Junkbin GPS Stratum 1 NTP Clock Source (A Work in Progress)

I don't know where most of these parts came from, but when I opened my electronics junk drawer the other day I found an Orange Pi Zero+ and a serial GPS of dubious quality that also featured a PPS out.  With these two parts in hand and a suitable project box, my weekend free time is suddenly consumed with a pending project: build a stratum 1 NTP server using only parts on hand.

OK, but what even is that word salad of a title?

Network Time Protocol (NTP) is a method of synchronizing clocks over the internet.  Wikipedia has much better information than I could ever hope to provide here, but the gist is NTP servers are organized hierarchically based on their distance from known stable clock sources.  This distance is referred to as the 'stratum' of the server.  Stratum 0 is a master clock itself, such as a GPS, atomic clock, WWV signal, or other authoritative time source.  Stratum 1 is any NTP server directly attached to a stratum 0 clock.  Since my junk drawer project welds a microcomputer and GPS receiver together, it will (eventually) qualify as stratum 1 (with caveats).

Pulse Per Second (PPS) is a signal put out by time sources to define the precise beginning of a second.  A GPS connected via serial port can vaguely define the time in its NMEA sentences, but PPS provides a stable 'tick-tock' to the time sentences.

New Years' Day aurora

Weather has been weird this winter, with precious few clear nights for stargazing. We got a decent one a week ago though, right as a big solar storm ripped through. I took these shots from my bedroom window.  You can see my weather station and one of the HF antennas in the foreground.

Gull Rock Trail

Hiked about halfway down Gull Rock Trail in Hope today. Reminded me just how out of shape I am, but it was worth it. Hard to take a bad picture on this trail.

AREDN Mesh Access via PFSense Firewall

After several months of wrestling with integrating an AREDN node into my home network, I finally arrived on an iteration that I think I am content with.  It isn't perfect, and I will detail the limitations below, but to sum it up, I am treating the AREDN node as a second WAN, with a bit of tomfoolry to get DNS working properly.

This guide will only allow for access to resources on the mesh.  It will not allow access to the wider internet via the mesh.

Most of the configuration followed the PFSense dual-WAN guide word for word (which can be found here).  As seen in the screenshot above, the connection is set up as DHCP.  One area where I deviated from the guide is unchecking both boxes under the 'Reserved Networks' header, as AREDN utilizes the 10.0.0.0/8 private address space.  On a side note, your home network better not be using the same address space or you're probably going to have a bad day.

The most important key to making all this work is DNS.  If you try and enter your AREDN node's IP address as a DNS resolver for the AREDN connection gateway, PFSense will puke out an error.  This leads to my workaround utilizing PFSense's internal DNS resolver, Unbound.

In PFSense 'services' menu, select 'DNS Resolver' and scroll all the way to the bottom where you will see the header 'Domain Overrides'. Add an override for the domain "local.mesh" pointing at the IP address of your local AREDN node.  This allows unbound to redirect all DNS queries ending in local.mesh to the mesh node.

And that's it! Point your browser at your node and browse around the mesh to make sure everything works as expected.  Note that this is not a perfect solution.  For example, if you host a service behind PFSense that you also wish to expose to the mesh, you will have to add a second set of rules to expose that device and specific port.  In that scenario, it would also be beneficial to add a static IP in your mesh node as well.  However, for simple access to the larger mesh, this solution is hard to beat.

~ moose

Hermes Lite 2 on the air

I spent last weekend tromping through the woods to get a wire antenna up.  It ended up being longer than I expected, and I eventually would like to get it up higher. Maybe this weekend?  Point being, I have a working receiver. Shown in this picture is SparkSDR, a host program compatible with the HL2, running 8 digital skimmers across 4 different bands simultaneously.

I can't get over how cool SDR'S are.

Next step is getting the antenna higher and after that, transmitting. Hope to be checking into sniper's net soon!

KL1V 

HF APRS IGate

 Nothing like a simple fix to a problem you've been banging your head against for months to humble you...

As a bit of background, one of the APRS systems I manage for the KL7AA club is an HF APRS igate, running robust packet (RPR) on 30m at 10.1473 USB.  Its not my favorite mode, given its closed-source nature, but I will grudgingly admit it performs well.  Having a free software modem version available helps make it more accessible, but that's a rant for another post.

This system has been down for most of the winter, and given the harsh winter storms we've had, I believed the issue to be with either the feedline or the antenna, and began to troubleshoot.  Another club member happened to be close by, and we began discussing the issue.  It was at this point they asked 'is this cable supposed to be plugged in?'

It was the interface cable from the modem to the radio.

All winter this cable had been unplugged, making me chase my tail for months trying to troubleshoot it.  Plug it back in, and the packets immediately started to flow again.

Putting my silly moments out there helps keep me humble.

KL1V

Milestones

 Fiber is pulled all the way through the conduit, into the garage and house.  Confirmed as good end to end with equipment connected on both ends.  Next step is to get radios and hamputer relocated, everything on a UPS, vlans set up, etc etc.  The important takeaway though is I now have a working layer 1 between house and garage!

~shotgun moose