A Few thoughts as we start 2025

Hi I was wondering...

I was trying to remember which frequencies are 'new' and which are the 'old' ones. Then I recalled that the h.f. bands  changed 40 years ago!

So I set out to find the up to date charts and listings of our frequencies. Noting that the h.f. bands aren't the only ones to have changed over the years.

You may recall that in the start of Amateur Radio they were given "all those useless bands!" 

I have created a document that details the h.f. and V/UHF Bands for the Radio Amateurs in South Africa. It is a 'work in progress'. So comments are desired please. DO NOT PRINT IT.

Link:-  SA-ZA_Bandplans

One thing that caught my eye the other day was the two tone oscillator. This is used to 'test' an SSB Transmitter for purity of output. This 'test' requires a "dummy load" of sufficient power rating for the full output power of the transmitter. Also a connection to the microphone input socket of the transmitter. 

 

So this circuit which originates from the ARRL book has some interesting features. 

It uses a pair of back-to-back diodes to regulate the output. I wonder if it really 'works' at that. So I shall put it on a proto board and check for distortion...

 

Ham-Comp - before the Pi

Yes before the Raspberry Pi we had computers of all sorts. As a radio amateur I had some experience of using a microprocessor for an application. It was the 80s and RTTY was in great favour. This usually meant acquiring a teletype machine. Which the post office of the day was dumping in large quantities. These were hernia-inducing electro-mechanical machines weighing the best part of 50kg.

They also only ran at 50 Baud. Most radio amateurs were already running at faster speeds. And ASCII was just 'allowed' so long as it wasn't faster than the Posts and Telecommunications could read! So 300 bits per second of 7 bit ASCII. Packet Radio was just around the corner.

On my return from the UK with a ZX81 I unwisely mentioned this on the Johannesburg repeater. Being told that this was just a toy incapable of doing much. I should buy an Apple which could do much more. At this time CP/M personal computers were flooding the market with reasonably priced models. Much lower cost than the Apple II. With inexpensive software and adequate performance they were taking the word processing and spreadsheet market by storm. The Z80 versions were also quicker than the 8080 versions. Hard disks were starting to become available. I know you will laugh when I tell you the size of 5 Megabytes was considered enormous by us then.

So onto this scene came the low cost ZX81 later the Z80 based 'Spectrum'. Both had reliability 'issues' with the back connector. Which always seemed to fail at the worst possible moment. But onto this connector could be plugged all sorts of 'peripheral' cards/adapters.

As I was working at a company that had just invested in an 8080 development machine, I started taking an interest in the microprocessor. This unit had an EPROM programmer as part of the front keyboard and screen. This allowed you to write an assembler program [in 8080 code] and program the EPROM with the code. Hang on! How was I going to write for the Z80 based ZX81? ...

Well it wasn't easy but the assembler would allow 'define byte' inserted into the code. This is where I was exposed to 'code compatibility' in no uncertain terms. The Z80 had literally grown out of the INTEL 8080. Because the founders of Zilog had left Intel and designed the Z80 as 'replacement' for the 8080.

So the majority of the instructions were applicable to both processors. The assembler would produce a program that would run on the Z80 without problems.

With the help of a friend and colleague I programmed the ZX81 by hand. Wrote the program into an EPROM and took it home to try it...every night!

This 'project' taught me everything about the hardware interfacing with the software writing that forced me down a path I had not considered. I learnt how to set up the 8251 UART for 5 bit operation [Baudot]. I also learnt how to read and write to the registers and memory. It took a month but I did demonstrate it working to the Rand Amateur Radio Club. This used the TV screen and the ZX81 'listening' to a cassette tape of a RTTY transmission. 

I still have the sterilisation lamp I bought to erase the EPROMs. It is in the garage. I used to test the program I had written and erase the ones from the previous night. Then sit down with the Z80 Assembly Language Programming book by Lance A. Leventhal and pencil in the next bit of the program. I still have the book. 

The wires went to the PCB connector which was cut to size and a key added to ensure I didn't plug it round the wrong way. The 8251 is above the 5 Volt regulator heat sink. The crystal is the baud rate generator crystal with a DIP switch to set the required baud rate. As time went by I added another 2k of RAM as well as some 8 bit parallel ports. 

I don't think I could wire it up these days!

 A more complete picture with the connector/extender. Oh yes there was all sorts of possible expansions.

Later there were Z80 Assemblers and EPROM programmers. But this was 'hand-crafted'. The EPROM is missing probably somewhere amongst the EPROMS I still have somewhere! The program listing? I know I wrote it all into an exercise book. But again it is somewhere - to be found later...

73 ZS6WL John Brock

RAE Backgrounder Article 01

What is the most critical part of a car? The tyres. (tires in us English)

What is the most critical part of a HiFi (High Fidelity) setup ? The loudspeakers.

[We can argue about what constitutes a HiFi later.]

What is the most critical part of an amateur radio station?

It is the antenna installation. Which includes the matching circuitry in the output stage and the cable connection. We usually refer RAE students to the "maximum power transfer theorem" when discussing this. Forgetting the other bits and pieces that make up the whole installation.

When discussing a 'loudspeaker', we usually refer to it as a 'transducer'. It converts electrical signals into sound or air pressure changes. With a radio station it is similar. The radio frequency energy is transferred to an electrostatic wave (also an electromagnetic wave). In the 'very old' days this was called the 'aether'. This field fades away as you get further away from your transmitter. The magnetic field quite quickly. But the electrostatic field not as quickly.

Figure 1: From: Radio & Electronic Laboratory Handbook by Scroggie  

Most times Radio Amateurs get very concerned about 's.w.r.' (Standing Wave Ratio). And the notes also refer to this as a 'bad thing'. Essentially what you need to worry about is getting the maximum amount of power in your transmission 'out there'.

So recently with the supply of 'vector network analysers', it has become possible to measure the antenna with great accuracy. This leads to critical testing of the antenna and a very worried Amateur.

In the early part of the 20th century a current meter in the antenna wire was all that was required. Certainly the s.w.r. was an issue. But the valve power amplifier would ignore this 'reflected power'. Only when the voltage wave became extremely high and broke down insulators, was it 'noticed'!

With the advent of power transistors it became of vital interest to make sure the 'reflected power' did not damage the expensive transistors. Most CB radios in the 60's and 70's had a simple 'reflectometer' in the output connection. These would usually announce a bad s.w.r. in no uncertain terms.

s.w.r - How do you measure it?

Standing Wave Ratio is a ratio of transmitted radio frequency voltage or current, to the reflected voltage or current from the 'load'. The load is usually the antenna system. A 'dummy load' should provide a perfect match for the transmitter. That is no reflection of voltage or current. All of this is complicated by the fact that we are talking about radio frequency voltages. And the phasing of voltages and current will definitely not be 'in-phase'.

What is required is some 'directional' coupling to the circuit. To allow measurement of 'forward' r.f. at the same time as the 'reverse' r.f. . Most radio amateurs reach for a transmission line 'reflectometer'. This works fine over the h.f., 1 to 30 MHz range. As the coupling is usually quite small with regard to the wavelength. The well known example of this is the "Bird Thru-line Wattmeter."

Antenna Measurement

An alternative method is to 'measure' the antenna electrically. With h.f. it is relatively easy to build a 'bridge' which will indicate the impedance of the antenna. Note that I said 'impedance' not resistance. This is simply because most wire antennas 'look like electrically', a resonant LC tuned circuit. This is why an ATU proves very useful in matching an antenna to the transmitter. The bridge type circuit is the most common with transformer types the next most common. Recently though it seems that a lot of amateurs have lashed out and bought a VNA. The VNA has the advantage that it 'sweeps' the frequencies around the antenna resonance. Showing the resultant matching on a display. What about the 'monetary challenged' Radio Amateur? He/She will have to build a test unit to check the antenna.

Bridge Test Unit

The simplest form is a resistive bridge. With some provisos this can be fabricated in a tin box using readily available resistors. The downside to this is the fact that when the 'bridge' balances, nothing 'comes out of it'! So a simple diode detector stops working at the load matching frequency...

In the 'old days' this would use 2 to 5 Watt carbon composition resistors. Which in the 'old days' were readily available from component shops. Usually 'downtown'. Those shops have long ago closed never to be seen again. Component suppliers today will insist on 'minimum order quantities' and prices that bring a tear to your eye!

So what is the alternative? Radio Amateurs and Electronic Enthusiasts have become 'Electronic Scavengers.'

Let us see if we can't make a simple 'bridge'. Some of us and some clubs have a stock of resistors. Either bought over the years or left to the club as part of a deceased estate. So what can we use?

[I actually bought some decades ago 51 Ohm resistors.] It is highly unlikely that you will find them near you! But two 100 Ohm resistors in parallel make 50 Ohms. With twice the power handling of a single resistor. Or four 220 Ohm resistors in parallel make [erk! I had to check using a calculator!] 55 Ohms. Just remember that resistors in parallel have also 'self-capacitance'. Which when you use four in parallel makes four times the self-capacitance...

Figure 2: A 'simple' bridge

So this is the circuit of a 'simple antenna bridge'. It is really quite simple. BUT turn the transceiver power output down to a Watt. Otherwise the resistors will get hot! Maybe even burn out. So before checking or testing, connect your dummy load and turn the output power (CW) DOWN!!! [Don't have a dummy load? Another article link!]

The 'balanced' condition when the antenna is approximately equal to the 51 Ohm resistance produces the lowest signal level out of the 'bridge'. Which is why the bridge needs a Watt or so to drive the diode to provide a d.c. reading. A germanium diode is used as it has a low forward voltage for conduction. To give a reading at 'balance'.

There are of course other methods of measuring the antenna impedance. And it doesn't have to be at a set frequency. The source could be a swept oscillator covering the adjacent frequencies. This would show up any 'out of band' resonance. That could be corrected quickly. Also the antenna impedance can be measured accurately. So that the compensating reactance could be connected to get it resistive at the desired frequency.

...

NOTE

Even a Watt will go a long way. So other methods of lower power signal sources have been used over the years to reduce the chances of interference. The lower level of d.c. from the diode is usually amplified by an operational amplifier.

...

I intend adding to this article. Please let me know in the comments if you would like more information on this subject.

73 John Brock ZS6WL

One of the 'things' I was going to ask the students

Just a thought...

You might have noticed I used a Solar Garden light in the session on QRM/EMC, well it occurred to me to check the design in the UK. Slightly different but essentially the same simple circuit. Which oscillates around 1 MHz!

What? Yes it does. The question I was going to ask is this; "How do you get a L.E.D. to light when you only have a 1.2 Volt battery?"

When you did the section on transistors did someone tell you about 'inductive loads'? Or why you need a 'protection diode' across a relay? The same applies to a r.f. circuit with a coil in the collector circuit. Tuned or not it will swing above the supply rail voltage to double the collector voltage rating. So if you connect a transistor to a 12 Volt rail, remember the Vce rating must be 24 Volts or greater.

Remembering that a coil stores the energy in the magnetic field. So when you turn off the current the coil tries to maintain the field. Generating a 'back emf' that in some cases can be kiloVolts! Just arrange a relay as a 'buzzer' with the contacts making and breaking the circuit. Don't touch it! Depending upon the coil inductance the voltage can reach a very high voltage.

So the simple circuit these days is a single integrated circuit. A coil, the solar panel and the L.E.D. With the i.c. doing the charging and switching on the L.E.D.

[I just a fruitless search for a circuit that I know I downloaded months ago! Now thanks to Bert's blog I have one. https://bertsblogs.com/garden-solar-light-circuits/]

He explains the circuit as well. As he and I was going to here is the simple fact. The LED is a 'super-bright' white LED which needs well above the typical 1.8 Volts to turn on. L.E.D.s are much better these days from the 60s and 70s versions which were always red and quite dim in comparison to the filament bulbs/globes of the day.

The one thing I noticed as a difference between the ones I had bought in South Africa and the ones in the UK, the batteries are NiCd in SA (cheap). The ones in the UK are Nimh. Nickel-cadmium versus Nickel metal hydride. Small pricing difference but on thousands of models makes a big difference.

So are they going to interfere with your h.f. reception? Probably not unless you have a few hundred in the garden.

They don't last long. Water ingress usually rusts the connections and screws. Treating the plastic with sealant is just not worth it. Replacing the NiCd battery with a shop bought Nimh helps. But then sealing with marine silicone will keep maybe a few years longer.

73 John ZS6WL
 

This weekend has been informative, instructive and wet!

A relatively peaceful weekend from Friday but with another 'incident' in Windows XP.

My friend Roy, came to me with a "Scareware Virus" called MS Removal Tool. (My first thought was - what a good idea - maybe Ubuntu...) But no, this turned into a 'major mission' to remove and recover control of his PC. It would not allow him to use any of the standard anti-virus measures nor run any diagnostic software like 'Task Manager'.

How did he get it?

Very simple, he went to a web site that had been 'click-jacked' and without him knowing, the 'virus' was installed on his PC. He was using Internet Explorer and he has Microsoft's Security Essentials. Unfortunately both are side-tracked and bypassed by this rogue software.

This is the same category of malware that disrupted another client's PC recently. There it was called 'AntiVir'. It would not allow the user to remove the virus without going into 'safe mode'. This is not the easiest of methods for an inexperienced user who may have never seen 'Press F8 to enter safe mode.'

[Since this time, a few more of my clients have come to me to 'remove' the 'ScareWare' worms and virri.]

Live Security Platinum is the latest 'scareware' worm to hit here in SA [2012]

This worm/trojan puts up a 'front' and shows you a scanning of your hard disk with a load of virii etc. While loading its 'hooks' into your system to 'own' (pwn) it.

Live Security Platinum – ThreatExpert submission [2012-07]

http://www.threatexpert.com/report.aspx?md5=e5602b9c25da9a41cf555b8e35af9742

This submission is dated 11th July 2012. So it is quite 'up to date'.

New and Improved Worms and Virii are being made right now.

'Scareware' does more 'damage' to user confidence and productivity than previous types. It also carries with it a 'payload' of worms and virii. Most are detectable but some are variations that have not yet been 'captured' in the wild.

[The 'variation on a theme' seems to be prevalent as well. Meaning that old and workable virusii can be 'recycled' into new and even more upsetting variations. In the 'process' they are disguised so that the latest anti-virus products do not recognise them.]

“Data Recovery” - what a joke!

This was to be expected. As more and more 'black hats' discover the usefulness of 'bots' and worms that really can do 'damage', they are getting to release these on the day of your anti-virus 'update'. Otherwise known as 'zero day exploits'.

DO UPDATE YOUR Microsoft Security Essentials when you can.

DO NOT HAVE TWO OR MORE Anti-Virus products installed on your PC. The Microsoft Security Essentials, formerly called 'Windows Defender' works. Don't accept Mcafee as part of ADOBE's update. You will have to de-install it later if you do.

Sent at 8:45 AM on Thursday

John: I see my M$ sec essentials has gone from 411 to 601 in a few days. Your contribution I am sure has helped 'update' it...

This is on my 'no 2' PC not my 'no 1' PC. This one was updated yesterday. And this morning. Thanks Nick!

Now you should start using FireFox and or Chrome. Also update Internet Exploder to the latest possible version.

Sent at 9:20 AM on Thursday

John: I think you should run 'Windows Update' as well now. The IE8 version has just

're-installed' the activeX control for IE8 and Windows Update. I think that the previous version has been 'compromised'.

Yes! Install it.

[Alternate 'Data Recovery' removal instructions:

1. First of all, you need to unhide the files and folders. Select Run... from the Start Menu or just hit the key combination CTRL+R on your keyboard. In the Open: field, enter cmd and hit Enter or click OK.

At the command prompt, enter attrib -h /s /d and hit Enter. Now, you should see all your files and folders. NOTE: you may have to repeat this step because the malware may hide your files again. --- This does work. But does not remove all the 'hooks'. ]

'By the rivers of Babylon' – To 'remove' Babylon...

Open a dos shell, or execute "RegEdit" through the launch menu.

Find the key: [taint there! WinXP]

HKEY_LOCAL_MACHINE

...

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\About URLs\Tabs

and change the entry that points to babylon search, to the one you desire (be it google, bing, or whatever)."

Alternate removal: run

C:\Program Files\Babylon\Babylon-Pro\Utils\uninstbb.exe

Microsoft Security Advisory (2719615)

Vulnerability in Microsoft XML Core Services Could Allow Remote Code Execution

Published: Tuesday, June 12, 2012

http://technet.microsoft.com/en-us/security/advisory/2719615

[reply to email from client]

Hi Steven

Thank you for the nice compliments. I have never liked making money from the misery of others. The sort of virii and worms we have today have a far more devastating impact on the running of a business than last century.

Your 'incident' has actually taught me a new way of counteracting the 'scareware'. I can now boot the infested PC with a memory stick or CD. Then copy the Microsoft 'search and destroy' software to the hard disk. Also at that time, I can remove any obvious infestation. Files that are placed as a 'payload' by the scareware. Then rebooting into safe mode with networking, I run the msert program. The program can be deleted now as it only works for 10 days. Requiring an update at that time. If you had let it alone, the PC would have 'announced' itself on the Internet as a PC that can be 'owned' and run as part of the extensive networks of 'Bots'. These 'Botnets' are used to deny access to major servers and spam vast numbers of recipients. All operating without your knowledge and participation.

Little wonder that 'organised crime' have found this more profitable than drugs!

All of the best for the future.

Best regards
John Brock

--------------------------------------------------------------------------

Tools of the trade

Various web sites offer software 'tools' that will 'get rid of' this malware. One is:

Spyware doctor

http://www.spyware-experts.com/ms-removal-tool/

another is:

MalwareBytes Anti-malware

http://www.malwarebytes.org/

There are a lot of others, too numerous to go into here. Some give manual methods for removal. But state that this will be limited in effectiveness as the 'virus' changes the file names and registry entries on a daily basis. This also confirms the conclusion that I had come to, that no single anti-malware product is going to be 100% effective.

What did I use?

I used the latest 'Hiren's Boot CD' to boot his PC into mini Windows XP. [You can download it from: http://www.hirensbootcd.org/download/] Then I ran three of the malware removal tools on that CD. All ran and said that they had completed a 'removal' or 'clean'. We then rebooted into his Windows XP and ran 'msert'.

 

That is Microsoft's Safety Scanner tool that you can download from:

http://www.microsoft.com/security/scanner/en-za/default.aspx

This 'tool' runs, scans and removes with an up to date malware table. It 'expires' in 10 days so that you will always need to download the latest version.

When we rebooted his PC into Windows, we found no trace of the virus. Thank goodness.

Memorial Service Christine Susan Edith Brock

Some 'Radio Amateur Radio' thoughts...

Hi All. 

If you have a Google email address - you also have access to Google Books.
This means you can 'read' any book using any of your devices.

So long as you have 'data' access to the Internet.
Some books are costly, some are free. I went looking for free 'Radio Amateur Books'.

Found them! The one book; "The_A_R_R_L_Antenna_Book" is available for free and can be downloaded. It is a *49MB PDF*. So download it if you wish.
*Or* sign in to Google Books in your browser or use 'Google Play Store' to load the application on your device.

Some useful stuff:- 

https://www.analog.com/en/resources/analog-dialogue/articles/turning-pc-sound-card-into-sampling-oscilloscope.html

https://www.analog.com/media/en/training-seminars/design-handbooks/Basic-Linear-Design/Chapter4.pdf

For a really good explanation of all things amateur:-       

www.ifwtech.co.uk/g3sek

http://www.eznec.com/Amateur/Articles/Baluns.pdf

73 John Brock ZS6WL

 

The Kingdom Resort - Pilansberg Park

 

The Rest on Google Photos

From a "Grumpy Man"

I am fed up with load shedding. I am fed up with being woken up when the power comes back on in the middle of the night.

This post was written in anger.

So I have been a 'Grumpy [] Man' for a while now. Lots of things tend to annoy me. If it isn't the dog from the back house above us barking, its something else...

Anyway Blogger [this site] has some advantages over the Wordpress site. Especially as it is free. It provides a simple means of getting whatever out there for the rest of the 'internet'. It does not appear to have a limit on storage and it doesn't impact your Google storage either. 

It can of course be accessed from anywhere you have an internet connection. 

Alright it doesn't have the 'social network' aspect built in or applied. Though you can earn cents from adverts on your 'blog'.

I find it so much easier to work with. My jbcs site was 'converted' to Wordpress a while ago by Edith's son. And he left me to upload content into the 'editor'. This proved to be too time consuming for me. I am a retired electronics engineer with a dependent wife. I would take about three-quarters of a day to type and place pictures into the 'editor'. It is NOT a word processor. Which I would have preferred to use. 

My usual 'thing to do' on a monthly basis was to upload the YL News. This did not get done! As I would be always diverted or distracted by something/someone else. 

With Blogger, I can copy and paste text directly and upload pictures. Final corrections and adjustments would take minutes. Sure things tend to jump around on screen. Especially when you have a 'hesitant' connection to the internet. But you can change the settings to suit when you need to.

It does spell checking and auto-saving when you are not typing. You will see a little cloud change to a whirly circle and back to a cloud. A cloud with a slash through it means it didn't manage to connect. It will try again and become a cloud with a tick in it.

There is more to come...

I can't handle Wordpress!

 I tried. I really did. But it needs far too much of my time to handle a post.

So I am giving up. Maybe I shall use this again.

Lets see...