Geseënde Kersfees - Beste wense vir 'n ware Christus Fees!

 

 Somerkersfees 

 

[1]

Welkom o stille nag van vrede,
Onder die suiderkruis,
Wyl stemme uit die verlede
Oor sterrevelde ruis.

[2]

Hoor jy hoe sag die klokke beier
in eeue-oue taal.
Kyk, selfs die nagtelike swye
vertel die ou verhaal.

[3]

Voel jy ook nou Sy warm liefde
As ons die dag gedenk,
Toe Hy sy Seun aan ons gegee het –
Ons grootste Kersgeskenk.

KOOR

Kersfees kom, Kersfees kom -
Gee aan God die eer.
Skenk ons ‘n helder Somerkersfees
In hierdie land, o Heer.

[1]

Enter in quiet peace filled night
beneath the Southern Cross
Lend now your ear this starlit night,
to whispers from the past.

[2]

Do you hear how softly the bells
are chiming, in ancient dialect
Even the evening's starry silence,
on prescious history reflects.

[3]

Can you also feel the warmth of His love,
as we celebrate the day
God loved us so much He sent his son,
no other gift as great.

CHORUS

Christmas nears, Christmas nears
Bow before the King
Grant by Your grace in this great land
A bright summer's Christmas Lord.

 

Namens die ZS-Link Netwerk Administrateurs, Suid Kaap Area 

On behalf of the ZS-Link Network Administrators, Southern Cape Area

25 Desember / December 2025

The ZS1I - 6 Meter Magic Band Project in the Southern Cape Area of South Africa. (Part 1)

 

Images:  Southern Cape Area, South Africa (Grid - KF15BT)  (Click on images for larger view.)

I have decided to embark on a 6 Meter Magic Band Project which started in September 2025.  Through the years many of the older radio amateurs living in the Southern Cape Area of South Africa would "discourage" younger radio amateurs to operate on 6 Meters in the area.  One of the reason being "we are to far away from the equator and we are located  to far south" away from the majority of 6 meter operators.  Is this true?  I do not believe this "hogwash" for one minute.  Today we have all the tools,  equipment and software available to create activity on the magic band even from the Southern Cape Area of South Africa.

Interested to join the fun using the 6 Meter Magic Band?  Wait no further.  Let's find out what the "Magic" of 6 Meters is.  I will not go into detail here but will provide a short / cryptic overview instead.  It does not take much to operate on the 6 meter band - your existing HF+6 meter radio and a simple antenna, even a dipole will work.  The Magic Band or six meters is from 50 - 54 Mhz.  It is located midway between the HF Bands, ending with 30 Mhz and the higher VHF Bands starting with 144 Mhz.  In this position it provides virtually all forms of propagation familiar to HF and VHF operators, along with a few that are much more prevalent at six meters.  Modes of operation entail CW, SSB, and WSJT-X but also FM Simplex, Beacons and FM Repeaters.

The Six Meter Band offers a great deal.  That includes white noise during the tragic times but also some exceptional operating conditions during the magic times.

Before I tell you about my 6 Meter Magic Band Project one need to provide an intro to what the magic band involves.

Image VK3FS  (Click on image for larger view.)

A "6 meter magic band project" for amateur radio involves building or using equipment (radios, antennas) to exploit the unique, unpredictable long-distance propagation (Sporadic-E, F2 skip, Aurora) on the 50-54 MHz frequency, offering both short-range VHF and surprise HF-like DX (long-distance) contacts, often using simple DIY antennas like halo loops or Moxons for great results and rewarding challenges. Projects focus on maximizing these propagation modes, especially during peak seasons like summer (Sporadic-E) and solar maximums (F2). 

What Makes it "Magic"?

• Diverse Propagation: It exhibits nearly every known radio propagation mode: Sporadic-E, F2-layer skip, Aurora, Meteor Scatter, and Troposcatter, says Icom America and Ham Radio Secrets.
• Sporadic-E (Es): Dense patches of ionization allow contacts from hundreds to thousands of miles, peaking in May-July and December.
• F2-Layer (Solar Cycle): During high solar activity, the ionosphere reflects signals globally, similar to HF bands, say ve3ips.wordpress.com and Fleetwood Digital.
• Trans-Equatorial Propagation (TEP): Exciting long-distance paths near the equator in March/April and September/October, according to ve3ips.wordpress.com and Fleetwood Digital. 

Project Ideas & Components

1. Radio: A transceiver with 6m capability (like an Icom IC-756 or IC-705), even a simple one, is needed.
2. Antennas:
   • DIY: Simple wire antennas like a Hula Hoop Halo, Moxon, or simple dipoles work surprisingly well, notes PA9X and the Nashua Area Radio Society.
   • Commercial: Verticals (like the Diamond V-2000) are popular, says Ham Radio DX.
3. Techniques:
   • Listen: Leave your radio on 50.125 MHz or scan for openings.
   • Explore Modes: Use SSB (voice), CW (Morse code), or digital modes like JT65 for DX, as mentioned in the QRZ Forums.
    

Now that we know more about the 6 Meter band it is time to provide a few frequencies that will be used and monitored from Mossel Bay  KF15BT, South Africa. 

Let’s have some fun on the 6 Meter Amateur Radio “Magic” Band in South Africa and Abroad

PDF file listing frequencies available HERE

6 (Six) Meter Amateur Radio Frequencies

50.125 Mhz SSB Calling

50.100 Mhz CW

50.100 Mhz to 50.125 Mhz DX Window

50.313 Mhz WSJT-X FT8

50.323 Mhz FT8 to Europe

50.318 Mhz FT4

50.260 Mhz MSK144 Meteor Scatter

50.275 Mhz Q65 in 30A Mode

50.000 to 50.080 Beacons

50.293 Mhz WSPR Beacons

 

6 (Six) Meter Amateur Radio Beacons – Africa – Nearby Islands

1. South Africa, Western Cape ZS1SIX Bellville 6m Beacon 50.080 Mhz 25khz JF96HB

2. South Africa, Wolkberg ARC ZS6TWB Wolksberg 6m Beacon 50.044 Mhz 12.5 khz

3. South Africa, PEARS ZS2SIX P.E. 6m Beacon 50.005 MHz UPE Building

4. South Africa, ZSLINK ZS1I Mossel Bay 6m WSPR Beacon 50.293 Mhz KF15BT

5. South Africa, Centurion ZS6DN Doornkloof 6m Beacon 50.050 Mhz KG44DC

6. South Africa, Krugersdorp ZS6JON Paardekraal 6m Beacon 50.051 Mhz KG33VV

7. Namibia V51VHF Windhoek 6m Beacon 50.018 Mhz JG87MI

8. Malawi 7Q7SIX Malawi 6m Beacon 50.003 Mhz KH75FX

9. Réunion Island (Indian Ocean) FR5SIX 6m Beacon 50.022 Mhz LG78RQ

10. Ascension Island ZD8VHF (Atlantic Ocean) 6m Beacon 50.032 Mhz II22TB

11. Gabon TR0A Radioclub AGRA 6m Beacon 50.048 Mhz JJ40QL

12. Zimbabwe Z21SIX ZARS Harare 6m Beacon 50.052 Mhz KH52ND

13. St Helena Island ZD7VC (Atlantic Ocean) 6m Beacon 50.007 Mhz IH74D

 

Antarctic 6-meter (50 MHz) beacons

These amateur radio propagation beacons are used by scientists and amateur radio operators to study radio wave propagation, particularly the rare F2 layer openings that allow long-distance communication with the continent. 

Several research stations operate, or have historically operated, 6m beacons: 

• LU1ZV (Esperanza Base, Argentina): A multimode 50 MHz beacon that operates continuously.

• DP0GVN (Neumayer III Station, Germany): This station has new hardware for a permanent WSPR (Weak Signal Propagation Reporter) beacon system covering 160m through 6m, which was planned for commissioning in early 2025. The call sign for the operator there is DP0GVN.

• VK0RTM, AX0GR, VK0GR, VK0MA (Various Australian Bases): Australian National Antarctic Research Expedition (ANARE) bases have historically run beacons, including VK0RTM on 50.300 MHz and others at Casey and Mawson stations.

Purpose and Operation

These beacons transmit continuous or periodic signals on the 6-meter amateur radio band (around 50-54 MHz), typically using Morse code (CW) or digital modes like WSPR. The signals are monitored by amateur radio operators worldwide to: 

• Study Propagation: Beacons provide stable reference signals to indicate when atmospheric conditions (like the ionospheric F2 layer) are suitable for communication over vast distances, including to Antarctica.

• Scientific Research: The German project, for example, is a science project that uses a "swarm-source of data" from ham radio operators around the world to gather information on propagation over a full 11-year solar cycle.

Monitoring and Frequencies

Amateur radio operators often monitor frequencies between 50.025 and 50.080 MHz (in some regions) or dedicated segments for WSPR and other digital modes to hear these signals. Specific frequencies can be found on amateur radio beacon lists like those provided by the Wireless Institute of Australia or the UKSMG. The Reverse Beacon Network is another resource where automated receiving stations log beacon reports. 

Image:  Ultimate 3 WSPR Beacon

On to the project itself.  What will it entail?

As indicated the project was started in September 2025.  It will be undertaken in several stages/phases. 

• Constructing of the Ultimate S3  Six Meter WSPR Beacon. (Currently active on 40 meters WSPR.)
• Constructing the 6m SummerLoop II Magnetic Loop Antenna to monitor the WSPR Beacon (Constructed, pedestrian mobile ready.)
  
• Constructing the 6m Moxon Antenna for the WSPR Beacon (Constructed, need to be installed on the mast.)
  
• Constructing the 6m Halve-Wave Flower Pot Antenna (Constructed, monitor 6 meter band for openings.  Need to be installed on a separate mast.)
• Incorporate a Yaesu FT-690R Radio and Amplifier into the project (Await the arrival of the radio and amplifier as send by Fred ZS5SAM. More on this equipment in a future posting.)

Images of the above projects:  (Click on images for larger view.)

End of Part 1.  In Part 2 we will be looking in more detail at the aim of the project.  The aim of a project is its overall, overarching goal or purpose—what it ultimately intends to achieve, providing direction and a shared vision for success, while specific, measurable actions to reach that aim are called objectives (which should be SMART: Specific, Measurable, Achievable, Relevant, Time-bound). It's the "why" and the big picture, guiding decisions and defining the final unique product, service, or outcome.

To ensure you "do not miss out on the project".  Visit this Blog regularly!!

Staying Connected on AllStarLink Version 3 - Keep your nodes connected after Internet Failure/Dip or Power Outage!

I recently decided that it is time to re-locate the DMR AllStar ASL3 Node Bridge to my Fiber Internet Subscriber as I needed the LTE Internet Router for the DMR Repeater. I experienced a few hick-ups after relocating the DMR Bridge to the Fiber Internet Router/Modem.  I was able to fix the hick-ups but would experience connectivity dropouts from time to time.  This would result in the DMR Bridge connection being disconnecting from the 49355 Hub Node.  When the connection returns the DMR Bridge would not reconnect and I had to manually make the connection.to the Hub Network.  This was really frustrating as I do not monitor the setup every few minutes.

Well thanks to Freddie KD5FMU (Ham Radio Crusader) I was able to fix this annoying issue in a few minutes.  All credit goes to Freddie who published a video and script file to keep nodes connected.

The ASL3 script file will check for a specific node connection and it it is not present (connected) the server will re-connect to it. 

(Click on image for larger view.)

The YouTube video is available HERE

Information on the ASL3 script file is available HERE

I made the necessary changes and this solve the issue that I experienced.  

Feedback: WSPR Beacon to monitor propagation conditions from the Southern Cape (Part 3)

In Part 1 - HERE and Part 2 - HERE we looked at:

Why would one setup a WSPR Beacon in the Southern Cape?  

Particulars of the ZS1I Ultimate 3S Beacon.

Construction of the Southern Cape Beacon.

First station to spot the ZS1I WSPR Beacon on 40 Meters.

Reception of the ZS5SAM WSPR Beacon on an SDR and Antenna inside the Shack and other spotting stations that received the ZS1I WSPR Beacon on 40 Meters.

In Part 3 I will be looking at two Antarctic Research (WSPR) Stations that spotted the ZS1I 40 M WSPR Beacon recently.  One fixed station and one a maritime mobile station.

Station 1:   DP0GVN Antarctica

Neumayer Station III
Ekstroem Ice Shelf
Atka Bay, Dronning Maud Land
Antarctica

Station 2:  DP0POL Antarctica

Research Vessel "Polarstern"
Home Port: Bremerhaven
Germany

Both the above stations spotted the ZS1I WSPR Beacon on 40 Meters on the 14 December 2025.  See image below.

DPØGVN is a club station located at the German Antarctic Research Station "Neumayer III" in Dronning Maud Land, Antarctica. Find more on this outpost of global research at https://www.awi.de/en/expedition/stations/neumayer-station-iii.html. 

WSPR Beacon

• Station Info

The setup consists of a receiver and a transmitter which independently of each other operate in the WSPR segments of the amateur radio HF bands.

• Receiver

The receiver is located at the "SpuSo" which is the station's air chemistry laboratory. SpuSo's main purpose is to collect continuous, year-round and long-term data records for important gaseous and particulate trace components of the troposphere. This observatory is located about 1.5 km south of the main station where it finds an outstandingly clean air environment.

This is a perfect place for a receiver setup because the RF environment, too, is amazingly  QRM-free with a noise floor well 20, 30 or even more dB below of what we are used to in urban areas.

The receiver is a SDR built around three Red Pitaya (StemLAB 125-14 with 50 dB preamplifier). They permanently observe all eleven WSPR band segments between 160m and 6m and upload the spots to wsprnet.org. A BananaPi and a RaspberryPi single board computer take care of control tasks.

The antenna setup consists of two two triangle-shaped horizontal loop antennas with 1:4 baluns. The lower bands are received by an antenna with a circumference of 171 meters, the upper bands use a shorter loop of 61 meters.

The antennas are mounted on short masts about one to two meters above the ice shelf. This is not "above ground" as the ice shelf is almost invisible to HF. You even can use antennas lying flat on the ice to do HF QSOs! The real ground is about 200 meters below as this is the average thickness of the ice shelf in this area. Every year precipitation adds about one meter of snow and ice. Therefore the antennas have to be reestablished regularly to not risk having them covered by snow.

• Transmitter

The transmitter is located at the main station and is based on the TX design of the Charly-25 SDR project. Ats it heart is another Red Pitaya StemLAB 125-14 which feeds a rock-solid PA designed to emit up to 20 watts RF. The Red Pitaya runs Pavel Demin’s WSPR transceiver software. A PC Engines APU2 single board computer is in charge of control and monitoring tasks. RF output, SWR and system temperature are constantly monitored.

The antenna is an approx. 20 meter long wire installed on the southern part of the station’s roof. The wire runs in North-South direction and is matched by a 1:9 Unun-type RF transformer. While not being a high-performance antenna it is well suited for the task because it is broad band and believed to be able to stand the stress caused by the extreme Antarctic whether conditions.

The transmitter transmits on all WSPR segments between 160m and 6m on a round-robin schedule. One complete cycle takes 30 minutes. The bands between 40 and 17 meters are served twice per cycle because these offer the best chances for the signal to be heard. So these four bands are visited four times per hour, the other bands twice per hour. The RF output is 5 watts on all bands.

Update June 2020: On 2020-06-04 something in the RF transformer feeding the long wite antenna broke causing the antenna to be unusable. Therefore we are currently transmitting with the 5.5m vertical antenna which was already in use for the project before 2020. This antenna offers a less favorable radiation pattern when compared to the long wire, so expect somewhat degraded reception opportunities. Maintenance work at the antenna can only take place during Anarctic summer so that the repair will not be executed before January 2021.

• The Project

This setup is a long-term project realized by the Technical University of Munich (TUM) and the Hochschule Bremen City University of Applied Sciences (HSB) in cooperation with the Alfred Wegener Institute Helmholtz-Zentrum für Polar- und Meeresforschung (AWI) and the German Amateur Radio Club (DARC). AWI operates the Neumayer Station III and provides logistics. DARC builds and maintains the receiver and transmitter setup.

The project is meant to run several years to gain long-term data on radio propagation and spectrum pollution in a very specific HF environment as the station is located within the southern auroral oval. The setup will see changes in the future -- we will keep you updated here. As the station is inaccessible from the outside world for about eight months during south polar winter modifications will usually happen during the Antarctic summer season between November and February.

DP0POL is only operated from the vessel when it is en route in international waters, so the call sign always is DP0POL/mm.  You can follow the ship's research activities in our Polarstern Web App. For the ship's current position, please check the SEAICE portal.

I made two adjustment on the ZS1I Beacon and it is now running flawlessly.  Before I had to "reboot" the beacon every second day. Since the setup adjustments I just left the beacon and it operated continually.

In Part 4 we will be looking at changing the band and frequency as what the beacon was intended for.  More on this in Part 4.

Images:  (Click on the images for larger view.)

Suid Kaap Netwerk Groep Aktiwiteite: Sluiting van die 06h00 Dagbreek Span Net tydens die Vakansie Seisoen

Foto:  Sonsopkoms by Die Punt op Mosselbaai  (Klik op foto om te vergroot.)

KENNISGEWING:  Die Dagbreek Span Net wat weeksdae  om 06h00 in die oggende op die Aasvoelkop Herhaler en ZS-Link Hub plaasvind se laaste bymekaarkoms vir die jaar, sal op 12 Desember 2025 plaasvind.  Die net-kontroleerder en storie verteller gaan so 'n blaaskansie neem tydens die vakansie seisoen.  Die Dagbreek Span Net sal weer op die 12 Januarie 2026 in aanvang neem.  Radio amateurs kan nogsteeds om 06h00 weeksdae informeel gesels. Daar word vertrou dat die net-kontroleerder en storie verteller die rustyd sal geniet. 

LET WEL:  Die Ontbytsake Span Net, Sonsak Span Net en Aand Span Net gaan egter steeds voort op weeksdae onderskeidelik 06h30, 16h30 en 18h30 SAST op die Aasvoelkop en Stilbaai Herhalers.   Meer besonderhede oor die frekwensies en netwerk nodes word op die lug aangekondig maar is ook beskibaar op die ZS-LINK Blog.  Klik HIER vir meer besonderhede.

Radio Amateurs wat in die Suid Kaap vakansie hou is welkom om in te skakel en saam te gesels.

Image:  Sunrise Still Bay  (Click on image for larger view.)

Southern Cape Network Group Aktivities:  Closing of the 06h00 "Dagbreek Span" Net during the Holiday Season

NOTICE: The "Dagbreek Span" Net, which takes place on weekdays at 06h00 in the mornings on the "Aasvoelkop" Repeater and ZS-Link Hub, will have its last meeting for the year on 12 December 2025. The net controller and storyteller will take a break during the Holiday Season. The "Dagbreek Span Net" will resume on 12 January 2026. Radio amateurs can still chat informally at 06h00 during weekdays. It is hoped that the net controller and storyteller will enjoy the break. 

NOTE: The "Ontbytsake Span" Net, "Sonsak Span" and Aand Span Net will however continue on weekdays at 06h30,16h30 and 18h30 SAST respectively on the "Aasvoelkop" and Still Bay Repeaters. . More details about the frequencies and network nodes will be announced on air but are also available on the ZS-LINK Blog. Click HERE for more details.

Radio Amateurs holidaying in the Southern Cape are welcome to tune in and chat.

APRS Activity increasing in the Southern Cape, South Africa

Above Image:  OSCAR 44 (also called Navy-OSCAR 44, PCSat-1, Prototype Communications SATellite and NO-44) is an American amateur radio satellite for packet radio. It was built by Bob Bruninga at the U.S. Naval Academy.

What is APRS?  No APRS is not new in amateur radio.  APRS was developed in the late 1980s by Bob Bruninga, call sign WB4APR, a senior research engineer at the United States Naval Academy.

 

APRS, or Automatic Packet Reporting System, is an amateur radio-based system for real-time digital communication of information like GPS coordinates, weather data, and text messages. It transmits data packets over radio frequencies, allowing users to display real-time information, such as object locations on a map, and is widely used for emergency communications and asset tracking. 

How it works

• APRS uses packet radio technology to send digital information over specific frequencies.

• A GPS receiver is often combined with a radio modem to automatically transmit a station's location, a process known as tracking.

• Data packets can include callsign, GPS coordinates, altitude, weather telemetry, status messages, and short text messages.

• Other users can receive these packets and display the information, typically on a map, allowing for shared situational awareness.

• Information can also be relayed through the internet via APRS-IS (Internet System) gateways, enabling global access to local data.

What it's used for

• Emergency Communications: Quickly sharing tactical information, such as weather alerts or the location of emergency personnel, during a disaster.

• Tracking: Monitoring the real-time movement of vehicles, such as in a rally or search and rescue operation.

• Asset Tracking: Locating mobile stations or other assets on a map.

• Information Exchange: Sending short messages, announcements, or weather station data to other operators.

Above is just a short explanation in a nutshell what APRS entails.  Many radio amateurs think APRS is all about tracking vehicles and objects.   APRS is far more that watching objects on a map.

Want to know more about APRS and it's History.  Click HERE

APRS Activity increasing in the Southern Cape, South Africa

APRS is not new in the Southern Cape / Garden Route Area.  I will in a future article provide more information on the history of APRS in this area and what roll it played during "Exercise Double Barrel."

There is definitely an increase and renewed interest in APRS in the Southern Cape.

Herewith a list of all the ZS1 APRS stations as displayed by aprs.fi.  Click HERE

Stations active on 2 December 2025 at 15h00 SAST:

Click on images for larger view.

Further reading:

How to configure APRS Reporting in South Africa

How to configure a radio for APRS location and data reporting in South Africa

Donation towards the ZS1I DMR Repeater Project by Anonymous Donor

Now here is once again a story of  real amateur radio spirit.  In today's life buying equipment are rather expensive when it comes to amateur radio.  There is a song with the name of Money, Money, Money which reminds me that nothing comes for free nowadays.  I was however once again proven wrong.  Last week I received a private WhatsApp containing an image of a Voltex UPS / Inverter that the author would like to donate to me for use as a power back-up system when necessary.  I tried to buy the equipment but the donor was adamant that he does not want any money as long as the equipment will be used to further amateur radio projects and installations in the Southern Cape.  He refused to accept anything for the equipment and I arranged for the transport of the equipment to my QTH.  The package was delivered by Jacobus ZS1JDJ. I want to thank Jacobus for going out of his way to pick up the package en delivering it in Mossel Bay.  This UPS / Inverter will be used in conjunction with the ZS1I DMR Repeater that will be permanently installed early in December 2025.  This repeater will be connected to the ZS Link Network here in the Southern Cape.

I would like to thank the Donor for his generosity, great amateur radio spirit and for donating this equipment, to provide power to the DMR Repeater and possibly other equipment used as part of  the ZS Link Network in the Southern Cape.  Highly appreciated and once again a big thank you!!

Some might ask "Why using a UPS / Inverter for a repeater?"  Quite simple .....The DMR Repeater currently works of the 220v mains power.  This equipment will provide 220v AC,  12 DC as well as, Solar Panel and Battery Charging in the event of a power outage. 

I will later post images where this equipment is connected to the DMR Repeater in an operational state.

Images (Click on images for larger view.)

 

Opgedateerde Vloei Diagram: ZS1I ZS-Link Netwerk - Besoekende Radio Amateurs aan Mosselbaai, Hartenbos en Danabaai

Images: Click on image for larger view or download below

Ek is by verskeie geleethede gevra om meer inligting te verstrek rondom die ZS1I HUB Netwerk in Mosselbaai. Die vloei diagram is slegs gebasseer op nodes, herhalers en netwerke wat tans aan die ZS1I HUB gekoppel is.  Ek het 'n nuwe vloei diagram saamgestel wat die nodige inligting bevat  rondom die HUB en hoe radio amateurs kan inskakel by die HUB.  Weereens is dit baie moeilik om al die inligting op een velletjie papier beskikbaar te stel.  Ek beoog om later 'n volledige "handleiding" van die algehele ZS-Link Netwerk in die Suid Kaap en ander dele van Suid Afrika saam te stel soos wat die tyd my dit toelaat.  Ek vertrou dat die vloei diagram van hulp sal wees vir diegene wat dalk nie verstaan hoe die network funksioneer nie.  Vrae op die lug asook op "Die 625 - 6 Uur  Half 5 Span" WhatsApp groep rakende die ZS Link Netwerk is meer as welkom.

Aflaai / Download: Vloei Diagram / Flow Diagram

Updated Flow Diagram: ZS1I ZS-Link Network - Visiting Radio Amateurs to Mossel Bay, Hartenbos and Dana Bay

I have been asked on several occasions to provide more information about the ZS1I HUB Network in Mossel Bay. The flow diagram is only based on nodes, repeaters and networks that are currently connected to the ZS1I HUB. I have compiled a new flow diagram that contains the necessary information about the HUB and how radio amateurs can connect to the HUB.  Again, it is very difficult to make all the information available on one sheet of paper. I intend to later compile a complete "manual" of the complete ZS-Link Network in the Southern Cape and other parts of South Africa as time permits. I trust that the flow diagram will be of assistance to those who may not understand how the network functions. Questions on the air and "Die 625 - 6 Uur  Half 5 Span" WhatsApp Group about the ZS Link Network is more than welcome.

Large Wildfire threatened Danabay near Mossel Bay!! (26 November 2025)

Image: Danabay Fire - Gerrit ZS1KLO (Click for larger view.)

During the Sonsakspan Net on the 26 November 2025 at 16h30 the following interesting question was asked by Jacobus ZS1JDJ.

What impact does ash, smoke and flames have on radio communications while a veld fire is burning?

Danie ZS1DL reported that there was a lot of interference on his radios while the emergency personal attended to the fire and other incidents. 

Videos:  Provided by Danie ZS1DL

Herewith a short explanation:

Wildfire ash and the associated smoke and flames can significantly impact amateur radio signals

Wildfire ash and the associated smoke and flames can significantly impact ham radio signals by causing signal attenuation and refraction, particularly at higher frequencies like VHF and UHF. The effect is dependent on the density and chemical composition of the smoke/ash, and the frequency band used. 

Effects on Radio Signals

• Signal Attenuation: The primary effect is a degradation of signal strength. Smoke and ash contain particulate matter (like graphitic carbon and potassium) and ionized gases (plasma) that can absorb or scatter electromagnetic waves.

• Frequency Dependence: Higher frequencies (UHF and above, such as 70cm amateur bands, Wi-Fi's 2.4 GHz, and cell signals) are generally more affected by the particulate matter than lower frequencies (VHF and HF bands).

• Refraction and Ducting: The intense heat from a wildfire creates a "thermal bubble" or "thermal lens" in the atmosphere, leading to temperature inversions and changes in the air's refractive index. This can sometimes cause unexpected signal bending (refraction) and even enhance long-distance propagation (tropospheric ducting) in certain conditions, where radio waves bounce further than normal.

  
  
  What is a Thermal Bubble?

  A thermal bubble is a concept used to describe a buoyant mass of hot air and emissions that rises from an intense fire. 

• Formation: Continuous heating of the surface air mass by the fire causes the air to bulge upwards into a "bubble". The intense heat creates strong thermal buoyancy, making the air less dense than the surrounding cooler air.

• Ascension: Eventually, this hot air mass can break away from the surface and ascend into the atmosphere as a distinct cell.

• Atmospheric Dynamics: As the thermal bubble rises, cooler air from aloft moves downward to replace the ascending warm air, initiating a circular motion or horizontal roll vortices at the edges of the plume. This process is part of the formation of a pyrocumulus cloud (fire cloud) and is most prominent in strong vertical wind profile environments. 

  
  
  Image:  Pyrocumulus cloud, or fire cloud - Wikipedia
  

         What is a Thermal Lens? 

A "thermal lens" in the context of wildfires

refers to the atmospheric distortion caused by a fire's heat, which can negatively impact radio communications. The intense heat creates a "thermal bubble," which acts like a physical lens, bending radio waves and causing signal degradation. This phenomenon requires specialized communication strategies and technologies for effective firefighting and operational coordination during a wildfire. 

How it works

• Atmospheric distortion: Wildfire heat creates a plume of hot air, smoke, and debris, which alters the air's density and refractive index.
• Radio wave bending: This change in the atmosphere causes radio waves to bend or refract, similar to how a glass lens bends light.
• Signal disruption: The bending can cause the signal to be weaker, distorted, or lost entirely, making it difficult for emergency responders to communicate using standard equipment.

Impact on radio communications

• Coverage gaps: Areas directly under or near the plume experience significant radio dead zones.
• Interference: Other radio signals can interfere with one another, leading to unreliable communication.
• Operational challenges: Firefighters need to have a backup plan, such as using different radio frequencies, satellite phones, or establishing direct line-of-sight communication.

Solutions and strategies

• Specialized equipment: Firefighting agencies often use specialized radio equipment that can better penetrate or adapt to the challenging conditions.
• Backup systems: Relying on multiple communication systems, such as satellite phones and handheld radios, can ensure redundancy.
• Strategic planning: Planning for the thermal lens effect is crucial. This includes identifying areas likely to be affected and developing contingency communication plans.
• High-frequency radios: Some high-frequency radios are less affected by atmospheric conditions and can provide more reliable communication over longer distances.

Radio Operations During Wildfires

Image: The illustration above shows high altitude troposheric ducting - VK3SF.

Despite these challenges, amateur radio operators play a vital role in emergency communications during fire events, often filling in when traditional cellular or landline infrastructure fails. They adapt their operations by: 

• Utilizing lower frequency bands (HF or 2m VHF) which are less susceptible to severe attenuation from smoke than UHF.

• Employing tactical positioning of antennas to work around dense smoke plumes or terrain features.

• Leveraging enhanced (though unpredictable) propagation events like tropospheric ducting to make long-distance contacts.

Temperature inversions significantly disrupt radio communications during wildfires by creating

anomalous propagation conditions that can cause signal path loss and unpredictable signal patterns. 

Effects on Radio Communications

• Signal Trapping and Bouncing: A temperature inversion creates a "lid" of warm air over cooler, denser ground-level air, which traps smoke and pollutants. Radio waves get bounced or "trapped" within this cooler surface layer, leading to signals ricocheting around rather than propagating normally through the atmosphere.
• Signal Path Loss: The environment created by the fire plume itself and the inversion is "sub-refractive," which can cause significant radio signal path loss, especially over long distances.
• Unpredictable Behavior: The turbulent, ionized, and smoke-laden atmosphere within and around a fire can cause radio beams to spread out or bend in unpredictable ways, making consistent communication difficult.
• Increased Range for Some Signals: In some instances, the "sandwich effect" of an inversion layer can cause sound and radio waves to travel further than normal, leading to unexpected signal reception from distant sources, though this is generally unreliable for operational communication within the fire zone.

Operational Impact During Wildfires for Firefighters

 

For firefighters, these disruptions mean that traditional radio communication systems can become unreliable, particularly in valleys or areas where inversions settle overnight. This communication failure poses a significant safety risk during active fire suppression efforts. 

Mitigation Strategies:

• Situational Awareness: Fire crews are trained to observe and report weather conditions, including signs of an inversion (e.g., low-hanging smoke, hazy atmosphere), to anticipate potential communication issues.
• Alternative Technologies: Modern approaches utilize technologies that do not rely on traditional, centralized radio infrastructure. Mobile mesh networking, where each device acts as a relay station, creates a more resilient network with no single point of failure.
• GPS and Situational Apps: Firefighters use smartphones with downloaded maps and situational awareness applications (like ATAK) that use GPS, which functions independently of cellular networks, to maintain awareness of their location and the fire's movement even when voice communication is lost.
  

Amateur Radio and Wildfires 

Amateur radio is a crucial tool for communication during wildfires because it is independent of traditional infrastructure like cell towers and power grids, providing a reliable backup network. Amateur radio operators can provide vital information to emergency services and the public when other communication systems fail, report fires, coordinate logistics, and even assist in long-range communication for isolated communities. This independence makes them essential for public safety and personal communication in disaster situations. 

Benefits of ham radio for wildfire communication

• Infrastructure independence: Amateur radio does not rely on the cellular or power grids, so it remains functional even when they are down due to damage or overload.
• Reliable communication: Operators can communicate directly or use repeaters to extend range, enabling them to report fires, provide status updates, and request assistance.
• Emergency support: Trained ham radio operators can integrate with official emergency response efforts to provide communications support, as seen with programs like California's Provincial Emergency Radio Communications Service (PERCS).
• Long-range capability: With appropriate equipment and antennas, ham radios can facilitate long-distance communication, which is crucial for large-scale disasters or reaching remote areas.
• Sustained operation: Radios are designed for long-term use, making them ideal for extended emergencies where other devices may run out of power.

Examples in practice

• Reporting fires: An amateur radio operator used his radio to report a wildfire, and within minutes, emergency services were dispatched, a helicopter arrived, and firefighters extinguished the fire.
• Evacuation support: In the 2017 Mossel Bay Heiderand Fire, radio amateurs helped residents receive timely updates and evacuate safely, even as there houses were under threat.
• Official integration: HAMNET are officially incorporating amateur radio operators into their disaster plans, training volunteers and establishing radio stations to ensure communication continuity.

 Interesting reading:  Radio Propagation in Fire Environments