OPEN UNIVERSITY AMATEUR RADIO CLUB
NEWS LETTER no:52
G0OUR/G3OU Affiliated to the OU Club and the Radio Society of Great Britain
I trust this finds you in good health. We'll be holding the 2025 AGM in the shack, at 12.30 on Thursday 16th January. Those who can’t make it in person can join us online, please contact Paul for a link/invite: p.a.maher666@gmail.com
Early in the year we completed a Risk Assesment covering general club activities, as requested by the OU Club. This covers our Thursday lunchtime meetings, and general low level maintenance. Antenna work that involves telescoping/luffing the towers is covered by specific RAMS for those activities.
Early this year we worked with IT and Estates to get access to The Cloud open WiFi network provided on the router in the shack. As installed the router only gave access to secure staff systems. This was finally completed after jumping through a few hoops. This means we can now solve the telnet problem, by connecting the shack PC via Wi-Fi rather than Ethernet, although there is a Wi-Fi time-out (three hours?) so it’s not a fix for everything.
In July Estates organised for contractors to check the winches and cables on our telescopic towers. A representative from the OU insurers was also present to check compliance with LOLER (Lifting Operations and Lifting Equipment Regulations 1998), along with representatives from Estates. Everything checked out okay and we were given a clean bill of health. While the masts were down and partially luffed over, we were able to carry out some quick maintenance tasks. This included freeing up the LF dipole that had got stuck in a tree. Both ends of the 40m and 80m have been tethered to new positions, and the dipoles are finally back properly in operation. On the HD P60, we were able to replace the rope that supports the slack coax. cable around the rotator. The old rope had broken. All in all a very successful day.
More recently we installed a Topband (160m) inverted L antenna, which is working well, although is very noisy on receive (S8 in SSB bandwidth). We have used separate receive antennas in the past so will revisit this. The Topband antenna is fairly close to the 80/40m dipoles, and there is some interaction, so we need to retune those antennas.
Adrian has been approached by the keeper of historic callsign G2OU. This had been used by Farmor’s School Radio Club. The callsign holder has now retired and the school club disbanded, so we were offered the callsign for the OUARC. This was very welcome news and we are persuing this with Ofcom.
We welcome back Alan Wyatt G2DXU into the club. Alan was a member in the distant past, but became inactive on the radio for a while due to a house move.
Thank you to Adrian for manning a stall at the OU Well-being drop-in event. Adrian was also representing the OU Astronomy club, and reported a fair amount of interest, although mostly for the Astronomy club!
Our HF linear amplifier still has an annoying intermittent fault which is proving difficult to track down. Something on the RF output side is arcing internally (nothing visible), which usually trips out the amplifier immediately, or if not badly distorts the signal. This happens on all bands regardless of antenna, or into a dummy load, and usually when the amplifier has warmed up (which doesn’t take long, especially in summer). Using Adrian’s ‘scope we’ve checked out all the supply/bias rails, and found no problems there. We’ll continue fault finding as time permits.
In August Ian G4JXZ provided a Meshtastic 868MHz 150mW node which we have temporarily fitted to P60 mast. This is a light weight low power transceiver/node, attached to a 4dB gain colinear vertical antenna. As it’s so small and light weight we were able to just attach the whole thing to a spare halyard and pull it up to near the top of the P60 mast. The only connection being a 12V supply cable, which converts down to a 5V USB supply at the node. It can be controlled locally by Bluetooth or Wi-Fi, or remotely, e.g. from Ian’s house (~8 miles away). The node worked immediately and Ian showed us a map of other nodes it could see being populated on his smart phone. This node appears on the network as G3OU.
Thank you to Ian for providing the following detailed description:
Many people have not heard of mesh networking, but it is becoming used increasingly in home Wi-Fi systems for interconnection of nodes, relying on each device acting as a router for other devices, creating a mesh which self-heals and does not rely upon point-to-point connections.
Well, the Internet of Things (IOT) also relies upon this type of connectivity for most applications. IOT is generally used for the management of a group or multiple, interconnected groups of devices, mainly designed to pass telemetry data back to a main source, or between each other. It is often used in home automation systems to great effect. LoRA, as it is known (meaning Long-Range, although this has to be put into context) uses the licence-free public bands of 433MHz and 868MHz, of which 868MHz is the most popular. 433MHz tends to be cluttered with spurious transmissions from automatic garage door systems, gate openers, car tyre pressure sensors, home outside weather stations, etc. The max eirp permitted is 27dBM or around 500mW. The system is unique in that is uses ‘Chirp’ Spread Spectrum modulation. There is a Meshtastic group who publish really helpful info, and good link to an introduction on the meshtastic.org website.
Well, a group of techs got together, (initially in the USA, I believe) and decided that this may be a suitable system in which to pass short messages, without relying upon any infrastructure, such as the internet or mobile phone networks. Off-grid, so to speak. They gave it the name “Meshtastic”. (Now you can see why I believe that it was developed in the USA). It is an open source project with software and data available on GitHub.
The devices themselves are tiny and also have full Bluetooth and WiFi connectivity for remote management.
At the moment, I am operating a node in Cranfield (CFD) to try and link Bedford and MK. It has a full node list of 100 user nodes most of the time. The 868MHz node is on the arm sticking out top-right with a 6dBi gain colinear, the 433MHz test node is using my dual-band 2m/70cm colinear at the top.
The unit installed at Walton Hall is identical to the 868MHz node and has been operating for some time. It also has a high node count of around 40 nodes currently. Its node name is G3OU. It is mounted temporarily atop one of the two towers while it is tested, but will be re-affixed to a more permanent location if found worthwhile. Remote management of nodes is possible over the mesh network using Python commands, although I am setting up a remote management and data link using the protocol MQTT (Message Queueing for Telemetry Transport), an original IBM IOT protocol used on most domestic home management systems.
The nodes are great for portable use, linking to your phone via Bluetooth so you can send and provide detailed maps with location and node lists and any other telemetry traffic that the node is equipped to measure.
The hop count can be adjusted from 0 to 7. The OU is set to a hop count of 3 (recommended value) Max eirp is 27dBm or about 500mW on 868MHz. It is 12dBM or 16mW on the 433MHz band. Range is, like all VHF/UHF systems, dependent upon height and terrain. Mine can cover up to about 15-20km line of sight unless a lift is on, in which case it can be 120km. The record for 868MHz in UK is about 200-odd km, but that is usually from a mountain top with a yagi.
That’s all for now and I hope it has provided a brief overview of the Meshtastic system, which is a good source of topics for research. There are papers online describing the Chirp spread spectrum, if you are mathematically inclined. I will put more information in the next newsletter with news on new developments, and how our node at Walton Hall is doing.
All the best and a very merry Christmas and happy New Year to all!
Ian Terrell G4JXZ