I’ve always been interested in homebrewing equipment as one of the best ways to be productive as a cheap ham. Generally, the components for a simple transceiver are less expensive than buying such a transceiver or even buying a kit that is already made for you. There are lots of great resources out there for homebrewing, but I’ll just mention two.

The first is the book Experimental Methods in RF Design by Wes Hayward W7ZOI, Rick Campbell KK7B, and Bob Larkin W7PUA, often referred to by its initials as EMRFD. It is a fairly gentle yet expansive introduction to the basics of homebrewed radios from simple CW rigs and direct conversion receivers to single sideband phone transceivers and even digital signal processing (DSP). The book has a mix of instructional material combined with complete buildable projects defined by schematics and discussion of the circuits.

The second is a website that is heavily influenced by EMRFD, “QRP and SWL Homebuilder”, or as I always think of it qrp.pops.net. The site itself often refers to itself as “the popcorn site” in reference to its approach to design and building. In the words of the author VE7BPO, “The emphasis is fun. The hope is that it will attract new people to electronic design, measurement and experimentation. Hopefully, this site stimulates interest in QRP homebrew electronics.” It certainly has for me and I appreciate his focus on even simpler and easier to build designs than those in EMRFD which are often (rightly) concerned with very high performance.

Getting started

To get myself started, I read my way through the first two introductory chapters of EMRFD as completely as I could and then skimmed the most interesting parts of the rest of the book looking for project ideas and design tools and tips. My current goal is to make a portable, monoband QRP CW station and the book has more than enough detail to get me there.

The authors of EMRFD as well as the author of the popcorn site emphasize measurement and understanding as the basis of homebrew radio. So, rather than building an entire device and waiting until the end to test it, they advocate building in stages and at every stage using test equipment to verify the operation of that stage. As a result, the test equipment is one of the more important pieces of their puzzle.

Following their lead, I’m going to be homebrewing the basic pieces of test equipment that I will need to start building and measuring and understanding simple transmitters and receivers. The first few projects I have in mind are this popcorn RF power meter and a homebrew frequency counter, either a simple prescaler/Arudino combination like this one, or this very interesting version using a prescaler, a sound card, and a Python program.

Incoming!

Once I get project ideas like these, I start to gather together the parts that I’m going to need. I have been making use of all of the scroungy parts sources I can think of.

1. Scavenged CB radios: A friend who heard I was into “radio stuff” brought me a box of old CB radios that he had collected at garage sales. He had been a CB fan when he was in high school and felt like scooping them up when they were going for a dollar.

   I promptly took them apart, removing all of the metal cases and ending up with a stack of mainboards, a huge pile of knobs and screws, and some miscellaneous meters and speakers. The mainboards are full of transistors and variable resistors and variable inductors and on and on. Those chromey CB front panels are also rich with potentiometers and switches. (I plan to make use of my haul of switches in a switched inductor antenna tuner.) One of the meters will probably go into my homebrew RF power meter.

2. eBay: The often maligned auction site is also a global marketplace for anything and everything that is for sale. From resistors and capacitors to BNC connectors and even a digital clock kit, everything you could ever want is there for the asking. I bought some resistor and capacitor assortments so I could look at a schematic without blanching at the thought of trying to order all of those components one at a time from Mouser. I also bought some additional lots of bypass capacitors in the most common values (0.1 and 0.01 uF).

   Most of the items come from China and the shipping times can be long, but the prices with shipping included are amazingly low, almost pocket change low.

3. Engineering Samples: The heart of the rf microwatt meter is an Analog Devices AD8307 log amplifier chip. They go for around $10 in the DIP package that is easiest for homebrew use, but Analog has a wonderful program for academics to order free samples of their products. Since I am currently still a professor, they sent me one of the AD8307 chips for free. They even shipped it FedEx for me.

4. Mouser: Of course, not all the parts can be free, scavenged, or imported cheap from China. For the rest of the parts, there is Mouser.com. They have a flat-rate $4.99 shipping rate for residential customers and they have almost everything under the sun. Most components cost just a few coins each, so it makes sense to get a raft of them in one shipping box. That’s why I’ve got the ICs for two different frequency counters coming along with the supporting parts for the power meter and a -10 dBm calibrator.

   The flat rate shipping is just regular USPS First Class so it can take up to a week, which is why I have the AD8307 from FedEx but I’m still waiting on an op-amp chip to complete the microwatt meter. First world radio builder problems.

More to Come

I’ve got lots more to put up on the blog about the current status of my gear as well as the rest of the homebrewing projects I’ve got in the works: antenna, antenna tuner, keyer, paddle, and so on. Look for more posts shortly as this blog winds back up.