The Care of Power Supplies

By

Mitch Stern, W1SJ

This appeared in tile February 1999 (electronic) edition of the TSRC Newsletter of the Twin States Radio Club, Mike Maynard, WB1GRR Editor.

With all the high-tech toys out there, what can be so interesting about the lowly power supply? Well, when the power supply dies, many of the toys also stop working. Knowing how to maintain and service your power supply will keep you on the air, while others are scratching their heads.

Recently, I was on a trip and had the radios and power supply with me. One night, as I was about to connect the power cable from the supply to the radio, the cable slipped from my hand and the exposed negative lead brushed up against a power transistor on the supply. When the lead touched the transistor it produced a loud spark and the supply ceased to function. This meant no power for the HF, VHF and UHF radios, the laptop computer and the GPS! The supply had to be fixed!

Power supplies come in two general varieties: Linear and Switching. There are other types, but they tend to be rare. A linear supply uses a transformer to drop 120 volts to around 6 volts AC, which is rectified with diodes, filtered with capacitors and regulated with transistors and/or IC's. A switching power supply, or switcher, rectifies the 120 volts directly and voltage is dropped and regulated by chopping or oscillating the voltage, and then, finally filtering back to pure DC. You can easily tell the difference between a linear and a switching supply. If you have a 20-amp supply and can pick it up without getting a hernia, it's probably a switcher. A linear supply requires a transformer large enough (heavy) to handle the current. Switching supplies are almost always used in computers.

The linear supply is quite simple if something goes wrong, it is often a transistor or IC in the regulator. The switcher is very complex, and any part can fail. Don't ever open up a switching power supply when it is on. There are peak voltages over 200 volts all over the place. Leave that to someone who knows what he is doing. You should also be careful when working around a large linear supply. Those large capacitors inside pack quite a wallop. There's not enough voltage to kill you, but the current they can provide, even when unplugged, can weld your watch or ring. Use a 100 ohm resistor across large capacitors to discharge them before playing around.

If your power supply has power transistors mounted externally on the case, you might want to make some modifications to avoid shorting them out. With a voltmeter, carefully measure the voltage from the transistor case to both the positive and negative leads of the supply. The case is often "floating" and is neither positive nor negative. If you see voltage, it would be prudent to construct a guard to keep metal objects from shorting out the supply. A piece of hard plastic or bakelite should do tile trick. The two things you must consider is that the transistor and heat sink often gets really hot and anything you put over the transistor should not interference with air getting around it to keep it cool.

If you cannot stand to be without a working supply, keep some spare parts inside of it, if there is room. Most linear supplies use IC regulators like the 7812 or 723, and these are usually the first items to fail. Another part known to fail is the pass transistor, usually a 2N3055, a big metal job, mounted with screws. If your supply uses discrete transistors in the regulator, try to identify what they are and match them up with replacements. Usually the garden variety 2N2222 will often suffice. Put the parts in a blister pack and secure them inside the supply dont let loose parts rattle around in there or you will really be in trouble.

Always, always, always have a multimeter available. Check your voltage regularly and keep it around 13.5 volts, measured at the supply. Make sure the leads are fat enough For the current draw. If the voltage drops more than a few tenths of a volt in transmit (while staying steady at the supply), use fatter leads.

One nasty thing about linear supplies is that the pass transistor sometimes shorts out. The result is 25 volts on the output. If you have anything connected, you end up with dead supply and dead radio. When hooked to a transceiver, that usually means that the power amplifier chip or transistor on the transmitter is destroyed These devices usually cost around $100. I had a circuit called an overvoltage protector, which would short out the supply if the voltage got above 16 volts. Unfortunately, any RF in the shack set off the protector. It now resides in the junk box. Yes, I live dangerously! Mitch Stern-wlsj @ vbi-mail.champlain.edu

KN

 

 

 

 

40 Meter Double Extended Zepp Antenna

By

Rick McKee, KC8AON

 

This appeared in the March 1999 issue of "Hello Radio", the newsletter of the Lawrence County (OH) ARES and RACES organizations, Ken Massie, WN8F Editor.

Imagine working all bands - 10 meters through 160 meters with one antenna. Imagine having a multiband antenna with none of the tune up problems you have experienced in the past. You may think that this is something that is too good to be true, but the fact of the matter is that it is very possible for such an antenna to exist.

The 40 meter double extended zepp antenna is a non resonant antenna. A non resonant antenna is simply an antenna that is neither a full wave, nor a multiple of a full wave on any of the Ham bands. Say that you are using a 160 meter dipole and you want to do some work on 80 meters, so you attempt to load up your 160 meter antenna with a match and find it very hard to get a match. And when you do get a match, it is very narrow banded and causes TVI, RFI, and other problems. The fact of the matter is, that the 160 meter antenna is a full wave on 80 meters and is being fed at a high voltage node on 80 meters. This causes all kind of problems, like feedline radiation, arcing of the transmatch at higher power levels, and even 'Hot' grounds.

Since the double extended zepp is neither a full wave nor a multiple of, on any bands, then the high voltage feeding problems are eliminated. This makes it very easy to load on any band - I0 through 160 meters.

Now for the trick that makes this antenna work. You see, this antenna isn't fed with ordinary coax, but with low loss ladder line. Since you will be using a transmatch to make your transmitter happy, ladder line will allow more of your power to be radiated rather than being lost through feedline heating due to high SWR. Yes, I said high SWR. Well, won't a high SWR burn out the finals in my transmitter you ask? In this case it won't, since you are using the transmatch your transmitter will be looking into a 50 ohm load, bottom line. And since ladder line is very low loss, even with high SWR, the antenna system is still very efficient.

If you want to learn more about feedline losses, be sure and get a copy of the ARRL Amateur Radio Handbook, or the ARRL Antenna Handbook Both of publications go into detail about why some feedlines work better than others.

The dimensions of this 40 meter Double Extended Zepp are given in the figure. If you have the room, put one up and have a ball. Good luck on the low bands.

 

 

 

 

 

Conquering the PL-259

By

Walt Stinson,W0CP

 

This appeared in the February 1999 edition of B. A. R. C's Bark", the newsletter of the Boulder Amateur Radio Club, Mary Ciaccia Editor.

New year's resolutions for hams. Among the ones I've heard recently is "l will always solder the braid to the PL-259." That got me to thinking about what a hassle it is working with coax and PL-259's (not to mention hardline and N-connectors!).

Well, many years ago after consulting with Mr. Murphy, I made that same resolution. I faithfully followed the instructions for assembly of connectors in the Handbook. I remember using the tip of a nail to unravel the braid and trimming it with scissors.

Two moods would fall over me after a session of soldering 259's: Self righteousness, for I was truly entering the ranks of the deserving; and klutziness, because about half the time l would have to cut of the end I was working on and start ail over again.

Finally, after years of trial and error. I devised a fast and foolproof method of assembling the little buggers. If you follow my prescription, I assure you that you too will enter the ranks of the deserving (of course you will also need an antenna.)

Gather up the following tools: (There are no guarantees unless these tools are used!)

Weller D550 240/325 watt soldering gun

1" adjustable pipe cutter (Rigid No. 104)

Tape measure with sixteenth inch scale

Razor blade style cutting tool

Triple core 60/40 solder, .047" diameter Black felt tip pen

Household style pliers

Vise

Here are the steps: (POST THIS BY YOUR WORKBENCH)

1. Using the razor, cut off 1-1/8" of insulation.

2. Put the Weller on high and tin the braid

3. Measure 13/16" from the end of the coax and mark it.

4. Using the pipe cutter, cut through braid and insulation.

5. Slip off the insulation & tin the exposed center conductor.

6.Slip on the coax fitting sleeve!!!

7. Screw the coax fitting onto the coax using the pliers.

8. Heat a hole in the coax fitting, touching tip to braid.

9. Apply solder through all holes. Keep fitting hot.

10. Solder the tip of the fitting and check continuity.

KN

 

 

EDITORIAL

By Bill Ruth, KB8USZ. This appeared in the March 1999 edition of "Sierra News", the newsletter of the Sierra Intermountain Emergency Radio Association, Bill Massie, K7NHP Editor.

There're two basic kinds of radio stations: mobile and fixed. Mobile can be pedestrian, bicycle, motorcycle, car, marine, and aeronautical; fixed can be campsite or workplace, but a fixed station is usually a home station.

Ahhh, Home ... one of the nicest four-letter words, and where we like to be. As a recent first-time home-buyer, I now know how good it feels to be in one's own home, even though the bank says it's theirs for a few decades yet.

Home, no place like it. Home's where the heart is, and the cat, and the radio. Home's where you can be reached on simplex. Home's where you hang your hat, and your antennas. If you're married, home's where you hang your head.

Until my antennas could be moved from the rental to the backyard -- with a lot of help from my friends -- I didn't feel completely at home. And now that the almost-impregnable hull of the house has finally been breached with coaxial cables and the soil has been claimed for Hamdom by driving the first eight-foot ground rod into it, fixed station operations have begun in earnest.

I have a theory why it could be that so many Hams tend to be homeowners. I call it the Frog/Pad Theory. Once a frog finds a good lily pad and his belly is full of sweet, juicy bugs, he commences to emit the loudest RIBBITs he can, to proclaim to the other denizens of the pond that he found his pad and his bugs and he's ready to rock and roll.

The Homeowner Ham sends out electromagnetic RIBBITs to proclaim to the world he is on the air, has a nice pad, even sweet bugs (if hes a semi-automatic-leaf-spring-collecting Morse op), and is ready to QSO-party down.

Homeowner's Pride compels the Homeowner Ham to electromagnetically expand his house by putting up the biggest and highest aerials he can so that he can sit on tile Great Global RF Porch and pleasantly pass the time with other Hams, entertaining and being entertained by the ever-present on-air Ham community.

In this unpredictable world it's good to have a feeling of constancy and security that a happy home life provides, even if the home scene is within an apartment. Having such a stable platform in one's life is conducive to activities which are not directly related to making a living: reading, socializing, hobbies, crafts, and learning Iife self-enrichment. Ham radio incorporates all these activities into itself. A flowering civilization enables its citizens to have the time and opportunity to pursue the finer things in life instead of being condemned to work and worry from womb to tomb. By being an active fixed station op you're proclaiming that you live on one fine-business pad, that you have reclaimed your rightful time and space, and that you can't help RIBBITing with joy to the world.

Traveling Hams feel at home when they get on the air from their cars and motel rooms and connect with the on-air Ham community, or drop in at local Ham club meetings, or have eyeball QSOs with Hams met on the air. One of the nicest things about being a Ham is that you gain the trust of other Hams and they will open their homes to you when they find out you're a Ham. Home is where they want to take you in.

Home is a state of mind. Having a sense of belonging to a community is a homelike state of mind. The most wonderful aspect of Amateur Radio is not found in the study guides and technical texts, and that's the friendship and community of Amateur Radio Culture. Where else can you huddle over a workbench with your cronies getting high on solder fumes one moment, and ragchew with faraway strangers like old friends the next?

The home station is where we want to be. Our desire to have some space and time which we can call our own can be as strong as the desire for bed and sex, and the Ham At Home can experience the kind of sustained bliss in the shack that may cause some to lose interest in anything but radio. In fact, Paul M. Sega, W9EEA, the author of the Amateur's Code, was aware of the dangers of radiophilia as far back as1928 when he reminds us that "...the Radio Amateur is balanced ... Radio is an avocation, never interfering with duties owed to family, job, school, or community."

That said, being at the home station feels like being the guy who's chased by a man-eating tiger and comes to a cliff, where he jumps over the edge and slides down the steep face of the hill until he grabs onto a bush halfway down. He sees another man-eating tiger waiting for him at the bottom of the cliff. After a while he realizes the bush he's hanging onto is a strawberry bush full of ripe wild strawberries, and he decides to try them. He's never tasted anything so delicious.

Ham radio is one of the finest varieties of wild strawberries we can enjoy while we're hanging around at home.

KN

GRUMMAN AMATEUR RADIO CLUB

MINUTES OF GENERAL MEETING 8/18/99

BY Pete, N2PYV

The meeting was called to order by Pat at 5:08 PM.

All present introduced themselves.

TREASURER'S REPORT

Ted, KD2UB read the financial statement. Finances continue to be in good shape.

REPEATER REPORT

Gordon, KB2UB reported that since a recent lightning storm he cannot interrogate the controller at the Hauppauge site. Pat reported that he had talked to the Northrop-Grumman real estate people who are in charge of finding a buyer for the tower in Hauppauge. They stated that now that much of the property had been sold, they could concentrate on the tower. They said the tower would be put out for bids. Any buyer would be given a list of the present leaseholders that have antennas on the tower. The Club is a leaseholder. They felt that there would not be any pressure to remove our antenna because there is plenty of room on the tower.

VE REPORT

Bob, W2ILP reported that Cathy Davis, a member of our Club, passed the theory and 13 WPM code tests for General. There were no other applicants.

WAG REPORT

Bob, W2FPF reported that there was no WAG activity this month.

HOUSE REPORT

Zak, WB2PUE reported that the Sunday Morning Net had about nine check-ins and conditions were good.

 

Pat reported that contractors hired by N/G were working on sprucing up Plant 5. They painted the shack area and got rid of some material that we did not need. Pat also stated that the Club Website had been updated to include the Special Event Station operation that was held in June to commemorate the 30th anniversary of the first manned landing on the moon in a Grumman made Lunar Module. A proposed Special Event QSL card was shown to the group by Marty, NN2C.

NEW BUSINESS

A motion to appropriate $300.00 to have the Ten-Tech radio repaired and aligned was approved.

Marty, NN2C reported on a meeting for the presidents of all of the radio clubs on the Island. There were only six attendees. It was decided to hold a Ham Radio University (HRU). This will consist of a series of seminars to be held on January 23, 2000. The seminars will be in separate rooms and the series would last about 4-6 hours. There will be booths for each club. There will be further publicity released on this activity.

The meeting was adjourned at 5:30 PM.

A video called "Man on the Moon" was played. It was created by N/G to commemorate the 30th anniversary of the first manned landing on the moon. It featured several managers of the LM Program. Dave AB2EF has offered to make copies for anyone who brings a blank tape and $2.00 to the next meeting.

 

 

NETS

Twenty Meters: 14.275 at 12:00 PM EST Wednesdays.

Forty Meters: 7.289 at 7:30 AM EST Sundays.

Two Meters: 146.745 at 8:30 PM EST Thursdays.

145.33 at 8:45 PM Thursdays,

At 9:00 PM EST Mondays (ARES/RACES)

VE EXAMS

VE exams for all classes of amateur licenses are held on

the second Tuesday of each month at 5 :00 PM in the Plant 5

Cafeteria. (See page 7 for directions to exam site.) The exam fee for 1998 is $6.35.

Thanks to Bob Wexelbaum, W2ILP for this information.

MEETINGS

General Meetings of the GARC are held on the third Wednesday of each month, at 5:00 PM in the Plant 5 cafeteria. All who are interested in Amateur Radio are invited to attend. Board meetings are held eight days before the General Meeting and GARC members are invited to attend, but please call Pat Masterson, KE2LJ, at 346-6316 to confirm place and time of meeting.

Attendees should enter at Grumman Road West (A)(Hazel St.) and drive down to the new entrance at the north side of plant 5, then go to the same visitors parking lot as before.