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

DIY Bluetooth Module for your Yaesu FT817ND Radio

(Click on image for larger view.)

This project started after I constructed the YO3GGX FT817ND DIY data modes miniature USB Sound Card Interface V2.  Available HERE  

This interface works great with my Yaesu FT817ND using my desktop PC or Laptop.  But what about pedestrian mobile operations where the laptop is to big to carry around.  Well I found FT8CN a mobile FT8 communication software based on Android system developed by BG7YOZ. The FT8CN is developed for easy mobile operation, especially outdoors and can be used at any time  to make FT8 contacts. The operational logic is as simple as possible, easy to use, with basic FT8 operation.

Another irritation was cables with regard to pedestrian mobile operations. The ultimate goal is to have as few cables as possible.  FT8CN can control a cellphone through various methods such as voice control, USB serial port, bluetooth, network, etc.  I decided to use bluetooth as I already had a new module and 8pin Din Plug which I did not use in a previous project.

The bluetooth module I had was a HC-05 Bluetooth Module, the one with the reset button.  I decided to attach wires to the module and solder them to the ACC 8 Pin Plug.

The cables were connected in the following way:

HC-05 Module      ACC 8 Pin Plug

TXD Bluetooth     TX D ACC Plug

RXD Bluetooth     RX D ACC Plug

GND Bluetooth     GND ACC Plug  Also connected to the - of the 5v external power supply unit.

5 V DC VCC         ACC Plug not used.  Used 5v  external power supply unit.

Pin outlay printed on the back of the HC-05 Bluetooth Module.  The ACC pin outlay is available on page 5 of the  FT817ND Operating Manual.

I decided not to make any software changes using a TTL USB programmer and TeraTerm terminal software.  The bluetooth unit was plugged in and it worked with the default settings and wire connections.  I however needed to alter the FT8CN settings as prescribed in the FT8CN Quick Manual.

Receive via FT8CN and the Bluetooth module works great.  However for the time being I will use the VOX of the Yaesu FT817 radio for the PTT.  I tested this setup and it works as it should.

I intend going pedestrian mobile during the holiday season and hope to make a few contacts on 10 meter using the FT8 mode and this setup.

Finally:  The images and video provide more information on how I constructed a DIY Bluetooth Module for my Yaesu FT817ND radio.

Video:

Images:  (Click on images for larger view.

Building Low Budget Antennas - DIY Magnetic Loop Antenna for 20 (14Mhz) - 6 (50 Mhz) Meters (Part 1)

I continue with the series of low budget antenna "builds".   In the series I will be looking into building antennas that is:

• Highly Portable
• Cheap to Build
• Easy to build (Novice and Experienced builders)
• Use readily available material from the local hardware store
• Needs minimal tools to construct
• Needs only a SWR Meter to do some final tuning and adjustments.  However if you do have an antenna analyzer, that will be a bonus.
• Highly affective with possible gain.
• Light weight and easy to install or to dismantle
• Fun to build and play around with.            

Please note that none of the antennas that I will be constructing is my personal designs.  Credit will be given and links provided where you can find more information about the antennas.

I trust that new, novice and experienced radio amateurs that will be building some of these antennas  will find them of great use and enjoyment.  Isn't this what amateur radio is all about?

Now lets look at a short explanation of  "What is a small transmitting magnetic loop antenna?"

A small transmitting magnetic loop antenna is a compact, resonating antenna made of a conductive loop with a high-voltage capacitor. It is designed for use in situations with limited space, such as in amateur radio, and can provide good performance when carefully constructed to minimize losses. The antenna operates by using the magnetic fields of radio waves and has a unique, doughnut-shaped radiation pattern with nulls at right angles to the loop's plane. 

How it works

• Loop as an inductor: The main loop acts as a large inductor in a tuned circuit.
• Capacitor for resonance: A variable capacitor is placed in the loop's break to form an LC circuit that resonates at a specific frequency.
• High-Q circuit: This high-Q parallel-tuned circuit results in a narrow bandwidth but high efficiency, making it excellent for receiving weak signals and transmitting.
• Coupling loop: A smaller, secondary loop (the "feed loop" or "coupling loop") is placed near the main loop to transfer the radio frequency energy from the transceiver to the antenna.

Characteristics

• Small size: Its circumference is typically less than one wavelength, making it ideal for portable use or areas with antenna restrictions.
• Directional pattern: It has a doughnut-shaped radiation pattern, with the signal being strongest in the plane of the loop and weakest at the points perpendicular to it.
• High efficiency: Despite being small, its design can achieve high performance, especially in the HF bands, with careful construction that minimizes resistive losses.
• High voltage: The voltages across the tuning capacitor can be very high, so it's important to use high-quality components and to be careful not to touch the antenna while transmitting.

Common uses

• Amateur Radio: Its compact size makes it popular for portable operations, like Field Day, and for home use where outdoor antennas are not permitted.
• Military applications: Its small size and high performance make it suitable for military use.
  

In any project one needs a plan, diagram, guidelines and information.  At least that is my way of constructing any DIY Project.  I research the project thoroughly before I start any work.  I did exactly this before I started on this project.

Now the Internet is your friend but can also by your enemy if you just jump in and start constructing the first plan you find.  I was looking for the dimensions of  DIY Magnetic Loop Antennas and ran into a Small Transmitting Loop Antenna Calculator at 66pacific.com

Small transmitting loop antennas, commonly called "magnetic loops" or "mag loops," can give surprisingly good performance when they are carefully designed and constructed. Although this online calculator is intended to assist with designing and building homemade, ham radio loop antennas for use in the HF bands, magnetic antennas have been constructed that function in the VHF or even the UHF frequencies. This calculator enables you to test the design of an octagonal loop antenna and to answer "what if" questions until you arrive at a design that meets your needs without a lot of experience in electronics.

The small transmitting loop antenna calculator was fed with the following data:

Length of Conductor (Antenna "Circumference")  =  1.360 meters

Diameter of Conductor = 2.5 centimeters

Frequency = 50.2

Transmitter Power = 5 Watts

After calculating the following information were provided:

Antenna efficiency: 94% (-0.3 dB below 100%)
Antenna bandwidth: 209 kHz
Tuning Capacitance: 13 pF

Capacitor voltage: 545 volts RMS
Resonant circulating current: 2.20 A
Radiation resistance: 0.484 ohms
Loss Resistance: 0.032 ohms
Inductance: 0.785 microhenrys
Inductive Reactance: 248 ohms
Quality Factor (Q): 240
Distributed capacity: 4 pF

Antenna "circumference": 1.360 meters

Side length: 0.170 meters

Antenna diameter: 0.4 meters

Comments:
The specified conductor length of 1.360 meters is OK.

Conductor length should be between 0.725 and 1.45 meters at the specified frequency of 50.2 MHz.

For highest efficiency, the conductor length for a small transmitting loop antenna should be greater than 1/8 wavelength (greater than about 0.725 meters at the specified frequency of 50.2 MHz).

To avoid self-resonance, the conductor length for a small transmitting loop antenna should be less than 1/4 wavelength (less than about 1.45 meters at the specified frequency of 50.2 MHz).

Input Values:
Length of conductor: 1.360 meters
Diameter of conductor: 2.5 centimeters
Frequency: 50.2 MHz
Transmitter power: 5 watts

The transmitting loop I decided to construct was inspired by Peter VK3YE and he calls the antenna, "The SummerLoop II" a pedestrian mobile magnetic loop for 20 to 6 Meters. Here are the links to some of his videos where he explains and demonstrates the antenna.

The SummerLoop II 14 - 50 MHz pedestrian mobile magnetic loop 

Tiny loop works 'Magic Band' DX on 50 MHz

With all the information now on paper I was ready to move onto the next phase and that was to gather all the materials I was going to need.

Materials that I used:

1 x 25mm x 3mm x 3m  Aluminium Flat Bar

1 x 25 - 50 pF Beehive Trimmer Capacitor

1 x 25mm x 80mm x 2mm Single Side PCB (Must be single sided to lessen capacitance)

1 x 16 mm x 1820mm Wooden Dowel 

2 x 80mm x 80mm x 4mm Plastic Cutting Board 

1 x SO239 Connector (Optional)

1 x Electrical Eye Lug (Terminal)

1 x 205mm x 2mm Brazing Rod or Stiff Copper Wire

2 x 35mm x 4mm Stainless Steel Bolts + Washer + Lock Nut and Wing Nuts

1 x 12mm x 4mm Stainless Steel Bolts and Lock Nut

2 x 15mm x 3mm Stainless Steel Bolts and Lock Nuts

Odds and Sods:

Cable Ties

Hot Glue Sticks

Self Amalgamating Tape

Solder

Solder Paste

Coax Cable (RG58CU Mil Spec) 50 ohm

Marine Silicone Sealant

 

Tools:

 

Metal Punch

Drill

Drill Bits 4mm + 3mm

Hack Saw 

Hot Glue Gun

Soldering Iron

Screw Driver (Small flat)

DIY 135 Degrees Bender to form Hexagon (See image and description)

 

Test Equipment:

 

SWR Meter

Antenna Analyzer (If you have one but not compulsory)

Amateur Radio Tranceiver

Coax Patch Leads

Mast (Non conductive)

Coax feed line cable  5 m  RG58CU 50 ohm

Power Supply for Radio 

Soundcard Interface

WSJT-X Software

 

Building the Antenna:

I am not going to go into detail how I constructed my version of the antenna. I will however describe my findings in constructing and testing the antenna.  The images below provide good detail of how I constructed the loop.

Image:  Peter VK3YE  (Click on image for larger view.)

More information on the build and use of the antenna available at:

 

Website Peter VK3YE (Click to view website) 

My build observations and findings:

 

Now how did I bent the hexagon figure of the antenna?  I decided to construct a jig to assist me to bend the 135 Degrees needed to turn the aluminium flat bar into a hexagon configuration aka Loop Antenna.

I uses stainless steel bar and scrap that I had lying around in the workshop.   See images below.

Now the bending process is quite simple as illustrated in the images below.

 

 

The measurement at the open end of the loop is 85mm - 85mm = 170mm.  To provide space for the capacitor and PCB cut 10mm of each side making each side 75mm.  The PCB with the capacitor will now fit comfortable in the cut out space.  See images below:

I used a 25 pF Beehive Capacitor as this is all that I had on hand. According to the calculator I only need 13 pF for 6m operation.  The 25 pF also allow for 10 and 11 meter operating. 

The  Beehive trimmer is mounted on a 25mm x 80mm x 2mm piece of single side fiberglass printed circuit board. This must be single sided copper to lessen capacitance. I used a hacksaw to separate the copper into two large pads, each connected to a terminal of the capacitor.

Screws hold as much of each pad as possible against each end of the flat aluminium loop. Sand the facing surfaces to lessen resistance. If the loop is to be used permanently outside as a courtyard or balcony antenna, consider the risk of reaction between dissimilar metals and waterproof accordingly.  I intend to change the above arrangement.  An update will follow in this regard.

I used 2 x 35mm x 4mm Stainless Steel Bolts + Washer + Lock Nut and Wing Nuts to hold the loop ends to the circuit board. Install so their heads are pointing down. They should be long enough for there to be about 20mm thread protruding from the nut. The reason for this is mentioned later.

2 x 80mm x 80mm x 4mm Plastic Cutting Kitchen Board material adds rigidity to the top and bottom of the loop and lessens stress on the circuit board. Two 16mm holes allow a snug fit with the 16mm vertical dowel that comprises the antenna's handle.

An insulated knob on the capacitor lessens hand-capacitance and makes adjustment easier. I used an old fibre pen casing as an isolation knob. The one end happened to fit snugly onto the rotating section of the trimmer capacitor.

Feed Arrangement:

 

Image:  Test feed arrangement

My feed arrangement measurements differ from that of VK3YE.  I also used the gamma-style feed. I tried the measurements of VK3YE but the SWR was above what I wanted. I decided to extend the feed by another 40mm of copper wire.  The SWR came down but was still not ideal. I added another 70mm and played around with the position.  Well this extension lowered the SWR to 1.15 on 28.1200 Mhz to 1.53 on 50.2400 Mhz.  Good enough for me.  I then constructed the final gamma-style feed using brass brazing rod.  The brass rod is very sturdy and works fine.

Now what about the other bands?  20m, 17m, 15m and 12m.  For the project that I intend to use the loop with, I currently do not need the other bands.  However others might need more bands.  Firstly you will need to add more capacitance.  This is achieved by adding a fixed capacitance across the trimmer. Peter used a 68pF polystyrene capacitor that serendipitously allowed coverage of 14 MHz with the trimmer nearly meshed and 18 MHz with it nearly open.

A 630 volt capacitor is adequate for five watts. If you only have lower voltage rated capacitors, then two or more wired in series relieves voltage across each one. 120 and 150 pF in series will provide close to the required 68 pF.

Though desirable for low resistance, a soldered connection is impractical as the capacitor must be removed for higher band coverage. Peter mounted it on a piece of chopping board. It has two banana sockets which mate with the 4mm bolts that hold the beehive trimmer.   See images by clicking on the link above.

I have a 470pf  750 volt fixed capacitor but as yet have not tried it.  I will use a wing-nut arrangement to fix this cap to the beehive capacitor.  An update will follow in this regard.

I am quite happy how this antenna turned out but as they say the proof is in the pudding.  I will later provide a performance update but for the time being I would like to share my findings up to now:

• I enjoyed building this antenna and would like to thank  Peter VK3YE for making the information available about this antenna.
• This antenna is very sensitive to tune and also has a very narrow bandwidth.  Loop antennas is highly dependent on being precisely tuned to a specific resonant frequency. For small loop antennas, their size is often less than half a wavelength, making them inherently narrow-band and requiring constant re-tuning if the frequency changes. This characteristic, however, makes them highly selective and good at rejecting unwanted signals and noise, which can be an advantage in certain applications like receiving in crowded radio environments.
• I found that the capacitor and feed arrangement work in "tandem" and in my case I used a 25pf capacitor and had to lengthen the gamma-feed as a result.
• In my humble opinion the antenna I constructed lends it very well to pedestrian mobile operations.  If you live close to sea level then special precautions need to be taken to prevent corrosion even while pedestrian mobile.  Seal areas between the aluminium and PCB with marine silicone to prevent moisture getting in between the two metals. If not sealed properly the performance of this antenna will deteriorate with time.

Preliminary Test Results:

I really did not go into a full out testing and using this antenna.  The only testing I have been doing is with the Nano VNA and a test or two on air RX and TX "excursions" in my shack between four walls and two windows with metal burglar bars.  Surely not the way to test this antenna but in Part 2 I will describe a full "work out" for this antenna.  Images below depict the "Faraday Cage" operations.

Herewith more images regarding the antenna  (Click on images for larger view.)

 

Part 2 to follow soon