FOSDEM is a free event for software developers from all over Europe to meet, share ideas and collaborate and it held this year in Brussels on the 1st & 2nd of February 2025.
Out of the 1000+ lectures, a few were radio related...
Saturday - 1st Feb 2025 Using AI hardware accelerators for real-time DSP on embedded devices - NPU, TPU etc, M17 and OpenRTX: one year later The AFF3CT framework for building numerical communication chains HAMNET - Status Update RF Swift: A Swifty Toolbox for All Wireless Assessments SDR++, a modular, cross-platform SDR utility Broadband data transfer over USB for GNU/Linux: 1-2 GHz (L-band) SDR receiver Meshtastic - off-grid communication for everyone Yet another new SDR runtime?
Some of these talks have slides available in PDF format and there are links if you want to explore the subject more.
HAMNET is a Highspeed Amateur Radio Multimedia NETwork developed from an experiment into a stable infrastructure, particularly in German-speaking countries. It generally connects unmanned amateur radio stations via microwave links using the IPv4 and BGP protocols and provides a platform for networking amateur radio applications.
M17 is an open source protocol for digital radio and its goal is to allow radio amateurs to communicate via digital voice and data. The M17 team are also developing open source hardware in conjunction with this. The net result is to have hardware and software that is designed for the amateur radio community and is not dependant on commercial companies or third parties. In other words, M17 is designed by radio amateurs for radio amateurs.
Meshtatsc is described as follows... "Meshtastic is an open source, off-grid, decentralized, mesh network built to run on affordable, low-power devices. It uses Lora-P2P with dedicated radio chips and forms ad-hoc meshes. In HAM mode the encryption is switched off and the ISM airtime restrictions are lifted."
Meshtastic goes beyond the confines of the amateur radio bands and allows anyone with an interest in electronics to experiment on the UHF licence free ISM radio bands like 868 MHz in Europe and 915 MHz in North America. Radio amateurs have the ability to use higher power on bands like 433 MHz.
Thanks to Amateur Radio Weekly, I came across a recent contact on the 10 GHz band that took place between the states of Tennessee and Virginia in the United States.
The video shows a successful contact on FM between N4OFA in grid EM86RS and K4LY in grid EM85WB. The distance was about 190kms or 120-miles which on FM over an obstructed path is impressive.
I looked at the path profile and it seems that the most likely mode of propagation was knife edge diffraction over the mountains in between.
It was curious to note the QSB (fading) on the signal as well. Reason? Vegetation moving? Some aircraft scatter?
In the video description, Mike N4OFA writes... "This is a video that amazed both of us, signals were very strong, I found Doug's beacon where he was portable near his house. A quick touch up with my wonderful tripod and he was hitting S9 with quick QSB. What kind of propagation is this? Doug's FM signal sometimes hits S9 on my little FT817nd. Note: no elevation on the dish at all, no rain cells between us. We did not try CW as there was no need since we could carry on a conversation even on FM."
See video below...
Addendum: Jacob, KG4AUW on Twitter suggested that the path might have been possible by bouncing signals off fire watch towers on the skyline ridge of the mountains.
Over a path of 190kms, it's probably impossible to be sure but there seems to be plenty of reflective metal surfaces there.
I recently came across details of this remarkable contact on the 1296 MHz (23cms) band.
On the 22nd January 2025, the PI9RD station at the Dwingeloo radio telescope facility in the Netherlands managed to make a contact with HB9Q in Switzerland by bouncing signals off an INMARSAT satellite in geosynchronous orbit.
While it is reasonably common for stations on the 1296 MHz band to bounce signals off the moon and for geostationary satellites like QO-100 to relay microwave signals, the signals on this occasion were physically bouncing off the metalwork of a geosynchronous satellite.
When you consider that satellites in a circular geosynchronous orbit are at an altitude of 35,786 kms rather than a few hundred kms for satellites in low earth orbit then it's even more remarkable.
Jan, PA3FXB gave this account of the contact...
Today at PI9RD (25m Dwingeloo telescope) we succeeded in completing two QSO’s on 23 cm with HB9Q via reflection off geostationary satellites.
This journey started in May 2013 when Andreas DJ5AR and I (PA3FXB) had our first 23 cm ISS bounce QSO using our 3 m dishes. We started experimenting with the big dish using smaller satellites.
In 2016 we (DJ5AR and PI9CAM) had a QSO via reflection off an old orbiting weather satellite. Since then, we started thinking of a QSO via reflection off a geostationary satellite. Much much, farther away but virtually fixed so no tracking challenges.
With HB9Q we tested using a cluster of ASTRA satellites using the double tone of JT65. We did not hear or see anything, but computer analysis showed that the signal was there! We did it again and got the same result. People familiar with the satellite world suggested us to use INMARSAT as passive reflector.
120W into a 25m dish on the 23cm band
The first INMARSAT-test with HB9Q was at the end of 2023 and produced a nice stable -23 dB and decoding signal on our screen. We then used Q65-120A. Our output power is much less so Dan did not see our signal and a strange thing happened: After a few minutes the signal disappeared….
Thinking about this and talking to satellite operators brought us to the conclusion that the orientation of the solar panels of the sats is an important thing to get good reflections. Nobody could tell us how it works on the different sats but there appear to be two systems. Constant moving of the solar panels and moving them in big steps every now and then. This might have happened when the reflection disappeared….
With this uncertainty about the solar panel position we decided to simply try a few INMARSATs. Today was the day ??
We started with the same INMARSAT GX5 we used in 2023 and we immediately saw -21 dB signals from Dan. This time we used Q65-60A to save our SSPA’s. After calling several times we received R-32 from Dan! Thanks to averaging!
And some minutes later after sending our RR73’s several times we received 73 from Dan. So, we made it!!! Just barely but we made it ??
Then we decided to try another sat. We went for INMARSAT 4A F2 (Alpha) and we experienced much stronger reflections! -15 / -24 dB. Dan was speaker copy in Dwingeloo! We had an ‘easy’ QSO??
After that we tried two other INMARSATs but with no result at all. So, here we are, two QSO’s via passive reflection off two INMARSATs. We think this has never been done before by radio amateurs.
It made us very happy! Thanks to Dan and his patience and many tests!
***
Well done to all concerned. For some details of other interesting contacts on the 1296 MHz band, see my Microwave page.
High-frequency Active Auroral Research Program (HAARP) is based in Alaska and it's a high-power, high frequency (HF) transmitter for studying the ionosphere. The principal instrument is a phased array of 180 HF crossed-dipole antennas capable of radiating 3.6 megawatts into the upper atmosphere and ionosphere. Transmit frequencies are selectable in the range of 2.7 to 10 MHz.
Update: Note that due to hazardous winter road conditions along the highways leading to the HAARP facility, the January Research Campaign has been delayed by 1 day. Dates updated below.
The research team have announced that they will be carrying out tests from the 28th of January to the 2nd of February 2025.
The press release is shown below and I've added a map to show location and distance.
To: Amateur Radio & Radio Astronomy Communities
From: HAARP Program Office
Subject: Notice of Transmission
The High-frequency Active Auroral Research Program (HAARP) will be conducting a research
campaign with operating times specified in the table below. Operating
frequencies will vary, but all HAARP transmissions will be between 2.75 MHz and 10 MHz. Actual
transmit days and times are highly variable based on real-time ionospheric and/or geomagnetic
conditions. All information is subject to change.
This campaign is being conducted in support of research proposals from UAF, the University of
Florida, the Naval Research Laboratory, Los Alamos National Laboratory, Cornell University,
Dartmouth College, Embry-Riddle Aeronautical University, and the University of Houston.
Research topics for this campaign include VLF generation and ducting, studies on STEVE airglow,
and space debris detection.
This campaign will also support the GIRAFF rocket launch from Poker
Flat Research Range, which is investigating the mechanisms that cause flickering and pulsing
within the aurora. More information on GIRAFF is available here:
Note that a number of experiments will be conducted based on the critical frequency (f0F2)
determined by the Gakona ionosonde. The included transmission notice supplement contains
information on the frequencies HAARP is authorized to transmit. HAARP transmissions will only
occur on our authorized frequencies.
There are no specific data collection requests from funded investigators, but reception reports are appreciated and may be submitted online via our web form
The image above is an annotated ionogram from HAARP that describes features that may be of
interest. Note that f0F2 is calculated at the top left.
f0F2 is the critical frequency of the F2 layer of the Earth’s ionosphere. This is the frequency at which radio signals stop refracting off the ionosphere and begin passing through to outer space. For certain HAARP experiments that deal with interactions in the ionosphere, transmission frequencies below f0F2 are desirable, while for other experiments (such as those involving high altitude satellites), staying above f0F2 is required.
The 145 Alive Group are organising an activity period on the 2m amateur radio band in the UK & Ireland on Sunday the 26th of January 2025 from 12:00 to 15:00 UTC.
This is not a contest and the aim is to promote more activity on the 2m amateur radio band. The approximate location of the net controllers are shown in the map above and they will be operating on the FM channels from 145.250 to 145.575 MHz.
Don't worry about who is operating where, just tune around and see who you can hear. All you need to do is to call in and give a report. If you listen for a few minutes, you'll get the format of the exchanges.
The weather isn't looking great with a named storm crossing over the UK & Ireland on Sunday. This may result is fewer stations taking to high ground.
While the summer Sporadic-E season from late April to early August is well known, there is also a much smaller Sporadic-E season during the mid-winter.
On the 14th of January 2025, there was one such opening in North America. This one was a bit unusual in that it happened during the hours of darkness and the maximum usable frequency (MUF) went as high as 107.7 MHz.
Mike Schaffer, KA3JAW writes... "There was a good Sporadic-E opening on the 88-108 MHz FM broadcast band on the 14th of January 2025. There was USA Winter Season FM Es reported on three spotters, Wlogger, FMLIST, DXMAPS during the midnight hours up to the top of the band.
Two events - the first occurred from 0506 - 0655 UTC from the Northeast to the upper Midwest. The second shorter event from 2313 - 2323 UTC was from the Northeast to the lower Midwest."
Looking through the logs, the minimum skip distance was 952kms while the longest was 2289kms, close to the maximum for one hop Sporadic-E.
Every Tuesday evening, there is a local net here in Cork on the VHF bands where a few of us get on air for a chat for about an hour. Over the course of the month, we alternate between 2m FM, 70cms FM, 4m FM and 70cms DMR.
If there is a fifth Tuesday in a month, we sometimes use it for experiments. As Tuesday the 31st of December was the fifth Tuesday in the month, a few of us tried the Rattlegram app.
Rattlegram is an app for a smartphone and it allows users to send short text messages over the radio. The beauty of the app is its simplicity. There is no need for wires or interfaces, the user just needs to hold their smartphone next to the microphone and loudspeaker of their radio.
The burst of data from the Rattlegram app only lasts for about two seconds. It's really simple to use. You just compile a short message on the app, press PTT on the radio and tell the other person you're sending a message, hold the microphone of the radio next to the smartphone and press 'TRANSMIT' on the app. The person on the receiving end gets the error free message on their app a second or two later.
Test Results... There were four of us on air for the net... Denis EI4KH, Robbie EI3GGB, Don EI8DJ and myself EI7GL. Over the course of about two hours, we successfully exchanged short text messages with the app over the air.
The tests on FM on the 145 MHz and 50 MHz bands were nearly all 100% successful. The main thing here was to make sure that the volume on the radio was turned up to a reasonable level and the phone was held near the radio.
It was interesting to see that the tests on 50 MHz SSB were also successful. The digital burst of Rattlegram is made up certain audio frequencies and on FM, these frequencies are copied exactly.
On SSB, you will never tune exactly to the other persons frequency. You can tune your radio to make the other person sound ok but if you were to relay something like music then you'd know something wasn't quite right.
With Rattlegram over SSB, the tones must be off slightly but it didn't seem to matter.
We also tried using Rattlegram with DMR via a local repeater and simplex. Both tests were a failure and it looks as if the Rattlegram audio signal is distorted to such an extent that decoding wasn't possible.
As for why DMR failed? One theory put forward was the time division multiplex nature of DMR as the signal is chopped up.
(Addendum: Brian, EI8EJB reports using Rattlegram without any issues on FM simplex but there could be issues when trying to go through a FM repeater. See comments to blog post)
The image above shows what the Rattlegram app looked like on my phone for the tests. The oldest traffic is at the bottom and the newest messages appear at the top of the screen.
The three dots at the top right allow the user to access the menu items. From there, you can select CALL SIGN to put in your call as otherwise, you will appear to others as ANONYMOUS.
To clear the screen of all the text messages, select DANGER ZONE and then Delete Messages.
The longest message that you can send seems to be around 3-4 short lines of text.
Rattlegram - What's its purpose??? ... The question that obviously arises is why would you need to Rattlegram anyway? The example often offered is that in the case of a natural disaster like a flood, storm, hurricane, wildfire, etc, mobile phone cell towers can be destroyed.
In that scenario, your mobile phone without cell coverage reverts to being a fancy camera with a calculator. Rattlegram allows the user to send short text messages over the radio until full communication is restored.
I can also see Rattlegram being used a simple tool in an scenario where I just want to pass on some basic information like say a phone number to someone.
In conclusion... The purpose of our experiment was to introduce participants of the net to the Rattlegram app and to gain experience of seeing it in use. As with the conclusion of many experiments, it raised for me more questions.
1) How well will it perform under weak signal conditions on FM or SSB? How far down into the noise will the signal go and still work?
2) Will it work on the HF bands with multipath? Will it work on a circuit with multiple hops?
I get the feeling that Rattlegram is a bit like a solution looking for a problem. It's a tool that I'm sure some resourceful operators will find a use for.
Further information... There are plenty of videos on YouTube about Rattlegram or under its older name Ribbit.
Andreas HB9BLA has a nice video below which gives a good overview of the Rattlegram app.
