I presented this talk at the 2019 RSGB convention on 13th October 2019 at Milton Keynes. It is more of a polemic and call-to-arms to work on ways to push the limits of VHF/UHF/SHF weak-signal communications in the way the LF enthusiasts have, working with Eb/N0 very VERY close the the theoretical limit, but we are up against stochastic processes which spread troposcatter and other DX propagation modes on the sub-metre wavelengths and make the LF approaches less than useful.
I am calling for the implementation of an adaptive feedback channel using perhaps 146 or 71MHz datacomms, perhaps New Packet Radio or something dedicated, to give us a way to close the loop and modify transmit parameters on the fly. This is not going to be easy, but it could be a nice challenge. It also might fit the Ofcom criterion of “Not just more of the same” on the new allocations.
This is a Microsoft Powerpoint pptx file. Please don’t copy it to other websites, just create a link pointing the this page.
Time to turn the CAD design into something physical. Brass rod and my ancient Colchester 1800 and Bridgeport have come up with this as a first try. The barrel adjuster permits positioning the back of the waveguide flush with the inner end of the 8mm cavity, and up to about 6mm inside the reamed 4mm tube. Normal setting will probably be around 1.6mm
Based on the excellent work being done in Australia with the boards using the SiliconRadar 122GHz chips, I decided to have a go at making a version of their diplexer with a thread and locknut instead of a sliding piston and grubscrew. Also I am using brass. No particular reason other than the fun of making things. I did some initial sketches in Fusion360, and made a few of the locknuts last night, now making some horns to see how they look in real life.
There are some very useful changes to the available registry entries to control Windows Time Service in recent W10 versions:
Slewing during leap-second events
Maximum slew rates for corrections
Spike detection thresholds
Max/min polling intervals
Configurable update interval during slews
I have configured it pretty much the same as I had configured the NTP from Meinberg, with a set of UK-based pool.ntp.org servers, and a minimum poll of 64s and max poll of 1024s.
At initialisation, it does a DNS lookup for the hostnames of configured time servers, returning multiple addresses as expected when I use the 0.uk.pool.ntp.org address (or the 1., 2. or 3. of course).
It then sends a single NTP request to the first address in each of the pools, using NTP version 3.
and gets back a response:
It then polls again after 64 seconds. Once the dispersion and offset
are within limits, it backs off to 128s, then 256s and finally to 1024s
between polls. Only a single request each time.
Initially, the HostPoll value is 64s.
After 20 minutes, it has backed off to 256s between polls
Checking sync with other ntp servers out in the internet, it looks
like we are within 10ms, but again that is probably closer than you
could verify using a simple request as the network latency is at least
The slewing controls need some serious verification, as does the
spike detection. For an SNTP server, this isn’t too bad. It does look
as though there isn’t quite the equivalent of the drift file in NTP, but
there is a record in the registry showing the current clock rate, which
can be offset from the default 156250 and may offer the same
drift-control facility (mine is at 156249 at the moment).
In HKLM\SYSTEM\CurrentControlSet\Services\W32Time\Config I have:
I have enabled verbose logging, checked the HoldPeriod is set to the
default 5 attempts and set the Max and Min poll intervals to 2^10
(1024s) and 2^6 (64s) respectively.
The UpdateInterval only applies where you have configured a Type 1
NTP server, and there is a special update interval setting to match
that. I am using only Type 3 server entries (the default) which says
“Dear Server, please feel free to configure my time, but I won’t try to
mess with yours”.
In the HKLM\SYSTEM\CurrentControlSet\Services\W32Time\TimeProviders\NtpClient registry section I have:
SpecialPollInterval isn’t used except with a type 1 server entry.
Blocking the replies from the currently-selected source results in
the ValidDataCounter for that source decrementing by one after each
update interval. Despite the update interval being dropped to 16s, the
W32Time client process only appears to poll at the rate of the overall
application, and it is now 256s, so I have a long wait for it to time
out. It has decremented the reachability to zero and the same for the
ValidDataCounter and puit the server intp “Pending” status after about
1000s. No sign of any DNS lookups since the client first started. Also
(weirdly) no sign of a DNS TTL in the DNS returned by my broadband
router, and neither is there any entry in ipconfig /displaydns for the
After 2400 seconds, the client decided that the server was dead, and
it did another DNS lookup for the missing host, and started sending
single ntp queries to the new IP address.
I’ll keep an eye on it to see if it remains at this sort of offset. 10
to 20ms is fine for all the hobby digimode stuff I’m doing, but it would
be pants for forensics or trading. After a few hours is it running at
5ms ahead of a range of other ntp servers, climbing slowly. It hit 8ms
and the clock value changed and now it is ramping slowly downwards.
So at the moment, this up to date Win10 1903 desktop is running a slightly-more-configurable SNTP with decent audit logging, but not “proper” NTP. Is there a trick to make it do “proper” NTP like Meinberg does? I tried making the servers type 0x1, that had no effect.
Also, when a normal human being is asked to make a load of registry
changes just to get a useable time facility, the response is usually a
bit less positive than “Oooh, great, no problems”.
Can’t say I’m over-keen on putting the necessary keys into a .reg
file for distribution, but I guess that is the only way except for
Meinberg beats this hands-down for simplicity and performance at the
moment, and the Meinberg monitoring tool and CLI tools are better. OK, I
could run a load of CLI things in Powershell or the Windows Linux
subsystem, but it still feels like the usual MS way of reinventing the
wheel, late and poorly.
We shall see if the stability and handling of spiked or drifty sources is better or worse than “proper” NTP.