GPS-Clock/362758051388?hash=item547610963c:g:yFIAAOSwgztdgfM9
> >>
> >>
> >> George, N2FGX
> > OK, I ordered one. I missed the part about the 10MHz output being
> > "optional". (Optional? Really?) So I ordered one and it arrived 2 days
> > ago. Delivery took about 3 weeks. Looks nice, well packed, no damage. It
> > includes an active GPS antenna with about 20' of RG174 and a 12VDC
> > wall-wart. Unit, antenna, and PSU, nothing else. No doc and no software.
> > No problem ... so far.
> >
> > Plugged it in. Power supply LED comes on and the Sync LED is flashing at
> > about 2Hz. About 20 seconds later the SV LED comes on. about 2 minutes
> > later the Sync switches to 1Hz. I am guessing it has achieved some sort
> > of lock. I connect the 10MHz output to my FA-2. Of course, no 10MHz
> > output. (More on this later.) I plugged it into the network. Looked at
> > my DHCP server. No IP address assigned. Huh. How do I find this thing on
> > my network?
> >
> > eBay message back to the seller. Seller sends me a link to a zip file
> > with the software and doc. The first 'uh oh' is that all the file names
> > are in mandarin. I must admit, I find <mandarin>.pdf and <mandarin>.exe
> > amusing. I have an old laptop that dual-boots Linux and Windows just for
> > this sort of thing, i.e. annoying software that only runs on Windows. I
> > extract everything from the zip file and try things out. One of the
> > programs shows just an ip address of 192.168.0.100 and has three windows
> > separated into dotted-quads. Could this be the tool that sets the IP
> > address, subnet mask, and gateway? I run the PDF that opens with a
> > picture of the unit through google translate. OK, yes, that is what the
> > program does. There is a picture of the window and, guessing at the
> > examples, I was right, IP addr, mask, and gateway. With 5 buttons to
> > click on in varying orders, it tooks me several tries to finally get it
> > to change its IP address to one on my network. It is now pingable.
> >
> > I look at some of the other programs. These are mostly in English, being
> > open software, and do things like let you look at the status of the GPS
> > receiver. After successfully setting the IP address of the unit, I was
> > able to run the utility 'PowerGPS.exe' and have it report GPS status
> > from the box.
> >
> > So I pointed ntp on my linux server at the box as a server. It synced
> > right up and chose it as the primary ntp source. Clearly it works just
> > peachy as an NTP server and is running in my network that way. Now to
> > tackle the lack of 10MHz output.
> >
> > Opening up the box it clearly has a 10MHz OCXO so getting something out
> > the 10MHz BNC connector should be fairly straight-forward. Examining the
> > bottom of the board, the path from the OCXO to the 10MHz BNC output is
> > pretty clear. It goes through a single buffer op-amp and then drives the
> > BNC jack. The only problem is, the op-amp is missing. The pads are for
> > an SO-8 package. Following the traces it is pretty clear it is a
> > standard, single-op-amp pinout, i.e. :
> >
> >   1. n/c (null)
> >   2. inverting input
> >   3. non-inverting input
> >   4. V-
> >   5. n/c (null)
> >   6. output
> >   7. V+
> >   8. n/c (null)
> >
> > Lots of parts could go there. Looks to me like it should probably be
> > something like an LT1227. The op-amp is operated at a gain of 2 with a
> > 100ohm FB resistor and 100ohm to ground. This should be pretty stable
> > with 100ohm pretty much swamping any parasitic capacitance in the FB
> > loop. The input is a 300 ohm/300ohm voltage divider so the overall gain
> > of the stage is unity.
> >
> > Input to the buffer from the OCXO is capacitively-coupled as is the
> > output. There is a 50ohm resistor in series with the output. The
> > unloaded voltage output of the OCXO is a 3.5V positive square wave.
> > After passing through the buffer it is probably supposed to approximate
> > a 3V p-p sine wave. (At least, that is what the marketing verbiage
> > suggests.)
> >
> > The board is already populated with linear +5v and -5v regulators (74L08
> > and 74L09 respectively) and associated bypass/filtering. +5v is present
> > at pin7. No -5v is present. Tracing the board back to the source of the
> > -V at the input to the -5v regulator, one arrives at an empty 4-pin
> > through-hole area marked u14. This has +7.5V on pin 2 which also feeds
> > the input to the +5V regulator. Pin 3 is the -V output that feeds the
> > input to the negative analog regulator. So the 64-dollar question is:
> > does anyone know of a chip/module that is a 4-pin, 0.1" pin spacing,
> > single-output, inverting regulator module, producing -7V from a +7V
> > input? I need to find something like that to populate this board and get
> > the 10MHz output. I haven't been able to find anything on Mouser or
> > Digi-Key. I am guessing that this is something that already exists as a
> > module but ...
> >
> > Yes, I have asked the seller about the parts to populate the board or
> > the option of returning it and getting one already populated. If the
> > seller tells me to go pound sand I would like to manage to make this
> > work anyway.
> >
> > Hmm ... if I DC couple the input and run the op-amp with a single-ended
> > +5v supply, it might work without the negative supply at all. My only
> > worry would be latch-up because the input would be going right to the
> > negative rail and approaching within 1.5V of the positive rail. OTOH,
> > most op-amps now are pretty immune to latch-up. Just thinking aloud
> > here. I am sure someone here has some ideas about getting this to work.
> >
> > Thanks in advance for humoring me.
> >
> >
>
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-- 

Brian Lloyd
706 Flightline
Spring Branch, TX 78070
brian at lloyd.aero
+1.210.802-8FLY (1.210.802-8359)