Ham To Ham #8 - May 1996

73's Ham To Ham column

c/o Dave Miller, NZ9E

7462 Lawler Avenue

Niles, IL 60714-3108

Spring is rapidly approaching and it would be nice to see more ideas and suggestions for those spring and summer antenna projects that we all have planned. What have you found that the rest of us could benefit from? As always, any "general" ham-related ideas are also very much welcomed...here are a couple of my own.

A "customized" connector

I recently needed a 7-pin male DIN connector to plug into the accessory socket on my Kenwood TS-430S in a hurry...they're not the easiest of connectors to locate! So instead, I bought an 8-pin DIN plug from Radio Shack (their # 274-026) and was able to cut down the center 8th pin far enough (using a pair of small, diagonal side-cutters) so that it fit nicely into the 7-pin socket on my transceiver. The spacing of the 7 remaining pins is the same as that of a true 7-pin DIN plug.

DE Dave, NZ9E.

A good tape for use inside electronic equipment

Some hand-held VHF/UHF transceivers come from the manufacturer with plastic tape laid across solder connections that might touch other conductive surfaces when the small circuit boards are finally "layered" together. After time, the tape and its adhesive dry out, literally turning to "dust". I've found that a suitable replacement tape, one that won't leave much residue when lifted up, is as near as your local drug store.

The type that I've been most happy with is made by Johnson & Johnson; it's their 1/2" wide waterproof First Aid tape. It's a cloth based tape, with serrated edges, and has an effective, yet non-gumming, adhesive backing. Of course it's intended to be used to secure a bandage around a wound, but it also makes a good general purpose insulating tape for use with low-voltage electronics. Since it's formulated to be waterproof, it doesn't seem to hydroscopic either (prone to pickup mositure from the atmosphere), making it suitable for use in radios that will spend most of their lives in a mobile or marine environment.

DE Dave, NZ9E.

Don't blow money away on blown fuses!

This is a good tip to keep in mind when troubleshooting a piece of ham gear that refuses to stop blowing the primary AC fuse, from Herb Foster, AD4UA, of Melbourne, Florida. Here's an easy way to test a piece of equipment that continually blows the AC line fuse, without having to keep feeding it those expensive little fuses.

Make up a trouble-lamp with well-insulated clip leads on the ends of the AC cord, instead of the normal 2-prong AC plug. Install a 60 to 100 watt standard 120 volt lamp into the socket. Leave the fuse-holder in which the fuse keeps blowing empty, and clip the trouble-lamp across it. When you apply power to the piece of equipment, the lamp will shine at near full brightness if the short in the circuit is close to zero ohms, a bit less if it's not right at zero ohms, but still fairly brightly. Once you've managed to clear the short by lifting components or opening circuits, the trouble-lamp across the fuseholder will glow very dimly when power is again applied, depending upon the amount of "normal" current that the device is actually drawing from the AC line.

Now you can disconnect the trouble-lamp and reinstall a good fuse, knowing that the fuse will more than likely "hold" this time around.

Herbert L. Foster, AD4UA

3020 Pennsylvania Avenue

Melbourne, FL 32904-9063

Moderator's note: Herb's suggestion works because a "cold" 120 volt lamp has very low resistance, and will therefore allow enough current into the troublesome circuitry if the short has been cleared, but not enough to cause harm if the short still exists, since it's "hot resistance" is acting to limit the maximum current. A 60 watt, 120 volt bulb will be 15 to 16 ohms cold, a 100 watt 120 volt bulb about 9 or 10 ohms cold. It's a good way to dynamically test a piece of equipment without causing further harm, just make sure that everything is well insulated - as Herb mentioned - and that you stay clear of the 120 volt circuitry anytime the device is plugged in.

Measuring PEP

In the "old days", an amateur could determine his or her legal transmitter power by simply multiplying the anode voltage of the final amplifying stage times its current (the DC power input to the final transmitter stage), and as long as that figure was kept under the maximum allowable, that was all that the FCC expected the individual to know. It's not quite that easy today.

The FCC now expects an amateur to keep their PEP (Peak Envelope Power) output under a certain maximum, depending upon the power restrictions of the license class and within the band that's being used. It's 1500 watts PEP for most operators on most of the bands, but that maximum is only 200 watts for everyone in Novice 80, 40 and 15 meter sub-bands and for Novice class licensees within the 10-meter band. Novices are permitted only 25 watts PEP on the 1-1/4 meter band and 5 watts PEP at 1270MHz. All classes of licensees are restricted to 200 watts PEP throughout the 30-meter WARC band. It's 100 watts PEP for all beacon stations and 50 watts PEP within the 70 CM band in certain geographical regions. Refer to a current copy of the FCC rules for the specifics on any of these figures.

The point behind all of this is that we can't just say "I'm running well under 1500 watts PEP so I'm safe". You're expected to know that you're within the legal limit, based upon your class of license and band of operation, and here's the way to do it.

PEP, or Peak Envelope Power, is the average RF power being fed into the antenna's transmission line (down at the shack), during one RF cycle, at the peak of the modulation envelope, with an SWR of 1:1 and under normal operating conditions. The most accurate way to measure PEP is with a monitor scope, coupled to your transmission line, and terminated in the line's characteristic impedance (usually 50 ohms). The presentation on the scope face will be a peak voltage, so it's averaged by multiplying its value by .707. That answer is then squared and that result divided by the 50 ohm transmission line impedance to get actual PEP power in watts. Sounds confusing, but here are some examples that might help clarify the description. I'll start by assuming 1 volt of RF is displayed on the scope, then 10 volts and so on:

1 volt times .707 = .707 and .707 times .707 = .5 divided by 50 = .01 watts PEP

10 volts times .707 = 7.70 and 7.07 times 7.07 = 50 divided by 50 = 1 watt PEP

22 volts times .707 = 15.554 and 15.554 times 15.554 = 242 divided by 50 = 4.84 watts PEP

50 volts times .707 = 35.35 and 35.35 times 35.35 = 1,250 divided by 50 = 25 watts PEP

70 volts times .707 = 49.49 and 49.49 times 49.49 = 2,450 divided by 50 = 49 watts PEP

100 volts times .707 = 70.7 and 70.7 times 70.7 = 5,000 divided by 50 = 100 watts PEP

140 volts times .707 = 98.98 and 98.98 times 98.98 = 9,800 divided by 50 = 196 watts PEP

387 volts times .707 = 274 and 274 times 274= 75,076 divided by 50 = 1500 watts PEP

1000 volts times .707 = 707 and 707 times 707 = 500,000 divided by 50 = 10,000 watts PEP

Table 1

The important FCC peak power limitation points are shown in bold print.

To calibrate your scope for for 100 volts peak, put 100 watts into dummy load, with the scope in line, by adjusting the transciever's CW key-down output while monitoring a wattmeter of known accuracy (some transceivers and dummy loads have an output wattmeter built right into them). 100 watts average into 50 ohms comes out to 100 volts peak (an interesting coincidence of numbers); Ohm's Law tells us that voltage is equal to the square root of the wattage times the resistance. 100 average watts of power times 50 ohms equals 5000, and the square root of 5000 is 70.7 (average voltage). 70.7 times 1.414 (1.414 is the multiplication factor that's always used to convert average to peak) = 100 volts peak voltage. Take a second to look it over again, don't get average and peak confused nor power and voltage mixed up. Also remember that "normal" wattmeters read average wattage, and the FCC wants us to know our PEP power output. Scopes will read peak voltage, and once the scope is calibrated correctly, you can use Table 1 to determine the PEP wattage from the peak voltage that you've read on the scope.

Also notice that the relationship between peak voltage measured on the scope and PEP power is a logarithmic, rather than a linear one. When the voltage doubles, the power increases by a factor of 4 to 1. When the voltage goes up by a factor of 10 to 1, the power increases by a factor of 100 to 1.

There are also peak-reading wattmeters commercially available to us as hams, but using a scope is the most accurate way of determining PEP power and, it's the only way to check the accuracy of a PEP meter. It's a good idea to be aware of (and practice) the "scope" method, just in case the legality or your PEP power output is ever questioned by the Commission.

Ken Guge, K9KPM

1107 E. Woodrow Avenue

Lombard, IL 60148-3126

A "Different" chimney-mounted antenna

Bill Thim, Jr., N1QVQ, of Broad Brook, Connecticut has a very "different" approach to a stealth chimney-mounted HF long wire antenna. Here's a suggestion for hams or SWL's living in a condo or other development that prohibits the installation of "visable" outdoor antennas of any type. Wanting to have a long-wire antenna that was totally invisable, and having a chimney made of brick and mortar, I started out at the bottom of the chimney, where a good ground is available, and laid #22 wire into the mortar joints between the bricks (see Figure 2). I used a zig-zag pattern as large as the chimney width permitted, then applied another "cover-up" layer of mortar on top of that. Upon reaching the chimney top, I dropped the wire through an unused flue pipe for entry into the house. The average two-story chimney can accommodate 250 to 500 feet of wire - depending upon the width of the zig-zags - by using this technique...and it's completely invisable except for a few inches at the base and a few inches at the very top. I was able to end up with nearly 500 feet of wire, which, via an antenna tuner, allowed me to copy all of the HF bands from 160 to 20 meters with surprisingly good results.

William Thim, Jr., N1QVQ

50 Miller Road

Broad Brook, CT 06016-9676

Moderators note: Bill also mentioned, that in his case, he had to get management's approval for the "tuck-pointing" work, but in areas where single family detached homes are the norm, that probably wouldn't even be needed. Bill hasn't used his stealth antenna for transmitting, but it should be usable on at least some of the HF bands, with the proper tuner in line and at reduced power levels. As he also pointed out, it's certainly a lot better than no antenna! I wonder what the radiation pattern would look like on 20 meters?

A cure for intermittent connectors in today's radios

On the subject of manufactured connection failures, Richard Measures, AG6K, of Somis, California, offer this very good tip. The sub-miniature push-on, crimped-on coaxial connectors, used in many ham transceivers to interconnect RF or IF signals between circuit boards, can become intermittent or exhibit higher than near-zero ohms resistance on occasion. A poor connection at the center pin of these connectors can result in numerous intermittent output problems, in the case of a transmitter section, or the result can be varying sensitivity problems if the offending connector is somewhere in the receiver's circuitry. The crimp-on pins in these connectors have a tin-plating, which, when crimped against the copper inner conductor of the sub-miniature coax, can create a dissimilar-metal electrolytic action that eventually turns the crimp connection into a semi-insulator.

Deftly soldering the tiny end of these connectors, without damaging the coax cable inside, can be more problematical than some may want to risk, so another solution may have applicability if you're in that category. GC Electronics - and others - makes a conductive paint, called Silver Print R - or other brand-name - that can often be sucessfully used in these cases. It's normally sold through electronic component dealers, locally or via mail-order. The silver conductive paint can be applied to the tip of the tiny coax connector by using a straightened-out paper-clip, "coating" the tip junction of both the protruding wire and the connector pin-surface so that good contact is once again restored, following its prescribed curing time.

This same scheme will often also work for intermittent or high-resistance crimps on the small multi-pin control-cable connectors used in most modern rigs. The suspected female pin on one of these small connectors can usually be removed fairly easily by first carefully removing the connector, then depressing the tiny "locking tab" - accessible through the rectangular hole over each pin - with a scribe or small jeweler's screwdriver - and finally carefully slipping the pin back out of the connector body itself toward the wire's entrance. Don't pull too hard, or you may break the wire off completely. If the "locking tab" is depressed enough, the pin should able to be extricated fairly easily. Again, a small amount of some conductive silver paint can be applied to the crimp connection with a straightened paper-clip, alowed to dry and the pin inserted back into the connector. Don't forget to bend up the little "locking tab" again before inserting the pin back into the connector. You should hear or feel a very slight "click" as the tab engages upon re-insertion of the pin into the connector body.

Richard L. Measures, AG6K

6455 La Cumbre Road

Somis, CA 93066

Moderator's note: Unless a crimped connection is so tight that air is unable to reach the two conductive crimped-surfaces, the electrolytic action that Rich speaks of is virtually inevitable, especially in areas of high humidity situations such as might be found in a mobile installation. There are very well applied crimped connections (partly dependent upon the design of the connector itself), but not every one of them can be assumed to be of that type.

Rich is a well-known author of numerous tips and equipment modification suggestions - perhaps most noted for his diligent work on HF amplifier parasitic suppression problems. Rich has delved into a number of modern transceivers and ferreted out the problematical areas in those radios and it's with much appreciation that he makes his contribution to this column this month. Watch for others from AG6K in the coming months. Thanks Rich.

Testing transistors with the engine running!

This month, Peter Albright, AA2AD, of Lakewood, New York, offers another of his handy tips for

quickly testing transistors in-circuit. The first "quick tip" that appeared in this column dealt with

testing transistors statically and out-of-circuit, but it would be handy to do some preliminary

testing without removing every transistor from the board! Here are some tips for locating

defective transistors while they are still mounted on the board. The tests are run with the case

opened and power applied, so please BE CAREFUL. In additon to the danger to yourself, the

job of troubleshooting a piece of equipment can be complicated by one slip of the test probe; you

don't want to "create" additional circuit problems!

Good technicians always begin the troubleshooting process with careful observation. Is a

transistor too hot to touch? Remember to keep one hand in your pocket when you stick the other

into the equipment's guts, and keep both hands away from high-power R.F. circuits! Transistors

can become quite warm, even in normal operation, but generally not hot enough to raise a

blister. Conversely, if a transistor looks like it is designed to dissipate heat (a big case mounted

on a hefty heat sink is a good clue), but it's cold to the touch even after several minutes of

operation, it may not be conducting. Watch for those clues. Is there a resistor that's discolored

from excessive heat? Has any component become so hot that the board is discolored? It may

be normal, or it may be another clue.

After careful visual inspection, it's probably time to break out your trusty voltmeter. By the way, a

digital voltmeter is generally better for these tests because of the often small relative differences

involved. You'll see what I mean.

Transistors that are conducting normally show predictable voltage patterns. Specifically, the

voltage drop between the emitter and base of a silicon transistor should be between 0.6 volts

and 0.7 volts (about 0.3 volts for a germanium transistor). The voltage at the base should fall

somewhere in between the voltage at the emitter and the voltage at the collector. For an NPN

transistor, the collector will be more positive than the emitter. For a PNP transistor, the collector

will be more negative than the emitter. While the voltage difference between the emitter and the

base is 0.6 to 0.7 volts, the difference between the base and the collector is generally much

greater. Remember that these values are relative to each other. Here's a chart of six imaginary

transistors, showing logically possible voltages for each, relative to ground, that you're likely to

find on a good transistor - one that's conducting normally. Note that these patterns do not apply

to a good transistor acting as a switch in the "off" mode. Also, transistors acting as higher power

R.F. amplifiers may check somewhat differently. But the chart does give you a good idea of the

viability for the bulk of the other transistors you're likely to find on a board.

NPN

-------------------------------------------------

e + 2.0 e -12.0 e - 0.5

b + 2.7 b - 11.3 b + 0.2

c +12.0 c - 3.8 c +48.0

PNP

---------------------------------------------------

e +12.0 e - 3.8 e +48.0

b + 11.3 b - 4.5 b + 47.3

c + 2.0 c -12.0 c - 0.5

Remember, the chart shows typical voltages measured with respect to ground, so don't expect

them to be exact in any particular circuit that you might be troubleshooting. Again, what we're

looking for here are indications of parameters that are grossly wrong.

Often it's easier to simply measure the voltages across the legs of the transistor, as opposed to

measuring one junction to ground. If you can identify the emitter, and put one voltmeter probe on

that lead, you will measure about 0.6 volts to the base with the other voltmeter lead; the meter

will measure a greater differential to the collector. The polarity of the voltage will tell you whether

the transistor is NPN or PNP; you can often identify the lead configuration of a good transistor by

the voltage differences on these three junctions. Again, we're looking for relative differences

across the device itself.

Although some physical lead configurations are more common than others, you can never

assume that the lead configuration on two transistors is the same, just because they happen to

look alike. The transistor manufacturers have done that just to keep us on our toes!

Peter Albright, AA2AD

28 E. Summit Street

Lakewood, NY 14750

Moderator's note: Peter offers some good, practical advise in his treatment, advise worth hanging

onto. As before, it's probably worthwhile cutting this information out and keeping it handy, for the

next time you're faced with an involved troubleshooting job. A small plastic card file, with tips like

these on the cards, will save you additional time and frustration trying to remember when and

where you saw the information you need.

An aluminum soldering technique

This is a method of soldering to aluminum sent in by Klaus Wolter, N8NXF, of Ann Arbor, Michigan...you might give it a try sometime. It's possible to solder to aluminum without the need for special solder or equipment. Here's a technique that I've used several times with success:

1.) Carefully scrape the area to be soldered so that it's good and clean, and so that fresh, raw

aluminum is exposed.

2.) Aluminum carries away heat very rapidly, so you must use an iron that's hot enough to keep

a ball of solder molten once it's in direct contact with the aluminum.

3.) Firmly and consistently "scrub" the area on the aluminum to be soldered, then slowly apply

regular 60/40 rosin core solder, trying to "rub it into" the aluminum with either a back and

forth or a circular motion.

4.) If all goes well, you'll begin to notice that some of the solder ball is sticking to the aluminum;

keep working the area until you've created the pad size that you want.

You should now be able to attach wires or component leads to this pad of solder. It's not easy, and it does require persistence and a bit of skill, but it can be done. Practicing on the inside of an empty aluminum beverage can will hone your skills in the procedure before trying it on a finished project.

Klaus Wolter, N8NXF

910 Pinetree Drive

Ann Arbor, MI 48103

Moderator's note: Klaus' idea does work on certain types of aluminum, I've used it myself in the past. It may not work on all varieties of chassis material, since what we singularly call "aluminum", can take on many, many variations in actual formulation percentages of other metals. I've also successfully used a soldering flux containing Zinc Fluoroborate, and Mono- and Di- Ethanolamine for soldering to some aluminums and stainless steels. One such product is manufactured by Henry Mfg., P.O. Box 155, Westville, IL 61883. Long ago I heard that the "big secret" to soldering to aluminum is to not give the raw aluminum surface a chance to oxidize, which it does immediately upon contact with the air, and that seems to be why Klaus' technique works when used with the persistence he mentioned. Be cautioned that a copper to aluminum solder joint may not have the strength of a copper to copper solder joint, and it may "change" its conductivity over time. Good long-term conductivity in any solder joint requires that there be an "alloy bond" between the metals involved...this may not always be the case between tin/lead solder and some aluminum formulations.

At the end of your rope?

If so, here's a tip from Robert Blacka, N2WSO, of Pennsauken, New Jersey that bears remembering when you you go shopping for new rope for that upcoming spring antenna project. I was browsing through my local Home Depot R home improvement center when I came across a variety of rope that immediately yelled out "amateur radio"...needless to say, I bought a couple of packs! The product is called "Camouflage Poly Rope", SKU # 71514 00012, and it's made by The Lehigh Group of Allentown, PA 18105.

It's reasonably priced, quarter-inch in diameter, rated at 113 lbs. working load and virtually invisable against a background of trees or other vegetation. Perfect for ham antenna work! Side-by-side comparisons between the "Camouflage" rope and standard white nylon antenna support line of an even smaller diameter confirmed the night-and-day difference in visibility to my eyes. Even if the background isn't vegetation, the "Camouflage" rope is tough to see in comparison with other solid-colored rope, because the human brain easily interprets straight lines of one color, but not of broken or random colors. The military discovered this decades ago and even Mother Nature herself has equipped many animals with a similar multi-coloring idea.

I've had several sections of Lehigh's "Camouflage" 1/4" rope out in the weather for over a year now, with no signs of deterioration. It costs between $3 to $4 for a 50 foot length, and appears to be conservatively rated by its manufacturer. It also appears to be a "seasonal" item, so ask about it if you don't see it stocked in your own particular area. It would probably find more widespread use among hams if it were available for sale at "hamfests", now there's another idea for all of you weekend entrepreneurs!

Robert Blacka, N2WSO

8275 Maple Avenue

Pennsauken, NJ 08109

Correction

Please note that in the January 1996 Ham To Ham column, pgs. 50 & 51, there were several errors in the schematic diagram for 4X1UF's ultra-compact CW QRP transmitter. The errors were in the emitter, base and collector circuits of the first transistor stage and a corrected diagram is shown below as Figure 1. We apologize for any inconvenience that this might have caused any builders. Izzy also noted that a fundamental - not an overtone - crystal must be used in this circuit and that you might want to give it a try on 15 meters as well, as long as a fundamental crystal for the 21Mhz band is used.

And that concludes another month of Ham To Ham. Thanks to all for sending in their suggestions, tips, ideas and short-cuts...how about you? We've all discovered "better" ways of doing the average, everyday things that each of us faces in the pursuit of our hobby. How about sitting down for a few minutes, jotting down your ideas and sending them to the address at the masthead? I'll acknowledge all contributions and give you an idea of if and when the tip will be used in the column. If it is used, Uncle Wayne's elves will send you ten bucks for your time and postage expenses. What a deal! I'll be back next month with many more worthwhile ideas.

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.