Ham To Ham #12 - September 1996

73's Ham To Ham column

c/o Dave Miller, NZ9E

7462 Lawler Avenue

Niles, IL 60714-3108

Ham To Ham is particularly well-stocked this month, so we should get right into it. Just a brief note to say that this month we mark one year of Ham To Ham...thanks to all of the contributors who've made it possible. As we embark on the second year of the column, I'd like to invite all readers to keep sending in their favorite tips, ideas, suggestions and short cuts...without your input, we couldn't continue to achieve our goal...many ideas passed on from many hams to many other hams...not just my own soliloquies. Having said that, however, here is one of my own "inventions" that I thought you might like to hear about...but needn't stop there, feel free to go ahead and make one for yourself.

Just the right tool!

It's often been said that having the right tool for the job is half the battle! It's also true that a reasonably good assortment of tools is something that just about every ham and electronics hobbyist needs to enjoy the pastime to its fullest. Even today, when most of us buy many things ready-made, there are still those times when we find ourselves building those little extras that no one seems to offer anywhere else.

I've built any number of these electronic accessories over the past 40 years in the hobby, but this tip isn't about building an electronic circuit...not exactly...rather it's about making a tool that will help you in building electronic projects in the future.

I know you're thinking, "make my own tools...no thanks!" Well I'm not usually the type to consider making my own tools either, that's definitely not my primary interest in electronics, but this tool is different. Follow along with me and you'll see why...plus it's not all that difficult to fabricate - otherwise I certainly wouldn't have been able to do it! I've never seen one like it offered by any of the manufacturers who normally supply tools to the electronics hobbiest market, so as such, it qualifies for my own personal test of build-or-buy, which is: "if it's already made, I'm probably better off just buying it, but if it's not, then perhaps I should consider making one myself!"

Like most hams, I find myself using a great many of the 1/8" (3.2mm) miniature and the 3/32" (2.4mm) sub-miniature phone jacks on all sorts of different projects. These are the common panel mount variety of small phone jacks sold by Radio Shack (Registered), and others, for bringing audio - and any number of other signals - into and out of a piece of equipment.

They're great; they're inexpensive, do the job, are easy to wire, and on and on. The problem I've always run into, however, is in how to tighten down those tiny slotted nuts that are used on these jacks, so that they aren't ruined, physically or appearance-wise. Sound familiar? Most of us simply end up using a pair of ordinary pliers, or perhaps a very small straight-blade screwdriver, in an awkward attempt to tighten down the tiny mounting nuts on these little jacks. I almost always ended up marring the slotted nut itself, or the panel behind it, or both! I've done a pretty good number on some of these over the years...but not any more!

When faced with a problem such as this, I've always found it best to sit back and try to

imagine...if I had the perfect tool to use on this, what would it be?

That approach usually works, and in thinking about this one, I finally came up with what I call the Slotted-Nut Tightening-Tool. It's shown in the mechanical drawings of Figure 1 and 2, and in Photos 1, 2 and 3.

Here's what I had pictured: the slotted-nuts used on these jacks would require a tool of the correct diameter, with the correct size of mating pins (or projections) built into its end. It would have to be made of a material that's harder than the material that the nuts themselves are made of, and it should be reasonably easy to grip. With these basic parameters in mind, I began to develop the two tools shown.

Oh, that's right, you'll actually need two tools - one for 1/8" jacks, another for the 3/32" variety, but the 1/8" one is probably most often used, so it would be the best one to start with (the 1/8" tool can also be used on some miniature toggle switches that use the same type of slotted-nut for their mounting). And it's for this reason that I'll describe the 1/8" tool specifically, but most of what is said will apply to the smaller diameter 3/32" tool as well...if you decide to make both.

The slotted-nuts used on the miniature panel jacks appear to be made of a nickel-plated brass. The first prototype tool that I made for myself was also brass, but I wouldn't recommend using a material that soft for the finished tool, because it's too easily damaged - that particular one was strictly a prototype. Once I had proven to myself that the tool dimensions were correct, Bud Hollibaugh, a friend who's also an accomplished machinist, made several more for me out of steel. These have proven to be very serviceable. Tool-hardened-steel isn't really necessary, just garden variety steel is fine, since those slotted-nuts you'll be using it on aren't made of a very hard material.

Following the dimensions shown in Figure 1, the steel rod should be about 5" long for an easy grip and good control. It's made of 5/16" (.3125") diameter steel rod with a 5/8" long 7/32" (.221") hole drilled directly in the center, this can be the tricky part. If you can locate a section of hollow steel tubing with these dimensions instead - such as steel fuel line tubing - it will make the job much easier for the average home constructor. Solid rod perhaps has a little bit better"feel" to it, since it's heavier, but tubing will work as well dimension-wise, as well as from the stand point of the basic end result.

Filing or grinding down one end of the tubing, so that two "male projections" remain, is the only other critical part. Take your time. Follow the dimensions in Figure 1, with the tool clamped tightly in a bench vise, you should have little trouble matching up the projections on the new tool with the slots on an 1/8" panel-jack nut.

That, of course, is the final determining factor, to make the tool mate as closely as possible with a representative sample slotted-nut.

The remainder of the tool's "handle" can be covered with rubber tape, heat-shrink tubing,

appropriately-sized cable jacket, or whatever you might have, to add some "grip" and "cushion" to it. If you have or know someone with a lathe, a knurled handle gives it that final professional touch.

In everyday use, the slotted nut is started onto the jack with your fingers, as you've no doubt always done, and only the final tighening for installation or for initial loosening for removal, is accomplished with your new tool. It works like a charm, and like so many things, you'll wonder how you ever did without it for so long!

By the way, Bud and I tried a couple of other things. He made up one tool with the proper

dimensions on one end for the 1/8" slotted nuts, and then turned it down for the 3/32" nuts on the opposite end. It looks great and works fine, but I've found it somewhat uncomfortable to use because it always has projections (one end or the other) biting into the palm of my hand from the end that's being used as the handle - one of those ideas that's pictured better than it actually works in real life!

Another variation, in the interest of simplicity, was to take a fairly wide, flat-blade screwdriver and simply notch out the material from the center of the blade, leaving two projections that fit over the slots of the slotted-nut. Again, it works, but doesn't seem to work as well as the tool described in the main body of the article - it can slip off too easily and damage the nut or the panel.

In my own experience, I've found that using the suggested configuration shown in Figures 1 and 2 works best, and then one tool for each individual size of phone jack, ie., one for 1/8" and another for 3/32" jacks.

This is the sort of item that you'll probably only ever need one of (for each size), and it should last nearly forever if it's made as shown. You'll thank yourself over and over again in the future for spending the small amount of time needed to make one of each of these now.

I must reserve the copyrights on multiple quantities of the tools shown here and for their

commercial manufacture and marketing, but readers of this column should feel free to duplicate individual pieces for their own personal use.

DE Dave, NZ9E

Measuring up!

Speaking of tools, here's one from Peter Bergman, N0BLX of Brainerd, Minnesota:

"Here in the U.S., we've been very slow in accepting the metric system into the general population, yet in ham radio circles, we use metric terminology daily. For measuring wire antenna lengths and coax cable multiples, I often thought that it would sure be nice to have a tape measure that read out in metric - as well as English - graduations. I finally found a company that makes such tape measures, Stanley Tools of New Britain, CT 06050. I have one of their No. 30-575 (7.5 meter/25 foot) steel tapes, and have my eye on their No. 34-827 PVC coated fiberglass 30 meter/100 foot jobs...Santa, take note!

Most of the big "super home centers" don't seem to carry metric tapes, but if several radio club members can get together on a single order, you might try one of the smaller, family-owned hardware stores to see if they can special order some of the Stanley tapes - or the metric replacement blades - that are shown in Stanley's catalog. It can make your next antenna project go much more quickly and with more confidence that everything has been measured out correctly."

Moderator's note: I have an inexpensive 25 foot locking power tape made by Trophy - their No. 21925/T - that has continuous markings in centimeters, as well as in feet and inches, and Peter is right, it does make measuring for ham radio related cuts a good deal easier.

Well grounded...continued

Last month, I talked about improving the RF grounding properties of ham equipment enclosures and covers, and I referrred to the Alinco DR-1200T as an example. I picked it (as opposed to picked "on" it) because I own a couple of them, and have had the opportunity to work on a couple of small problems I've run into. I noticed that in the wintertime in Illinois, when the air is very dry, the high-voltage static build-up that can be generated by sliding across an automobile's synthetic seat cover, can cause the DR-1200T to "reset" its memories when the mic connector is touched. Fortunately, it didn't do any more damage!

When I examined the mic connector grounding technique on the inside of the radio, I felt that it might be improved by taking a couple of additional steps. Those steps are pictorially shown in Figures 3A and 3B.

First, place a dab of solder on the display shield tab, looking at the radio's top, on the control printed circuit board, rather than depending upon mechanical grounding connections only - see Figure 3A. Don't overdo this step, you may need to remove the shield sometime in the future, and it's not a good idea to go overboard!

Next, from the bottom of the radio, solder the microphone connector grounding ring to the shell of the microphone connector itself. The nickel plating on the connector should be scrapped-off at the point of soldering, and a small amount of solder paste used, to insure a good alloy-bond. Also shown in Figure 3B is an added short insulated wire from the microphone connector grounding tab directly to the circuit board's corner (ground) mounting screw, via a toothed soldering lug. This eliminates any ground impedance in the traces on the control PC board, and permits any static discharge to take the shortest possible path to chassis ground.

These two easy modifications should help to protect your DR-1200T's "innards" from unexpected zaps from the outside, at least they did on mine.

DE Dave, NZ9E

The great equalizer

From William Thim, N1QVQ of Broad Brook, CT:

"If you find an inexpensive audio equalizer at a garage sale, flea market or hamfest, latch onto it and try inserting it between you transceiver's audio output jack and an external speaker. It can make a world of difference in improving the intelligibility of many signals you'll run across on the ham and shortwave bands.

Since the human voice centers around the 1,000Hz mark, bring that control up first, then adjust the other equalizing bands for the best clarity of overall sound. You can often eliminate much of the noise or other disturbing background, while accentuating the intelligibility of the speech range. The more bands the unit has, the better. It won't replace a good DSP for noise and hetrodyne reduction, but it can make a very worthwhile difference on a minimum budget."

Moderator's note: If you do have a DSP, try an audio equalizer after it (as I have) and you'll probably find that it enhances the DSP's audio as well. Often too, a second speaker located in another part of the room, will make some signals "pop out of the mud" better than a single speaker alone. Varying room accoustics, and your own hearing "curve", makes experimenting with various speakers and equalizer settings an inexpensive and intriguing continuing project.

Warm-up your rotor

From Richard Mollentine, WA0KKC of Overland Park, KS:

"It's not a bad idea to think about now, while the weather is still agreeable. In bitter cold weather, an antenna rotor may tend to bog down due to the grease on the gearing stiffening-up with the temperature extremes. We cold weather hams often have to wait for warmer, sunny days to coax our rotors into turning again! Working that weak DX station off the back of the beam isn't necessary anymore, if you install a magnetic automobile engine-block heater on the bottom gear-case of your rotor's housing, during nice weather.

The unit that I'm referring to is sold at many local auto parts stores or via the popular JC Whitney/Warshawsky catalog and is in the $18 to $25 range. It has a powerful permanent magnet on its base and a length of 120 volt AC cord for powering the heating element from a standard wall outlet. Simply stick it to the bottom portion of your rotor's casing and run the AC cord to a switched outlet. It will heat up your rotor's gear box to a "toasty" temperature in only 20 to 30 minutes time...just don't forget and leave it on when the outside temperatures rise much above freezing!"

Moderator's note: Nice idea, Richard. In my own case, the housing on my antenna rotor is a non-ferrous casting, so the magnet-mount block-heater won't work, in and of itself. It could, however, be strapped to the rotor's base using an aluminum strap or two, or roof-eve and gutter exterior heat-tape can be neatly wound around the rotor's base to warm-up the rotor's gear box in sub-freezing temperatures. You may have to experiment a bit with the idea to get it just right. Remember, however, don't get too close to the rotating top portion of the rotor housing or allow the rotating portion to rub against the heat-tape, the engine block-heater, or its AC cord. Be careful to follow all proper out-of-doors electrical practices if you need to extend the heater's AC cord or when plugging the heater into an exterior outlet. A ground-fault-interrupter outlet may be required by your local codes, please don't try to do without it. Even if the GFI tends to trip when you're on-the-air, your rotor's gears will probably be warm enough to turn easily for that particular ham radio session.

"S" meter readings exposed

From Klaus Spies, WB9YBM of Niles, IL:

"The following S-meter values shows the correlation between actual signal strength in microvolts at the antenna terminals of a properly calibrated receiver vs. the 'S' unit reading on that receiver. Note that there is an older 'ham' standard, and a newer 'world' standard. Both values are shown in Table 1:

"S" Units Old "Ham" Standard Newer "World" Standard

S9 50.00uV 40.00uV

S8 25.06uV 20.04uV

S7 12.56uV 10.04uV

S6 6.29uV 5.03uV

S5 3.15uV 2.52uV

S4 1.58uV 1.26uV

S3 .79uV .63uV

S2 .39uV .31uV

S1 .19uV .15uV

Table 1

Two current "standards" of S-meter readings relative to micro-

volts of input signal to the receiver.

Some of this information was heard on the Voice of Japan in March of 1994, the rest was calculated from their 6db per 'S' unit specifications."

Moderators note: Each 'S' unit is 6db more as you go up the scale from S1 to S9. 6db represents a doubling of the voltage, but it takes 4 times the power to do that. To go up two 'S' units, the transmitting station would have to increase its power from 100 watts to 1600 watts, or 100 watts over the legal limit! That, of course, is assuming that the receiver's 'S' meter is right on the money. That's why it's difficult to put too much credence in some of the reports received over the ham bands. This is another of Klaus' handy tables that you might want to clip and paste somewhere over your workbench or at your operating position.

The importance of self-control

From Peter Albright, AA2AD of Lakewood, NY:

"The primary purpose of a voltage regulator in a power supply, whether it's in an external, separate supply or in the ham transceiver/receiver itself, is to provide a source of stable, consistent voltage, either for reference or for powering the circuitry directly. Some circuits function quite well without power supply regulation and can afford to take power directly from the output of a power supply's output filter network, while others demand a more stable voltage or current for proper operation. It's always best to assume that the equipment designer knew which his equipment needed, and take any necessary measures to correct regulation problems that may develop, as soon as they're noticed.

There are several symptoms that can indicate a faulty or defective power supply regulation circuit. If a short exists in the regulator, the fuse will generally blow, even though other sections of the power supply circuitry may be functioning normally - some devices use a so-called 'crowbar circuit' to deliberatly blow the fuse in the event of an over-voltage condition.. More commonly, however, voltage regulators tend to open, failing to supply their regulated output; only rarely, in very basic regulator circuits, do they supply full, unregulated output voltage...which is fortunate, since some circuits wouldn't tolerate the full unregulated output without developing additional problems. For that reason, don't be tempted to 'by-pass' a failed regulator unless you're absolutely sure of what you're doing.

Here, then, are the common regulator configurations that might be found in ham power supplies and within the destination equipment itself.

The simplest regulator is a zener diode - in series with a current limiting resistor - from the power supply's output line to ground. Zener diodes begin to conduct at a set voltage, so that any excess voltage will be shunted to ground across the current limiting resistor, and the diode itself, by 'brute force'. Simple 'shunt zener regulators' like this are for low current demand applications only, and they provide no overvoltage protection in the event of a failure of the diode or its limiting resistor.

To enhance the current-carrying capacity of the simple zener regulator, it's quite common these days to use the diode as part of the base circuit of a higher-powered 'pass' transistor, with the primary current flow between the emitter and collector of that transistor, and the zener acting strictly as a low-current control element in the transistor's base. 'Pass' transistors are generally mounted on a heat sink for greater heat dissipation capabilities and can be paralleled - with appropriate equalizing resistors - for even greater current handling ability.

For a number of years now, voltage regulators have been available in handy-to-use integrated circuit packages. They range from the simple three-terminal packages - available in both fixed and variable voltage outputs - that we've all seen (and perhaps used), to multi-pin programmable IC's that are capable of many more options as far as voltage and current selection are concerned. A fully automatic battery charger with voltage sensing capabilities would be one example of the latter...like the one that I recently built for my own needs.

Just in case you're into 'older' wireless, I should briefly mention the 0A2 and 0B2 series of gas tube voltage regulators that might be found in some of these sets. They function in a similar manner to the simple zener 'shunt' regulator circuit mentioned first, and are also strictly low-current regulators. The pleasant pink-blue color is unmistakable in the back of a tube-type rig, when 'real' radios had to glow to be working!"

Moderator's note: Peter does a nice job (as always) of explaining the basic voltage regulators to be found in today's ham power supplies. Also note, that it's safest to disconnect the circuitry that's being fed the output of the supply when repairing and initially testing the defective voltage regulator circuit. The regulator - if it's doing its job - should put out very close to its correct voltage with or without a load on it...and if it isn't...at least you might prevent further damage to the secondary circuitry. Also, as Peter mentioned, the present day line of IC regulators is generally very handy to use, but be sure to follow the recommended input/output capacitor by-passing, along with any other special considerations, as stated by the manufacturer of the device. Regulator "chips" can oscillate under certain conditions, and in addition to not doing their job properly, can be a really tough problem to troubleshoot.

A sticky antenna idea!

From Chuck Wilson, N6MUJ of Baywood Park, California:

"My 1995 Volvo wagon came from the dealer with an antenna for the AM/FM radio stuck to the inside of one of the rear windows. In an attempt to maintain the no-outside-antenna appearance of the vehicle, I decided to try the same approach for a 2 meter antenna on the opposite inside rear window. I used two 19 inch lengths of 1/2" wide adhesive-backed copper ribbon, formed in a 'V'shape, opened at the bottom of the 'V', and fed with 50 ohm coaxial cable as shown in Photo 1 and Figure 4. Surprisingly, I was able to easily access the repeater some 15 miles away from inside of my garage with just my HT and my new 'V' antenna inside the car.

I later replaced the 2 meter HT with a dual bander, and the same antenna works well over the same distance on 440Mhz now as well. I'm not sure what the SWR is - and I'm not sure that I want to know - but I do know that it works and that's really the bottom line...especially when I found that I could hit the same repeater from 40 miles away and from behind the hills that block its 'radio view'. It's an idea you might want to try if the XYL says 'negative' to an outside antenna on the new family buggy!"

Moderator's note: If you have trouble locating the self-adhesive copper ribbon Chuck mentioned, Radio Shack sells 3/8" wide self-adhesive window "alarm" foil (cat. #49-502) and self-adhesive foil connectors (cat. #49-504), that might be worth trying. By the way, 440Mhz is the third harmonic of 146 Mhz, but a separate "V" for the 440 band - with about 6-3/4" of conductive tape in each leg - would most likely give even better results on that band. I would also only use low power - under 5 watts - into an antenna of this nature, both from an RF-in-the-car standpoint and from the standpoint of possible mis-match stress on the radio itself. I wonder how much the SWR would change with rain, ice and snow on the windows?

VHF harmonic bug spray

Richard Measures, AG6K, of Somis, California:

"Here's the solution to a problem that's often caused by VHF harmonic energy leaking out via the external cabling from your transceiver. If you experience TVI from your amateur transceiver, even while transmitting into a well-shielded 50-ohm dummy load this may well work for you. Try adding one or two VHF attenuator ferrite beads over each of the two active wires (hot and neutral) that make up the 120 volt AC line input.

Just in case you've not used ferrite beads before, they do not have to be in metal-to-metal contact with the wire that they're filtering to be effective, and in the case of the AC line cord, they definitely should not be. These ferrite products work by 'choking' the RF energy that's attempting to pass through the wire, and need only be around the wire's insulated outer covering to function correctly. The beads are generally rod-shaped, with a center hole large enough to pass the insulated wire completely through the bead's core, so the insulated AC wire is simply separated and 'strung' through the bead.

Additionally, it may also be helpful to add a 470pF, 1KV disc-ceramic by-pass capacitor from the AC line side of each bead to ground. Replace any two-wire AC line cord with a three-wire grounding cord, connecting the "green" or ground terminal of the new cord to the transceiver's chassis gound. This provides a low-impedance ground-return path for both the unwanted harmonic energy and the small 60Hz AC current that flows through the by-pass caps. If any exposed 120-volt AC connections exist within the radio when implementing this cure, be absolutely sure that they are contained within an insulated, well-marked covering of some sort."

Moderator's note: Ferrite beads and choke cores are available from Radio Shack retail stores nationwide (#273-104 and #273-105), All Electronics Tel: 1-800-826-5432, Amidon Associates Tel: 714-850-4660, Palomar Engineers Tel: 619-747-3343 as well as other sources. 1KV disc caps are obtainable from All Electronics Tel: 1-800-826-5432 and from Digi-Key Corp. Tel: 1-800-344-4539. All Electronics and Digi-Key also carry a number of pre-made, packaged RF Line Filters - at a slightly higher cost than doing-it-yourself - but they're often much easier and safer to use. Sometimes, simply wrapping a few turns of the AC line cord through a ferrite toroid core of sufficient diameter is all that's needed to quench VHF harmonics emanating from an amateur transceiver...try that as well. Other input/output cables to your transceiver might also benefit from being passed through a ferrite choke or core to suppress both in-band and out-of-band energy...it's very often a 'try it and see' situation."

And this ends another month of Ham To Ham...thanks to all who've submitted their tips, ideas, suggestions and operating short-cuts, you're the ones who make the column work. Let's hear from more of you...the more input that I have, the better the results will be, and the more we can expand the column's scope in the future. Send whatever you would like to pass on to the address in the masthead, sending them to 73's offices in Peterborough directly only delays their use here.

As always, many thanks to this month's contributors:

Peter A Bergman, N0BLX

3517 Estate Drive SW

Brainerd, MN 56401

William Thim, Jr., N1QVQ

50 Miller Road

Broad Brook, CT 06016-9676

Richard Mollentine, WA0KKC

7139 Hardy

Overland Park, KS 66204

Klaus Spies, WB9YBM

8502 N. Oketo Avenue

Niles, IL 60714-2006

Peter Albright, AA2AD

28 E. Summit Street

Lakewood, NY 14750

Chuck Wilson, N6MUJ

660 Santa Ysabel Ave.

Baywood Park, CA 93402-1144

Richard L. Measures, AG6K

6455 La Cumbre Road

Somis, CA 93066

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.