Homebrew Ham Radio Projects - Components

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Published on Tuesday, 12 July 2011 22:56

Written by David L Norris

Ham Radio has always been about building your own equipment.  Now, sure, you can study, get a license and go buy almost anything you need.  But historically that has not been the case.  When I was younger pretty much everyone had built a Heath Kit or Conar or some other piece of gear at one point or another and almost everyone had built their own antennas.  Kits aren't all I'm talking about.  Building something of your own design from scratch is a very valuable learning experience and I strongly encourage everyone to do this.

Sometimes building kits was to learn but often it was out of necessity.  Kits are often quite inexpensive compared to the prebuilt options and if you are careful and patient and follow the directions they are normally easy to build.  Easy to follow and inexpensive kits still exist and are amazing compared to old school kits.  You can find anything from simple meters up to full digital DSP HF-VHF Transceivers comparable to, or better than, any commercial factory-built rig.

The very first piece of electronic gear of any kind I built was a 2 Meter Heath Kit HM-2102 25W/250W Wattmeter in the late 1980s.  It was new in the box and had been sitting around unbuilt for some years.  So my uncle gave it to me to try and get me interested in Ham Radio.  Well, I was hooked.  I immediately started studying for my novice class license.  Afterall, I needed a license and a radio now that I had this awesome meter!

You can begin with a kit but you may find yourself needing to provide your own chassis and hardware to complete the kit.  Many kits only provide the basic electrical and electronic components and leave cabinetry and other details to you.  Sure, you can go out and buy all the parts you need new from a nice hardware store.  But that takes money and I'd bet most of you throw away all kinds of stuff all the time that would be hugely valuable in a homebrew project.

Regardless whether you are building your own design, building a kit or just providing your own custom chassis for a kit you will need a few things before you begin.  You will need tools, some hardware supplies and some electronic components.

Parts to Scavenge

• Sheet Metal chassis covers, brackets, shields, etc
• Screws & Nuts (Machine, Sheet Metal, not wood)
• Washers (Metal, Teflon, etc)
• Gears, pulleys, clutches, etc
• Rubber Gaskets, O-Rings, Seals, belts, etc
• Rubber Feet, spacers, shock absorbers, etc
• Brakes (felt, paper, etc) - adds friction to make a knobs more precise\
• Wire, wiring harnesses
• Connectors, plugs, jacks, etc
• Meter movements
• LEDs, lamps, etc that are easy to remove
• Potentiometers, High Power resistors, rotary encoders and other knob-like bits
• Knobs!  Plastic knobs to turn potentiometers, inductors, capacitors.
• Heatsinks, Radiators, Heatpipes (chunks of aluminum & copper with fins that conduct heat)
• Electrolytic Capacitors
• Transformers & Power Supplies
• Inductors, magentic coils, anything with enameled copper wire is invaluable.
• LCD Computer/TV Monitors (good bartering material with a TV shop, they usually cost $4-10 to fix if the screen itself is intact.  High resell value and low cost to repair.)

Parts to Buy

If you have other scavengers nearby ask them before buying new. Like me, they may have significant stores of NOS (new-old-stock) items they have scavenged from TV/Radio shops, fleamarkets, hoarders, etc.  They may be willing to barter with you; I know I will.  I have been known to give away parts that are interesting but not particularly valuable.  For instance, I have a box of 8088 CPUs which are utterly worthless to sell but they are a brilliant CPU to learn how CPUs work.  If nothing else its a good chance to see what types of things others scavenge to give you ideas on how to go about doing so.  And, hopefully, they can give you storage ideas to keep the space needed to a minimum.  The goal is to have useful parts on hand without spending much money; not to be buried in parts no one will ever use.

• Microcontroller, CPU, RAM, ROM or any other IC Chip (Frys!)
• Resistors (Newark, Digikey) - Buy 100 of each standard value/precision and you're set for years.  In bulk you're looking at $30 total for every possible standard resistor.  At Radio Shack you're looking at $20 for a pack of 50 with 43 values you'll never use.
• Capacitors (Newark, Digikey) - NOS is best.  If you must buy new avoid Korean high-density electrolytics.  There is a near 100% chance of failure on high density electrolytics unless you know precisely what you are doing.

• Inductors (Newark, Digikey, specialty shops) - Learn to make your own!  Its trivial and cheap.  (Enameled copper wire you scavenged above)

• Vacuum Tubes (Buy NOS from scavengers if possible, Russian-made if not.)
• Transistors (Newark, Digikey, Frys)
• Proto-Circuit boards (Frys)

Standard Electronics Components

This is a list of basic electronics components that I keep on hand at all times for experimenting and building simple circuits.  I also have a vast number of other devices on hand but I don't replenish those until I need more.

Resistors

Resistors come in standard values.  These values are based on a geometrical progression of the tolerance.  All resistors with a 5% tolerance have values spaced 5% apart.  10% and 20% resistors are fairly unheard of these days but were very common in the first half of the 20th century.  So you are likely to find them in salvaged items or older gear.  Here is a table of standard values that I suggest you keep on hand.  ¼W carbon resistors are sufficient for most circuits.  Sometimes you'll need a value not listed in my table and for that you can combine several smaller values at least until you can buy the exact value you need.  For example, if you need a 150kΩ then a 100kΩ + 47kΩ is only 2% off.

Capacitors

Your best bet is to grab an assorted parts bag from someone or somewhere.  Honestly, you don't need all of these values.  Which values you'll need are entirely dependent of the types of devices you build.  When in doubt, remember you can (almost) always combine smaller values effectively.  Tolerances on capacitors are pretty loose unless you're dealing directly with RF and usually you can adjust the other nearby components a little to make up for not having an exact value.  These tables may also help you select the correct type of capacitor for the function it will be performing.

Transistors

There is such an awe inspiring variety of transistors available you could spend forever looking through catalogs.  However, for most mundane purposes a few will suffice.  You will need to seek out some specialty parts for high power RF amps and odd devices.  But for day to day circuits I think this table will serve you well.  Most transistor applications are going to use NPN or their equivalent.  Sometimes you'll need a complimentary pair; for example, to drive a transformer such as an IF inter-stage amp you should be using complimentary pairs here.  These are usually low power situations.  The faster the device needs to switch the more likely you are to need more exotic devices like JFETs and MOSFETs.

Diodes

I'm not even going to bother listing every single part because it doesn't matter much and its like listing the names of all the stars in the sky.  Buy some rectifiers (e.g. 6A, 50V), buy some switching diodes (e.g. 1N914) and I will list the Zeners I keep on hand.  Zeners are used for voltage regulation and shunting (shunting: voltage gets too high and you shutdown the circuit; keeps things from exploding and/or catching fire.)

Integrated Circuits

This is just a very short list of useful ICs to have on hand.  I have a few hundred times more than this but these are a good start.

Just as an example, this inventory from a single storage box of IC chips I have on hand:

My list is not exhaustive.  I could type until the end of time and not cover half the things you might need.  I am utterly amazed all the time at the vast variety of things I've come across over the years.  Most people look at a device and see only the thin veil of the outside.  Me, I see through it for what it is: A big pile of parts that is eventually going to be obsolete.