The Club Sandwich Project

Club Sandwich in Altoids Box

Recently, at our local QRP club meeting, someone joked that it would be a marvelous sight to see all our various Altoids-packaged projects connected together to form a station. We all chuckled at the visual suggestion, but later I got to thinking more along those lines.

What I propose here, as an outgrowth of that interesting suggestion, is a project I have dubbed the "Club Sandwich". As the title implies, the project is intended for amateur radio clubs. It provides a unique opportunity to exercise individual creativity under the umbrella of a team project, increase overall knowledge of radio system hardware design, and provide a continued base for experimentation in the club. The most promising and rewarding aspects, however, may well be the opportunity for increased comradery, renewed interest in club activities, and just plain ol' radio-fun. As conceived, the project is sure to interest both newcomer and old timer alike, and bring the two together.

The Club Sandwich takes the form of a simple construction project; in our example, a QRP CW transceiver. It is composed of several smaller sub-projects, representing modular functions, to eventually be connected together to form a working transceiver. Imagine a half-dozen or more Altoids boxes, interconnected with shielded cables. Larger clubs may want to consider more complex projects. When completed, it may be used for field day, or "checked out" by members for a short time.

What Kind of Project Should We Pick?

The specifics of the project should be tailored to the interests and skill-levels of the club membership. Common hardware elements should be defined, simply so everyone is on the same page, interconnection wise. Likewise, it's important to have a technical goal (sometimes called a "specification") and a plan to go with it (sometimes called a "system design"). I hestitate to use the latter terms, because informality should be modal in a project like this. Aside from the specifics of the hardware and design, there are some intangible but esssential elements for the Club Sandwich; we'll speak in terms of of our example, a QRP CW Transceiver:

Sounds Cool! How Do We Get Started?

Begin by assigning a team coordinator. Did I say assign? OK, elect or proclaim a volunteer as your team coordinator. If at all possible, that should be a person with good people skills and broad technical experience. This is the person who will coordinate the participating members, and keep the "big picture" in mind should things go astray. Once you've selected your team coordinator, you're ready to begin.

The "system design" approach suggested here is loosely based on proven techniques used in commercial engineering. System design consists simply of the following: Agree on the goal, formulate a plan, produce a preliminary design, implement the prototype, test and modify it, integrate the system, and document what you've got. In the case of the Club Sandwich, individual modules are designed, built, tested, and documented by individual club members on their own time (though perhaps with the help of a mentor or assistant). Integration of individual modules is done at a club meeting, so the project can be appreciated and discussed by all. Let's look at these individually:

The All-Important Block Diagram

The Block Diagram is probably the easiest way to "put-down-on-paper" what you specifically want to accomplish. I suggest one block for each assignable sub-project (module). I also highly recommend a set of written input/output specifications, so people constructing the individual modules understand exactly what's coming at them, and what they're expected to provide. This is all really pretty simple, but worth the time and effort in the long run. At the bottom of this page, I'll provide an example, based on a QRP CW Transceiver, which you may review as a model for your own project, or adopt outright.

When creating the block diagram, keep the following in mind:

Once the block diagram is drawn, make a list or table of the requirements for each block element. This will form the module specification. Include:

From Block Diagram to Individual Designs

When creating the block diagram and module specs, stay flexible, but keep the "big picture" in mind. Individuals may want to alter their module's specifications, and in some cases this will certainly be warranted. But in a project like this, changing specifications can have a ripple effect. For example, let's say the person building the keying circuit decides to use 5 Volt logic, when 12 V was specified. Now, every module that used keying (and there are many) will need to be redesigned. It is the job of the team coordinator to "see the big picture" and steer individuals back to a reasonable solution.

This is not to say that individuals constructing sub-projects do not have latitude. In fact, they have a lot. Circuitry, parts selection, and construction methadology are all at the descretion of the individual or sub-project team. Want to do something innovative? Do it! Use proven methods! Go ahead! Use surplus parts? Why not? Use an exotic sample? Who's to stop you? Machine your own capacitors? Grow your own silicon? More power to you. The point is, there's a lot of room for individual expression here, while staying within the agreed guidelines and specifications.

Every participating individual should receive a copy of the block diagram. This helps them keep the "big picture" in mind, a valuable reminder when you're designing and building a part of the whole. As the sub-projects are completed, give each individual a chance to "show-and-tell", and put their schematic and parts notes into the comprehensive project notebook. Make sure their name and call are on the paperwork. Hand-drawn schematics and hand-written notes are fine.

This is guaranteed to be a learning experience for every club member. Members who have no building experience will have to crack a book, and ask questions. Experienced builders will have to work within the bounds of specifications, expand their horizons, and help others. Everyone will see how their little piece support the whole, whether it be a piece of hardware, some documentation, the acquisition of parts, or some individual expertise.

An Example, and a Proposal for the First Club Sandwich

As a starting point, we offer the attached block diagram of a QRP CW Transceiver. Frequencies have not been specified; you should select a band, and decide on an IF frequency. We suggest, for starters, 40, 30, or 20 meters. Use cheap microprocessor crystals for the IF filter and mixer injection, all the same frequency. If you use both transmit and receive mixers (as shown in the example), you'll generate sidetone directly. If you want to keep it really simple at first, ditch the IF and build a direct-conversion receiver, and/or use a VXO for your transmit source. We'll go all the way with our example, showing a single band, 3-5 Watt CW transceiver, with good flexibility and expansion capability to SSB or digital modes. We'll show a conventional VFO, but there's no reason a DDS or PLL couldn't be substituted (thus getting the digital and software types involved). Or, build all 3 individually, and try them all out (that's the power of modularity). Here's our Block Diagram:

Click on the picture above to see a larger version
Click -here- for a printable diagram in MS Word format (188 KB, 1 page)

Click -here- for the block diagram and block specifications on one complete web page

Click below on the block/module names below for a sample specification of a particular block:

Receiver: RX BPF
Receiver: RX PREAMP
Receiver: RX MIXER
Receiver: IF AMP w/ AGC (1)
Receiver: IF FILTER
Receiver: IF AMP w/ AGC (2)
Receiver: AF PREAMP
Receiver: RX MUTE / AF AGC
Receiver: AF FILTER
Receiver: AF AMP
Transmitter: TX MIXER / OSC
Transmitter: RF DRIVER
Transmitter: POWER AMP
Transmitter: LOW-PASS FILTER
Misc: VFO

Click -here- for the block diagram and block specifications in printable MS Word format (228 KB, 14 pages)

Hope all this generates some interest, and spurs on all you latent homebrewers ;-)

monty N5ESE

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