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.

162 Mhz Slim Jim Project by Christi ZS4CGR, Luckhoff

Image: First page of original article.  See VK8BN link for the complete article.  (Click on image for larger view. )

Why is the Slim Jim so much more efficient than the popular 5/8 wave or other ground plane
antennas?

The Slim Jim vertical angle of radiation is almost parallel to ground so maximum radiation is
where it is needed: straight out and in all directions. The vertical angle from the Slim Jim is about 8 degrees, while the common 5/8th wave ground plane antenna is about 32 degrees. With all ground planes, including those with radials a wavelength long, the vertical angle radiation is tilted upwards at an angle of 30 degrees or more.

This gives the Slim Jim a "gain" over a 5/8th wave of about 6dB when measured parallel to the
ground!

Herewith some interesting links on the Slim Jim Antenna:

Build the Slim JIM Antenna by Jose I. Calderon, DU1ANV

Slim Jim and J-Pole Calculator M0UKD

The Slim Jim Antenna, VK8BN   (Contains original published article by F.C. JUDD, G2BCX)

Is the B25 Radio the most respected and well known radio of the South African Bush War?

 

Images above:   ZS1CT  (Click on images for larger view.)

Before one can possibly answer the above question we need to take a look at the B25 Radio and its history.  I will only provide a short overview as there are more than enough information and reviews on the Internet relating to this radio.  

During the South African Bush War, the B25 radio was a key piece of communication equipment used by the South African Defence Force (SADF), particularly for long-distance communication, and it was a fixed station radio. 

Here's a more detailed breakdown:

Type:  The B25 was a fixed station radio, meaning it wasn't designed to be portable like a manpack radio.

Components:  It consisted of a power supply (12/24 V), a transceiver, a controller for an automatic antenna tuner, and the tuner itself. 

Frequency Range:  It operated in the frequency range of 2.0 to 29.999 MHz. 

Modes: The B25 supported various modes including A2J (CW), A3H (AM), and A3J (USB and LSB).

Antenna:  The B25 radio could be used with a whip antenna, long wire antenna or 50-Ohm antenna. 

Use in the Bush War:  The B25 was a crucial tool for the SADF, particularly for long-distance communication during the Bush War. 

Other Features:  The radio was solid-state and watertight, and the manpack battery had a built-in charger.

B25 Web Pages:

1. Fuchs B25 / B26 HF Radio Thomson TRC-300 ( French ) 

2.  Cape Town Amateur Radio Centre

3. Rudi's  ZS6DX Photo Gallery - military equipment  

As can be seen from the above links the B25 radio found another use after the South African Bush War. The amateur radio fraternity obtained a large quantity of these radios and many were put onto the air and used on the HF bands.  Others just kept the B25 as a nostalgic/display radio in their radio room.  I obtained a B25 radio as well as two sets of peripheral boards should a board decide to let out smoke.  I replaced the original radio's microphone with a homebrew ZS1I special microphone.  I did not make any other modifications even the microphone socket was left as originally intended.  The homebrew microphone worked great actually so good that many stations did not even know that I was using a B25 Radio.  Well as I moved on I decided to sell the B25 and all the spare boards in 1995.

Finally there were many SADF radios used during the South African Bush War and it would not be fair to answer the title question.  The B25 is a "brick" of a radio and will still be around for many years to come.

Images:  ZS1I (Click on images for larger view.)