The Best Homebrew Power Supply Ever?

 This power supply was originally featured in Practical Wireless (PW) in June 1983.  This is the first ever electronic project that I built after becoming a Radio Amateur.  A month before I wrote the amateur radio examination at the Post Office Head Quarters in Pretoria I joined the then Verwoerdburg Stad Amateur Radio Club today the Centurion Amateur Radio Club.  

One Friday night at the club, power supplies were discussed and this is where I was introduced to the Marchwood Power Supply.  Not long thereafter a club member produced the PCB and the components were bought from the club's electronic parts shop.  I started to build the power supply unit at home and then taking it to the club on Friday evenings when I experienced building issues.  With the kind help of several members at the club I was shown where I made mistakes.  These were then rectified and I would carry on building the next week. 

 About a month later the power supply was completed and it was time for the smoke test.  Several radio amateurs gathered around the table  to see if  my power supply would go up in smoke.  I was told that if it does its not the end of the world and it could be fixed.  Thankfully with the first switch on there was no smoke and the supply worked flawlessly. 

 I build the supply as it provided various protections as described in 1983 PW article. The power supply was further described as a highly reliable unit as it has over voltage protection and over current protection and also Short circuit protection built in.  After 15 years of constant battering in my shack delivering power to HF Radios and  Linear Amplifiers consuming up to 30 Amps I eventually sold the power supply to a new radio amateur.  No I am not sorry as it went to a good shack. 

 Now after 28 years I think it is time to construct another Marchwood Power Supply to be used by the GRHub Network,  if I can find all the parts at a reasonable cost.  Another issue would be to find a suitable transformer.  I will lookout for the parts.  This will not be a quick homebrew project and will require patience and good planning to finish the project.  In the mean time here is a few images of my Marchwood Power Supply Mark I that I constructed.

HERE is a copy of the PW article for those that might be interested to build simply the best homebrew power supply for amateur radio and electronic experimenters. Please excuse the dust and muck in the cabinet but at the time of taking the images I did not want to "scratch" in the supply.  Like they say if it works do not scratch around unless you are looking for work when it goes bang!!

 

Where and how did I obtain the parts:

Cabinet - Jack Sinden ZS6QJ SK
Transformer 19 volts 40 Amps - Tim ZS6TIM
Heat Sinks - Pretoria Flea Market (Hal Lund premises)
Capacitor 45 000 uF 63 volts (ZS6CEN)
Components - Club Component Shop and other electronic shops
PCB - Herman ZS6HVV
Odds and Sods - Computer Scrap Shops

UPDATE: Thermo-Fan to keep your Raspberry PI, Radio, Power Supply and Amplifier Cool

(Click on image for larger view.)

Here is another take on the Thermo-Fan Controller using different component than those mentioned previously.

In many areas of South Africa temperatures soar to 40 degrees celsius during the summer

months. With Global Warming, we might all have the same problem in a few years from now.

New equipment is designed with built in thermo-fans and is fairly well protected against abnormal heat. Older equipment and home brew stuff may appreciate the acquisition of a thermal controller to cool things down. The project described is to ensure that your equipment is never allowed to exceed a preset temperature. It is extremely sensitive, and can easily be set so that a few degrees change is enough to activate the fan/fans.

The controller uses one or more ordinary silicon diodes as a sensor, and uses a cheap op-amp

as the amplifier. The circuit is designed to operate with 12 volt computer fans. These fans typically draw about 200 mA when running, so a small power transistor will be fine as the switch. A BD140 (1A, 6.5W) was used, but almost anything you have to hand will work just as well.

All diodes are 1N4004 or similar, and Q1 must be on a small heat-sink or may be mounted

to the chassis. Make sure it is properly insulated, and use thermal grease. Maximum dissipation will be about 2 watt, but Q1 will overheat very quickly if there is no heat-sink.

The temperature is set with VR1. Operate the piece of equipment to be fitted with the thermo-fan until the normal temperature is reached, then adjust VR1 until the fan starts.

Back off very slowly until the fan stops again. Any increase over the normal temperature will start the fan, and promptly bring the temperature back down again.

It will not matter if the voltage is a little higher than 12V, as the fan will work fine as long as voltage is kept below about 14V. If the voltage is higher than 14V, R5 and R6 will have to be changed.

To calculate the resistor values for R5 and R6 you will need to check the current that your fan draws. Connect the fan to a 12 V supply, and measure the current. Calculate the resistance of R6 with

R6 = (+ve - 12) / I Where +ve is your supply voltage, and I is the measured fan current.

Select the closest resistor value larger than calculated. You will also need to work out the power:

P6 = (+ve - 12)2 / R6

Now you can work out the value for R5 (1/2 will be OK) - here, use the next smaller value if an odd resistor value is calculated.

R5 = (+ve - 10) / 0.01 Where +ve is your supply voltage.

Having worked these out, you can adapt the circuit to any voltage, as long as it is less than

30V and 12V or more. Any other combination is quite acceptable, including the use of fans in series/parallel (current will be double thou) or anything else that you might want to do.

This circuit is very flexible and I am convinced that there are many other uses for this sensitive thermal controller in amateur radio.

BACAR launched from theTRMC Model Flying Airfield near Secunda

 The Secunda Amateur Radio Club Launched a Balloon Carrying Amateur Radio (known as the BACAR project) on Saturday 30 October at around 07h15 SAST. Several interesting payloads were active, including the new AMSAT-SA AfriCUBE linear transponder, Slow Scan TV, a crossband FM repeater, and an ion thruster scientific experiment. Amateurs from various Amateur Radio Clubs were involved in this project.   Herewith a few APRS images of the flight.

 I want to thank Gert ZS6GC and Cor ZS6CR for providing me with information and operating frequencies used during the BACAR flight.  Unfortunately I am situated right in the Southern part of South Africa and nothing was heard on any frequencies, but APRS-fi provided some data and images.

The GRHub Network is being automated to give the owner of the network more freedom and flexability.

 Automation is not always  a good thing but in this instance it saves time and gives the owner of the GRHub Network more freedom and flexibility.  Several tasks or functions can be automated and I will only discuss those that I already implemented iro the nodes that I am currently running.

Before I continue I would like to make it clear that the GRHub Network is NOT an unmanned device as stated in the post:  

Setting the record straight iro the GRHub Network! Rant??

Now lets continue.  The following functions are currently automated:

• Connection to three Echolink servers from AllStar Node 49355 and control of all Echolink Stations via this AllStar node
  
• Connection to a local Weather Station in Mossel Bay. AllStar Node 49355 obtain WX data and transmit weather conditions every hour to all nodes and the RF Link on 145.550 Mhz Simplex.
• Connection to a local Time Server.  AllStar Node 49355 obtain the local time and transmit the time every hour to all nodes and the RF Link on 145.550 Mhz Simplex.
• The SARL News Bulletins, Pretoria Amateur Radio Club News Bulletin and Amateur Radio Today are automatically relayed to  Echolink ZS1I-L,  Allstar Nodes 49355 + 46765  and RF Link on 145.550 Mhz Simplex every Sunday.
• The Bo Karoo Amateur Radio Klub Bulletin is automatically relayed to  Echolink ZS1I-L,  Allstar Nodes 49355 + 46765  and RF Link on 145.550 Mhz Simplex every Sunday afternoon.
• PEARS ("PE Mobile Net") daily relayed from 06h30 - 07h45 (except on Sunday) on Echolink ZS1I-L,  Allstar Nodes 49355 + 46765  and RF Link on 145.550 Mhz Simplex.
• Pretoria ("Legends") Morning Net. Transmission: Daily relayed from 07:45 - 09:00 except on Sunday on Echolink ZS1I-L,  Allstar Nodes 49355 + 46765  and RF Link on 145.550 Mhz Simplex.
• Auto play the weekly ARRL Audio News Bulletin every Tuesday at 20h00 on Echolink ZS1I-L,  Allstar Nodes 49355 + 46765  and RF Link on 145.550 Mhz Simplex.
• Auto play the weekly Amateur Radio Audio News Bulletin every Wednesday at 20h00 on Echolink ZS1I-L,  Allstar Nodes 49355 + 46765  and RF Link on 145.550 Mhz Simplex.

Please take note of the following:

The GRHub Network will connect automatically to some of the above nodes 15 minutes before the start of the Net or Bulletin.  This does not mean that there is no supervision of the GRHub Network. I get an audio alert every time the network connects to another node or network. In the event that something goes wrong or there is other activity on the guest nodes, I will disconnect the GRHub Network immediately.  I monitor all activity on the GRHub Network at all times.  There might also be times that the mode of operation is in Receive/Monitor Mode Only. 

I will continue to automate the GRHub Network in future if I think it could enhance the capabilities of the network and only if it is to the benefit of listeners and users.

Finally:  I want to thank all the repeater, link, network owners/keepers/administrators/clubs etc. for allowing me to use their facilities and installations.  Highly appreciated.  I again say it is not about me, my image or pride, I do it for amateur radio and as a service to my fellow radio amateurs.  Enjoy!!

Update: The impact of Load-Shedding by Eskom now also "breaks" the GRHub Network

 Just a short update in Afrikaans:   Ek het gou 'n paar toetse gedoen en is die 7 aH battery is tot niet.  n Vinnige soektog op die Internet vir 'n goedkoop vervanging maar ek het die battery soos in gister nodig.  Besoek 'n paar elektroniese plekke vroeg vanoggend en ons kyk na R400 + .  Val my toe by dat ek by die Chinese Winkels gaan kyk.  Nou ja almal praat van kwaliteit?  Die batterye waarna ek by die elektroniese plekke gaan kyk het word almal in China gemaak.  Een van die Chinese winkels het 'n groot verskeidenheid.  R200 later en ek het dieselfde battery wat een van die elektronies winkels vir R424 verkoop.  Nou ja hoekom so groot prys verskil, maar 'n man mag seker maar vra wat jy wil.  Of die battery gaan hou sal tyd wel leer.  Nie alles is goedkoop by die Chinese winkels nie maar moet nie vergeet om daar te gaan kyk nie.  Ek gaan die datum op die battery skryf en kyk hoe lank hy gaan hou.

Fotos: Nuwe battery se spanning en die prys van R200 op die pienk plakker.

The impact of Load-Shedding by Eskom now also "breaks" the GRHub Network

  Need I elaborate on the impact of load-shedding on you the consumer.  I do not think it is necessary as we already know what  the cause is and why it is happening. 

For those who would like to find out more on how load shedding can effect electronic equipment, read the following article:

THE IMPACT OF LOAD SHEDDING ON ELECTRICAL EQUIPMENT

The current power backup system run by the GRHub Network now also suffers as a result of phase 4 load shedding. The protection circuitry that I use for the battery power supply shut down the complete GRHub Network this afternoon as the system could not re-charge the battery fully before the next period of load - shedding started.  It would appear that the current battery is either on its way out or the charging unit is at fault.  I will look into this tomorrow morning to see why the protection circuitry was activated.  Sounds like an Eskom statement. Hi hi!!

Another problem that I experience is to connect to certain nodes when there is load - shedding or Internet - shedding.  Ya a new term.  My Fiber Internet outages is even worse than the old copper cable ADSL that I had.  The best system I ever  used was Wireless Internet.  I am ever so sorry that I moved to fiber but this will teach me a lesson not to listen to the advice of others.  Be as it may I do not use my Fiber Internet for the GRHub Network.  I use a 4G LTE connection which so far ("touch wood") works great without any outages.  Rather expensive but VOIP use very little data.

Another problem is the fact that overseas connections will drop at any time when load shedding is implemented.  So to our listeners please understand that outages is beyond my control.  I will do my utmost best to render a good service but as you know by now the GRHub Network is not a one man show and I rely on my fellow radio amateurs, clubs and others to keep the system running.

I hear many shout "We told you if the Internet goes down you will be left in the cold!"  Agree BUT there is always an alternative.  I am currently looking into linking the GRHub Network to AREDN and even more RF equipment and amateur radio systems like WinLink, Digital Modes etc.  This will ensure that when Internet or Power Outages occur, that the GRHub Network will still be in operation.  Yes you will not be able to use Echolink but AllStar will still be working and will keep the GRHub Network up and running with even more features.  Now this is what I enjoy about amateur radio.  There is always an alternative means of communication be it VOIP, RF, HF VHF or UHF.

Experimenting is what it is all about.  I will in the next few days feverishly work on several systems and ideas and hopefully can come up with several solutions for the current glitches being experienced due to load-shedding and Internet Shedding/Outages.

Finally:  I apologize for outages and break in transmissions at times.  I am sure that it is not going to take too long to come up with alternatives. I am looking forward to implement new features and to the challenges ahead.

The beauty of nature in and around Mossel Bay (Part 1)

 Not amateur radio related but the images below reflect the beauty of nature in and around Mossel Bay.  I am sure that you will agree that we live in the most beautiful part of the country.  With all the daily challenges it is great to experience such beauty to "re-charge" the tired mind.  (Click on images for larger view)

 

 

I needed either a UPS or Backup 220v Power Unit for my desktop computer in the Shack ASAP!!

Warning:  Never try to connect any power back-up system to your home electricity distribution box or for that matter to any plug adapter.  You can start a fire and will void your insurance.  I am in the lucky position to have a fully qualified electrician in the house that can perform such tasks and issue the necessary certification certificates that is needed.  Remember electricity is dangerous and can kill you and others!!

The title of this post say it all.  I looked at the price of UPS units but the prices just keeps on going up and up.  Next best solution is to roll my own backup power unit.  Here I had several options.  After some scrounging in my junk boxes I came up with the items shown in the images.  When load-shedding started way back then I bought a small inverter and a few odds and ends but only used the inverter maybe a few times as a stand alone mobile/portable unit, after which it went to the junk box for storage. (plastic ammo case) 

 The cabinet was built maybe 5 years ago for mobile contest work and is fitted with wheels to move it around.  The battery is where the cost comes in, but if you need it you buy it.  I bought this one a few years back and it is still holds a charge well. Never seems to drop down to damaging voltage.  The inverter is a Meanwell 300 Watt Modified Sine Wave unit.  The computer does not complain.  I would have liked it the be a Pure Sine Wave but you cannot always have every thing your way .

After starting the GRHub Network and the latest spate of power outages I was looking to build an ugly style unit as I needed it ASAP due to the implementation of regular load-shedding.

I started getting together every item that I would need and started work on the project this morning.  I plan to add 12v outlets tomorrow in the event that I needed them.

Here is a few photos of today's work.  The unit is not completed but is operational and providing 220v AC for my desktop computer in the Shack.  I will update and add images as the project progress.  The intention is to coat the cabinet with stone chip spray coating and to add a few enhancements at a later stage when the current load-shedding is hopefully suspended.

I do however predict that we are in for a rough time as far as power generation and supply is concerned in South Africa. No, at my age I am not looking at installing a big solar power system at my house.  There is really no need for this as one can find alternative solutions to easily curb any power outages. 

I am also working on my own solar power unit which I will be able to move around to where ever I need 12v, 24v, and 220 v power.  I call the unit:  "ZS1I Smart Power Trolley". More on this in a future post.

 

This R50.00 Scrap Metal UPS keeps the lights on!

Warning:  Never try to connect any power back-up system to your home electricity distribution box or for that matter to any plug adapter.  You can start a fire and will void your insurance.  I am in the lucky position to have a fully qualified electrician in the house that can perform such tasks and issue the necessary certification certificates that is needed.  Remember electricity is dangerous and can kill you and others!!

Here is my R50 UPS (battery not included in the R50 deal)  that keeps all my lights burning inside and outside my home during load-shedding.  The UPS was scrounged from a scrap metal dealer.  I removed the dead 7aH batteries and connected the shown battery and the unit started up without any problem.  Been running now for the past 3 years without any issues.  As for the plugs and other electrical equipment I use a back-up diesel generator if necessary.  However seeing that the warm water geyser and the stove runs off gas, we never  use the generator.  Just there for a backup should we experience a total blackout.  Not a bad buy for R50 from nogals a scrap metal dealer.

New page called "Down Memory Lane" added to the GRHub Network Blog

 Going through a few of my CD's that I created through the years I discovered some valuable information and photos that could be of benefit to my fellow radio amateurs.   All to often I have seen that when a radio amateur becomes SK his collection of amateur radio photos, QSL Cards  etc. goes to the rubbish heap as there is no interest in the "junk" he or she "collected" as a radio amateur.

I have also discovered that we say that we will remember them, but after a few years we seldom speak about those who went SK. 

I decided to create this page to post information and photos of my collection of amateur memorabilia that I collected through the years.  Now this is not a museum or exhibition  of some sorts as many photos reflect radio amateurs still alive and kicking.  All this is about remembering the "good old days" or maybe "not so old days".  Surely the camaraderie and friendship can never be taken away and we will remember them. 

The above picture was taken in 1998 at a meeting of the then Garden Route Radio Club ZS1GRC.  It was one of  the biggest, if not the biggest amateur radio club gathering in the Garden Route area.  A headcount of 24 of which 8 has since become SK.

The new page will be available HERE.

If you have any photos or information that you would like to add please send it to me.  Hopefully we can preserve amateur radio history and prevent so called "junk" from going to the rubbish bin.

Send info and images to Johan ZS1I by clicking HERE.

What happens to the GRHub Network in the event of a Power- or Internet outage?

Internet outages the past 24 hours in the Mossel Bay area.  Telkom, MTN and Vodacom  experienced several outages in the past 24 hours.  The latest early this morning.

 In short:  Power Outage - No big deal.  The GRHub Network including the RF Links just switch over from mains power to battery power.  Internet Outage -  The only real drawback is that all connections to "outside" nodes are dropped leaving the network operational only in the Southern Cape area.  Current Internet outage is not a train smash and I am working on bringing AREDN and WINLINK back on line should all else fails.  The importance of Repeaters, RF Simplex Links, Cross Band Repeating etc. cannot be underestimated.  The GRHub will in future be linked to more RF links.  The current 145.550 Mhz link works well.   I also have a UHF link radio on 433.400 Mhz coupled to the 49355 node but currently not switched on.  I need to buy another Diamond X50 Antenna for the UHF band.  I hope to have the UHF RF link operational before the December holiday season.

Like they say Rome was not build in one day.  Those who have experience in building RF and AllStar networks will know this all to well.

Finally:  I like a challenge and with Power- and Internet Outages comes new challenges and problems that need to be solved.  Each new installation/alteration brings satisfaction and fulfillment.  No problem is to big to overcome in life. Giving up is NEVER and option or the easy way out!

The GRHub Network activity log for Sunday 24 October 2021 up to 15h30 SAST

 Great to see that activity is on the increase on the GRHub Network especially for the Bo Karoo Amateur Radio Club iro their Sunday afternoon news bulletin at 15h00.  Welcome to all the new call signs.  The GRHub Network is also looking forward to welcome many of the new radio amateurs that wrote the exam on Saturday.   Please feel feel free to use the GRHub Network.  I am currently in the planning phase for new activity on the network.  Watch this space!!

Buy your Raspberry Pi 4 2GB now if it is not already too late!

In response to supply chain issues, particularly around semiconductors, Raspberry Pi is increasing the price of the version of the Raspberry Pi 4 sold with 2GB of RAM. The increase, which CEO Eben Upton says is the company’s first ever, will see the Pi 4 2GB’s price rise by $10 from $35 to $45. To serve the needs of customers on tighter budgets, the company is reintroducing the 1GB Pi 4 for $35, which was discontinued last year.

“These changes in pricing are not here to stay,” Upton writes. “As global supply chain issues moderate, we’ll keep revisiting this issue, and we want to get pricing back to where it was as fast as we can.” Upton said supply chain challenges are likely to continue through next year, echoing the predictions of larger companies like TSMC, Nvidia, and Foxconn, but added that the company sees “early signs that the supply chain situation is starting to ease.”

It’s a significant price increase of over 25 percent for the 2GB Pi 4, a computer prized for its affordability, that could have a big impact on the industrial customers that use Raspberry Pis. Upton says that although the world appears to be slowly emerging from the pandemic, semiconductors continue to be in high demand thanks to companies panic buying components to ensure they have enough to meet their own demands.

The changes effectively revert the price drop Raspberry Pi introduced in February last year in response to falling RAM prices. It came just weeks before the COVID-19 pandemic began to upend demand for, and the supply of, consumer technology. Since then everyone from games console and graphics card manufacturers to automakers has had to grapple with shortages of key components, limiting their ability to produce enough products to meet demand.

Raspberry Pi adds that it’s deprioritizing production of the the Raspberry Pi 3B Plus, and is advising customers who rely on this model to migrate to the 1GB Pi 4 if they want to ensure uninterrupted availability. 

Source: theverge.com

ED. We in South Africa should know by now that this price increase would be substantiate due to the Rand/Dollar/Pound equation. Furthermore everything in South Africa goes up and never comes down. Will this also be the case with the Raspberry Pi?

 

New Telegram Group: Amateur Radio 101

 I created a new Telegram Group named "Amateur Radio 101".  Why and what is it all about?

 “This group is everything Amateur Radio. News, notifications, severe weather, projects, memories, hints and kinks etc. etc. Share anything amateur radio on this group. Stay in touch and in tune and most of all enjoy this wonderful hobby!”

Waarom die Groep?  Hoekom nie? Nie alweer 'n nuwe groep nie en dan hardloop jy weg na 'n paar maande.  Wel julle het seker die reg om dit so te stel maar ek het my redes hoekom ek WhatsApp totaal en al verlaat het.  Kyk maar na die nuutste gebeure rondom Mnr "Sukkelberg" en WhatsApp en dan sal julle sien hoekom ek WhatsApp waarwel toegroep het. 

Language? Op die groep skryf en praat ons Afrikaans en Engels.  Jy kies jou taalgebruik.  You choose your language preference.

Who can join?  Enige iemand selfs nie-radio amateurs is welkom on by die groep aan te sluit. 

Invite/Uitnodiging?  We need your knowledge and expertise in this Group.  Nooi jou amateur radio vriende uit om aan te sluit.  Kom deel jou kosbare kennis met ons.

How do I join? / Hoe sluit ek aan?  Just send me an email (click HERE)  or Telegram message (Johan Terblanche ZS1I) and I will forward the invitation link to you. 

Kom ons maak die groep nog beter as die vorige WhatsApp groep.  Onthou julle maak of breek die groep.  I am looking forward to talk to you on Telegram.

This is not a one man show!!

Important:  The invite link expire after 24 hours and you will have to ask for a new link.
Belangrik:  Die uitnodiging skakel verval na 24 uur en dan moet jy vra vir ‘n nuwe skakel.

QSX (PEARS) Power Supply now powers the GRHub Network 145.550Mhz RF Link Radio.

Recognition :  Al Akers ZS2U,  Andre Botes ZS2ACP and Bryan Haefele ZS2BH (SK)

An article by Al Akers ZS2U describing a power supply appeared in the June 1993 issue of Radio ZS.  The circuit, to which a fourth 2N3055 has been added to enhance the current handling capability.

In addition to this ZS2CP has produced a circuit board which incorporates an over voltage protection circuit adapted from n article by the late Brian Haefele ZS2BH in QSX Newsletter of April 2000.

The original article, schematic diagram, PCB outlay and component outlay can be downloaded by clicking HERE.

I constructed this power supply in early 2001 and it has run flawlessly for the past 20 years.  This power supply is now connected to the GRHub 145.550 Mhz RF Link Radio and also powers 2 x Fan Controllers discussed on this Blog.

I opened the power supply this past Friday to clean the inside and to fit a auto fan controller to run the fan. (Not shown in the images.)  I have tested the fan controller installed to the power supply.  It works great and even reduced some of the fan noise considerably.  

With both the radio and power supply now fitted with a automatic fan controller, it is really an "assurance of mind" that I do not have to manually switch fans on and off.  As the temperature rise it switches on automatically and once the temperature falls below a set level it switches off automatically.  Fingers crossed that the fan controllers do not fail which could destroy the radio or the power supply if they overheat. I however do have a plan in mind to inform me should they fail.

Here is a few diagram images of the power supply.  Images of the fan controller is also available on this Blog. Just click on Fan Controller in the Labels column.

Images:  (Click on images for larger view.)