Let's build a 100 and 20 watt Dummy Load!

Above Image: Large RF dummy load for shortwave transmitter at the Moosbrunn transmitting station of the Austrian Broadcasting Service, Moosbrunn, Austria. It uses a sodium hydroxide solution to absorb the radio energy, which is circulated through the radiator (center) to cool it. It has a capacity of 100 kW.  - Source:  Wikipedia

At some stage of your amateur radio "career" you will need a Dummy Load.  Now what is a dummy load and what is it used for?

A dummy load is a device used to simulate an electrical load, usually for testing purposes. In radio a dummy antenna is connected to the output of a radio transmitter and electrically simulates an antenna, to allow the transmitter to be adjusted and tested without radiating radio waves. A dummy load is connected to the output of an audio power amplifier to electrically simulate a loudspeaker, allowing the amplifier to be tested without producing sound. Load banks are connected to electrical power supplies to simulate the supply's intended electrical load for testing purposes. 

Above Image: Small RF dummy load with capacity of 1 kW at frequencies up to 450 MHz. It consists of a 50Ω resistor immersed in oil to absorb the heat.  Source:  Wikipedia

In radio this device is also known as a dummy antenna or a radio frequency termination. It is a device, usually a resistor or many resistors, used in place of an antenna to aid in testing a radio transmitter. It is substituted for the antenna while one adjusts the transmitter, so that no radio waves are radiated so that the transmitter does not interfere with other radio transmitters during the adjustments. (As no dummy load is ideal, however, some radiation does occur). If a transmitter is tested without a load attached to its output terminals such as an antenna or a dummy load, the power will be reflected back into the transmitter, often overheating and damaging it. Also, if a transmitter is adjusted without a load, it will operate differently as compared with a load, and the adjustments may be incorrect.

The dummy load ordinarily should be a pure resistance; the amount of resistance should be the same as the impedance of the antenna or transmission line that is used with the transmitter (usually 50 Ω or 75 Ω). The radio energy that is absorbed by the dummy load is converted to heat. A dummy load must be chosen or designed to tolerate the amount of power that can be delivered by the transmitter. 

The ideal dummy load provides a standing wave ratio (SWR) of 1:1 at the given impedance.

Veterinarian-grade mineral oil, an inexpensive form of mineral oil, is frequently used by amateur radio operators as coolant in RF dummy loads. 

Above Image:  ZS1I external 100 watt Dummy Load.  Built many moons ago and never bothered to put it in a container of project box.  Still working as it should though!

Now that we know what a dummy load is it is time to put one together.  The dummy load we are going to construct can tolerate 100 watts of RF Power for one minute.  More than enough time to test a transmitter etc. The load uses carbon non-conductive resistors  mounted between two PCB's.

The dummy load we going to construct can be used internal or externally. Here I am talking about a project cabinet.  Your choice.  Mine has been used externally with no cabinet. The dummy load can be made up of  54 x 2k7 2 watt or 48 x 2400 Ohm carbon non-inductive resistors that are sandwiched together, with air spacing of 5 mm, between two identically drilled circuit boards.  The resistor ends are mounted flush with the non-clad side of each circuit board.  Then the leads are soldered to the foil side and cut.  Keep wiring including coax cable as short as possible.  This keeps the ground connection short, which eliminates stray reactances at the higher R.F. frequencies. The finished dummy load, shown in Fig. 1 is capable of dissipating at least 100 watts. 

I also constructed a 20 watt dummy load using 11 x 560 Ohm 2 watt carbon non-inductive resistors.  See images.

Calculation Results:

100 Watt Dummy Load

54 x 2K7 Resistors in Parallel = 50 Ohm

48 x 2K4 Resistors in Parallel = 50 Ohm

20 Watt Dummy Load

11 x 560 Ohm Resistors in Parallel = 50.91 Ohm 

Congratulations to all the candidates who passed the October 2025 RAE Examination!!

 As per the above title the Southern Cape Link Network Group would like to congratulate all the RAE candidates on passing the RAE. They wrote the examination last Saturday (18 October 2025).  A special word of welcome to every new radio amateur and we trust that every single one that passed will be and active radio amateur for the rest of his lifetime on this planet.  We as "older" radio amateurs would like to take this opportunity to share our knowledge that we gathered throughout the years. Let's be realistic there will by experienced radio amateurs that might not share their knowledge but they are definitely far and in between. There are also a few "soar plums" around.  Please ignore them and find a friendly helpful radio amateur.  The only thing that you must do is to ask questions on the airwaves, and NOT social media as we would like others to also learn from you questions.  After all we talk about amateur radio here and NOT social media!  If you do not ask questions you will not gain the knowledge of experienced radio amateurs. Yes, there is Google, YouTube etc. but they do not always explain the "nitty gritty" and definitely not the way experience radio amateurs will personally assist you with any problems you might experience in your amateur radio career.  The worst thing you can do is to "disappear" after you wrote the RAE.  Please get into the swing of things as soon as possible!! 

The following candidates passed the RAE in the Southern Cape Area:

1.  Ingrid ZS1ILL

2.  Juah ZS1JUA

3.  Divan ZS1DZA

4.  Vladimir ZS1VR

Finally:  Many thanks to all those who are/were involved in the RAE, PR and the recruiting process.

                                                           ************************

Soos uiteengesit in die bogenoemde titel wil die Suid-Kaap ZS Link Netwerk Groep al die RAE-kandidate gelukwens met die slaag van die RAE. Hulle het die eksamen verlede Saterdag (18 Oktober 2025) afgelê. 'n Spesiale woord van welkom aan elke nuwe radio amateur en ons vertrou dat elkeen wat geslaag het, vir die res van sy leeftyd 'n aktiewe radio amateur op hierdie planeet sal wees. Ons as "ouer" radio amateurs wil graag van hierdie geleentheid gebruik maak om ons kennis wat ons deur die jare versamel het, te deel. Kom ons wees realisties, daar sal ervare radio amateurs wees wat dalk nie hul kennis deel nie, maar hulle is beslis in die minderheid. Daar is ook 'n paar "suur pruime" in die rondte. Ignoreer hulle asseblief en vind 'n vriendelike en behulpsame radio amateur. Die enigste ding wat jy moet doen, is om vrae op die luggolwe te vra, en NIE sosiale media nie, aangesien ons wil hê dat ander ook uit jou vrae moet leer. Ons praat immers hier oor amateur radio en NIE sosiale media nie! As jy nie vrae vra nie, sal jy nie die kennis van ervare radio amateurs opdoen nie. Ja, daar is Google, YouTube ens., maar hulle verduidelik nie altyd die "nitty gritty" nie en beslis nie die manier waarop ervare radio amateurs jou persoonlik sal help met enige probleme wat jy in jou amateur radio loopbaan mag ondervind nie. Die ergste ding wat jy kan doen, is om te "verdwyn" nadat jy die RAE geskryf het. Kom asseblief so gou as moontlik aan die gang!!

Die volgende kandidate het die RAE in die Suid-Kaap gebied geslaag:

1. Ingrid ZS1ILL

2. Juah ZS1JUA

3. Divan ZS1DZA

4. Vladimir ZS1VR

Ten slotte: Baie dankie aan almal wat betrokke is/was by die RAE, PR en die werwings proses.

The 5 Band Inverted L-Antenna of Len Paget GM0ONX (Part 1)

Click on image for larger view.

Very few of us these days have gardens that will allow the “traditional” 40m long dipole (for the 80 Meter band) to be erected.  Fewer still have space for the double sized dipole for “Top Band”.  So, essentially, this means for many of us that 80 Meters is totally out of the question.  Or such a full sized antenna has to be bent into various contortions to get it to fit into the available space.

The antenna I am describing here was intended to allow operation on both 80 Meters and 40 Meters in less than half the space of the traditional dipole.  However, it will, in most instances, give a performance equal to, or greater than its full size cousin.  The antenna will also give a good account of itself on 14, 21 and 28 Mhz being electrically similar to the W3DZZ dipole.  

The antenna system will almost certainly require some impedance matching to suit rigs with solid state power amplifiers – again, this is just like the W3DZZ antenna.  Antenna purists will often tell you that  an antenna of this type requires radials, or a sophisticated earth system for optimum performance.  But in practice the antenna works very well with a modest earth system, although this is dependent on soil conditions.

The prototype antenna was constructed from heavy copper earth wire.  There is a single 7 Mhz resonant trap to make it more efficient on that band. The general layout of the antenna and the theoretical lengths of the antenna are shown in Fig. 1.  The antenna is fed with 50 ohm coaxial cable, with the coaxial screen connected to the earth rod.  This connection is secured using an earth clamp intended for earthing water pipes.  The center core of the coaxial cable is connected to the antenna via a single 15A “chocolate block” connector. Cover all connections with a waterproof tape.   No balun or other matching network is needed for 80 Meters and 40 Meters as the antenna’s feed point impedance is close to 50 Ohm.  The 7 Mhz trap is constructed from 11 turns of RG58 coaxial cable wound on a 100 mm piece of 40mm PVC pipe as shown in Fig. 2.  In this type of trap the coaxial cable acts as both capacitor and inductor and is capable of working at power levels in excess of 400 watts.

It is imperative that screen and center cores of the coaxial cable are parted as close to the point the cable passes through the hole in the pipe as possible.  This is to ensure the correct value of capacitance and inductance.  The center core of one end of the coaxial cable is soldered to the screen at the other end.
As with the feed-point, the ends of the coaxial trap and other joints must be weather proofed. The capillary effects of coaxial cable are legendary and water ingress will total ruin your trap.  The height at which the antenna folds over from vertical to horizontal is not critical but generally the higher it is the better.  Extra height, not only aids the DX performance of the antenna but also significantly reduces the amount of horizontal space required.  Tuning the antenna is quite simple but it is imperative that it is done in the correct order.  

Firstly cut both sections of the antenna about a half a metre longer than the dimensions shown in Fig. 1.  To start the tuning operation, begin on 7 Mhz and trim the wire length at the end nearest the earth connection 50 mm at a time until he lowest s.w.r. is achieved.  I managed an indicated s.w.r. of less than 1.2 : 1 over the whole of 40 Meter.  Then move to 80 meters and repeat the process, but this time trimming the side of the antenna furthest away from the earth i.e the side nearest the shack in Fig. 1.  The S.W.R. on the 3.5 Mhz band should be less than 2:1 over the whole of the band falling to about 1.2 to 1 at the point of resonance.  So it is worth setting the lowest S.W.R. at the section of the band you normally use, if you have a preference.

ED: I have had a lot of fun using the antenna and thoroughly recommend it to anybody not having enough garden room to erect a full size dipole in the optimum direction. 

Images:  (Click on images for larger view.)

What to do when your antenna rotator needs a new "starting" capacitor?

 

Image:  Antenna Rotator Control Unit.. Click on image for larger view.

I overheard a conversation recently between two radio amateurs in the Western Cape trying to scrounge a 130 mf 50-volt capacitor for a dead rotator.  The rotator suddenly died after several decades of faithful service.  The control unit of his Ham IV Rotator ceased to function.  A postmortem examination revealed a dead alternating current motor starting capacitor.

These capacitors are hard to come by in South Africa and if you can find one, it will be very expensive.  Ask me how I know that.  To solve the problem, two 150 mf, 50 volt electrolytic capacitors and two 100-volt, 3 ampere silicon rectifier diodes were used in the circuit shown.  The control unit was resuscitated.

Image:  Capacitor circled in red in the Control Unit  (Click on image for large view.)

For those interested in the theory of the functioning of the circuit, the explanation is simple. During any half cycle one capacitor is shorted by its associated diode. It might be presumed that having two capacitors in series, the resultant capacitance would be halved. This, however, is not the case because the diode acts as a bypass for the capacitor during every half cycle.

It is NOT a motor starting capacitor!!!

The purpose of the cap is to cause a 90-degree phase shift across the windings of the motor, which determines which direction the motor will turn. Some old capacitors dry out and the value changes.  This does result in the motor not starting to turn.  Replacing the cap (if you can find the correct value) will make the motor work again.

Note:  A larger value cap will allow more current to flow, but will also effect the phase angle, which will actually decrease the starting torque.  An infinitely big cap would be a short!  So don’t damage your motor!  A non-polarized cap if obtainable would also do the trick. If it is impossible to find the correct cap, well then back to our schematic.

Image:  Schematic Diagram of the Diodes and Capacitors (Click on image to enlarge.(

Use two back-to-back electrolytics as indicated in the above schematic.  Connect the negative sides of the electrolytics together, and connect the diodes so that the “bar” is at the positive end of each cap.  You want no current to flow through the diode when the voltage at the positive end of the cap is positive.

Another idea is to move the cap/s directly to the rotator, properly weatherproofed of course.  This eliminates the cable resistance in series with the cap.  Now use the two wires in the cable which went to the cap, and double up on the motor wires, cutting the resistance down there to.

Image:  ZS1I successful test setup. Click on image for larger view.

Hopefully this article will resuscitate those dead rotator control units.

-  Compiled many years ago by ZS1I for QSX, the monthly newsletter of PEARS. 

- Source 73 Amateur Radio

Southern Cape Repeater History - Period 1966 tot 2025 (Part 2)

History of the first 145.600 Mhz Danabay Repeater in Mossel Bay.

First some background relating to repeaters in the Garden Route Area. Circa 1980's there was only one repeater in the area and that was the 145.700 Mhz George Mountain Repeater.  This repeater was a free standing repeater and the only repeater in the Garden Route Area.  The repeater belonged to Eskom but through their kindness radio amateurs could use the repeater.  The repeater worked great but the coverage area excluded large parts of the Mossel Bay district. 

There was definitely a  need for another repeater in the Garden Route Area.  OM Stan Jones ZS1T took it upon himself to obtain and install the first ever 145.600 Mhz repeater in Mossel Bay.  Stan a then member of the Boland Amateur Radio Banch resided in George and was for many years the Head of the Radio Technical Division of the South African Police Force in George.  In April 1996 he contacted Rassie ZS11YT of the then Boland Amateur Radio Branch and it was not long afterwards that he informed me that he picked up the then Groenberg Repeater on loan to him to install as the 145.600 Mhz repeater in Mossel Bay.  Stan re-tuned the old Storno CQM 600/662 Mobile Radiophone/Professional land mobile transceiver that was converted to a amateur radio repeater. 

 

 

It originally was a 9-12 Channel Radiophone. By the early 1970's this was state of the art equipment, very well manufactured. In this time period there were only three authorized suppliers of equipment, Storno, Pye and Marconi. The installation typically consisted of a control head, handset and loudspeaker fitted in the front of the vehicle, connected to a transceiver unit usually mounted in the boot connected to a whip antenna. Storno also produced a transportable battery operated version for pedestrian use.The CQM600 with it's stylish remote control head and 'cornet' microphone won a design award in Denmark when introduced. The rugged, waterproof mobile unit was adaptable to a wide variety of applications and included marine and duplex versions. 

Specifications of the Storno Radio courtesy RigPix:

Type:	Professional land mobile transceiver
Frequency range depending on version:	68-88 MHz 132-156 MHz 146-174 MHz 420-470 MHz
Mode:	FM
RF Power output:	6-25 W
Receiver system:	N/A
Sensitivity:	N/A
Selectivity:	N/A
Image rejection:	N/A
Voltage:	6, 12 or 24 VDC
Current drain:	RX: ? mA TX: Max ? A
Impedance:	50 ohms
Dimensions (W*H*D):	? mm
Weight:	? Kg
Manufactured:	1968-197x (Discontinued)
Other:	9 -12 channels, XTAL

The repeater was tested on the test bench by Stan ZS1T after adding a Low Loss Helical Band Pass Filter on the receive side and a Cavity Filter on the transmit side.  After a few weeks of testing the 145.600 Mhz repeater was ready to be installed on site. The only problem was that there was no site available at short notice to install the repeater on.   Yours truly offered to host the repeater for the interim up high in Heiderand, Mossel Bay at my QTH.  My QTH was situated quite high up on the ridge in Heiderand and would have to suffice until a permanent site could be found.  It was an ideal high interim site,  situated in a quiet area (free of interference then but not today), line of sight to George and in a safe area.

Myself and Stan arranged for the installation of the repeater on a Saturday morning at my QTH.  When Stan arrived I already installed the 5/8 vertical antenna for the receive side.  Stan brought a folded dipole which was installed underneath the 5/8 vertical antenna with enough space between the two to prevent de-sensing. The Band Pass filter was installed on the RX side and a cavity filter was installed on the TX side. The power supply was installed and the repeater was switched on. The necessary final checks and tuning were done.  It was not long before contact was made with Isak ZS2I (Now SK) in Klein Brak River which confirmed great signal strength and audio.  The output of the repeater was tuned down to 10 watt as we did not have a full set of cavity filters for RX and TX.  For the newer generation of radio amateurs this is how repeaters worked in years gone by as cavity filters were scarce as hen's teeth and very expensive if you can find one.

Now to find a suitable high site for the repeater.  Thanks must go to Chris ZS1M who at the time was working for the Mossel Bay Municipality.  He was able to obtain the current site on a water tower at the entrance to Danabay.  This site gave great coverage and it was decided to use the site for the 145.600 Mhz repeater.

The time arrived for the repeater to be moved from my QTH in Heiderand to the DanaBay water tower.  In the mean time Stan ZS1T again came to the rescue with a full set of cavity filters on loan from the Boland Amateur Radio Club.  This would solve the use of two antennas.  We now only have to install one antenna.  We still used the small band pass filter on RX as an extra filter.  The repeater was installed in December 1996 inside the water tower pump room with the folded dipole high up on the top of the tower.  Standing on top of this water tower revealed a clear 360 Deg take off with no obstacles in the way.  To secure the repeater, filters, power supply etc. the repeater was housed in a old computer main frame cabinet that I donated.  This cabinet was ideal as it came with great cooling fans to keep things cool. 

This repeater functioned great for several years and I had the privilege of maintaining this repeater on behalf of Stan ZS1T who could not always visit the site. As these Storno Radios are build like tanks, it was not necessary to re-tune them at regular intervals.  From time to time the cavity filters were re-tuned to ensure optimal functioning.

The repeater was enjoyed by many local and visiting radio amateurs from all over.   This was the first 145.600 repeater installed on the Danabay Water Tower in the Mossel Bay area.  A few years before the year 2000 the repeater and cavity filters was returned to the Boland Amateur Radio Club as Chris Scarr ZS2AAW and his late father Trevor ZS2AE installed a new 2m repeater, antennas and 70cm link on the Danabay Water Tower which was a great upgrade.  This upgrade amongst others allowed for the 600 and 700 repeater to be linked via DTMF.  This setup functioned  well for many years and was maintained by Chris ZS2AAW and Trevor ZS2AE (Now SK).

I would like to thank every single radio amateur that was involved in making the first 145.600 Mhz Repeater in Mossel Bay a reality and bringing it to life.  I do not like to mention names as indicated in many of my posts as I might leave somebody out in the cold but I must mention the following radio amateurs, clubs and organizations:

1.  Stanley Jones ZS1T, George

2.  Boland Amateur Radio Club (Members and Committee)

3.  The then repeater keeper of the  Boland Amateur Radio Club (???)

4.  Chris ZS1M, Danabay

5.  Mossel Bay Municipality

6.  All those who assisted and not mentioned in the article

7.  Garden Route Radio Club

8.  Rassie Erasmus ZS1YT, Strand

Finally:  I would like to plea to the younger and older generation radio amateurs.  Please if you have any information, images and articles on local (SA) amateur radio history make it available for publication and preservation.  You can forward the info to Johan ZS1I by clicking HERE.

Images:  (Click on images for larger view.)

           Coverage of the then 145.600 Mhz Danabay Repeater - Mike Hanslow then ZS1RMS

Satellite and Street Maps Courtesy -  Satellites Pro / Apple Map

- End

Best wishes to all the RAE Candidates writing the examination today, 18 October 2025!!

Die ZS Link Netwerk Groep wens al die RAE-kandidate vanoggend alles van die beste toe vir die eksamen. Julle avontuur het sopas begin in amateurradio en onthou dit is 'n lewenslange avontuur en nie net vir 'n paar maande nie. Julle sal baie dinge leer dwarsdeur julle amateur radio "loopbaan".

Ons hoop om baie van julle binnekort op die lug te hoor. Ons verwelkom julle by die amateur radio stokperdjie en sien daarna uit om julle touwys te maak in hierdie wonderlike stokperdjie.

'n Groot dankie moet ook gaan aan al die dosente, assessors en opsieners vir hul harde werk en tyd, Julle bydrae word hoog op prys gestel!!

Laastens: Sodra jy jou amateur radio lisensie ontvang, is jy meer as welkom om by ons aan te sluit by die ZS-Link Netwerk Groep via WhatsApp, Echolink of via die RF-skakels en herhalers (indien beskikbaar in jou area). Ons sal julle graag help om by ons in te skakel op die ZS-Link Netwerk en die Groep.

Sluit gerus aan by die dinamiese ZS-Link Netwerk, jy is meer as welkom!!

Kontak ons ​​deur HIER te klik.  Besoek ook gerus ons webtuiste deur HIER te klik

                                                          ********************

The ZS Link Network Group wish all the RAE Candidates the best for the examination this morning. Your adventure has just started in amateur radio and remember it is a life long adventure and not only a few months. You will learn many things throughout your amateur radio "career".

We hope to hear many of you on the air soon. We welcome you to the Amateur Radio hobby and look forward to "show you the ropes" in this wonderful hobby.

A big thank you must also go to all the lecturers, assessors and invigilators for their hard work and time,  highly appreciated!!

Finally:  Once you receive your amateur radio license you're more than welcome to join us on the ZS-Link Network Group via, WhatsApp,  Echolink or via the RF Links and Repeaters (if accessible in your area).  We will gladly assist you in connecting and joining us on the ZS-Link Network and the Group.

Give the dynamic ZS-Link Network a try, you more than welcome!!

Contact us by clicking HERE.  Visit our website by clicking HERE

Simple method to test 1:1, 4:1, 9:1 and 49:1 Baluns

 

This article was written to aid new radio amateurs in  testing a homebrew balun.

Using a transceiver, SWR meter and 1:1 balun with resistor to test the balun:

You can test a balun by connecting a simulated antenna load on the output (antenna) side of the balun.  Connect your transmitter ( with an SWR meter) on the input side.  In the case of a 4:1 balun, use a 160 to 340 ohm resistor as your simulated antenna.  (See Fig 1)   If the balun is functioning properly, you should see a low SWR (less than 1.5:1) when you key your transmitter.  This means that the 4:1 balun is matching the nominal 200 ohm load to 50 ohm (200/4 = 50).  If you have a 1:1 balun, you can use the same test. Simply substitute a 40 to 60 ohm resistor for the load.  A 50 ohm dummy load
may substitute the resistor if available.  The SWR should be 1:1 or very close to it. WARNING:  The load resistors must be non-inductive and capable of dissipating the output power of your transmitter for a short period of time.  If you turn your transmitter output down to 10 watts, you'll still need a heavy duty 10 watt resistor.   

I have used this inexpensive old school method for many years but you could substitute your transmitter and SWR meter for a expensive antenna analyzer which will have the same end result.

Testing a 9:1 Balun with a Nano VNA:

 

Images:  (Click on images for larger view.)

I decided to measure the "SWR and Impedance" of the 9:1  Balun with my NanoVNA.  Although this is not the correct way to do it, it gives me some indication that the Balun is working.  Let's call the measurement a fault finding mission.  I used a 270 Ohm resistor across the connecting points and obtained the readings as depicted in the images.

Testing a 49:1 Balun with a Nano VNA:

Images:  (Click on images for larger view.)

To test the balun before adding the wire and counter poise I used a 2K7 resistor on the ground of the coax connector and antenna connection.  The attached NanoVNA image provide info on the results I obtained from the balun.  I am sure the SWR readings will change once I add the antenna wire to the balun.  The height and closeness of objects will also play a roll.

Suid Kaap Herhaler Geskiedenis - Periode 1966 tot 2025 (Deel 1)

Bo:  Die W6MEP-herhaler, oorspronklik K6MYK, word beskou as die oudste ononderbroke werkende amateur radio herhaler wat bestaan, met sy eerste uitsending in 1956. Dit is gebou deur Art Gentry, wat as die "Vader van Amateur Radio Herhalers" beskou word.

RED.  Stan Jones ZS1T was vir baie jare gemoeid met die installering en instandhoudng van herhalers in die George / Mosselbaai omgewing.  Die artikel soos deur hom saamgestel gee vir ons 'n terugblik van hoe 2 Meter aktiwiteite toegeneem het deur die jare.  My opregte dank aan hom vir die artikel.  Ek is seker dat lesers dit baie interessant sal vind.

STAN ZS1T SKRYF: “Ek het Desember 1966 na George toe gekom. Ek het op daardie staduim nie ‘n 2 Meter stel besit nie. Twee meter was in daardie jare nie so gewilde manier van kommunikeer nie. Hier was net ‘n paar radio amateurs gewees nl myself, Chris ZS1FA, Rusty ZS1WQ, Tom Watson (roepsein nie meer beskikbaar nie), Stan French ZS1YD, Bill ZS1J, Dennis ZS1UV, Piet ZS1ZK. Dup ZS1GC het later by ons aangesluit. Die ledetal het so gegroei en het ons maar op HF gesels. Stadig maar seker het 2 Meter sy kop uitgesteek. Ek het by ‘n sekere Mnr v.d. Walt, ‘n klompie 15 watt PYE stelle gekry wat toe beskikbaar was. Ons moes natuurlik die frekwensie verander om by ons behoeftes te pas. Die frekwensie was 145.500, wat ons op daardie staduim gebruik het. Ander radio amateurs het beskikbare stelle gekoop, soos dit beskikbaar geraak het.
John Fletcher (ZS1ZR) het by my eertydse werk aangesluit en later die amateur radio eksamen geskryf. Hy is die roepsein ZR1CI toegeken. Ons het met toetse begin, versterkers gebou met 5894 of 829B lampe en saans met Andre ZS2BR in Port Elizabeth gesels. 

 

Bo:  PYE Cambridge Radios (15 Watt) - PYE Telecom History Group (Klik om te vergroot)

Op ‘n staduim is herhalers bespreek en het die gebruik van herhalers na vore gekom. Ek het by Derek Siegel ZS1DP ‘n PYE CAMBRIDGE stel gekry wat ons omskep het in ‘n herhaler. Nou kom die beste, die slyp van die kristalle. Ek het in ‘n ou Radio Amateur Handboek gelees hoe Amerikaners kristalle geslyp het. ‘n Stuk glas is gevat asook baie fyn sandpapier. Die kristal is uit sy doppie gehaal en dan versigtig geskuur tot die regte frekwensie verkry is. My werk het ‘n frekwensie teller gehad wat dit natuurlik maklik gemaak het om die regte frekwensie te verkry. Die skuurwerk moes natuurlik baie versigtig gedoen word. Die kristalle wat ons gebruik het was nie ver van die frekwensie af nie. So het ons eerste herhaler op 145.800 MHZ die lig gesien. Die herhaler is later ook toegerus met ‘n “G” kode maw die letter “G” is in morse kode uitgestuur. (Red. G staan natuurlik vir George) Die “G” kode is later verwyder, aangesien ‘n versoek ontvang was van radio amateurs dat ek dit moet doen. Op ‘n staduim was ons versoek om die frekwensie te verander na 145.700 MHZ aangesien die 145.800 Mhz frekwensie vir satelliet komunikasie gebruik sou word. Ons het maar redelik rondgeval om ‘n geskikte plek te kry vir die herhaler. Ek was op ‘n staduim versoek om na die olieboor se FM toerusting om te sien. Die toerusting was op die George berg in Eskom se gebou. Voordat ek die toerusting kon versien moes ek ‘n sekerheidsklaring by Eskom kry. Die sekerheidsklaring
is aan my toegeken en het Dave Perry ZS1SG van Eskom my gevra dat wanneer ek na die olieboor se toerusting omsien ek dan ook na hulle stelle sal kyk. So het die moontlikheid ontstaan om die herhaler in Eskom se gebou te kry. Ek het vir Dave Perry genader, waarna hy met sy departement geskakel het. Die groen lig is gekry en is die PYE herhaler met twee gevoude dipool antennas daar geinstalleer. Die SAUK het egter ontdek dat daar ‘n vreemde stel naby hulle stasie was en moes die herhaler eers weer verwyder word. Dave Perry het sy departement genader wat aandui het dat hulle een van hul stelle (Storno) daar sal installer vir gebruik deur radio amateurs. Die naam “Eskom Radio Club” is aangebring op die Storno en is die 145.700 Mhz herhaler vandag nogsteeds in gebruik op die George berg. Ek het later ‘n adres gekry van ‘n firma in Engeland vanwaar ek kristalle bestel het teen R5.00 per kristal afgelewer. Dit was vir die PYE stelle wat ons bekom het. 

Bo:   Voorbeeld van die Mobiele Storno Herhaler (10 Watt) soos geskenk deur TAK: BOLAND (Klik om te vergroot)

Later soos die amateur lede toegeneem het, het die behoefte vir ‘n tweede herhaler onstaan in die Mosselbaai omgewing. Ek het met Rassie ZS1YT in verbinding getree en ons behoeftes verduidelik. Hy het met die destydse TAK BOLAND gesels en het hulle toe vir ons ‘n Mobiele Storno Herhaler (145.600 MHZ) laat kry. Die herhaler is tydelik by die QTH van Johan ZS1I geinstalleer. terwyl ‘n geskikte perseel vir die herhaler gesoek was. Ek het later om persoonlike redes toe afstand gedoen van die 600 herhaler. Die Garden Route Radio Klub wat toe gestig was het die herhaler oorgeneem. Ek weet nie wie almal betrokke was by die installering van die 145.600 MHZ herhaler op Mosselbaai nie, maar ek dink dat Chris ZS1M toestemming gekry het vir die perseel te Danabaai. Amateurs het beter stelle aangeskaf soos dit beskikbaar geraak het. Dit in kort die ontstaan van 2 Meter aktiwiteite in die Suid Kaap omgewing.

Later jare het Eskom sy eie tegniese afdeling in George geopen. Met die gevolg dat hulle toe ook die 145.700 MHZ herhaler se herstelwerk en versiening oorgeneem het, so ook die olieboor se radio kommunikasie. 

Bo:  1958 Motorola stel die Motrac-radio bekend, die eerste tweerigtingradio vir voertuie met 'n volledig getransistoriseerde kragtoevoer en ontvanger. Die lae kragverbruik maak dit moontlik om die radio te gebruik sonder om die motor se enjin te laat loop.

Nou so ‘n kort oorsig oor die toerusting wat die S.A Polisie vroeër jare gebruik het. Toe ek in die Suid Kaap begin werk het, het die toerusting bestaan uit 50 Watt Motorola “T/POWER” stelle. Die frekwensie was in die 37 Mhz band gewees. 

 Bo:  Motorola “T/POWER” 50 Watt Radio

Bo:  Motorola Micor Radio en Herhaler (100 Watts)

Hiedie stelle is heelwat later met Motorola “Motrac” stelle vervang en ook later met Motorola “Micor” stelle. Ek het gedurende my dienstermyn begin met eksperimente met herhalers vir die S.A. Polisie. Ek het later ook magtinging verky om voort te gaan met die installering van die herhaler. Die herhaler het bestaan uit ‘n basis stel wat hooggleë was. Die Poskantoor het vanaf die bestaande ligging ons van ‘n telefoon lyn tot by die polisiestasie voorsien waar dit gekoppel was aan ‘n afstandsbeheerde monitor. Hierdie stelsel het baie goed gewerk tydens my dienstermyn. Die stelsel is egter vervang na my dienstermyn met ‘n meer moderne en gevorderde stelsel in die BHF band op die SAUK perseel op George berg.

-Einde

Down Memory Lane - To all HAMNET Members - Compiled by Pierre Tromp ZS1HF (Before he became SK)

 

Which 6146 Tube? (Valve)

Yes, the popular 6146 tube is still widely used in many amateur radio equipment  today.  However some radio amateurs might not be familiar with the  different types of 6146 tubes.  New radio amateurs might find the description of the various  types  interesting and useful for future reference.

6146  -   The original design with a plate dissipation of 25 Watt.

6146W  -  A rugged version of  the 6146.

6146A  -  The first generation of improved 6146 design, also with a plate dissipation of 25     
                watt.

6146B  -  A significantly improved tube design that offers 35 watt plate dissipation as well as
                an improved heater design that allow much cooler operation.  The 6146B was
                designed specifically for SSB service and was used as a workhorse in many CW
                and SSB radio's.

Remember if you must use a 6146, 6146A or 6146W adjust your radio's final amplifier section so that the maximum plate dissipation rating is not exceeded. 

Further reading compliments of the Antique Wireless Association of Southern Africa.  The 6146 Family of Tubes by Glen E. Zook, K9STH

"Refurbish" a 9:1 QRP Balun after 5 years in the Sea Air

I decided to to build a End Fed HF Dipole Antenna in April 2020 during Covid19 Lockdown.  The antenna known as the ZS6U Mini Shack Special Antenna with a 9:1 Magnetic Longwire Balun/Unun.  The article relating to this antenna is available HERE.

I recently decided to take the antenna down to refurbish the balun as it has now been up in die sea air for 5 years and I was sure corrosion was "eating up" the balun.  After taking it down I was quite surprised to see that the balun was still in a very good condition (outside and inside).  See images.  The only part I replaced was the eye bolt and nut.  The bolt was lightly rusted and could have lasted another 5 years, however I decided to replace the eye bolt.  The only other part that I replaced was a nut that came loose on one of the connecting bolts to which the counter poise was connected.  The lock washer did not lock and in turn the bolt would turn around when tightening the wing nut.  I replaced the nut with a lock-nut and this solved that problem.  I installed the new eye bolt and nut and the balun was ready to be put up again.

The red cabinet has a watertight seal that keeps rain water out but I again sealed the unit with silicon to keep it water tight. 

I also decided to measure the "SWR and Impedance" of the 9:1  Balun with my NanoVNA.  Although this is not the correct way to do it, it gives me some indication that the Balun is working.  Let's call the measurement a fault finding mission.  I used a 270 Ohm resistor accross the connecting points and obtained the readings as depicted in the images.

Finally:  This QRP balun served me well since 2020 and is now ready to use for another 5 years.

Images:  Click on images for larger view.