QRP and the Oscilloscope

This weekend I have been working on projects related to a book about using the oscilloscope to characterize and evaluate simple QRP transmitters. I’ve built a simple test jig that will let me do most of the testing I will be discussing in the book.

QRP Transmitter Test Jig

It includes everything needed to key the transmitter with a string of dits, provide a dummy antenna, and regulate the power supply (in a way that allows measurement of the DC input power).

I’ve gathered most of the test data to characterize my Tuna Tin 2 QRP transmitter.

Tuna Tin 2 QRP Transmitter

The results and the book should be out in a few weeks.

73 de

“With a soldering iron in one hand, a schematic in the other, and a puzzled look on his face…”

Hello and Welcome!

Let me make a quick introduction of myself and this blog.

I am Jim, W4JBM, and first began tinkering with radios when I received a crystal radio kit for Christmas at the age of 6 back in 1969. I have been hooked on radio, electronics, and (later) computers as both a hobby and a career ever since.

While I enjoy reading (on technical as well as other topics), I also enjoy the “hands-on” aspects of experimenting, building, and repairing gear. My Radio Shack 150-in-1 lab saw use all the way into college when it was largely replaced by my Heathkit ET-3100 experimenter’s breadboard.

As a teenager, All American Five vacuum tube receivers were plentiful and cheap at flea markets and garage sales. (I remember once picking up a box of over a dozen for a quarter–and being able to get most of them working again.) I have no idea how many I repaired, but it would be several hundred with probably around another hundred more being sacrificed for the parts needed to repair others. I would also end up building several simple shortwave sets including a three transistor regen kit offered by Radio Shack and, eventually, a Heathkit SW-717.

In 1980 I received my first computer  (an Ohio Scientific Instruments C1P) as an early high school graduation gift. Those were the early and exciting days of personal computing and I dove in with both feet experimenting and learning with both hardware and software. One achievement that stands out was a “programmable” computer built entirely from 7400 series TTL logic chips as a lab project in college. It had a 16 byte program space (consisting of 16 8-pole DIP switches that served as a primitive EPROM) along with four registers. We had to “write” and demonstrate a program that could load and multiply two four-bit numbers. We got bonus points for being able to write programs that would square a four-bit number and divide two four-bit numbers (with the result in one register and the remainder in another). I remember it also becoming an exercise in power supply construction once we passed the 1 amp capability of the power supply the school gave us along with a bag of ICs when we started the project.

This blog will consist of several types of content. I intend to primarily focus on hints and tips related to radio and electronics that I have picked up over the years. There will also be some reminiscing (and maybe even a bit of bragging) along the way. I will also post information related to the various books I have written and that are available from Amazon along with an occasional magazine article.

Until later!!!

73 de

“With a soldering iron in one hand, a schematic in the other, and a puzzled look on his face…”