K9GDT's Homebrew Notes  homebrew
 Circuitry  Existing & Original Design

    There's a wealth of information for ready-to-build projects or circuit design available from Internet based resources, parts manufacturers and other publications.  The RSGB and  ARRL (links open in a new window) publish some excellent books. One of my favorite is Solid State Design for the Radio Amateur, co-authored by Wes Hayward (W7ZOI)) and Doug DeMaw (W1FB-SK).  Another great book is Hayward's Introduction to Radio Frequency Design.

    One of the greatest sources of projects and RF design information is the ARRL Handbook (a.k.a. "The Radio Bible"). Consider ones from the early 60's to the most current edition.  Because much of the information is repeated from issue to issue, you won't need one for every year.  Acquiring every other issue will do the trick! Used Handbooks are readily available at hamfests for reasonable prices.

    If you're contemplating a project using vacuum tubes, consider handbooks going back to WWII. Should your project involve older tube technology such as those Jurassic 4 and 5 pin devices, collect even older ones.  There's some amazing information in those old books! They contain very detailed information about timeless items, such as antennas and transmission lines.

 Board Construction  Nothing I build ever works the first time!

    The last time I etched and drilled a printed circuit board was in the 1960s.  My original design needed several...well, all right, many tweaks before it would work properly.  Geeesh!  What a sorry looking mess it was!  There had to be a better way.

    The solution to this problem was simple:  Start out with a plain copper clad board and simply solder the parts to the copper side.  (Duh!)  The solid copper serves as an effective ground plane.  Circuit changes are easy.  There's no need to constantly flip the board over to see what's connected to that protruding lead.  Finding a suitable spot to hang a meter, scope or spectrum analyzer probe is rarely a problem. Troubleshooting is a breeze!

    We radio builders spend much of our available time working on our creations.  The irony is we don't communicate with each other.  Years later, I discovered that my construction technique was not so unique.  It had been given the name "Ugly Construction" and was in widespread use.

    This technique also works with integrated circuits.  Just lay `em down with the leads pointing up and solder away!  You can bend IC leads back (just once!) and solder them to the board if they need a ground connection.  Circuits using the ubiquitous Motorola 1496 chip and Mini-Circuits SBL-1 mixers are easy to construct this way.

    Be sure to solder the metal housing of any parts directly to the board at one spot.  Doing so will assure a reliable ground connection while providing some mechanical support.  Eligible parts include items such as RF/IF transformers, slug tuned coils, crystals, phono/coaxial jacks, and capacitor frames.  To keep component heating to the minimum, heat and tin the copper clad surface first.

    Need a shielded box?  (A good idea if your project has digital circuitry, multiple conversions, LO premixing, or a large IF gain block with a BFO.)  Simply cut up some PC board into appropriately sized strips, hold in place and solder a bead along the edges.  A 100-150 watt Weller solder gun is ideal for this task.  I recommend making the piece opposite the main board the last one to be soldered in place.  It can be easily removed to make circuit changes or repairs.  Also, the heat generated from the cover removal will be kept away from the circuitry.  Remember, polystyrene caps are adversely affected by even moderate overheating!

    Make the box dimensions smaller than the main board on two sides.  Holes drilled in the visible portion of the main board can be used for mounting the finished module.

    I get all of my copper clad board at hamfests.  There's always somebody selling scraps of board, often cut to the same size.  That's good because it will save wear and tear on your band saw's metal cutting blade!  The sellers asking price is usually very reasonable..  However, it's likely he got the stuff for free.  Make an offer for the whole lot. You could walk away with a near lifetime supply of copper clad for pocket change!

    After a while in storage, the unused boards will tarnish, turning an ugly dark color.  This is not a problem. Just get some Bar Keeper's Friend and follow the instructions on the container.  You will have a bright shiny board ready for soldering within several minutes.

 Test Equipment  It's a great time to be alive!
    It's very difficult, if not impossible to verify proper operation of newly constructed radio gear without some test and measurement equipment.  Here's some great news news for you: Laboratory grade T&M gear has never been more plentiful at reasonable prices.

    Allow me to explain.  Following the latest corporate fads, many companies have down-sized (dumb-sized) their engineering organizations, surplusing plenty of fine test gear in the process.  This equipment is showing up at hamfests in regions near once burgeoning electronics industries.  Much of it will carry a fairly recent calibration sticker.

    I'm talking about solid state equipment that's been meticulously maintained, not obsolete antiques employing vacuum tubes.  As much as I enjoy vintage radios, most of my boatanchor test equipment is gone.  I prefer spending my precious spare time working on radios, not maintaining test gear. However, I still have a GR 1205-B power supply (regulated HV/Bias/Filament) for supporting boatanchor radios.

    Do you remember when a Viking Ranger could be had for $30 or a fully accessorized Collins 75A-4 would sell for $120?  Well, those happy days are here for used test equipment.  Here are some prices I've seen during the last year for clean working gear:

    • Tektronix 475 200MHz Oscilloscope w/probes - $200 (almost followed me home)
    • Tektronix 465B 100MHz Oscilloscope - $250
    • H-P 331A Distortion Analyzer, mint condition, late s/n - $30 (followed me home)
    • H-P 5316A Universal Counter - $200 (followed me home)
    • H-P 8443A Tracking Generator w/cable - $250 (followed me home)
    • B&K 801 Capacitor Analyst - $24 (followed me home)
    • B&K 3011 2MHz function generator - $50 (followed me home)
    • Wavetek 3001 RF Generator - $150 (followed a friend home)
    • Tektronix 500 and 7000 series plug-ins - typically $50 to $100
    • Fluke DMMs - $50 to $80 (a model 79 followed me home)

    This affordable gear is so plentiful, I replaced my venerable SB610 station monitor with a Tektronix 2335 100MHz triggered sweep scope.  My friend Ron, K9KLT picked up a nice Elenco 40MHz triggered sweep scope for pocket change.  When you consider that a modern HF transceiver can cost in excess of $5,000, prices on quality used test equipment are indeed a bargain.
 Packaging  What to do with the ugly stuff!
 General Discussion

My earliest vacuum tube homebrew gear was usually constructed on a plain aluminum chassis. (I won't talk about the projects built on wooden boards with Fahnstock clips secured with nails. So don't ask!)  There were no control labels, cabinets, shielding or bottom covers.  This stuff was butt ugly and dangerous!   However, I was happy just to get the projects working.

Years later, I joined the 'Bud box and Dymo label' revolution.  Still, every project's appearance had a dull "sameness" suggesting it was an unfinished work.   Later, the tedious process of applying transfer lettering greatly improved front panel appearance.

I occasionally receive e-mail from folks curious about the packaging of the homebrew gear appearing at this web site.  The subject can be broken down into two basic elements: cabinets and front panels.

 The Cabinet

The cabinet for the 40m transmitter is from a surplus 70's vintage Hewlett Packard instrument.  The 40m receiver, 75 AM transceiver, and 600 watt linear amplifier were also built into junker instrument cabinets.

Instrument cases make ideal cabinets for homebrew projects.  They're usually several grades better than ones available from Radio Shack and TenTec. That quality is reflected in the pricing, too.  If you have any doubt, just check the catalog pages of industrial electronics distributors such as Newark or Allied Electronics.  Hewlett-Packard once sold plain cases in the back pages of it's T&M catalog.

The sometimes attainable objective is to build radio equipment at zero cost.  That's half the fun! For cabinetry, the next best thing to a free cabinet is to recycle the case of an old instrument.  One word: Hamfests! These instruments can usually be obtained for next to nothing.  They may be inoperative or missing accessories.  This means you can get them cheap!  I don't revere boatanchor instruments as I do BA radios.  So I turn them into radios without guilt or remorse!

There's another advantage to using old instrument cases for your projects.  A lot of the dirty work has been done for you.  There will be a line cord with a Heyco bushing or an IEC connector for a detachable line cord already installed for you.  There will be other items such as fuse holders, connectors, etc.  If you're lucky, you can use the existing power supply iron!

This is also a good opportunity to populate your "junque box" with the electronic and mechanical parts removed from the case.

I recommend searching for a case with a recessed front panel.  This will greatly enhance the appearance of your completed project once your new custom front panel has been installed.

 The Front Panel

The front panel for my 40m receiver was produced by a ham friend who is a professional graphics artist.  He imported my VISIO drawing into his program, tweaked it, then sent the file to one of his regular vendors for printing.  The end result is black epoxy ink silk-screened on light gray vinyl. The adhesive backed vinyl panel was placed over the original metal front panel.  While this attractive professional effort was done as a favor to me, it would have cost almost $100 to have a single panel made.  Ouch!

I tried a different approach with the 40m transmitter.  The panel was designed in VISIO and printed out on my old HP DeskJet 500.  The printout was placed between the 1/8" aluminum sub panel and an 1/8" piece of tinted Plexiglas.  The resulting "sandwich" is held together by the mounting hardware for the controls. The countersunk mounting hardware on the sub panel is hidden from view.

Working with Plexiglass is unforgiving of cutting or drilling mistakes. Ask me how I know!  For the 75m AM transceiver, I printed the front panel on my trusty old DeskJet 500 and took it to a local office printing/copy facility called Kinko's, where it was laminated. The laminated panel is held to a 1/8" aluminium sub panel by the control mounting hardware.  Again, the countersunk screw heads are hidden from view.  The small laminated strip above display was glued in place with Pliobond P141, available in 1oz. tubes almost everywhere.    November 12, 2014

The front panel for the 600 watt amplifier was too large to print on a standard 8½" x 11" sized paper.  So I took my VISIO file to work and printed it on a DesignJet 750C color plotter.  The printout was then laminated.  It is held in place by the mounting hardware for the power and mode switches, meter bezels, and four thumbscrews.

A word about the printouts... I use good quality 24 lb. bleached linen paper made from 25% cotton.  Ink doesn't smear and the paper will never become yellow with age.

About the meters on the 40m transmitter.  They're mounted to the aluminum sub panel. The visible portion of each meter extends just enough to fit snugly in the rectangular holes cut into the panel. Holes were cut on the printout along very thin guide lines using an X-ACTO knife.  (The work surface was an old piece of smooth marble.)  No meter holes were cut in the Plexiglas.

 Tooling  What do I need to package my project?
    • Drill press with a ½" chuck
    • Band saw with a metal cutting blade
    • Nibbler tool
    • Battery powered drill
    • File set - Don't forget that circular file!
    • Large countersink drill bit with a very large knob attached the the shaft.  (Used for deburring holes)
    • X-acto knife with a supply of #11 blades
    • Standard assortment of hand tools

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    November 12, 2014

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