Build your own 6 Way Coax Remote Antenna Switch (1.8 - 60 Mhz) - Nico ZS4N

During a recent QSO with my brother in law,  Nico ZS4N we discussed amongst other coax switches and he mentioned that he bought a 6 way coax remote antenna switch kit.  He assembled the kit and the switch is now daily in use in his shack.  He regard this kit as a very good buy and indicated that the switch is working very well.

Description:
The antenna switch has good isolation effect, and it adopts imported Austrian high-quality relays.

Specification:

• voltage: DC 12V
• max watt can handle： 1500W
• Size: 11.8*11.8*1.6mm
• Frequency: 1.8MHz--60MHz
• Weight: 139g

The kit is available from Giga Technology in South Africa

Images:  Click on images for larger view.

 

Lets modify a CM108 USB Sound Card to become an AllStar Sound Card Fob.

Now I know that there are thousands of  videos and web sites on the Internet that explains in great detail how to modify a USB CM108 and CM119 Sound Card to an AllStar Sound Fob.   Now what is a sound card fob?

A "sound card fob" (often referred to as a USB sound card or audio interface) is a small, portable, USB-powered device that provides audio input and output capabilities, commonly used in amateur radio applications like building AllStar Link hotspots.

Here's a more detailed explanation:

• Function:

  These devices act as a bridge between a computer and a radio, enabling audio signals to be sent and received. 

• AllStar Link Hotspots:

They're particularly popular for creating AllStar Link hotspots, which are systems that allow amateur radio operators to connect to the internet via VoIP (Voice over Internet Protocol). 

• Modifications:

The "fob" part refers to the small, keychain-like size of the device, which makes it easy to modify for specific applications, like connecting to a radio's PTT (Push-to-Talk) and COS (Carrier Operated Squelch) circuits. 

• Examples:

Some common examples include the KNACRO CM108 USB sound card. 

• Why use them?

They offer a cost-effective and compact solution for integrating computer audio with radio equipment. 

• Features:

They often have basic audio input/output jacks and can be modified to include features like PTT and COS signaling. 

• Audio Processing:

Sound card fobs contain a digital-to-analog converter (DAC) and an analog-to-digital converter (ADC) to process audio signals. 

• Applications:

Besides AllStar Link hotspots, they can be used for other audio-related projects, like creating simple audio interfaces for recording or playing audio.

From time to time the need arise to quickly test a radio or AllStar node in a modular fashion without the need to permanently install a fob to a Raspberry Pi or any other mini computer.  This might sound weird to the more experienced radio amateurs but in this country with it's high import and export rates we rely heavily on homebrewing our own "interfaces" at the lowest cost possible.

I normally use the SYBA CM119 module but your do not get the SYBA in South Africa.  For this project I decided to use the Chinese CM108 Blue PCB version.  Nothing wrong with the CM108 but it must also be imported from China.  I had one of these blue PCB versions left and decided to modify it into an AllStar Sound Fob.  The idea was to build this modified fob into a 3D Printed Project Box.

Now which method will I follow to "create" this Sound Fob?  I constructed my first fob in 2017.  It is still operational and in daily use since August 2017 without any problems or glitches.  I had a look at it but decided that the construction is to big for what I had in mind.  It needed to be small without any bells and whistles.  No LED's or Trim-pots removal of speaker or mic sockets,  just a bare-bones modification.  I ran into a article called "Using the Sanwu SW-HF07 USB sound adaptor for VKLink nodes".  Just what I was looking for except my blue CM108 was not from the Sanwu stable.  I decided to go ahead as the basic components looked the same.  If it does not work I will make it work one way or the other.

Components:

BC549 NPN Transistor

BAT52 Diode

4K7 Resistor

1N4148 Diode

0.01uF Cap (103)  (Optional - used on the PTT line.)

After obtaining all the parts from my component holders it was time for the tedious task to solder thin wires to Pin 13 (PTT) and Pin 48 (COS) on the CM108 chip.  This took quite a while as I took great care to do it correctly and to cast each connection into epoxy to protect the "new" soldering joints.  I checked my solder work with a large magnifying glass before embedding the pins into epoxy.  R6, R7 and C2  were removed as I did not want any strange bias voltages going to the radio.  The removal of C2 breaks the path between the ring contact and the rest of the circuit.  The rest was quite simple and you can follow the article. 

Note:  Break the two tracks between the tip and ring contacts on the Mic socket as this will allow the use of the ring contact for COS.

The rest of the construction should be straight forward if you follow the above article and my listed photos below.

Finally:  If you do need LED indicators (TX,RX Heartbeat,COS and PTT) it can be done via the Fob or the GPIO pins of the Raspberry Pi.  Google is your friend here.  The unit works great once you made a few software changes in the rpt.conf and Simple USB Menu.  In the next project I will build a "fully fledged" Fob interface with a few "bells and whistles" and a separate PCB for the components.

Images:  (Click on images for larger view.)

 

Amateur Radio Tower Maintenance and Upgrade: Johann ZS1AAC, Still Bay

This past Saturday, 29 March 2025 Johann ZS1AAC and a few radio amateurs undertook the task of  maintenance and upgrade his amateur radio tower at his QTH in Still Bay.  Johann indicated that it was time to reposition antennas and fit new LMR400 CoAx cable as well as installing a new Diamond X200 antenna on top of the tower.  Another task that was necessary was to install a red light on the tower as the tower was inline with the Still Bay Airfield.   The ground work was done by Johann ZS1AAC and Attie (ZS1ATTIE) before hand as this would allow ample time to do the other work on the Saturday.  As with many amateur radio activities the social part must also be under taken once the hard work were completed.

The following radio amateurs lend a helping hand on the day:

1.  Johann ZS1AAC

2.  Nicolene ZS1HAR

3.  Attie ZS1ATTIE 

4.  Danie ZS1DL

5.  Jasper ZS1WT

6.  Viv ZS1VIV

7.  Rassie ZS1RP

Once the task was completed successfully it was time to light the braai fire, sit back and relax.  From the reports received, Johann ZS1AAC is very satisfied with the positioning as well as the functioning of the antennas.  He indicated that the upgrade made a significant impact to the RX and TX of his station.

 

Finally:  Johan ZS1AAC would like to thank everyone present on the day also those who stood by on the air for signal reports.  To all the radio amateurs and non radio amateurs who assisted on the day and also for all the hard work that they put in, a big thank you!  

 

Images:  (Click on images for larger view.)

 

 

Videos:

Another Homebrew Two Way Antenna CoAx Switch - Francois ZS1Q

 

On the 17 March 2025 I published the following article: My Homebrew 2-Way VHF COAX Antenna Switch - Christi ZS4CGR

While looking through some om my old CD's I came across three photos of a  Two Way Antenna CoAx Switch that Francois ZS1Q constructed.  I remember that Rodger ZS1J (then) also published an article on how he constructed a coax switch.  Unfortunately I cannot find that specific article.  Maybe somebody knows where I can find that article.  I will include it in this article as the build is of similar nature.  If you have the article of Rodger you can send it to me by clicking HERE.

(Click on images for larger view.)

Kenwood TK80 CMOS battery replacement - Curtis ZS6CMO

 

After many years of operating the CMOS battery needs to be replaced. 

CMOS = complementary metal-oxide semiconductor

A complementary metal-oxide semiconductor (CMOS) is the semiconductor technology used in most 

of today's integrated circuits (ICs), also known as chips or microchips. CMOS transistors are based

on metal-oxide semiconductor field-effect transistor (MOSFET) technology.

Why? The question could be asked…

 

The radio is dependent on Custom settings and sometimes when the battery runs out of 

power, the radio does not keep the settings.

PLEASE NOTE: When removing the battery you will lose all the settings. Make 

sure to write the settings down.

The process below is not a complex one rather a normal repair process with not  a high level

of skills.

Tools require for the replacement:

 

• “Star” Philips Screwdriver

• Flat tip screwdriver

• Soldering iron

• Soldering Flux

• Soldering wire

• Pair of Pliers

• 2 pieces of wire RED (+) and BLACK (-) Length of wire depends where

  you are going to place the backup battery.

• Self Adhesive tape

• Small container to keep screws together

Process:

 

Take bottom and top cover screws out and remove covers.

At the side of the Front cover you will find 2 screws each side which has to be removed.

The battery will be visible on the panel.

The battery (if available) can be replaced with a standard battery or could be replaced 

with a “modified” setup.

In this guide it was replaced with the “Modified” one.

Desolder the battery from the board.Make sure that the soldering points are still in

good condition. Do some cleanup and apply an additional “blob” on those points.

To be able to fit the modified battery it was necessary to print a cage for the battery.

Here is the link to the battery holder 3D printer files. Click HERE. 

I bought the battery from a Security company selling Security equipment

I used some scrap material to fit a plate to the POS and NEG of the holder. Next you 

have to solder a black wire to the Negative and RED wire to the Positive end.

Find a place where the battery could be fitted (I used self adhesive tape) inside the radio 

or somewhere near the original battery.

Just next to the original battery was the most convenient place to fit the complete unit

(Battery). Note the position of the RED and BLACK Wire.

Finally, I use a piece of Duct Tape to ensure the battery stays in place.

Assemble the radio and test.

Please remember to restore all the settings Previously made by you.

Enjoy!

ED. Curtis thank you very much for this informative and useful article. I am

sure that many Kenwood TK80 users will benefit from it. So no excuses. Replace 

that flat CMOS battery if yours has been flat for some time.