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

Reflections on Electronics Parts Searches and China

I’m currently looking for parts to build a HF Antenna Analyzer from a much passed around plan by Beric Dunn, and the search has been somewhat difficult. The search has led me to start thinking about how dependent we are on China for electronics parts.

On the one hand, it’s great we can go to sources like AliExpress, BangGood, GearBest, and dozens of other Chinese companies to get parts inexpensively as hobbyists.

But on the other hand, many people in the “maker” space are rolling their own electronics as prepping activities, such as building battery packs for solar power.

So what happens when your supply chain stretches all the way to a country that is actively stealing product designs from US companies, and has been caught installing spy software/spy hardware in products they produce for us?

Food for thought.

Are there reasonably priced alternatives for parts and small run PCB’s in the United States?

If not, could someone make a go of it in a cottage sized industry, perhaps with desktop sized PCB milling machines?

Something to research.

DIY Portable Power Box Solar Charge Upgrade

Recently I finished building my first portable power box in an “ammo can”, and have been charging phones and testing radios with it.

However… now it’s time to top the battery off, so I’m upgrading the box with a charge controller, and external port to plug in a solar panel.

Here’s the video tutorial I’m following to upgrade.

Credit: JDS Outdoors

Parts Needed:

The solar charge controller used will only handle up to 7 amps of current, so make sure your solar panel does not exceed that output, or you’ll need a heavier duty controller instead.

Reviving Lead Acid Batteries with Epsom Salts

In this tutorial video from Car Groves, you’ll learn how to rejuvenate a dead lead acid battery by using Epsom salts to get rid of the scale that builds up on the battery plates over time.

This is a bit time consuming, but good to know in case the civilized world goes boom and you can’t run out and buy another one easily.

Or maybe, you’re just tired of ponying up another $150 for a battery…. either way, now you know why they want the battery “core” back!

Via Car Groves

Powerwall Battery Pack Construction with BMS

There’s a guy named Jehu Garcia in California who’s made it his mission to recycle laptop and other batteries in the United States instead of sending them back to China.

One of his ongoing projects is building DIY power walls (similar to the commercial ones made by Tesla at a premium price) using these reclaimed batteries and modular PCBs and commercial battery holders.

This is a lot easier than soldering the cells together with nickel strips and making your own brass buss bars.

Here’s his tutorial on putting together the battery packs, including how to match cells, and even build the ribbon cables for the battery management system monitoring.

via Jehu Garcia