Ham To Ham #39 - December 1998
You're Input is Always Welcomed!
73's Ham To Ham column c/o Dave Miller, NZ9E 7462 Lawler Avenue Niles, IL 60714-3108 USA E-mail: dmiller14@juno.com
It's the December issue again already, so Sue (KA9UCK) and I would like to take this opportunity to once again wish everyone a Holiday Season filled with peace, love and joy.
I would also like to encourage readers to keep sending in their tips, ideas, suggestions and short-cuts for a bigger and better Ham To Ham column next year. Just send your ideas to the address (postal or e-mail) shown above, and there's a good chance you'll see them in print in the coming year.
Keeping a cool watch What's perhaps the easiest way to destroy an expensive modern computer microprocessor chip? Heat! Today's computer microprocessors are compact, fast and reasonably robust, but they need to be kept cool to do all that they're called upon to do quickly. Most desktop computer microprocessors are fitted with a husky heat sink and a 12 volt DC cooling fan to help maintain a safe case operating temperature for the device - but lacking forced cooling, a high- speed processor can destroy itself pretty quickly via thermal runaway. But how would you even know if your processor's case temperature was too high? Perhaps, not until it was too late!
One day, the sleeve-bearing fan on my Pentium microprocessor (reg. trade mark) gave out without my knowledge. Fortunately, I noticed that the computer was behaving oddly before the microprocessor was damaged, but I was lucky! After that incident, I installed a ball-bearing fan for the processor (which will hopefully provide longer life) as well as a processor heat sink temperature indicator in the form of an inexpensive indoor/outdoor automotive digital thermometer.
I wanted a thermometer that would neatly fit on a standard 1-3/8" x 5-3/4" computer single-bay blank panel, and I found what appeared to be the perfect one at my local automotive supply store - it measured about 1-1/8" x 4-1/2". It was made for use inside of an auto or van, and came with an "outdoor" temperature probe coupled by about 10 ft. of small 2-conductor wire. I used this "outdoor" probe as my processor's temperature sensor, trimming the 10 foot interconnecting cable down to just what I needed to reach from the computer's empty front-panel bay to the processor's heat sink; I also installed a small 2-pin in-line connector in the cable. The remote sensing probe need only just touch the processor's heat sink, so I was able to put a small adhesive cable clamp on the socket rim that holds the microprocessor, to accomplish what was needed in the way of a tie-down for the probe. A spare 1-3/8" x 5-3/4" computer single-bay blank panel was then drilled to pass the remote sensor's cable, and the thermometer itself was attached to the panel via double-stick adhesive foam pads, to complete the modification.
The "indoor" position on the thermometer's probe selector switch now reads the computer's exterior case temperature (room temperature), and the "outdoor" position reads the heat sink temperature of the microprocessor itself, buried deep within the computer. The automotive thermometer that I found places the LCD display at a 45 degree angle, which makes it very easy to read even in subdued lighting. The electronics for the thermometer operate from a pair of built-in "AA" alkaline cells, and should provide a reasonably long service life (so the thermometer is on, even when the computer is off). I didn't feel the need to try adapting power from computer itself to run the thermometer, but I'm sure that it could be done if it was felt that it would be worth the added effort and expense. The 5 volt bus from the computer's supply could be tapped, and a simple series resistive voltage dropping circuit added if you prefer to be freed from ever having to change the batteries in the little digital thermometer. The added current drain of the thermometer is, of course, would be insignificant.
There are no doubt more elaborate ways of monitoring the temperature of the microprocessor's heat sink than what I've described above, but I was shooting for simple, inexpensive and easily accomplished ... which I feel that this answer was. A programmable audible alarm would be nice too, but that will have to wait for a later column. de NZ9E
Ahhh, middle-age! Here's some advice from Klaus Spies WB9YBM on how to deal with middle-age - in radio gear that is: "While much is written about both brand new and very old (antique) radio equipment, the most neglected group seems to be those radios in their 'middle years' ... and they can be a very attractive buy!
In the mid-seventies, there appeared a series of VHF transceivers for the 144MHz and 220MHz bands that were nearly identical, except for the front panel name plate. Clegg, Cobra and Midland all had 12-channel, crystal-controlled transceivers that can still be seen in many shacks, packet BBS's and repeater sites across the country. They've especially found homes in repeater usage because their receiver and transmitter boards are easily separated (for split receive/transmit sites) and like the famous bunny, they seem to just keep on goin'.
The unit pictured in Photo 1 is typical. It originally came equipped with a 4-pin connector on the rear apron, which was designed to provide easy access for adding a touch-tone (reg trade mark) pad or a discriminator output meter. Also, unlike the cluttered rear aprons of today's transceivers, there was plenty of additional room for adding connectors to bring signals in & out for frequency synthesizers and other useful add-ons ... pretty much as the owner deemed necessary.
Likewise, there was actually extra space inside the cabinet for carefully adding small PC boards for additional features, something that's nearly impossible to do in many of the current sets. If the extras are conscientiously built, they can actually be a bonus, rather than a hindrance, to resale.
Here are a few considerations to keep in mind if you decide to add-on to one of these transceivers. Obviously, every effort should be made to keep any add-on circuits reliable and low-profile, as well as making sure that any conductive surfaces are well insulated. It takes just a bit of carefully placed and secured waxed-cardboard to keep everything isolated, so that unforeseen shorts won't occur. Try to keep any add-on boards well away from existing RF circuitry, and digital logic boards should never be placed near low level audio stages where the clock pulses can end up being induced into your transmitted audio signal. A little time and effort in studying the problem at the onset (perhaps even sleeping on it) will pay big dividends.
Another advantage to middle-aged ham transceivers is their use of "standardized" (rather than specialty) components and semiconductors. There are almost always cross-reference equivalents available for the bulk of the parts used in these sets, and even more "modern" parts can sometimes be substituted if all other avenues for replacements fail. All in all, middle-aged ham equipment can be a very good buy, especially considering the fact that most of the initial purchase depreciation has already been assessed. So keep your eyes and ears open at hamfests, auctions, equipment trader publications, internet swap pages, etc. for these unsung bargains. See you the next fest!"
Do it your way! Here's a "current" kind tip from Herb Foster AD4UA: "If you're 'borrowing' 12 volts DC from your HF transceiver's power supply, and you've ever experienced a sudden, unannounced power supply shutdown, then maybe it's because your transceiver's power supply is being strained very close to it's limits. It's tempting to simply hook-up a number of peripherals across a transceiver's matching supply ... after all, it's just a few milliamperes here and there! It's so easy to loose count, but after some time, those few mils here and there add up! The result, of course, is a unceremonious shutdown of everything, and usually at the worst possible time (if Murphy has any say in the matter!).
My own answer to just this situation, was to buy a separate 3-ampere, regulated 12-volt power supply from Radio Shack (reg. trade mark), along with the parts shown on the schematic in Figure 2 from their parts peg-boards, and (happily) the problem has disappeared from my operating desk.
It's an obviously simple solution, but often one that we keep putting off until we see how someone else has done it. My new 3-amp, 12-volt supply feeds into a project box via a short length of #18 gauge lamp cord and a 3-ampere fuse, where it is paralleled off to six chassis- mounted, RCA phono jacks (use as many jacks as you think you'll need for now and the future). All of my 12-volt peripherals can now be plugged directly into the new 12-volt DC distribution box and easily connected and disconnected as desired. Use whatever style plugs and jacks that you wish, but the type specified are very inexpensive, fairly well-made, and will carry the peripheral current with little or no voltage drop. Of course the female connector should always be on the power supply side, and the male connector on the equipment side. Using only phono connectors with red plastic shells, or painting the connectors with red model airplane paint, will alert you to the fact that this is a power connector, not an audio cable.
Photo 2 shows you how mine turned out, but feel free to add as many frills as you think might be worthwhile (such as an LED to shown that power is being supplied to the box, or even a small, inexpensive panel-mounted digital voltmeter). There are some commercially-made voltage 'break-away' boxes on the market, but this one is a whole lot less expensive and it gives you the freedom to do-it-your-own-way!"
Murphy's Corollary: When all of your problems become crystal clear, that's the time when you need to begin worrying!
Many thanks, as always, to our loyal contributors. Remember, I'm always looking for interesting and innovative tips, ideas, suggestions and shortcuts to include on the pages of 73 Magazine within this column. Just jot down your thoughts and send them to the address at the masthead.
Those that accepted the challenge this month are:
Klaus Spies WB9YBM 1709 Dennis Apt. 3A Mount Prospect, IL 60056
Herb Foster AD4UA 3020 Pennsylvania Street Melbourne, FL 32904-9063
If you're missing any past columns, you can probably find them at 73's Ham To Ham column home page (with special thanks to Mark Bohnhoff WB9UOM), on the world wide web, at: http://www.rrsta.com/hth
Note: The ideas and suggestions contributed to this column by its readers have not necessarily been tested by the column's moderator nor by the staff of 73 Magazine, and thus no guarantee of operational success is implied. Always use your own best judgment before modifying any electronic item from the original equipment manufacturer's specifications. No responsibility is implied by the moderator or 73 Magazine for any equipment damage or malfunction resulting from information supplied in this column.
Please send any ideas that you would like to see included in this column to 73 Magazine's Ham To Ham column, c/o Dave Miller NZ9E, 7462 Lawler Avenue, Niles, IL 60714-3108, USA. We will make every attempt to respond to all legitimate ideas in a timely manner, but please send any specific questions, on any particular tip, to the originator of the idea, not to this column's moderator nor to 73 Magazine.