The device must do what its maker says it will 2 The device must survive in home power service 3 The device must offer good value

All the above criteria will be determined by the Home Power Crew in actual testing in working home power systems. You need not be an advertiser in Home Power to have your products considered for the Things that Work column. We follow Thumper Rabbit's advice, "If you can't say something nice about something, then don't say anything at all!" Devices not meeting the three above criteria will not appear in this column. All tested equipment will be returned.

Readers: If you see it in Things that Wok, then it does. Only products meeting these standards will appear here.

Things that Work

Home Power tests the Heliotrope PSTT 23 kW Inverter conducted by Richard P eiez & John Piyor

In the past, inverters have been weak links in our power chain. They were very prone to failure, and didn't work well. Well, those days are past. Heliotrope makes an inverter that works extremely well, survives gross abuse, and costs less than its worth. We like this inverter; it's built like a battleship!

Test Environment

We installed the Heliotrope in our shop on a pack of two Trojan L-16W batteries (12 VDC at 350 Ampere-hours). We used low loss 0 gauge copper cables with a combined length of less than six feet to feed the inverter. One of these cables is set up for current measurement, so we can measure the amount of current going into the inverter. Other instrumentation present to monitor the inverter's performance is a battery powered oscilloscope, a Digital Multimeter (DMM), and an iron vane type expanded scale AC voltmeter.

Packing, Installation Instructions, and Owner's Manual

The Heliotrope arrived in good condition being heavily packed. After unpacking we had enough styrofoam peanuts left over to just about insulate a wall in the shop. Shipping containers are important. Nothing is more disappointing than taking delivery on an inverter and finding it damaged in shipment. Heliotrope is obviously spending the money for first class packing so that this doesn't happen.

The installation and operation instructions provided with the inverter are adequate. They could be better. I have discussed this with Heliotrope on the phone and they assured me that a new manual is in production and will be included with future inverters. Complete and organized documentation is essential in complex items like inverters. The manual we received with the Heliotrope is complete, but it's too technical, and needs better illustrations.

Inverter Physical Examination

The first impression this inverter gave us was one of solidity. It's a large, solid, heavy unit. The case, heatsink, circuit boards, and everything connected with the inverter are made from heavy weight materials. Heliotrope has not scrimped on quality hardware. The inverter is 14 inches wide by 18.5 inches tall by 5.25 inches deep. It weighs 56 pounds, which for its power class is very heavy. The Heliotrope has the best and heaviest hardware of any inverter I have ever seen. All exposed metal parts and fasteners are well painted or plated to resist rust and salt water environments.

Inverter Installation

The Heliotrope is designed to mount on a wall. We liked this feature as there is more space available on vertical surfaces than horizontal ones around here. The heavy cables that feed the inverter from the battery are connected in a novel manner. Most inverters use a bolt. You must attach a heavy ring connector to the battery cables in order to bolt them to the inverter. Heliotrope uses power connectors like the heavy connectors in AC distribution panels. These 4/0 -250 MCM connectors are inside the inverter out of harm's (and shorts) way. These connectors are like sockets. The heavy copper cable is inserted inside the connector and a lug is tightened to hold the wire in place. No need for ring connectors and the result is a high contact pressure, low loss, connection that is easier for the user to make. We simply inserted the stripped ends of our 0 gauge cable into the connectors inside the inverter and tightened them down.

Heliotrope also uses two small wires that connect the battery to the inverter. These are in addition to the heavy cables that feed the inverter its current. These smaller wires enable the inverter's logic to measure the battery's actual voltage directly, without the loss present when running large currents through the main cables. This is a very nice feature, allowing the inverter to better control itself by more accurately monitoring the battery's condition.

This Heliotrope inverter has a feature that is unique among inverters of this large power size. IT IS REVERSE POLARITY PROTECTED. This means that you can hook it up to the battery backwards and while it won't work, it also won't destroy itself. Try this with any other large inverter and you're looking at hundreds of dollars in repairs. We investigated the manual and found that this reverse polarity protection is accomplished by two large series diodes in the main power line inside the inverter. We also learned from the manual that the voltage drop across these diodes costs us some 2% in efficiency. The manual has instructions for bypassing the diodes and gaining more efficiency. We did this before installing the inverter. The reserve polarity protection is an essential feature for folks who hook and unhook their inverter regularly. Those who wire it once and leave it are advised to get the polarity right the first time and increase the inverter's efficiency 2% by bypassing the diodes.

The Heliotrope inverter has the best connection methods for getting the 120 vac out of the inverter. Most inverters give you regular receptacle type female ac sockets. These are present, times four, in the Heliotrope. What is also present are standard wiring connectors within the inverter that will accept regular, 12 gauge, copper wire. While some other inverters offer interior hardwiring of their output, no one else has the size and installation ease of the connectors Heliotrope uses.

The Heliotrope is a programmable inverter. It has a number of user selectable features that allow you to set it for your own particular needs. The inverter protects itself against the following conditions: over temperature, over current, too low battery voltage, & too high battery voltage. Each of these protection functions can be either manually reset by the user or automatically reset by the inverter's logic. We chose the manual reset for the first portion of this test. This is easily selected on a small DIP switch on the inverter's printed circuit board.

The Heliotrope has two operating modes. One is called "Standard Mode" and the other "Battery Saver Mode". In standard mode, power is continuously available to run very small appliances like micro nicad chargers, electric clocks, etc. In standard mode, no load power consumption is 5 Watts. In battery saver mode, a 5 Watt or greater load is required to start the inverter. In battery saver mode, the inverter's no load consumption is 0.4 Watts and this is very, very low. Being basically tight with the electrons, we configured the Heliotrope for battery saver mode.

Once we wired up the inverter and selected our operating modes, we were ready to fire it up and see how it works!

Inverter Operation

We ran the Heliotrope WF12-2300 for about five weeks in what we like to call "user testing mode". This means that we just used it; we ran whatever we liked off it without paying particular attention to technical details. The idea is to subjectively see how the Heliotrope performed in relation to other inverters we have used.

We were not only surprised but very pleased with how well the Heliotrope worked. For one of many pleasant examples, Karen has a small hand mixer in her kitchen. No inverter we have ever used could spin this mixer as its ONLY load. At best, the hand mixer would sluggishly attempt to do its job. The Heliotrope not only powered this mixer, but ran it better than our ac generator could. This pattern of superb performance was carried through on all of our inductive loads. The Heliotrope inverter powers inductive loads better than any type I have ever used to date. Motors ran faster and cooler, the power supplies in our computer equipment ran cooler, and very small problem loads like electric scissors and electronic sewing machines ran as they never have before on an inverter.

Well, after weeks of enjoying completely trouble free and transparent inverter operation we started to wonder how the Heliotrope worked in a technical sense. We went into the technical testing stage. We watched the inverter's waveform on the scope, in addition to making voltage and frequency measurements. We abused the inverter to see if it would, in fact, protect itself. It did.

Here is a sample of the abuse we put the Heliotrope through.

We used the following loads (ac load amperage draw listed in parenthesis): ShopVac (6 amps.), 7.25 inch circular saw (10 amps.), Blender (3 amps.), Split-phase bench grinder (5.1 amps. running over 25 amp. starting surge), and a motley collection of incandescent light bulbs (about 4 amperes worth). First we started out with the circular saw and the ShopVac for a total ac current load of 16 amperes. Then we started the split phase bench grinder. This is a brutal test. The inverter was already loaded to 84 % of its 19 ampere capability and we asked it to start the grinder. This split phase grinder motor is a real inverter killer, and draws in the neighborhood of 25 amperes when starting. The Heliotrope grunted once and the grinder started & ran. We were amazed. We then started ALL the aforementioned appliances, with the grinder being started last. We basically overloaded the inverter, demanded a super surge to start the grinder and it did it all! We were never even able to get the inverter hot enough to make its internal fan operate.

The output waveform of the Heliotrope stayed incredibly stable over the entire test. Even when we grossly overloaded the Heliotrope, it did its job. We couldn't get it to change its output waveform no matter what, or how much, we plugged in. Voltage and frequency of the inverter's output are not only within Heliotrope's specifications, but according to our instruments better than their specs. In terms of gross wattage output, we were able to take well over the inverter's 2,300 watts out of the unit. By starting all the inductive appliances mentioned at the same time, we determined that the Heliotrope inverter does indeed supply surge power around 7,000 watts.

The Heliotrope inverter's efficiency is just as specified. We measured input current and voltage and compared this to output current and voltage. On very small loads, under 50 watts, efficiency was around 85%. At about the 165 watt level the inverter was 95% efficient. At loadings in the 700 watt range the Heliotrope inverter produced efficiencies up to 98%. The Heliotrope inverter is as efficient as or more efficient than any make we have tested.

We then tested the inverter to see if it would protect itself against too low or too high battery voltage. At about 14.5 VDC input, the Heliotrope shut itself off. On the low side, it turned itself off when the battery voltage fell to 10 VDC. Since the Heliotrope uses separate sense wires to the battery, these voltage switch points are very accurate and neglect losses in the main cables.

On the tech side

The Heliotrope, Phase Shift Two Transformer (PSTT), inverter uses two transformers instead on one. The output waveforms of the two transformers are opposite and compliment each other. To quote their manual, "Depending upon the current draw, the phase position of each transformer is matched to provide a perfect push-pull for each cycle of the 60 Hz. power pulse..." The manual provides a very complete technical explanation of Heliotrope's new inverter design. What really counts to the user is that the PSTT design works better than anything now available with inductive loads like motors, power supplies, fluorescent lighting, etc.

Inverter Overview and Other Stuff

A thermostatically controlled fan is standard equipment on the Heliotrope WF12-2300, PSTT inverter. At 2,300 Watts, it is the highest output inverter we know of that has a 12 VDC input. It is very simple to operate. If automatic mode is chosen by the user, then there is only one on/off switch to deal with. The installation of this inverter is relatively simple and no one should have trouble hooking it up. No battery charger option is available with this inverter. All details of the inverter's operation are indicated by a series of nine LEDs on the front panel. Remote control of this inverter can be accomplished easily via terminals already present on the inverter's printed circuit board. Other inverters charge extra for remote control functions.

Inverter Warranty

Heliotrope has the following warranty for this inverter, and I quote from their manual. "These products carry a 10 year warranty. During the first year replacement of defective merchandise with a tested replacement will be made at no charge. For years 2 through 5 replacement will be made for a service charge not to exceed 25% of the current list price and for years 6 through 10 the fee will not exceed 50% of the current list price."

Conclusion

We like this inverter. The Heliotrope PSTT inverter powers inductive loads better than any type we have tested to date. Heliotrope's new two transformer inverter design concept really works! This inverter is beautifully made; every part in it is of the highest quality. Heliotrope has obviously spared no expense in construction of this inverter. It meets, and in many cases exceeds, Heliotrope's specifications. We tried to kill it by overloading and couldn't. This inverter has a retail price of $2,300, and is a very good deal. At $1. per continuous output watt, the Heliotrope is priced in line with other inverters. Considering its excellent performance and the very high quality of its hardware, the Heliotrope PSTT inverter is an excellent value. Write: Heliotrope General, 3733 Kenora Drive, Spring Valley, CA 92077, or call toll free inside CA (800) 552-8838, & toll free outside CA (800) 854-2674.

PSTT™ Inverter

A new era in inverter design!

Phase Shift Two-Transformer 2300 Watt Output Input Voltages 12, 24 VDC, Output Voltages 117/230 VAC

Features:

* Fully protected, including:

Overcurrent Overvoltage Spikes Overtemperature High Battery Low Battery Reverse Polarity

* Efficiency up to 95%

* Surge Power to 7000 Watts

* Standby Battery Power under 0.5 Watts

* Unique patented design starts and runs any load

Charge Controllers and PV DHW Systems also.

Invest in The Best!

HELIOTROPE GENERAL

3733 Kenora Drive, Spring Valley, CA 92077 ■ (619) 460-3930 TOLL FREE: In CA (800)552-8838 ■ Outside CA (800)854-2674

Many photovoltaic systems begin as gas generator charged battery systems. As the system evolves with your needs and finances, the generator may be semiretired and used only for occasional back up. Either way, an efficient system must be used to deliver DC power to charge the batteries. There are three good methods of charging batteries from a generator.

DC GENERATOR

A gasoline powered DC generator/alternator is a direct approach for battery charging. None are available ready made to the best of my knowledge. Many people build their own using a common gasoline engine of 3 to 5 HP belted to a car or truck alternator. Get an alternator WITHOUT a built in regulator (do not use an auto regulator). A 5 HP engine will drive a 100 Amp alternator to full power (reduced some at high altitudes). Use a rheostat (25 ohm, 25 watt) to regulate the current manually. See Home Power #2, pgs. 23 through 26, for details on construction of this type of unit.

AC GENERATOR with BATTERY CHARGER

This is the most popular method because AC generators are so common and versatile. Many of our customers run an AC generator periodically to pump their water, wash their clothes or run tools. At the same time a battery charger is plugged in to make best use of the generator's capacity by charging their batteries. LP gas is a preferable fuel to gasoline, for cleaner burning and easier starting. Slower, 1800 RPM generators are longer lasting and more efficient than faster 3600 RPM models, but are heavier and more expensive. Many AC generators have 12 Volt charging capability but its current capacity in Amperes is small. The 12V output and the output of a battery charger may BOTH be connected to the battery bank at the same time!

WELDER/GENERATOR

A "portable welder" is a generator built to supply arc welding power. A welder puts out approximately 30 volts, at a current of 200 Amps or more. Perfect for charging a large 24 volt battery bank! On a low setting it will charge at 12 volts. If you KNOW you need to rely largely on your generator (like if you live in Alaska) or if you like to weld AND have a large battery bank (at least 1000 Amp hour) this may be the best way to go. Most portable welders also have AC output for tools etc. Get a DC welder. If you already have an AC welder, a rectifier may be built to convert to DC.

BATTERY CHARGERS

Battery chargers are common devices, available everywhere. Here are a few things to know about them:

(A) Any automotive charger can charge a very large battery bank; it only "sees" the voltage, not the battery's Ampere-hour capacity. If the battery is very large, it will take longer to recharge.

(B) More than one charger may be connected at once, and so can other charge sources such as PV. Each regulator responds as battery voltage rises, regardless of the charge source.

(C) Automatic (regulated) battery chargers tend to regulate too soon for the fast charging that is desirable with a generator AND they may regulate to a low current suited to a small (car) battery. Buy a "manual" charger, or switch your charger to manual. If you will be charging from utility power, use an automatic charger.

(D) Battery chargers are expensive. They contain only one expensive part though, the transformer. Transformers rarely fail. Big garage type battery chargers may often be found in scrap metal yards, beat to hell by such abuse as someone driving away with the charger connected. A little rewiring and replacement of small parts will almost always restore a charger to reliable use, however ugly.

(E) Truck and industrial battery chargers are available for 24 volt charging. If you're a junkie, check scrap yards.

(F) Two 12 volt chargers of equal capacity can charge 24 volts by connecting each one to each half of the bank.

(G) Industrial electric vehicle chargers are of higher quality and efficiency than automotive, but are expensive.

INVERTERS WITH "STANDBY" BATTERY CHARGING OPTION

Trace Engineering and Heart Interface inverters have an optional battery charging function, which works well. This option costs far less than a separate battery charger of equivalent capacity. This inverter's transformer is used "backwards" to step down the voltage. (Remember, the transformer is the expensive part of a battery charger).

The Trace inverters are particularly good in this regard

Engines because of their "programmable" regulating response, which you may set optimally for your particular system. Trace features an additional advantage, although not yet clearly documented charging is accomplished thru pulses of very high current which slightly vibrate the battery plates and knock off inactive sulphate crystals. This tends to restore some capacity in older batteries, and to extend battery life. To obtain the full effect, you need a generator with at least double the wattage of the inverter, and high (over 165 vac PEP) peak voltage output.

FAST CHARGING

Beware service station attendants and many auto mechanics do not know what it MEANS to fully recharge a battery. Less than an hour of high current charge on a dead car battery will allow a car to start, but cannot charge the battery anywhere near full. If you take batteries to town to have them charged, be sure they are kept on the charger at least 8 hours. A hydrometer reading is the best way to assure that they are "topped off". Failure to top off or "finish charge" batteries at least every two weeks will reduce their life greatly. Beware of excessive gassing when fast charging it's hard on the batteries and creates a very real explosion hazard! Don't make a habit of it.

extending battery life.

If your generator system is used only seasonally, a small PV module should be used to maintain your battery bank at full charge during the months you are gone. A typical deep cycle battery (in GOOD shape) will discharge half way in 6 months, and sitting in a low state of charge is VERY DAMAGING.

Whether you consider your fossil fuel generator to be a luxury, a convenience, or a necessary evil, making the best interface with your battery bank deserves your careful attention.

Windy Dankoff is the owner of WINDLIGHT WORKSHOP and FLOWLIGHT SOLAR PUMPS, POB 548, Santa Cruz, NM 87567 (505) 753-9699. Windlight's 1988 CATALOG AND HANDBOOK is available for $6. For information on DC well and booster pumps, inquire.

PHOTOVOLTAIC CHARGING AS SUPPLEMENT TO GAS CHARGING

Finish charging, as mentioned, is extremely important to long battery life. Any cell that tends to lag slightly behind the others will be brought up to full, instead of falling further behind. This requires long periods of low current "trickle" charging, which is very wasteful use of a generator BUT perfect use of a small PV array. Although a minimal PV array may contribute relatively little energy to a generator system, it will pay for itself by

Exercise Those Batteries

To Keep Them Strong

Internal Resistance in Lead Acid Batteries

by

Robert G. Hester

--Rich his article, by a Home Power reader, is the type of feedback that we are hoping to share in this magazine. While the approach is quite technical, it does demonstrate a simple technique for actually measuring the internal resistance of the batteries you are using. By keeping track of our batteries' internal resistance we can be informed on their condition and reliability.

The internal resistance (Ri) gets its name from the fact that it is located inside the case of the battery and is a characteristic of the battery itself. This resistance is a function of the chemical reaction taking place in the lead-acid battery. Ri is a necessity, an unavoidable evil; any power dissipated here does no useful work. In solar applications, the power dissipated in (Ri) represents wasted solar panel time.

If the useful load Ri is a very large wattage inverter, then the voltage drop caused by the battery's internal resistance Ri may be large enough to reduce the voltage at the battery terminals (Eb) below the operating point of the inverter. When several hundreds of amps are demanded from the battery, its internal resistance may reduce its operating voltage to an unacceptable level.

The internal resistance of a battery pack may be controlled by the system user by paralleling more batteries into the pack. Doubling the number of batteries reduces the pack's resistance by half, each time the number of batteries is doubled. The internal resistance of the batteries forces us to increase the size of the battery pack to handle large surge loads.

Operation of lead-acid batteries at low states of charge should be avoided, as Ri increases as the batteries are discharged. Car battery manufacturers get high cold cranking amps (reducing Ri) by close plate spacing and reasonably high specific gravity. Also, the depth of discharge in car systems is limited in normal operation.

The internal resistance (Ri) is equal to the change in battery voltage when a load is applied, divided by the change in battery current due to the application of this load:

SIMPLIFIED SCHEMATIC FOR TESTING Ri

A test was made to determine what kind of value Ri might have with the author's limited resources of batteries and test instruments.

Two Trojan T105 lead-acid batteries (205 Amp-hrs.) were connected in series (for 12 volts) and charged by 40 watt and 7 watt solar panels connected in parallel to operate an emergency Amateur Radio Station.

Amps.

Amps.

Test Load

Volts

Fixed Load

A digital Voltmeter having a one tenth volt resolution was used to measure the voltage change. A 300 watt Heart inverter was used to power a 100 watt light bulb as the test load. A 1 CP tail light bulb was used as a fixed load. The test load was calculated to be 9.16 Amps, the fixed load is 1 amp. (estimated).

The test load was turned on to take the "surface charge" off of the battery. After this the load was applied and the voltage dropped almost instantaneously from 12.4 volts to 12.2 volts, then leveled off at 12.1 volts after several seconds.

The behavior of the batteries under load is our concern. The total voltage change was 12.4 - 12.1 = 0.3 volts. The total current change was 9.16 amps.

If a 1,500 watt inverter had been the load the change of current would be 1,500 watts divided by 0.9 inverter efficiency equals 1,660 watts divided by 12 volts equals 138 amps. The voltage drop across Ri (0.0327 ohms) equals 4.5 volts. Therefore the inverter would receive 12.1 - 4.5 = 7.6 volts and would not operate at all. The internal resistance of the battery pack is important. This battery pack is obviously too small to effectively source a 1,500 watt inverter.

Batteries

0.3 Volts 9.16 Amperes

The fact that a fast decrease in voltage was followed by a slow decrease indicates that the equivalent circuit shown was perhaps too simple. We are probably seeing the effects of the mobility of the ions that make up the electrolyte. These ions of hydrogen, oxygen, and sulphate (H2, O2, SO4) must migrate to the battery's plates in order to participate in the chemical reaction. The O2 (oxygen) ion has 16 times the weight of H2 (Hydrogen) and has an equal but opposite charge.

THE REVISED EQUIVALENT CIRCUIT

The addition of Capacitor (C) in Parallel with R1 creates a time constant that was estimated at 3 seconds. Ri = R1 + R2

In electrical terms this 275 Farad capacity (in terms of electrical capacitance) of the battery pack is a remarkable value as few Farad capacitors exist. This is the electrical analogy, however.

These simple circuits allow determination of the actual internal resistance of our own batteries. Record the data generated from your tests and compare it to later tests at varying

DE .

_ 0.1 Volts

DI

9.16 Amperes

DE

= 0.2 Volts

DI

9.16 Amperes

T

_ S sec. est.

R1

= 275 Farads

= 275 Farads several states of charge. Probably goes up as the temperature goes down; but is it a linear relation? Editor's Note: The lead-acid battery's internal resistance certainly does rise under the following conditions: 1) low temperatures (below 45°F.), 2) at low states of charge (below 15% SOC, & 3) high states of charge (above 90% SOC. -Rich.

4. A plot of the dynamic (AC) internal resistance seen by a load which has high frequency components. (ie. an inverter load that pulses at a high frequency rate as when powering inductive loads). A plot of Ri (Internal Resistance vs. Load AC Frequency) would be helpful. This is of interest to Ham Radio Operators who power single sideband transmitters where the load varies at the frequency and amplitude of the human voice.

Volts

Amps.

Amps.

Variable Test Load

Fixed Load

Time Constant (Tsec.) = R1C = about 3 seconds

In my personal station a Kenwood TS-130SE 100 watt output high frequency transceiver is powered by stored solar energy. The voice load components on this transmitter interfere with the operation of a Heart HF-300X inverter used to power lights. This should have been predictable, but it wasn't. More battery data is needed by battery users than just Ampere-hours. Editor's Note: It is possible that this interference is due to RF getting into the inverter's logic, rather than changes in the battery due to loading.--Rich

Robert G. Hester may be written concerning this information at Box 226, Pearblossom, CA 93553.

temperatures and states of charge. By keeping a careful eye on our battery's performance we can detect weakening and possible battery failure long before it actually happens. If a battery pack shows a dramatic increase in internal resistance it is time to run an equalizing charge. If the internal resistance continues to rise in spite of repeated equalizing charges, then it's time to look for a good deal in new batteries.

I would like the following information from various battery manufacturers regarding their batteries.

1. A detailed description of the time constants encountered after the application of a load. How many are there? What are their magnitudes?

2. Is the variation of the internal resistance an inverse linear relation to the state of charge? Probably yes.

3. A chart of internal resistance as a function of temperature at

11 ^^ reak one-nine for the Jolly Roger. This is the Wolfhound frying." It was the beginning of a L^ new era; we were coping with an energy crisis. Gas and heating oil prices doubled, lines ^^ formed at gas stations and the speed limit was lowered to 55. So much for the negative. The up side was that we learned to conserve, started to explore alternative energy and everyone discovered citizens band radio (CB).

Truckers had been using CB for years. It wasn't until the gas shortage that "Joe Lunchbucket" began to take an interest in this cheap, effective means of radio communication. With a CB radio, anyone could find out which stations had fuel, where the highway patrol was lurking, or could just carry on a conversation to make the miles go faster. CB is fun, where else can a grown adult call himself "The Rubber Duck" and get away with it!

CB started out as low cost, two way, short wave radio communication. In 1958, the Federal Communications Commission (FCC) created CB from the 11 meter (27 MHz.) amateur radio band. Twenty-three radio channels (frequencies) were allotted to CB. On January 1, 1977, CB was expanded to 40 radio channels.

Once the gas crisis was over with in the early '80s, the CB boom was bust and the dealers couldn't give the radios away. Government sponsored renewable energy projects were abandoned. Alternative energy forged ahead with or without tax credits.

I'm sure that many folks have CBs stuck up on shelves. Those that don't have a rig around can buy one cheap enough ($50 to $150) at department stores. Now is a good time to start planning a worthwhile Spring project. Get a rig on the air and find out what is happening in your neighborhood. Leave a note on the local bulletin board telling people of your radio interests and what channel you monitor. Listen around on your CB, there may already be a local neighborhood channel.

CB was designed to use short ground wave radio propagation, which is more or less line of sight. These RF or radio frequency waves travel in a fairly straight line near the ground, from one transmitter to another receiver. Maximum range for the average CB radio is about 25 to 75 miles, and depends on terrain and antennas. One of the drawbacks of CB at his present time is that we are heading for a peak in the 11 year sunspot cycle. The increased solar activity ionizes the upper levels (between 50 and 250 miles above our surface) of the Earth's atmosphere. This makes these layers reflective to certain wavelengths of radio waves. When the ionosphere becomes reflective, your four watt CB transmitter can travel (skip) over 2,500 miles. This causes a problem, since you can hear at least 1001 stations, all trying to use the same channel at the same time. The good news is that after Sundown the atmosphere cools off and the skip generally fades.

Get It Together and on the Air

If you are going to get a CB on the air, here is what you need. A RADIO. Use a 40 channel type because the 23 channels radios are no longer legal with the FCC. A POWER SOURCE. The can be directly off your 12 Volt battery or via a power supply. A power supply converts 120 vac in 12 VDC if your don't have it readily available. COAXIAL CABLE. This feedline is the connection from your radio to its antenna. Coax has a center conductor surrounded by insulation, over this insulation there is a copper braided tube. Over the copper braid there is a waterproof vinyl jacket. The center conductor carries the signal and the shield braid keep this signal within the coax until it reaches the antenna. Radio Shack sells CB coax, Part # 278-1328 at 210 per foot. This a low loss 52W coax and comes with or without connectors on its ends. I prefer the RG8X type because of its small size and flexibility. ANTENNA- the center insulator.

The center insulator (see photo #1) of your antenna can be made out of a number of nonconductive materials, including 1/4" plywood. If you use plywood, give it a couple of coats of water proofing shellac. I used a piece of 1/4 inch thick plexiglass I found at the dump. INSERT PHOTO ANTENNA- Wire

Almost any copper wire will work. 12 or 14 gauge is a good size. Even the stuff you can get at the auto parts store in a 35 foot roll will do the job. Leave the insulation on except where soldering is required. Electric fence "egg" insulators, attached to the ends of the wire will insulate your antenna from the cords used to secure it.

Photograph 2 shows how to pig-tail the coax. A bit of silicone sealer is used to keep water from getting inside the coax.

soldered quickly with a high wattage soldering iron so that the insulation within the coax is not melted.

Checking Out your Antenna's Site

Things to think about: Where is the radio going to live? How long will the power lines to the radio be? Where is the antenna going to be erected? Where should the coax enter the house? How long of a coax run is needed? Try to keep the coax as short as possible to minimize losses.

Building the Antenna

If you are like me, this is the fun part. I'm only going to describe a simple dipole antenna. It will get you on the air for

combined length of both pieces of wire is 17.22 feet. This is 17.22 feet from end to end of the antenna. The feed point is at the center and each of the two wires making up the dipole is 8 feet 7 inches long. These length figures are strictly ballpark. I've had antennas tune up perfectly at this length & others need a bit of trimming. Always leave a little extra wire on the dipole elements for trimming. The dipole can be put up

Tuning your Antenna

I built an inverted V dipole antenna. Two 10 foot sections of Radio Shack antenna masting where get the antenna into the air. The center insulator was tied to the top of the mast. The mast was secured to the ground by hose clamps and a firmly planted T type fence post. A T post at either end of the antenna provided a place to tie down the nylon cords attached to the egg insulators at the ends of the pieces of wire.

I used a standing wave ratio (SWR) meter to measure the forward and reflected power in the antenna. The SWR meter allows you to tune the antenna for proper performance. If the wires that make up the antenna are too long or too short, then the antenna will reflect the RF energy back to the transmitter selected the reflected power reading on the SWR meter. Not bad, my home made antenna has an SWR of 1.3. Anything less than 2 is acceptable.

I checked the SWR on channels 1 and 40. This step is important because it tells us if the wires in the dipole are too long or too short. If the wires are too long then the SWR will be lower on channel 1 than channel 40. If the wires are too short, then the SWR will be lower on channel 40 than on channel 1. In my case, the SWR on channel 1 was the same as on 40, so I didn't need to trim the wires. If your antenna is not balanced like this, then add or remove 1/2 inch bits of wire from the ends of the dipole.

If the lengths of wire are correct and you still have some SWR, then another way of reducing SWR is to change the angle at which the wires meet. I my case, I reduced the angle of the wires from 120° to about 100°. This brought the SWR of the antenna down to 1.25 on channels 1 and 40, and to 1.2 on channel 19. I never cease to get a charge when a new antenna flys off the workbench. If you have any questions or experiences to share drop me a line. I'll do my best to answer

Vertical Dipole Antenna

- Egg Insulator

Horizontal Dipole Antenna o-□-o

Inverted V Dipole Antenna

<-1/4 Wave piece of Wire

Center Insulator

Coaxial Cable 4-

<-1/4 Wave piece of Wire

Egg Insulator rather than radiating it. The basic idea is to have all the CB transmitter's power radiated by the antenna rather than reflected back to the transmitter. If somebody in your neighborhood has an SWR meter to lend you, then fine. If not, Radio Shack sells one for $18.95 (part # 21-525). I leave my SWR meter in line all the time so I can see if everything is working properly.

With the radio all hooked up, I inserted the SWR meter in the coaxial line to the antenna. The moment of truth! I turned the radio on and lots of signals where coming into the receiver. The Skip was howling like a banshee. Well, I knew it would receive but would it transmit on my homemade antenna? I set the radio to channel 19 (the middle of the CB band), selected forward power on the SWR meter. I keyed the microphone to transmit and adjusted the sensitivity knob clockwise until the meter was indicating full scale. Next, while still transmitting, I

your questions or point you towards a source of information.

Operating your CB

The first rule of radio courtesy is to listen before you transmit. Only one person can transmit on a channel at a time without having chaos. So give others their chance to talk, just as you want yours. Channel 9 is reserved for emergency use. In some neighborhoods channel 9 is used as a calling channel. This means that after making contact the stations IMMEDIATELY move to another channel to talk. This allows everyone in the neighborhood to monitor channel 9 all the time and increases the chance of an emergency call being heard.

Some Good Antenna Reading

Simple Low Cost Antennas for Radio Amateurs by William I. Orr W6SAI & Stewart D. Cowen W2LX, Radio Publications Inc., Box 149, Wilton, CT 06897. $5.95

ARRL Antenna Handbook, American Radio Relay League, 225 Main St. Newington, CT 06111. Heavy on antenna and feedline theory $5.00.

73 Dipole and Longwire Antennas by Edward M. Noll W3FQJ, Editor and Engineers, Howard W. Sams Co. Inc, Indianapolis, IN 46268.

Well, enjoy talking to your neighbors on the CB! If you're around Interstate 5 and the California/Oregon border you can call Home Power People on channel 9 CB, call for Wolfhound, Jolly Roger, FourTrax, Pennyroyal, and/or Oilburner, if you're a Ham, call on 146.400 MHz. Simplex for N6HWY, N7BCR, and/or KF6HG. You can write me at 13109 Norman Drive, Montague, CA 96064.

73s Bri

RF Bands And Transmission Frequencies

Band

Frequency Spectrum (kilocycles)

Wavelength (meters)

VLF (Very Low)

10 - 30

30,000 - 10,000

LF (Low)

30 - 300

10,000 - 1,000

MF (Medium)

300 - 3,000

1,000 - 100

HF (High)

3,000 - 30,000

100 - 10

VHF (Very High)

30,000 - 300,000

10 - 1

UHF (Ultra High)

300,000 - 3,000,000

1 - 0.1

SHF (Super High)

3,000,000 - 30,000,000

0.1 - 0.01

EHF (Extremely High)

30,000,000 - 300,000,000

0.01 - 0.001

Ohm's Law by

Richard L. Measures

Electricity

Electricity is a form of energy that is carried by the flow of electrons through the atoms of a conducting medium such as a copper or tungsten wire. An electric wire is a long line of (usually copper) atoms. All atoms like to contain a certain number of electrons. If an atom has one too many electrons, it will immediately shed another electron. If an atom is missing an electron, it starts looking for an electron to steal.

The flow of electrons is like a long pipe that is completely filled with glass marbles. If an extra marble is poked into the input end of the already full pipe, a marble must simultaneously pop of the (output) end of the pipe. If five marbles per second are poked into the input end of the pipe, five marbles per second will simultaneously pop out of the output end of the pipe. It can be said that the flow rate of the marbles is five marbles per second. If a paddle wheel is connected to the output of the pipe, the flow of marbles can be made to perform work.

The flow rate of electrons is called current and it is measured in electrons per second. The ampere is the unit for the flow rate or current of electrons. One ampere is defined as 6.24 X 10 to the 18th power (6,240,000,000,000,000,000) electrons per second. That sounds like a lot of electrons but electrons are so small that the ampere unit is very practical. One ampere is the current required to operate the dome light in a typical automobile.

The process of pushing marbles through a pipe, or electrons through a wire is rarely 100% efficient. A certain amount of resistance to movement, due to friction, takes place with the marbles bumping and scraping along the way. Electrons also resist movement and this loss is called resistance. This loss appears as heat.

The electric force or pressure that pushes the electron current through the resistance of the wire is measured in units called volts. The standard unit of energy is the watt (per second) which measures work. A watt is equal to .73756 foot pounds/seconds or 101.9716 gram meters/second or .001341 horse power. One volt is the amount of electric pressure or potential that it takes to cause one ampere of current to dissipate one watt of energy per second. Work, or watts, equals volts multiplied by amperes. The resistance (R) to the flow of current can be described as the number of volts it takes to make one ampere of flow rate, or volts per ampere or volts/ampere. In this case the resistance (R) would be: one volt/ampere. This relationship can be written as R equals volts/amperes. The unit of the volt/ampere was named the Ohm to honor Georg Simon Ohm who was an early pioneer in the field of electricity. The abbreviation for the ohm is W.

The equations that describe the relationship between voltage, current, power, and resistance are referred to as Ohm's Law. Before getting into these equations, the not always logical, standard abbreviations need to be explained.

Other Abbreviations

Lower case letters are used for ac and upper case letters are used for DC. The abbreviations for alternating current (ac) voltage is v and V for direct current (DC) voltage. Voltage is referred to in Ohm's Law formulas as electro motive force which is abbreviated as EMF or just E for DC and e for ac. For example: E=3V means that the electro motive force is 3 volts of DC. Voltage is also referred to as a "potential" or a "potential difference", which is the difference between two voltages.

The ampere is abbreviated by the letter A for DC and a for AC. DC current in formulas is designated I; for AC i. For example, "the AC current is equal to 5 amperes" would be i=5a. Amperes are also referred to as amps.

Work or power is referred to as P for DC and p for AC. Watts are abbreviated by w or W. For example, "the DC power is equal to 4 watts" would be P=4W. "The AC power is equal to 4 watts" would be p=4w.

OHM'S LAW for DC

Resistance in Ws equals volts x amperes or R=E/I. Power in watts equals volts x amperes or P=IE. By using basic algebra, these formulas can be rearranged and/or combined to yield other formulas such as:

plus a few other variations of the same information.

For AC, the formulas are similar except that the letters would be lower case instead of upper case.

Next month I will show some practical applications for Ohm's Law.

Home Power 3

February 1988

Getting Started With Solar

Getting Started With Solar

Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.

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