Dedicated 5v Power Supply Distribution Board Project for your Raspberry Pi's

I have several Raspberry Pi's running in my shack on a daily basis.  Well some use the factory wall-warts you buy for the Pi and others run from cheap DC-DC Buck Converters.  It is always a schlep to find the correct wall-wart or converter lying somewhere underneath  a desk or on the floor.  I decided to build a dedicated 5v Power Distribution Board from items that I had lying around.

I found a switch mode power supply which I salvaged from and industrial appliance.  When I tested the output I found that it delivers 5v, 2v and -4v DC.  Unfortunately I could not find the amount of amperes it provides.  This will be tested under real operating conditions.  Looking at the construction of the power supply and the cooling fan, this unit is no small power unit and will work for my intended purpose. I decided to add a fan for cooling as in the original industrial cabinet the fan was built into the cabinet.  I removed the fan and install it on-top of the power supply.  Next I needed some means of distributing the output power.  I could add connection points to each 5v wire but decided to 3 D Print a "Bus-Bar" type  positive and negative feed point. I joined all the red positive wires and black negative wires to heavy duty lugs which I then added to each bus-bar.  The copper bus-bar is made of 20 mm copper pipe which I flattened in my bench vice.  Added brass-bolts and nuts which I had lying around and bolted both bus-bars to a piece of cutting board.  

That's it project nearly completed.  I just need to fit some acrylic covers to ensure that no short-circuits occur between the two bus-bars.  Once again a very cheap project with items that I had lying around.  Hopefully this distribution board will work much better than the wall-warts and DC-DC buck converters.  One could just as easily use the copper bus bars for building a 12 v distribution board.  Who knows might just do that one day.

Images:  (Click on images for larger view.)

 

Nico ZS4N build the DK3 Screwdriver HF Mobile Antenna

In this article we will be looking at how Nico ZS4N constructed his version of the DK3 Screwdriver HF Mobile Antenna.  I am sure many of you will agree that the construction of this antenna is not for the faint hearted. From the images it is quite clear that Nico ZS4N showed great building skills and craftsmanship in constructing this antenna.

Lets first look at the background of this antenna.  I will also add a few PDF files that explain the construction and performance of this antenna in detail.

Background of the Screwdriver Antenna

• The DK3 Screwdriver antenna was invented by Don Johnson (W6AAQ). The

DK3 is an HF antenna designed for operating on any HF frequency (10m through

80m) WITHOUT leaving the vehicle to change or adjust the antenna.

• The DK3 Screwdriver antenna is adjusted by remote control to give it multi-band

capability. A cordless screwdriver motor (which gives the antenna its name)

housed inside the lower mast unit of the antenna moves the embedded inductance

loading coil up and down. The portion of the coil that remains inside this lower

mast unit is inactive. The exposed portion of the coil provides inductance loading

to compensate for the capacitive reactance associated with short mono-pole

antennas like this one. The adjustable inductance loading allows you to achieve

resonance for a wide range of frequencies.

• The Z-match built into the bottom of the lower mast unit matches the antenna to a

standard 50-ohm coaxial transmission line. This eliminates the need for a tuner.

• Although the DK3 antenna is not plug-and-play, Don Johnson provides good

written instructions and suggestions, and even excellent telephone support to help you

set it up and make it work. 

• Due to its popularity, there are several different versions of the Screwdriver Antenna on the market. Some of the vendors offer improvements over the DK3(such as a plug-and-play version, 160m capability, or a lighter and more portable version of the DK3).

Diagram

DK3 Construction

More information  BIG DK3  By W6AAQ  (PDF Download)

Conclusion

The DK3 is probably the best mobile antenna for hf. It is also well known as the screwdriver antenna. It works on all hf bands (10m-160m) without changing the whip. Well, the DK3 is not really  inconspicuously, but still better than some other hf mobile antennas.

The whole antenna works as a quarter wave radiator. The body of the car is the ground.  There was a screwdriver antenna shootout at the parking lot during the International DX Convention in California (DK3, High-Sierra, Hi-Q, Drill Motor and one other brand). The DK3 took the first place in DX contacts at the convention. Please be aware for the cheep "remakes" of that fantastic antenna. Make sure you build or buy the original DK3 antenna by W6AAQ.

Congratulations Nico ZS4N on building the DK3 Screwdriver HF Mobile Antenna from scratch in your workshop.  

Images:  Click on images for larger view.

Building Low Budget Antennas - DIY Moxon Antenna for the 2m Band ( 144 - 146 Mhz)

In this article I will describe how I built my version of the 2m Moxon Antenna.

The Internet has an abundance of information on Moxon Antennas and I will not go into to much practical  and theoretical detail in this article.  Herewith a little AI information about the Moxon Antenna.

The Moxon antenna originated with British radio amateur and author Les Moxon (G6XN), who published it in his 1993 book, HF Antennas for all Locations, as a compact, high-performance two-element beam antenna (a radiator and reflector) with bent-back element tips, offering a great front-to-back ratio and 50-ohm impedance for easy coaxial connection, based on earlier explorations of folded-element designs. 

Key Aspects of its Origin:

• Inventor: Leslie A. "Les" Moxon (G6XN).
• Publication: Detailed in his 1993 book, HF Antennas for all Locations.
• Concept: A compact, rectangular variation of a Yagi-Uda beam, using bent ends (capacitive loading) on the radiator and reflector for efficiency and size reduction.
• Design: A two-element antenna (driven element + reflector) with folded tips, creating a directional pattern and high front-to-back ratio in a small footprint.
• Precursors: The design built on earlier ideas, including experiments with square-shaped antennas by Fred Caton (VK2ABQ) in the 1930s and 1950s.

Why It's Popular:

• Compactness: Occupies much less space than traditional beams.
• Performance: Offers good gain and excellent front-to-back (F/B) ratio.
• Simplicity: Easy to build, often from wire, making it great for amateur radio (ham radio) and field days.
• Direct Match: Its design naturally provides a 50-ohm impedance, connecting directly to standard coax.

In any project one needs a plan, diagram, guidelines and information.  At least that is my way of constructing any DIY Project.  I research the project thoroughly before I start any work.  I did exactly this before I started on this project.

Now the Internet is your friend but can also be your enemy if you just jump in and start constructing the first plan you find.  I was looking for the dimensions of  DIY 2m Moxon Antennas and ran into an abundance of information which included a calculator.  

The dimensions for the antenna was calculated using the free Moxon Antenna Calculator program (available for download from here). I set my frequency to 145.625 MHz with a wire size of 12mm to represent the 12mm aluminium tubing I was using. The resulting calculation is shown in Figure 1 below. 

Image:  Figure 1  (Click on image for larger view.)

The Moxon  antenna calculator was fed with the following data:

Frequency: 145.625 Mhz (I want to use the antenna for a repeater link.)

Diameter Wire size = 12 millimeters

Transmitter Power = 1 to 15 Watts

After calculating the information listed from A to E were provided.

With all the information now on paper, I was ready to move onto the next phase and that was to gather all the materials I was going to need.

Materials that I used:

1 x 150 millimeter x 50mm x 3mm Aluminium Flat Bar

3 x 12mm x 2mm x 2.5m Aluminium Round Tube  (The thicker the wall thickness the better. 2mm is rather thin.)

1 x 1 meter x 10mm x 2mm Aluminium Round Tube

1 x 1 meter x 10mm Wooden Dowel 

2 x 22 mm Plastic End Caps to fit into the 25mm Boom ends.

1 x PL259 Connector

2 x Electrical Eye Lug (Terminal)

3 x 12mm Stauff Clamps (Insolaters between boom and elements.)(See images)

6 x 45mm x 5mm Stainless Steel Bolts + Washer + Lock Nuts

2 x 65mm x 6mm Stainless Steel Bolts and 2 x Lock Nut

8 x 6-16mm Stainless Steel Hose Clamps

2 x Stainless Steel TV - U Clamps

1 x 150mm x 80mm x 5mm Alimunium Flat Plate to mount antenna to boom.

1 x 500mm RG58 CU Mil-Spec Coax Cable (50 Ohm)

2  x 300mm x 4.6 Hellermann Cable Ties

Odds and Sods:

Hot Glue Sticks

Self Amalgamating Tape

Solder

Solder Paste

Marine Silicone Sealant

Heat Shrink Tubing

 

Tools:

 

Metal Punch

Drill

Various Drill Bits 3mm - 8mm

Hack Saw 

Hot Glue Gun

Soldering Iron

Screw Driver (Small flat)

Alen Keys 

Spanner Set

Small Pipe Bender (See images)

 

Test Equipment:

 

SWR Meter

Antenna Analyzer (If you have one but not compulsory)

Amateur Radio Transceiver

Coax Patch Leads

Mast (Non conductive)

Coax feed line cable  5 m  RG58CU 50 ohm

Power Supply for Radio 

Building the Antenna:

My final dimensions is listed in the image below:

Images:  Figure 2 and 3 (Click on image for larger view.)

I am not going to go into detail how I constructed my version of the antenna. I will however describe my findings in constructing and testing the antenna.  The images below provide good detail of how I constructed the Moxon Antenna.

More information on the build and use of the antenna available at the following sites:

 

(Click to view website) 

 

The Moxon-Beam  by DK7ZB  

The GW3YDX Super Moxon 11 by GW3YDX

 

 

My build observations and findings:

 

Now how did I bent the 4 elbows of the antenna?  I used a small pipe bender.   The 10mm aluminum tubes are cut to 4 x 200mm.  I made a mark in the center at 100mm and then two marks 20mm on each side.  The first mark on the left is placed on the 0 | 0 mark of the pipe bender.  Now start bending until the 0 on the top lever reaches the 9|0 mark on the bottom lever.  You now have a 90 Deg elbow that fits into the 12 mm antenna element.

To fit the elbows and hold them in place I used stainless steel hose clamps.  This allows me to easily tune the antenna for a low SWR to a frequency I want to use.  I had two options to join the elbows to the element.  I could have used stainless steel self-tapping screws or the hose clamps but I opted for the latter.

Mounting the elements I manufactured 2 x Element Brackets as displayed in Figure 3. I used stainless steel bolts and nuts and Stauff Clamps to install the 12mm thick elements.  

The last observation and finding pertains to the feed-point and co-ax connector.  No rocket-science here.  I used a short piece of co-ax and PL259 + Barrel Connector for the feeding point.  I add a ferrite bead / clip to the piece of co-ax as before installing the antenna.

 

Just a word on the isolated wooden dowels between the two elements.  I left the two 90mm dowels for 2 days in furniture oil to protect the wood from the elements.  The oil was soaked up by the dowels  and  should now last for many years to come.

Fitting the dowels to the elements is easy. Ensure there is a 50mm gap separating the ends of the folded elements on each side of the antenna. Lay the two 90mm  next to each other and measure and mark the dowel as follows -  20mm - 50mm - 20mm.  Mark the measurements with a permanent marker. Ensure that the spacing between the elements is 50mm. Now slide the dowel inside the aluminium element up to the 20mm mark on one side and also on the other side. You will now have 50mm dowel showing between the elements. I drilled small holes through the tubing and dowel and then secure them with stainless steel self-tapping screws  Re-adjust the antenna assembly as necessary to make sure the outer dimensions are still correct. 

Preliminary Test Results:

 

(Click on the images for larger view.)

 

I really did not go into a full out testing and use of this antenna at this stage.  The only testing I have been doing is with the Nano VNA and a test or two on air RX and TX "excursions".  See images above for the test results.

The next step will be to install the antenna.  I installed the antenna only for test purpose.  Two meters above the ground and drooping forward as per image.  This was just to check the SWR.  I also connected the antenna to my Baofeng UV82 and gave a call on the 145.625 Mhz repeater.  Danie ZS1DL returned my call and indicated that there are rain on the signal but that my audio is understandable.  Well once the antenna is installed about 6 meters from ground I am certain that I will receive the repeater full quieting at my QTH. Update to follow once antenna is installed.

Images:  (Click on images for larger view.

 

Please, adhere to the following guidelines when using the ZS Link Network!!

Guidelines to use the ZS Link Network in the Southern Cape
 
By default many hubs, repeaters and links are connected to the ZS Link Network.  The ZS Hub is an Allstar hub node which links AllStar nodes around the world to form a network.

Due to the size of networks there need to be  rules to ensure orderly use of systems/networks. Amateur Radio regulations are largely self-enforced and we all need to work together and adhere to the rules listed below:  

You must identify your station according to the regulations. If you do not know how refresh you memory by downloading the regulations from the SARL Website.   I request that before sending any DTMF commands, you must also identify your station, by announcing your call sign and your intentions sending DTMF.

Please limit conversations to 15 or 30 minutes.  Other hams probably want to use the ZS Link Network but might not be interested in the subject you're discussing.  

Please DO NOT activate any form of courtesy tones.  For those not familiar,  courtesy tones are normally transmitted after the operator release the PTT after an over or Ker-chunking.  Courtesy tones are used in the commercial radio world and is a source of nuisance in amateur radio.  Tones can and does cause issues when several networks are connected together.  Please refrain from activating courtesy tones!!

In addition, great time and expense was put into building the ZS Link Network.  In order for stations from across the world to log in from time to time, the Network/System must be free.  If you are hogging the Network, others can’t get in.

Please do not talk about politics or religion on the  ZS Link Network or for that matter on any other system/network.  Absolutely no obscene, indecent or profane language at any time.

Do not make comments on institutions, groups, or people.

When using the  ZS Link Network, you are a guest operator of its radio stations, nodes, hubs  etc.

Please don’t use phonetics for every letter you need to say.  You are talking on a network and repeaters, not a noisy station on 40 Meters.  Just talk normal.

PLEASE leave a "8 second delay" between replying to a station to allow ALL the systems to reset and connect.

Please note this is a global network and you will be transmitting on RF all over the world.

It is extremely important that you spend time ensuring your audio levels are correct before connecting and using the  ZS Link Network.

To do this on Echolink please connect to the *ECHOTEST* Audio Test Server Node 9999. Send a test transmission and your transmission will be replayed back to you.
On Allstar use the 49355 "Parrot" node for testing your audio and network connectivity. If you are familiar with the Echolink Test Server, this works in a similar fashion. Connect to the test node and send out a test transmission, then wait for two seconds for your transmission to be repeated back to you. As a reminder, always connect to the test node in isolation.  Ask the ZS Link Network administrator to assist you in this regard.  He will activate and deactivate the "Parrot" Function for you to test your audio.

When attempting to break into a conversation, please follow this procedure.  If you have an Emergency, interrupt the conversation by saying “BREAK – BREAK”.  The talking stations should immediately recognize this as an Emergency, and turn the system over to the "breaking" station.  If you just desire to join the conversation or make a comment, interrupt by simply giving your call sign. Regardless, if you’re in a conversation, when a calling or breaking station interrupts, yield quickly since you never know if they have an emergency or not.
Correct operating procedure is a distinct characteristic of Amateur Radio.  It’s important that you convey to the public, and to new hams, the image that Amateur Radio Operators are courteous, patient, and really know what they’re doing.  A friendly style is great, but we also need to operate professionally.  You never know who may be listening.  Even late at night, there are generally people listening to the ZS Link Network via Broadcastify, including non-radio amateurs.  This is important to understand for several reasons.

         The ZS Link Network serve many purposes.  One of the most important is the exposure it gives the hobby to the community.  It’s one of our most effective forms of publicity.

         We want non-radio amateurs to know that Amateur Radio is an interesting hobby and a good group of people to get to know – something clean and educational – something they would want their kids to get involved in.  Kids may or may not listen late at night, but their parents do.

         Don’t let our activities on the air become a weapon in the hands of people who want to discredit us.  Let’s all do our part to give Amateur Radio a positive image. We want any person that listens to us to think of us as good operators, not idiots.  Any time we talk on the network or repeater, we are ambassadors for the hobby.

Do not cause intentional interference, to links, repeater, hubs, nodes or conversations on the network.  Intentional interference is not only heard locally but World Wide.  Just remember that intentional interference can today easily be traced to your call sign as all connecting RF and Digital stations leave an identifiable script in a log file.  I am sure you would not like to lose your license. 

 

Arikaanse Weergawe:

Riglyne vir die gebruik van die ZS Link-Netwerk in die Suid-Kaap

By verstek is baie nodes, herhalers en skakels aan die ZS Link-Netwerk gekoppel van reg oor die wêreld om 'n netwerk van nodusse te vorm.

As gevolg van die grootte van netwerke moet daar reëls wees om ordelike gebruik van stelsels/netwerke te verseker. Amateur radio regulasies word grootliks self afgedwing en ons moet almal saamwerk en die reëls hieronder nakom:

Jy moet jou stasie identifiseer volgens die regulasies en kan jy jou geheue verfris deur die regulasies van die SARL-webwerf af te laai nie. Radio amateurs word versoek dat voordat jy enige DTMF-opdragte stuur, jy jou stasie moet identifiseer deur jou roepsein en jou voorneme om DTMF te stuur, aan te kondig.

Beperk asseblief gesprekke tot 15 of 30 minute. Ander radio amateurs wil waarskynlik die ZS Link Network gebruik, maar stel dalk nie belang in die onderwerp waaroor jy gesprek voer nie.

Moet asseblief NIE enige vorm van hoflikheidstone aktiveer nie. Vir diegene wat nie vertroud is nie, word hoflikheidstone gewoonlik uitgesaai nadat die operateur die PTT vrygestel nadat hy ‘n rondte geneem het. Hofflikheidstone word in die kommersiële radiowêreld gebruik en is 'n bron van oorlas in amateurradio. Tone kan en veroorsaak probleme wanneer verskeie netwerke aan mekaar gekoppel is. Vermy asseblief om hoflikheidstone te aktiveer!!

Daarbenewens is baie tyd en koste bestee aan die bou van die ZS Link Netwerk. Om stasies van regoor die wêreld van tyd tot tyd te laat aanmeld, moet die netwerk/stelsel vry wees. As jy die netwerk oorneem, kan ander nie inkom nie.

Moet asseblief nie oor politiek of godsdiens praat op die ZS Link-netwerk of wat dit betref op enige ander stelsel/netwerk nie. Absoluut geen onwelvoeglike of godslasterlike taal te eniger tyd nie.

Moenie kommentaar lewer oor instellings, groepe of mense nie.

Wanneer jy die ZS Link Netwerk gebruik, is jy 'n gasoperateur van talle radio stasies, nodusse, ens.

Moet asseblief nie fonetiek gebruik vir elke letter wat jy moet sê nie. Jy praat op 'n netwerk en herhalers, nie 'n raserige stasie op 40 meter nie. Praat net normaal.

Los asseblief 'n "8 sekondes vertraging" tussen rondtes om AL die stelsels toe te laat om te herstel en te ontkoppel.

Let asseblief daarop dat hierdie 'n wêreld wye netwerk is en dat u wêreldwyd uitsaai.

Dit is uiters belangrik dat u tyd spandeer om seker te maak dat u klank vlakke korrek is voordat u die ZS Link Netwerk koppel en gebruik.

Om dit op Echolink te doen, koppel asseblief aan die *ECHOTEST*-klanktoetsbediener groep 9999. Stuur 'n toets uitsending en u uitsending sal na u teruggespeel word.
Gebruik die 49355 "Pappagaai"- Node op Allstar om u klank- en netwerk konnektiwiteit te toets. As u vertroud is met die Echolink-toetsbediener, werk dit op 'n soortgelyke manier. Koppel aan die toets node en stuur 'n toets uitsending uit, wag dan twee sekondes totdat u uitsending na u terug herhaal word. Ter herinnering, koppel altyd in isolasie aan die pappagaai node. Vra die ZS Link Netwerk administrateur om u hiermee te help. Hy sal die "Pappagaai"-funksie aktiveer en deaktiveer sodat u u node se klank kan toets.

Wanneer jy probeer om in 'n gesprek in te breek, volg asseblief hierdie prosedure. Indien jy 'n noodgeval het, onderbreek die gesprek deur "BREEK – BREEK" te sê. Die stasies moet dit onmiddellik as 'n noodgeval herken en die stelsel oorhandig na die "onderbrekende" stasie. Indien jy net by die gesprek wil aansluit of 'n opmerking wil maak, onderbreek deur bloot jou roepsein te gee. Ongeag of jy in 'n gesprek is, wanneer 'n roepende  stasie in breek, gee vinnig oor, aangesien jy nooit weet of hulle 'n noodgeval het of nie.

Korrekte bedryfs prosedure is 'n duidelike kenmerk van amateur radio. Dit is belangrik dat jy aan die publiek, en aan nuwe radio amateurs, die beeld oordra dat amateur radio operateurs hoflik, geduldig en werklik weet wat hulle doen. 'n Vriendelike styl is wonderlik, maar ons moet ook professioneel optree. Jy weet nooit wie dalk luister nie. Selfs laat in die nag is daar oor die algemeen mense wat na die ZS Link Network luister via Broadcastify, insluitend nie-radio amateurs.