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

Antenna Theory – UnUn Transformers for Impedance Matching

Baluns and UnUns come up frequently when discussing antennas of different types and matching feed point impedance so you don’t burn up the final stage transistors in your expensive radio.

This video contains one of the best explanations I’ve seen so far of wave propagation in antennas, and how to build a transformer to convert and match impedances.


Calculating Power Ratios from Decibels

Decibels have never really made a lot of sense to me, though I memorized the relevant numbers to pass both my Technician and General class ham radio operator license tests.

I mean, 3dB = 2:1, 6dB = 3:1 and 10dB = 10:1? What sense does that make? And its bothered me that I didn’t know how to figure out where those numbers came from.

But I’ve finally found a formula to do the conversion from dB to a power ratio that I can remember and makes a sort of sense, especially when dealing with partial decibel numbers like “2.8 dB”.

So here it is:

Ratio = 10^(dB/10)

Research Gate

So using 2.8dB from the 2016-2020 Amateur Extra question pool (E9A15), 2.8 dB converts to 1.905 power ratio for calculating effective radiated power.

10^(2.8/10) = 1.905

And that means that a station with 150 watts of transmitter power and 2dB of feed line loss and 2.2dB of duplexer loss plus 7dBd antenna gain has an effective radiated power of 286 watts.

Total gain = 7 dBd – 2 dB – 2.2 dB = 2.8 dBd or a 1.905 power ratio.

150 watts x 1.905 = 286 watts effective radiated power.

Simple! Now I can move on to the next question in my study guide. Just 55% more to go!

Addendum: See solving decimal exponents here to deal with the 10^0.28 part of the equation without a scientific calculator.

Homemade Soldering Iron Tutorial

Just found this great tutorial on how to make your own soldering iron from bits of wire, fiberglass tubing, nichrome wire from a hairdryer, and a rough cross section of a branch.

When I was searching to find the video again to place it above, I found that there are MANY MANY different versions of the home made soldering iron made with slightly different parts, so there are lots of options.

For some of the other homebrew soldering iron options, follow this link to YouTube!

Apparently, this is a fairly common thing to make when you might not be able to get to your commercial soldering iron, and have a few minutes and the parts.

WSPR: Weak Signal Propagation Path Reporting

WSPR (pronounced “whisper”) stands for “Weak Signal Propagation Reporter”. It is a protocol, implemented in a computer program, used for weak-signal radio communication between amateur radio operators.

WSPR implements a protocol designed for probing potential propagation paths with low-power transmissions. Transmissions carry a station’s callsign, Maidenhead grid locator, and transmitter power in dBm. The program can decode signals with S/N as low as −28 dB in a 2500 Hz bandwidth. Stations with internet access can automatically upload their reception reports to a central database called WSPRnet, which includes a mapping facility.


Applications for WSPR

The protocol was designed to test propagation paths on the LF, MF and HF bands. Also used experimentally at VHF and higher frequencies.

Other applications include antenna testing, frequency stability and frequency accuracy checking.

Usually a WSPR station contains a computer and a transceiver, but it is also possible to build very simple beacon transmitters with little effort.

For example simple WSPR beacons can be built using the Si 570 crystal oscillator (see PDF for kit links and schematics), or Si 5351 (kit available here).

The Raspberry Pi can also be used as WSPR beacon.

Photo Credit: Gerolf Ziegenhain – Own work, CC BY-SA 3.0

Article Link: Raspi as WSPR Transmitter
Source Code:

Here’s another example DIY WSPR beacon project video:

Source Files for Project on Github

Download WSPR Software at the Official WSPR Site:

Build a 12v Portable Power Box for Your Mobile Ham Radio Gear

Ham operators often take their gear to different locations out in the field and need a battery to power up their radios and other gear.

The video below shows one way to put together a mobile power battery box using an inexpensive Plano field box.

Parts Needed

Tools Needed

JT65 Digital Mode HF Radio

Ham radio is no longer all about a guy with a mic and a stack of radios plugging away in analog radio, looking for far away contacts.

Now, there are many new digital modes becoming popular– fusing computers and radio together.

JT65 is one of those digital modes that melds a computer and software into the ham experience, and yielding something like an internet modem– without the internet.

JT65 operators can send images, forms, chat, and more, including using frequencies BELOW the audible range.

Here’s a quick introduction to JT65 for beginners from HamRadioConcepts.

Free software to run on JT65 is available for Windows, Linux, and Mac:

Build Your Own 3D Printer – Video

This 3-part video series from RZtronics shows how to home-build your own Arduino based 3-D printer. Uses a lot of purchased parts but there’s still a lot of savings over the expensive commercially available 3D printers.

3D Printer Build Part 1
3D Printer Build Part 2
3D Printer Build Part 3

The Arduino software, parts lists and sources can be found below the video on YouTube OR here at the RZtronics website.

Morse Code – Letter Shape Learning System

Morse code is no longer required for an amateur radio ham license, but its still beneficial to learn.

I found this neat system created by the fine people at to teach the basics of Morse Code (Also referred to as CW or Constant Wave) in about an hour.

The SHAPES of the letters are used to remember the pattern of “dits” and “dahs” (dots and lines) that make up letters and numbers.

There also is an app created by the same people to help you practice.

Of course this is just a temporary crutch to get you started remembering enough to practice, and eventually you’ll want to just hear the letters like you would a second language without the interim translation step.

Quick-Reference Morse Code Letters and Numbers Chart