Ham To Ham #6 - March 1996

73's Ham To Ham column

c/o Dave Miller, NZ9E

7462 Lawler Avenue

Niles, IL 60714-3108

SPECIAL 6-MONTH ANNIVERSARY COLUMN

Ham To Ham is now into it's sixth month of life within the pages of 73 Amateur Radio Today magazine, and the tips, suggestions and ideas keep coming in...good ones at that. Uncle Wayne and I had originally given the column six months to get off the ground, to see if it's what the reader's wanted, and we've made it! Please keep the ideas flowing this way, it's your column, I'm just acting as an intermediary and putting them all into one place, editing the texts for uniformity, but it's an open forum for everyone to share. In celebration of the 6-month mark then, the column is a bit longer this time, giving you more of the information that you've said you want, and also as a "thank you" to the many who've sent in contributions so far. Thanks also to Uncle Wayne Green for providing the forum.

By now, you can see the direction that the column is taking, so you'll know pretty much what we're looking for. But even if you'd like to see it take a somewhat different avenue, send me your favorite tip and let me know what other direction you feel that the column should be going in...I'll try to always keep an open ear for any serious reader-suggestions for improvements.

Poor solder joints

I've personally run into a number of poor solder joints, in well-known commercially-made ham gear, as have several friends of mine. The solution to these intermittent problems in all of these cases, was to simply re-heat - and perhaps re-wet - the offending connection. Re-wetting a solder connection is just another way of saying to put a bit of new solder on it as the connection is re-heated. If the connection looks mottled, ie., marked with spots or lumpy & dull, then removing the "old" solder with wicking-braid or a "solder-sipper", and applying all new 60-40 solder to the connection was the answer.

Just because a radio "came that way from the factory", doesn't mean that it was perfectly made. Here's part of the reason why. Between any two copper connections, such as the copper foil pad on a PC board and a copper wire or component lead attached to a board by a solder connection, there exists (internally) an alloy layer at the two junction points. In other words, there is: 1) the copper foil pad, 2) an alloy layer, 3) the solder mass itself, 4) an alloy layer and 5) the copper component lead or wire. This is true of every good solder-joint. If something happens to prevent that alloy layer from forming, at either copper junction, or if it degrades with time for some reason later on, then a high-resistance or an intermittent solder connection is the result.

What can cause a defective alloy layer? Any movement during the "plastic" phase of the solder cooling process is one reason. As solder goes through the liquid (melted) state to the solid (hard) state, there is also a "plastic" state, in all but one solder formulation. The length of time of the "plastic" state will vary with the respective amounts of tin and lead in the solder you're using or re-heating. Actually it's a plastic-state temperature range, ie., a range of degrees Fahrenheit in which the solder isn't liquid, isn't solid, but "plastic". "Plastic" here simply means "capable of being altered or changed." As an example, at the extreme end of the formulation-scale, there is 90-10 solder, 90% tin and 10% lead. 90-10 has a 700F "plastic" range, from approximately 4300F to 3600F. Any movement of either of the two pieces being soldered during that cooling range will result in a poor solder joint. At the other extreme is 10-90, 10% tin and 90% lead. It's "plastic state is from about 5800F to 4400F, or 1400F of cool-down range, when the solder is still "plastic". Movement anytime during this "plastic" state results in what's commonly called a cold solder joint. Insufficient heat at the joining point of the two copper pieces during the soldering process, can result the same condition. To make a good connection, the solder must go far enough into the liquid range, drop down through the "plastic" range and then enter into the solid temperature range without outside movement occurring. And those two good alloy layers must exist for the lowest resistance electrical connection to exist. If more than two wires or component leads meet, then a good alloy layer must exist between each, and the rest of the bulk of the solder mass forming the connection.

By the way, most of us use 60-40 solder, 60% tin, 40% lead, because it has the best "wetting" characteristics and that also helps to provide that good alloy layer. 60-40 only has a 90F or so "plastic state", from 3700F to 3610F, so it's also helpful from that standpoint. There is a

63-37 solder formulation, 63% tin, 37% lead, that has virtually no "plastic" state, it's called eutectic solder because the liquid to soild state is direct, that's the eutectic point. But that's the only formulation that skips over the "plastic" state.

Another reason why the alloy layer may not form properly is oxidation on either of the two copper metallic parts or some foreign substance on the parts that don't allow proper "wetting" and flowing of the solder. That's the prime reason why parts should be bright and "clean" looking and why only solders containing rosin-flux should be used on electrical connections. The rosin flux in the solder, or applied externally via soldering paste or liquids, "washes" the connecting copper pieces before the Alloying takes place. The flux is not a part of the connection itself, but rather it "floats" the surface-oxides from the two copper pieces and holds those impurities in suspension until the joint is alloyed. Remnants can then be cleaned away with a flux remover.

So why would a factory-made rig have poorly made solder joints? Perhaps the parts weren't clean enough when assembled onto the boards or the board itself was contaminated in areas, perhaps there was some movement of the parts during the "plastic" stage of the solder's cool-down period, perhaps not enough heat penetrated to the two copper connecting metals, perhaps the flux used wasn't doing its job, perhaps the solder formulation was off-specifications...any of these situations are possible. The issue is less one of "why" then, and more of "where", since the job at hand is to fix the intermittent, and finding the poor connection or connections will have to be the main objective. Why the connection from the factory failed is more academic than pragmatic once a piece of equipment is in our hands.

There are a couple of other interesting caveats to watch for in soldering, though admittedly one may not run into them very often. The first has to do with a connection heating, as large amounts of current pass through that soldered connection. All solder joints have some amount of finite resistance, but it becomes important when a connection must handle higher currents, such as in a high power linear's plate tank circuit; the solder connection can actually soften or melt if special precautions aren't taken. A higher melting point solder would be a 5-93.5-1.5 formulation, 5% tin, 93.5% lead, and 1.5% silver. This formulation raises the solder's melting point to about 6000F. Another "special" situation exists when soldering components that are silver plated. To prevent the silver plating itself from migrating, a high silver formulation solder can help. 96-4, which is 96% tin and 4% silver (no lead) will prolong the"wetting" time before silver migration takes place. It requires a higher melting temperature, about 4300F, but also provides a stronger connection. Radio Shack carries this under their part #64-025.

DE Dave, NZ9E.

Easy backyard coax cable protection

With Spring not too far away, here's an easy to impliment tip from Ken Guge, K9KPM, of Lombard, Illinois, for protecting a surface backyard coax cable from damage from pedestrian traffic and lawn mowing hazards. When I originally installed my 40-meter horizontal wire-dipole antenna in my backyard, the center-feed coaxial cable ran down the trunk of a large tree, across the grass to the house, and then through a small hole in the above-ground portion of the basement wall. Wanting to protect the coax from myself and other family members walking on it, as well as from other yard activities, I made a simple 3-sided wooden cover to lay over the top of the cable. It worked for a while, but keeping the wooden cover looking good with paint, and more importantly, keeping it from rotting underneath, became a too-often-avoided task!

While browsing through an office supply store one day, I spied the cable protection strip material used in many offices, to neatly hide across-the-floor cabling, and I immediately visualized it protecting my backyard above-ground coax instead. One brand goes by the name SL Waber "Cordgard" R and is usually available in 6 ft. or 15 ft. sections. It's basically a rugged vinyl casing that covers the entire cable, and has a curved top surface that greatly helps to prevent tripping, if someone doesn't happen to notice it running across my yard! Just as important, it requires absolutely no maintenance and should last for a number of years - even out-of-doors - before a replacement might be needed. It's a big improvement over the wooden cover that I was using before from the standpoints of protection for the coax, pedestrian safety and appearance.

Ken Guge, K9KPM

1107 E. Woodrow Avenue

Lombard, IL 60148-3126

Moderator's note: Good application, Ken. The same type of product could, of course, be used in the ham shack itself, if a cable or two are needed on the opposite side of the room from your ham station operating position, providing the same protection and safety that Ken has found that it does outdoors. It could also be run up a wall if a cable "drop" - both indoors or out - needs to hidden for protection or appearance purposes.

Extending the fun

Mike, N0ALJ, of Rogers, Arkansas is using this scheme to extend the fun of "reading the mail" from his off-the-air ham receivers out to his home's garage and patio. He writes, here's an idea I've used to enable me to enjoy my various radios in places other than just my ham shack. I've set-up a speaker in the garage so that I can listen to my favorite ham bands while I'm working on my HO train layout there. I've also extended a speaker out to the patio deck, so that I don't miss anything when relaxing out in the open air or working around the yard. I've also found that in the ham shack itself, a local extension speaker there can enhance the sound significantly. Figure 1 shows the simple circuit I've used to accomplish this, something that could most likely be duplicated, by even a beginning ham, in just an easy week-end.

The audio from my ham shack radios is routed through three DPDT toggle switches; when Switch #1 is in the local position, the audio stays just within the shack itself. In the remote position, however, the audio is available to be fed to the garage speaker, or extended on to the patio speaker, depending upon which (local or remote) is selected by Switch #2. The number of locations can be as many as you wish to have by simply adding more wire, switches and speakers. The final switch location should have the option of terminating into a 10 ohm, 1/2 watt resistor on the remote side of the last switch, then all speakers will be off but the feed source will still "see" a proper load.

At the ham shack end, a 1/8" miniature phone plug is plugged into the "external speaker" jack of whichever radio I want to listen to remotely, or an easily obtained adapter can be used if the radio requires something other than a 1/8" plug. You should be able to find all of the parts you'll need to duplicate this effort at your local Radio Shack R store.

Mike Schroeder, N0ALJ

402 North 38th. Place

Rogers, AR 72756

Moderator's note: Good idea Mike, the delegation switches can be mounted in small mini-project boxes, or they can be housed right in the cases that enclose the various remote speakers themselves. By using this form of "deligation", the absolute minimum amount of speaker wire is used, keeping costs down, and only one remote speaker can be on at a time.

Sure seal for outdoor connectors

Bill Thim, N1QVQ, of Broad Brook, Connecticut offers this tip for permanently sealing outdoor connections, such as those that might be used for coax, power, control cabling, etc. I recently had some work to do on my well and came across a power cable splicing scheme that could also be useful at times with coax and other types of cabling used for outdoor ham antenna work. Some home improvement centers (Home Depot R in this case) sell a splicing kit for submersible water-pump use that is truly water-tight when used as directed. After the splice is made electrically sound, the connection point is coated with a silicon-type of sealant, then a six inch long section of heat-shrink tubing is carefully slid up the cable to cover the joint and sealant. When the tubing is shrunk with a small torch or heat-gun, until the sealant can be seen oozing from both ends, you'll have a connection that defies the worst of elements without a doubt. The tubing supplied with the kit is large enough in diameter to fit over a PL-259 or SO-239, so it's just the ticket for ham antenna use as well. Once the process is completed, you'll have to cut the connection apart if you ever want to get into it again, because it is meant to be completely permanent!

William Thim, Jr., N1QVQ

50 Miller Road

Broad Brook, CT 06016-9676

Moderators note: Good find, Bill. Read the cautions on the label before using any silicone-type of sealant on antenna and other connectors though. Some sealants warn against their use directly on certain metals (in many cases, brass and copper). Perhaps wrapping the connection first with electrical tape, or a thin application of a flexible coax-seal product, to avoid direct contact with the metal, would offer enough protection to avoid the corrosive effects of some of these silicone-based sealants. Furthermore, if you are unable to locate the kit Bill mentioned, you might be able to purchase the essential parts separately and end up with basically the same end- job. It's a worthwhile process to remember next time you have antenna connections to permanently water-proof. Fast setting epoxy might also work in place of the silicone adhesive, but it wouldn't have any flexibility when cured, and expoxy often cracks if subjected to mechanical strain.

An emergency 12-volt DC power distribution system

Erling Gruel, WB9OJD, of Fond du Lac, Wisconsin sends in this nice layout for an emergency 12VDC UPS (Uninterruptable Power System) that he's using at his QTH. Here's an idea that's reasonably easy to duplicate for those who don't have a gas or diesel powered generator to allow them to stay on the air during an AC mains power outage. Emergency preparedness has been a long-standing traditional part of the amateur radio credo, and this one is economical, straight-forward and, I've found, very functional.

I was mainly looking for a means of powering my 50-watt, 2-meter solid-state transceiver, a couple of scanners, simplex autopatch, CB radio, some limited lighting and an elapsed-time 12-volt DC automobile clock (or an interval timer/clock such as the Radio Shack #63-884) so that I know how long the emergency back-up system has been running. Some of the newer 12-volt DC HF radios could also be powered from this set-up if transmissions are kept brief or minimum power is used.

The heart of my system is a wooden box, attached to the shack wall near my operating desk, approximately 8" high by 7" deep by 12" wide that contains all of the necessary metering, toggle switches, fuse holders and a 4-pole, double-throw relay whose 12-volt coil is normally held up by an AC mains-powered 12-volt DC power supply. When, however, the power fails, the relay drops and transfers everything normally powered by the station 12-volt DC supply to the 12-volt DC back-up system instead. A master cut-off switch disconnects the emergency back-up battery if the relay de-energizes for some other reason, or if I turn off the main 12-volt DC station supply. The emergency back-up battery is kept charged by a continual constant-voltage trickle charger, during the norm, when commercial power is available.

I've also extended the battery supply leg of the system into my garage, so that if the basement-shack back-up battery runs down, I can quickly and conveniently utilize my car's battery to keep the equipment going! The car, of course, can be started and backed out of the garage ahead of time, so that it will supply charging current to its battery, giving me virtually endless power....endless at least until the car runs itself dry!

From the garage to the basement ham shack, I used heavy Romex cable to keep the losses as low as possible, and I've terminated the cable in steel electrical boxes at each end, clearly marked as being 12-volt DC only. I have a cord and connector coming directly from my automobile's battery to the front grill, and an extension of this cable to get from the car's front grill over to the garage wall feed box. Whatever type of connectors you decide to use to impliment the system, they should not be easily mistaken for any other purpose and should be husky enough to carry the current that you anticipate that your particular system will draw under maximum useage.

I found that a marine-type of deep-cycle lead-acid battery works best for the basement back-up battery. Not including the battery - which will vary in price somewhat from one area to another - the whole system cost me under $100 to impliment...not a bad price for the extra sense of operating security that it provides. The drawing in Figure 2 pretty well shows my own particular set-up, but I'll be happy to answer any specific questions from 73 readers as best I can.

Erling A. Gruel, WB9OJD

434 Weis Avenue

Fond du Lac, WI 54935

Moderator's note: A 12-volt DC to 120-Volt AC inverter could also be included in your system for powering 120-volt AC only equipment, but of course, that would up the final cost. Also keep in mind that in any system like this, everything should be made easily and quickly disconnected, clearly marked and neatly installed, so that in an emergency, you'll waste as little time as possible having to "figure things out"! We all tend to forget the details if a system isn't frequently used. A diagram of the entire system, posted in both the shack and the garage, would no doubt be time well spent. Erling also mentioned that he's willing to supply more information to any reader having a sincere desire to duplicate his idea. It's nice when contributors are willing to specifically help others in similar situations, so please be polite and appreciative of the free assistance...and always include a SASE (self-addressed and stamped envelope) for a contributor's reply back to you..

SCR testing idea

Here's a suggestion from Herb Foster, AD4UA, of Melbourne, Florida on a simple method for SCR testing - In my experiences working on RCA television receivers on a part-time basis, I've come across an easy way to determine the proper operation of any suspected silicon controlled rectifiers in the circuit. It isn't "Hi-Tech", but it's worked for me everytime! All that you'll need to duplicate this method is a source of 12 to 20 volts DC, a digital multimeter and a 470 ohm 1/2 watt resistor. If the SCR happens to have a PIV rating of less than 12 volts DC, use that lower voltage, but most will not be harmed by the 12 to 20 range specified.

Completely remove the SCR from its circuit, connect the 470 ohm resistor in series with the device's anode lead, then to the DC power source. The sample diagram in Figure 3 shows the test circuit schematically. Connect the cathode of the SCR to the minus of the power source. Clipping the digital multimeter across the resistor, with the power source tuned "on" now, there should be no voltage drop across the resistor, because the SCR should not be conducting (or leaking). Now connect the gate of the SCR to the anode just momentarily. The meter should now read a 1 to 3 volt DC drop across the resistor if the SCR is conducting normally. Momentarily disconnecting the SCR's anode from the source voltage should again cause the device to stop conducting.

This simple test effectively checks the SCR for opens, shorts, leakage and the ability to fire normally and latch up, then return to its static state when the anode is momentarily opened...all you'll need to know about it. If it passes this test, then without question, it's good.

Herbert L. Foster, AD4UA

3020 Pennsylvania Street

Melbourne, FL 32904-9063

Moderators note: Herb has submitted a couple of good ideas to this column to date. Here's another suggestion to make remembering Herb's tip easier. Make up a cardboard card with a schematic diagram and description of Herb's testing steps on it; epoxy a 470 ohm, 1/2 watt resistor to the card over the schematic's resistor symbol. Then when you next need to test an SCR, you'll have all of the info handy (and even the correct resistor!). I've used this method for other little test circuits that I use only on occasion, and it's worked out well for me and my not-always-perfect memory! NZ9E.

This ends another month of Ham To Ham...and our goal of keeping Ham To Ham viable for at least six months. Thanks to all who've submitted their tips, ideas, suggestions and operating procedures, you've made it work. Let's hear from more of you out there. The more input we have, the longer the column will go on and the more we can expand its scope. Let me hear from you at the address in the masthead; sending your suggestions and ideas to 73's offices in Peterborough directly only delays their use since they have to be forwarded here.

We've all run into tips and short-cuts that we wish someone had told us about sooner, that's pretty much what we're looking for in HTH. Don't be shy, send in anything that you think might have value to others in the hobby. If your writing skills aren't your strong point, don't worry, I'll re-write your text so that it conforms to the conversational style that I'm trying to maintain for HTH...and be sure to look for a number of good new ideas here next month.

DE Dave, NZ9E.

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 all correspondence relating to this column to 73 Magazine's Ham To Ham column,

c/o Dave Miller, NZ9E, 7462 Lawler Avenue, Niles, IL 60714-3108, USA. All contributions used in

this column will be reimbursed by a contributor's fee of $10, which includes its exclusive use by 73

Magazine. We will attempt to respond to all legitimate contributor's ideas in a timely manner, but

be sure to send all specific questions on any particular tip to the originator of the idea, not to this

column's moderator nor to 73 Magazine.