Soda Can Battery From Trash

I really love DIY projects and proof of concepts with electricity and radio so when I saw this little project using soda cans, cardboard, copper wire, sand, and saltwater to build a battery, I was all over it.

(video from, an alternative to YouTube’s increasingly anti-free speech platform)


  1. Cut the tops off of old soda cans carefully and deburr the can edges.
  2. Draw circles around the bottoms of the cans on a sheet of cardboard to create the bottom insulators.
  3. Cut out the circles, and place each one inside the cans at the bottom.
  4. Cut out rectangles of cardboard to just slightly under the height of the cans and wide enough to form a tube inside the can. These will be your insulators for the sides of the can battery cells.
  5. Insert the cardboard tubes into the cans.
  6. Create a coil out of copper wire for each can with about an inch of the wire sticking above the can top.
  7. Place the coils inside the cans and center. Fill the cans with play sand around the coils nearly to the top.
  8. Add 2T of salt to 16.9oz of water, and mix well.
  9. Fill the cans with the saltwater mix until the sand is completely saturated.
  10. Check the voltage and amps of each cell by clipping tester leads to the center copper wire and the can top edge.
  11. Use hot glue to fasten the cans down in place to a piece of foamcore board or plastic. Leave a little space between each cell to avoid shorting out across the cells.
  12. Wire the cells in series, from center conductor of one cell to side of the next cell. (The side of the can is negative, the center conductor is positive.)

MagLoop Antenna Construction Resources

Surprisingly, though ham radio operators usually have a ton of radios, antennas are even more important. You can have the most expensive radio in the world, but without a good antenna for your location that is tuned properly, you’ll have a hard time getting contacts at all. So hams are always testing, building, and fiddling with antennas.

MagLoop antennas are useful for confined spaces, indoor, or stealth installs such as in apartments.

Here are some really excellent resources for designing and building MagLoops.

80-20m MagLoop Antennas – Very in depth discussion on the different variables and principals that make for a good MagLoop.

Multi-Turn MagLoop Antenna – Comparison table of variables for a 6.5ft magnetic loop antenna for 40 meters.

3-Band Magnetic Loop Antenna Design – Short schematic design for a 20-30-40 meters Magnetic Loop antenna. Includes construction details.

How to Update Your Address on Your Ham Radio Operator License

A requirement of maintaining an amateur radio operators license is that you must update the FCC with your current address if you move.

Failure to keep your address updated and accurate can result in losing your ham radio license, so you’ll want to make sure you don’t forget to update it.

There are a number of independent companies that will do this for you, for a fee, but you can actually do this yourself online for free if you know how.

The FCC provides instructions on how to update your address here.

You will need your FCC Registration Number (FRN number). If you have forgotten what it is, your can look it up by searching the FCC License Database for your call sign.

Go to the FCC’s Online License Manager to file your change of address.

Login with your FRN and your password you created when you got your FRN.

Find your license in the list and look to the right hand side of the screen where it says Work on this License.

There is an update link in the box. Click the link to start the process to update your address.

Follow the prompts to update your address, and certify the application.

You’re done! Easy and free.

A few useful FCC links:

Taking Part in Public Events as a Ham

I had the opportunity as an amateur radio operator to take part in the communications network for the “Trunk or Treat” event held by a neighboring town recently.

It was the first such event I had participated in, and I thought it would be a wonderful opportunity to get my feet wet with emergency communications– without an actual full bore emergency.

The event was projected to have up to 15k attendees and the city had used volunteer hams for event coordination on the previous two years.

The previous years, there had also been a couple of lost children, and at least one person with a medical issue, as well as booths running out of things, volunteers being sent where they are needed, and other issues.

Turning up in the early afternoon with my own handy talkie radio, headset, a spare battery, folding chair, and a bottle of water to the “Net Control” station I was handed a safety vest and given a final event briefing.

The volunteers had also met the week before at town hall to meet the event staff, discuss what to expect, learn the event layout, and what to bring, so we were prepared in advance– which was really useful.

We helped vendors find their way into their spots to set up before the event actually started and learned the “tactical” call signs being used for the event.

Tactical call signs were quite interesting as a concept. Instead of using our own FCC assigned call signs, each ham was assigned to a person or location, and that became their tactical call sign.

I can see the value of tactical call signs, because their are easier to remember and use at events.

Some example call signs– the event’s main coordinator’s name was Erica, so the ham assigned to roam with her went by ERICA.

Other tactical call signs were things like “Purple Trunk”, “Ticket One”, “Ashley”.

We had three frequencies that were being used and monitored by the group which we were given ahead of time- but one was a backup in case the first repeater went down.

Three or four hams were stationed at “Net Control” including me.

During the event, I listened to the broadcasts on the main frequency, providing a backup set of ears (sometimes it’s hard to understand what people said, and one person may have heard something another person did not) and helped give directions to people to find parking.

Later on, as parking filled up, we were taking turns metering how many people could enter and leave the lot we were next to. (You would not BELIEVE how hostile people can get when a lot is full and they want to park there anyway.)

During the event we had one missing child, two missing “rodeo queens”, and a case of “substance abuse” which required an ambulance.

All in all it was a very interesting and valuable experience.

Managing Website Backups in CPanel w/o Automated Backups Enabled

Some Cpanel web host providers provide automation for regular scheduled backups with their hosting plans for free, and some only allow you this feature as an expensive add-on.

If you are in the latter position and don’t want to pay an extra $50 a month for that, there’s a nice free backup script you can use to fudge it an protect your website with regular backups using cronjobs.

The script can be downloaded from free of charge.

Antenna Fundamentals, Propagation, Directivity and Bandwidth

A local ham radio group I occasionally attend events with recently had a very good antenna presentation with well known antenna inventor Edison Fong which inspired one member of the group to go looking for more information on antenna theory.

During that search, Brad uncovered three wonderful videos created by the Film Board of Canada for the Royal Canadian Air Force.

If you are looking for detailed information on how waves travel and radiate in antennas and how shapes affect direction and bandwidth of antenna propagation, check them out!

Antenna Propagation

Antenna Directivity

Antenna Bandwidth

Soft-Start Circuit Design to Stop Inrush Currents

Some appliances or components like solar inverters can trigger circuit protection to kick in when they care first connected.

The reason is that often they have large capacitors inside that can really spike current use while they are charging up on start-up.

In the video below, the Great Scott YouTube user, an electrical engineer from Germany, breaks down his solution to eliminating those huge start-up current spikes without sacrificing much power.

How To Test Transistors with a Digital Multimeter

Getting a very late start in electronics – I started at 50 years old! — has it’s problems that I need to work really hard to resolve.

My friends tell me I always jump in at the deep end of the pool, and I think they are right.

After all, I am always teaching myself things by reading, and experimenting. I taught myself how to work on cars, upholstery, software programming, and a billion other things. If I want to know something, I just go figure it out.

But electronics is really turning out to be the deepest pool I’ve ever jumped into. There’s just so much background I need to acquire to even understand basic stuff.

Right now I’m putting together a little Elenco kit radio that’s meant to teach you radio concepts, like how to solder, what the different stages of a radio are, how they work, what different components do, and how to test your work using standard testing equipment like an oscilloscope, a multimeter, and a signal generator.

However, the instructions in the booklet on how to test a transistor leave something to be desired.

So I went looking for better instructions and turned up this wonderful video that explains how to use a digital multimeter to figure out if a Transistor is NPN, or PNP type, and which pins are the base, emitter, and collector.

Kudos to Shawal SI for the fantastic video

Rediscovering Myst From a Ham’s Perspective

The Myst series of games from Cyan Worlds has always been one of my favorites. I love exploring the beautiful locations, the atmospheric music, and the puzzles.

In my younger days, I confess I almost always had to refer to walkthroughs to complete the game, and seldom actually understood the solutions fully.

But now, since studying for both Technician, General, and about halfway to the Amateur Extra License license test, replaying the games is much more enjoyable as I’m discovering the solutions are often based on real principals of electronics and mechanical engineering.

Take the Myst III Exile game which I just completed yesterday. In the age of Amateria, which is basically a giant pinball roller coaster, one of the first puzzles involves a sluice chute that has to be positioned using weights, and a movable support point. If not positioned correctly one end will be too high or too low, and the ice-sphere you need to roll across it will shatter.

In the end, you need 22 units of weight on one side (the side you can adjust is the left- you have no control over the weight on the right side) and to move the support point (otherwise known as the fulcrum) to the furthest left position of the three positions.

I started wondering afterwards, if there was a real-world formula for this puzzle solution. And there is!

I found this very enlightening article over on Engineer’s Edge that explains how to calculate how much weight is needed on one side to counterbalance the “lever” weight on the other if you know the length of each side of the balance beam.

Here’s the formula:

F x L = W x X

F = Downward Force on the right side
L = Length of the right side of the balance beam

W = Weight on the left side of the balance beam
X = Length of the left side of the balance beam

In the puzzle, F=11 (7 Wood Pieces of the Sphere + 1 Crystal Piece, which weighs as much as 4 wood pieces)

The total length of the balance beam is 3, and you can place it at positions 1, 1.5, or 2 units.

So in the left most fulcrum position ( L=2, X = 1, F = 11), we get this:

11 x 2 = ? x 1 — so W = 22

This comes out to 6 wood (6 x 1) and 1 metal (1 x 16) piece. (Metal weighs 4 x Crystal, Crystal weighs 4 x Wood)

That balances the beam at the correct position (equilibrium) for the ice-sphere to roll across both ends without shattering!

Today I just started replaying Myst IV Revelation, and the very first puzzle is very radio related. You’re looking at what is basically a MIXER/FILTER, where you are combining two signals (heterodyning), one external signal, and one from your local oscillator, to create a third signal matching or amplifying the signature of an age.

The controls represent AMPLITUDE, FREQUENCY, and PHASE.

This puzzle too, is much more entertaining now that I actually understand from an RF perspective what those terms mean.

It’s a pleasant surprise that the puzzles are not just meaningless, and there are known principals you can use to solve them.

DIY 3D Arduino Powered Printer Build

3D printers are all the rage these days, and are coming down in price gradually, but are still a bit out of reach for many.

So many capable electronics and maker hobbyists have turned to re-purposing all sorts of things to build their own 3D Printers on the cheap.

Here’s one great example (though he uses a number of prefab things like stepper motors, extruder nozzles, and Arduino boards).

The tutorial is in three parts, and is pretty complete, including showing how to program the Arduino, and actually use the printer to create parts. (Humorously, he actually uses the printer with temporary “duct tape and bailing wire” construction to make the last few printed parts brackets and then replaces them into the machine!)

Credit: RZTronics