Revisit - DIY MC3423 Overvoltage Crowbar Protection Circuit Project

The original article is available HERE.

This Over-voltage Crowbar Protection unit was running  from April 2024 day and night without any disruptions.  About a week ago I noticed that the ZS Link Hub Network radio was off one morning when I entered the Shack.  The Power Supply was running but there was no life in the "black box" which housed the Crowbar circuitry.  

The first thing I checked was the fuse that normally go up in smoke if the protection circuitry "kicks in".  There was nothing wrong with the fuse.  The next item to check was the BT152 Thyristor.  It tested OK.  Next would be the MC3423.  Replaced it and still no power.  A closer look at the Veroboard revealed that  the output (positive) track to the Motorola radio has lifted from the phenol board.  The copper track was cracked and there was no connectivity.  Well this told me that the Veroboard tacks could not handle the amps drawn from the power supply.  When I constructed the unit this was one of my concerns but I thought that with only the radio connected this would not be an issue.  Continues daily use proved otherwise and the Vero PCB track failed.

According to the original Vero spec the area of a strip is equal to 39g which is rated to carry 2 amps for 1 second before fusing.  Well if this holds true then the Veroboard that I  used lasted surprisingly well.  Fixing the unit was quite easy.  I joined two tracks together for the input and output side and soldered a 2.5 mm solid tinned copper wire on top of the tracks.  This is not optimal but I am sure that it will be able to carry the load and hopefully last longer than the Vero board strip.  In the event that it fails again I will use 3 - 5 mm tinted copper wire to which I will connect the main crowbar low amperage circuit board.  After all the main circuit board only suffice as sensing unit.

After the modification, the board was placed back into the "black box", the wires connected and the unit switched on.  It fired right up.  The Motorola specs shows 7.0 Amps current drawn on TX  @ 25 watts and a standby current of 400 mA.  I am sure that the 2.5 mm copper wire and the added track will be more than enough to handle the necessary current.  Time will tell!

Finally:  I will be playing around with a few other Crowbar Protection-  and Reverse Polarity Circuits.  More on this in future postings.

Let's Revisit the 2 Meter Two Element VHF Yagi by Albert ZS2U

Albert (Al) Akers ZS2U

 

The article about this small and compact "Sharp Shooter Antenna" was published in the PEARS  QSX News Letter of February 2008 by Al Akers ZS2U.  I constructed it in March 2008 and still has it today.  An article about this antenna was published on this Blog in December 2021 and is available HERE.  (Must read)

My final measurements using 3 mm Brass Brazing Rod were:

Driven Elements: 460 mm

Reflector Element:  1000 mm

Spacing between driven- and reflector element : 445  mm

PVC tubing length: 170 mm

Length of Coax:: 1100 mm 

Now why would one revisit this two element Yagi antenna?  There is currently once again an ARISS Slow Scan Television (SSTV) experiment from the International Space Station under way.  (More information HERE)

I decided to use this antenna to download SSTV images from the ISS.  But will it be any good?  This antenna has a very good track record here in the Southern Cape. I use this antenna as a "test antenna" when the need arises.  It is a practical, compact and fold able antenna.  It performs very well.  In  March 2008 I made the following "record breaking" contacts:

I managed to have a short QSO with Terry ZS2ABB in Port Elizabeth from Mossel Bay. A distance of over 300km. In the second attempt I worked Alex RW1ZC/MM on the 6/3/2008 on 2M Voice 144.400 Mhz Fm. Grid: KF35BP 368.3km again from Mossel Bay. 

 

Image above:  Did you know that the first contacts from the ARISS radio on the ISS happened on the 13 November 2000.  There were two test transmissions received in Russia and one in USA. The images of those contacts are now being transmitted via SSTV in the current series.

But what will the results be using this antenna to download SSTV images from the ISS?  Well you be the judge.  Here are some images I downloaded.  I specifically looked for "bad" passes with a low elevation level of between 0 - 25 Degrees.  The one image published here had  a maximum elevation of 49 Degrees.  Through the years I tried several homebrew antennas to download SSTV images.  This antenna performs well.  At a later stage I will write an article about the best antenna I used to download SSTV images from my QTH in KF15bt in Mossel Bay, ZA.

Images downloaded on 16 and 17 November 2024:

Submitted by: Johan Terblanche, ZS1I, Africa
Acquired: 2024-11-16 10:03:00

Mission: Expedition 72 - Series 22 Fortieth Anniversary

Minimum ISS Elevation: 10 Deg

Max ISS Elevation: 17.2 Deg

Antenna: Homebrew 2 Element ZS2U Yagi (Portable)

Radio: Baofeng UV82

Remarks: No Antenna Rotator or Auto Tracking used

Submitted by: Johan Terblanche, ZS1I, Select a region
Acquired: 2024-11-16 11:39:00
Mission: Expedition 72 - Series 22 Fortieth Anniversary
Minimum ISS Elevation:  10 Deg
Max ISS Elevation: 49.7 Deg
Antenna:  Homebrew 2 Element ZS2U Yagi (Portable)
Radio:  Baofeng UV82
Remarks: No Antenna Rotator or Auto Tracking used

Submitted by: Johan Terblanche, ZS1I, Select a region
Acquired: 2024-11-17 04:19:00
Mission: Expedition 72 - Series 22 Fortieth Anniversary
Minimum ISS Elevation:  10 Deg
Max ISS Elevation: 22.9 Deg
Antenna:  Homebrew 2 Element ZS2U Yagi (Portable)
Radio:  Baofeng UV82
Remarks: No Antenna Rotator or Auto Tracking used

In my opinion not to bad image downloads with a two element homebrew portable Yagi antenna.  I will download two more passes with this antenna and then switch to another portable antenna.

How versatile is this antenna really?   In my opinion a really versatile antenna and can be used for the following purposes:

1.  2m DX Long Distance Contacts

2.  Download SSTV images from ISS

3.  Satellite Contacts

4.  Foxhunting

5.  Interference Tracking Antenna 

6.  Baofeng Radio Distance Experiment  (ZS6 Region)

7.  Demonstrating Amateur Radio Communications

8.  Repeater accessing antenna

To mention just a few.

Other interesting aspects of this "Sharp Shooting" Antenna:

1.  Low cost to construct

2.  Easy construction with available hand tools

3.  Low profile when folded into parts (see image)

4.  Easy storage

5.  Vertical and Horizontal polarization by just turning the two elements by hand

6.  No large mast required but can be mounted on a tower or mast.

7.  Hand operated.  (No rotator necessary)

8.  Gain:  4 to 5 dB (Not officially confirmed) SWR:  1:1

9.  Elements can be constructed with Aluminium Wire, Copper Wire,  Coat Hanger Wire, 7 mm Aluminum Rod, 12 mm Aluminum Tubing, 3 mm Aluminium Brazing Rod or 3 mm Brass Brazing Rod. (Brass Brazing Rod Preferred)

10.  Can be used as a Half Wave Dipole by just using the driven element.  (Omitting the reflector element.)

This proved that this “little” antenna is worthwhile constructing and is a real asset to my antenna arsenal.

So what are you waiting for get to your nearest hardware supply store and gather the necessary hardware to construct this antenna. You will be amazed at it's performance!!

Many thanks to Albert ZS2U for making this antenna project available for homebrew construction.

Images:  Click on images for larger view.

Image: ZS1I operating position for the current series of SSTV images

Image:  The 2 Meter Two Element VHF Yagi dismantled for storage or transport

Lest we Forget !!

November is a time that all veterans reflect on the past.  A month that we stand in silence and pay our respects to the fallen soldiers.  Does not matter if that soldier once was your enemy.  He or she only fought in a war that was started by men that never saw the battlefield, the blood, the carnage, the fear, the tears and the heart ache.

When we stand with bowed heads on the 11th hour of the 11th month on Remembrance Day, we don't just pay respect to the fallen but we also celebrate life.  We are still alive and that gives us the opportunity to give out fallen brothers and sisters a salute.

In South Africa, Remembrance Day Commemoration ceremonies are usually held on the nearest Sunday, at which the "Last Post" is played by a bugler followed by the observation of a two-minute silence. Ceremonies to mark the event in South Africa are held at the Cenotaph in Cape Town, and in Pretoria at the Voortrekker Monument cenotaph, the War Memorial at the Union Buildings and other cities and towns.  Remembrance Day services is held to honor those who died in the two World Wars and the Border War. 

Remembrance Day is a national opportunity to remember the service and sacrifice of all those that have defended our freedoms and protected our way of life.

We remember the Armed Forces, their families and the vital role played by those who have lost their lives as a result of war.

“They shall grow not old, as we that are left grow old:
Age shall not weary them, nor the years condemn.
At the going down of the sun and in the morning,
We will remember them.”
― Laurence Binyon 

The Last Post ( Courtesy: Music Files Limited)

 

Listen HERE. 

Decoding SSTV Images from the ISS with a "Homebrew" Antenna. By Rulhof ZS4RM

The recent ARISS Slow Scan Television (SSTV) experiment from the International Space Station took place from Tuesday, October 8, at 16:00 GMT and run until Monday, October 14, at 14:10 GMT.  Click HERE to read more.

Here comes another SSTV event!  ARISS will conduct SSTV operations from the @Space_Station

beginning Monday, 11 November 2024. The theme is "40th Anniversary of Amateur Radio in Human Spaceflight. " You'll have almost a week to catch all 12 images. More on this event in the image below.

What will the Experiment entail?

"The SSTV transmissions will be made using the amateur radio station in the ISS Service Module. The transmission frequency will be 145.800 MHz (+/- 3.5 kHz Doppler shift) FM, using SSTV mode PD120.

Many FM rigs can be switched been wide and narrow deviation FM filters. For best results you should select the filter for wider deviation FM. Handhelds generally have a single wide filter fitted as standard.

The ISS call-sign will be RS0ISS.

Reports are requested: please send ARISS uploading your decoded pictures in the official ARISS SSTV gallery: https://www.spaceflightsoftware.com/ARISS_SSTV/

Useful information to receive the pictures can be found here: https://amsat-uk.org/beginners/iss-sstv/

Follow ARISS on X for official updates during the event https://x.com/ARISS_Intl

During the previous experiment in Ocober 2024,  Rulhof ZS4RM a young radio amateur from Bloemfontein decided to construct a simple antenna to receive the SSTV images from the ISS. Let's listen to what Rulhof has to say: ( Afrikaans Language)

 

Lets look at some images of the antenna that Rulhof ZS4RM constructed.

Images: Click on images for larger view.

 

Why not quickly build this antenna and join in the fun downloading SSTV Images from the ISS?

How I make a backup copy of an SDCard using Raspberry Pi OS

Switch on the Raspberry PI and let it boot.
Plug in a USB Hub Extender into one of the Raspberry Pi USB Ports
You need to know the name of the 2 x USB SD Card Readers you are going to use.

USB SD Card Reader  No 1 = Green FNK TECH  0100 Card Reader
USB SD Card Reader  No 2 = White Super Top Micro SD Card Reader

Now plug the No 1 Green card reader into the USB Hub Extender.
Type lsusb enter
Card will be listed as FNK TECH  0100 Card Reader
Remove the card reader from the USB Hub Extender
Now plug the No 2 White card reader into the USB Hub Extender.
Type lsusb enter
Card will be listed as Super Top MicroSD Card Reader
Remove the card reader from the USB Hub Extender
We now know the names of the 2 x USB SD Card Readers
This will help to prevent mishaps when you make a backup copy of a card.
One can easily select the wrong cards when copying on to the other.

Ensure that you have a “clean” new SD Card to which you want to copy to.
I format the new card with SD Card Formatter in Windows with one of the card reader.
I select which card to format and then add the Volume Label  Example:  svxlink bu
Once added you can now format the card.
Remove and keep the card and reader at hand.
First we going to plug in the Green SD Card Reader into the USB Hub Extender that is connected
to the Raspberry Pi.
Now go to Accessories and click on SD Card Copier
SD Card Copier window will open displaying:

Copy from Device
Copy to Device

Click on the down arrow of the Copy from Device and FNK Tech 0100 Card Reader (dev/sda) will be listed.  Select it.
Now add the White SD Card Reader into the USB Hub Extender that is connected to the PI
Click on the down arrow of the Copy to Device and Mass Storage Device (dev/sdb) will be listed
Select it.  Leave other settings as is.
Click on Start and the copy process will start.
Green SD Card Reader LED will flicker and partition 1 will be copied.  Later partition 2 will be copied.
Once the process is finish a screen will appear to say that copy has been finalized.
Click OK
Eject both SD Card Readers
You now have 2 x SD Cards.  One backup and one for use.

Store the backup in a safe place and do not forget to label it so that you know what is on the card.
This backup process will save you a lot of time and frustration in the event of a corrupted or error card etc.

Enjoy!!

My mede Radio Amateurs berig dat my Echolink Audio "opbreek". Hoe nou gemaak?

Die titel van die onderwerp is duidelik maar waar gaan kyk ek om die probleem op te los? 

Vir doeleindes van die onderwerp gaan ons na die volgende stelsel kyk.  'n Gekoppelde Herhaler / Link Stelsel.  Beter bekend as "Sysop Mode" in Echolink.

Om die probleem op te los gaan ons die konsep van eliminasie gebruik. Maak asb seker dat u 'n goeie Internet verbinding het alvorens u foutnasporing doen aangesien 'n swak Internet koppeling ook die oorsaak kan wees van audio probleme. 

Ons moet eerstens vasstel wat veroorsaak die probleem maw:

1.  Is dit 'n Internet Konneksie Probleem?

2.  Is dit 'n Rekenaar Probleem?

3.  Is dit die Echolink Sagteware wat die probleem veroorsaak?

4.  Is dit 'n koppelvlak probeem tussen die radio en die rekenaar?

5.  Is dit 'n Mikrofoon Probleem?

6.  Is dit 'n Radio Probleem?  (Gekoppeld radio of Draagbare Radio afhangende van die toerusting wat jy gebruik)

7.  Is dit 'n swak of droe las koppeling tov die stelsel?

8.  Is dit 'n klank-kaart probleem?

9.  Is dit 'n kragbron probleem?

10.  Is dit 'n Internet Diensverskaffer of Modem/Router Probleem?

11.  Is dit 'n "Firewall" Probleem.

12.  Is dit 'n geslote poort wat oopgemaak moet word op die"Router"?

Nou ja dit is 'n lang lys van moontlike oorsake maar om die probleem op te los moet jy alle moontlikhede ondersoek.  Vir die doeneindes van die artikel gaan ek net kyk na die Echolink Sagteware Program wat 'n probleem veroorsaak het tov 'n gekoppelde herhaler stelsel/netwerk.

DIE PROBLEEM:

Die audio van die stasie wat deur die herhaler stelsel/netwerk praat breek sleg op.  Groot gedeeltes van die gesprek verdwyn eenvoudig met net sekere gedeeltes wat hoorbaar is.  Wanneer die audio verdwyn, verdwyn die dragolf ook.  Dit maak nie 'n twee rigting gesprek moontlik nie.

Die stelsel / netwerk het voorheen goed gewerk maar na 'n kragonderbreking het die probleem onstaan.

FOUT NA-SPORING:

Daar was vermoed dit dit 'n Internet, Rekenaar of Echolink Sagteware probleem kon wees.  Eerste op die lys was die Internet.  'n Eenvoudige toets is om Echolink op 'n selfoon te aktiveer en dieselfte Internet koppeling te gebruik.  Die toets het aangetoon dat Echolink op die selfoon geen audio onderbrekings teweeg gebring het nie en dat Echolink korrek werk op die selfoon met dieselfde Internet koppeling as wat die Echolink Rekenaar gebruik.  Die toets het 'n Internet Konneksie / Diensverskaffer of Modem probleme uitgekakel.  Siende dat daar geen veranderinge aan die Stelsel/Netwerk gemaak is nie was die volgende moontlike probleem dat die Echolink Sagteware op die een of ander manier tydens die kragonderbreking foutief of korrup geraak het.

AANVANKLIKE OPLOSSING:

Ek het deur die volgende verstellings gegaan en vergelyk met my toetse wat ek so ruk gelede gedoen het.  Ek het net na die volgende gekyk. Buffering:  Klik op Tools,  Setup, System Setup skerm sal oopmaak.  Klik op Performance, dan Buffering.  Verstellings is soos per foto 1  Network Buffering  10,  Pc Buffering  5  Total Audio Delay 1.20  Klik OK  Die settings is nou korrek.  Dit is ook die rede dat die audio in en uit geval het omdat die buffering voluit oop was.  Hou maar by die default.  Die ander setup wat ek na gekyk het is Sysop Setup, foto 2.   Gaan na Tools, Sysop Settings dan na Sysop Setup.  Die toetse wat ek gedoen het was ook in VOX.  Ek het gevind dat die volgende verstellings goed by my werk en voorkom die Loops en Ping Pong effek.  Vox Delay = 500  Anti Thump = 200,  ClrFreg Delay = 3000.  Ek het ook Squelch Crash Anti-Trip geaktiveer met 'n  X en die Duration is 50  Na die veranderings klik OK   "Squelch Crash Anti-Trip:  If you are using VOX, check this box to enable a special feature that improves VOX behavior when your link is tuned to a local repeater.  When this feature is enabled and properly adjusted, EchoLink's VOX will ignore short noise bursts, such as squelch-tail "crashes" and courtesy tones.  This can significantly improve repeater-to-repeater linking."  Die laaste wat ek sou byvoeg is soos per foto 3:  Click Tools, Setup, Audio.  System Setup skerm sal oopmaak.  Ek het op die blokkie klik langs 300 Hz TX High-Pass Filter en die  filter geaktiveer.  Kan net TX audio verbeter.  Klik OK   

Foto 1 (Klik om te vergroot)

Foto 2 (Klik om te vergroot)

Foto 3  (Klik om te vergroot)

FINALE OPLOSSING:

Bostaande verstellings het die audio opbreek probleem met tye opgelos op die toets Echolink Stasie ZS1I-L.  Indien bostaande nie die probleem oplos nie stel ek voor dat die buffering "Reset to Default" geklik word.  Selekteer dan OK.  Jy kan ook die Squelch Crash Anti-Trip de-aktiveer deur op die regmerkie te klik en dan op OK. 

Die opbreek van audio met bostaande verstellings het met tye voorgekom.  Gedurende 'n 3 minute rondte sou jy twee keer kry wat die audio vir 'n paar sekondes uitval.

Die volgende verstellings is toe gemaak:

 

1.  In Sysop Setup klik op RX Ctrl.  Verander VOX Delay na 'n "Default" van 1200 ms.  Die res bly onveranderd.  Klik OK.

2.  Die final Buffering Setup in System Setup / Performance is soos in bostaande foto verander.  Klik OK. 

3.  Terug op die Hoof Blad van Echolink. Die Vox Threshold is ook verstel na 45%.  Jy kan slegs die verstelling maak as jy aan 'n stasie gekonnekteer is en jy TX.  Die bostaande aanduider verskyn en jy gebruik dan die "slider" om die "Vox Threshold te verstel".  Meer inligting HIER beskikbaar.  Onthou om altyd the rekenaar te "reboot"  as jy verstellings gemaak het. 

Daarsy en nou behoort Echolink goed te werk sonder dat daar onderbrekings is in die audio.  Onthou net wanneer die Internet "siek" is kan audio ook verlore gaan of jy kan selfs heeltemal uit die stelsel "val".

Tot dusver werk die verstellings goed en het die probleem van klank verlies nog nie weer voorgekom nie.  Hopelik is die probleem finaal opgelos.

'n Laaste woord of wenk.  Werk systematies deur die "12 punt foutlys" om die probleem na te spoor.  Merk die lys af soos wat jy deur hom werk en vastel dat daar nie probleme is by die aspek wat jy toets nie.  Jy sal wel gou vasstel waar die probleem le en dit dienooreenkomstig oplos.

Ek hoop dat die artikel ander stasies van hulp sal wees sou hulle 'n soorgelyke probleem ervaar.

Bloemfontein Voortrekkers leer meer oor Amateur Radio Kommunikasie - 2 November 2024

Hoerskool Sentraal in Bloemfontein was gister sommer lekker besig gewees.  Nee, dit was nie met skoolwerk of sport nie maar het die Bloemfontein Voortekkers meer geleer oor radio kommunikasie in besonder amateur radio kommunikasie.  Onder leiding van die Bloemfontein Amateur Radio Klub (ZS4BFN) het Rulhof ZS4RM, Ettiene ZS4EG en Michael ZS4BHF die Voortrekker Verkenners meer geleer oor amateur radio teorie asook die praktiese toepassing daarvan, beter bekend in die voortrekkers se taal as Radiospraak.

Maar wat behels amateur radio kommuniksie?  Radio-amateurs gebruik verskeie radios en modusse (analoog sowel as digitaal) asook VOIP ("Voice Over Internet Protocol") om met mede radio-amateurs reg oor die wêreld heen kontak te maak.   Wel nie net wereldwyd nie maar ook met ruimtevaarders aan boord van die Internasionale Ruimtestasie (ISS).  Kontakte word deur ARISS ("Amateur Radio on the ISS") gekoordineer.  Dit stel jong mense en studente in staat om met die bemanning op die Internasionale Ruimtestasie kontak te maak en vrae oor die ruimte en wetenskap te vra.  Hierdie is maar slegs een aspek van Amateur Radio.  Die tyd en spasie laat my nie toe om al die aspekte van Amateur Radio hier te verduidelik nie.  As jy meer wil weet klik op die skakel hieronder.

Die drie bostaande radio amateurs het ook verskillende radio toerusting / aparaat uitgestal tydens die geleentheid.   Daar is ook breedvoerig verduidelik hoe om 'n radio stasie op te rig en dan die toerusting te gebruik om kontak te bewerkstellig met ander amateur radio stasies.  Van die Verkenners het ook hul voortrekker radio kentekens verwerf tydens die byeenkoms nadat hulle die vasgestelde vereistes nagekom het.  Baie geluk aan die Verkenners wat radio kentekens verwerf het. Dankie ook aan Hoerskool Sentraal en die bostaande Radio Amateurs vir julle bydrae tot die sukses van die geleentheid asook om amateur radio te bevorder !!

Wil jy meer weet oor Die Voortrekkers?  Klik HIER

Wil jy meer weet oor Amateur Radio?  Klik HIER

Fotos (Klik op fotos om te vergroot.)