Ws I

Tilting the tower over is a one-man task with the Wilson bases. (Shown above is the RB-618 Rotor is not included i



Prices Effective 1 1 81 thru 1-31-81

4266 S. Poiaris Ave . Vegas, Nevada tJ9103

Randy tight W85UCV I van der Smissen WB5ASA K) Box U9

University of Te*ai Medical Branch Galveston fX 77550

Jerry Karlovich W B5PRD 1k17 Bittercreek Garland f\ 75040

During the last part of ■ July, 1979, storm Ctaudette hit the Galveston-Houston area, drop-piny from ten to fort\-five (yes. forty-five) inches of rain in various parts of the region in a very short time Although the area was well blanketed with repeaters tarrying emergency information, the iraprd rise of water at ight caught manv hams unaware; some did not know of the emergency until water started coming into their homes Al that time, there was no way of alerting the radio amateurs once they went to bed, since most of them turned off the^r two-rneter rigs so that the routine chatter on the frequency would not keep them awake

Claudette made it extremely clear that a method was needed to quickly and efficiently alert area amateurs that an emergency situation existed Two additional emergenties in rapid sequence made it imperative that we ac t immediately.

Our need was lor a simple, economical system that couid be put into effect almost immediately Discussion on the air and at the August meeting of the Tidelands Amateur Radio Society (1ARS) and the University of Texas Medical Uranc h (Galveston)-Emer-gency Communicat ions Croup tUTMB-ECC) developed criteria for a device similar to the tone-alert system ot the National Weather Service (NWS), a single-tone system

A system for decoding dual tones has been used in Dallas for the past two years. Of the approximately 400 Radio Amateur Civil I mergencv Service (KACIS) members in Dallas, one hundred have the tone alert available. The usual response to any use of the emergency tone alert is at least 50% of the hams equipped to receive it The local authorities are very impressed with the ability of the hams to respond to emergencies (lie Dallas system is the "A-1 one Decoder" using the DTMf A tone. The tone alert is initiated by Civil Defense Ini-tialiv, the alert is on the 146.28/.88-MHz repeater, but it ma\ go to other repeaters it the area of emergency is wider than can be covered by one repeater. The choice of the A tone for this metropolitan area was based upon the high possibility for abuse of other tones. The A tone generally is not available on the pads commonly used by hams. So far, Dallas has had no false alerts, even though some non-hams have gotten access to two-meter equipment and some hams have tried to jam the

Photo A Completed tone alert.


Tarrant County [Fort Worth), near Dallas, is interested in implementing a similar system in the near future.

The decision of TARS and UTMB-ECC was to develop a tone-alert device based upon the success of Dallas, the ideas expressed by WA3ENK,1 the WB5PRD design, and utilizing at least a four-second signal of the dual tones of the DTMF figure 9 (which most amateurs have available in a touch-tone7 or comparable pad) as the triggering signal. Use of a relay to silence the audio circuit to an external speaker until activated by the tone was considered the simplest alert device. The four-to-five-second duration of the tone in our tone alert causes a relay to close which then turns on an external speaker or alarm bell.

Twenty copies of the original WB5PRD board were ordered, and within three days the interest was so great that an additional 50 boards were ordered.

The original WB5PRD schematic was modified (but still using the original board) to fit our needs and to use the DTMf 9 (ones. Local sources of parts in quantity were inadequate, so parts were ordered to provide 50 tone-alert kits. Parts were ordered from companies advertising in the several amateur radio journals. Upon checking the parts when they arrived, we found one company had shipped 30% of the parts in an inoperable condition, so these had to be replaced By careful selection of sources, we were able to get the total cost (parts and board) down to $12 50 for each kit. (The prototype us* ing parts bought in small quantities was built tor about 518.00,) While aw ailing receipt ot parts, a construction and testing manual was written

Word of what we were doing spread rapidly and inquiries came from other < lubs and groups. Discussions concerning this system became quite active among several RACES and CD nets in Houston, Alvin, Clear Lake, and East Texas areas, Several groups asked jf the device could be adapted to their special needs.

The concept of TARS and UTMB-ECC calls for the Emergency Operating Cen ters (EOCs) or a duly-autho-rued operator to initiate the 9 tone whenever the need arises to activate the net tor emergencies. We also use the tone alert to call up our weekly repeater (147.75/15 MHz) and simplex (145.53 MHz) nets.

As others have discovered, in the absence of phone-patch capability, hams must rely on tone alert1 It soon became apparent that two levels of alert would be needed; a low-level alert for personal emergencies such as car trouble, and a high-level alert for general emergen-

Photo 8. Assembled PC board.

cies such as hurricanes, floods, or explosions A single-tone capability for low-level alerts can be added without additional circuitry , using a toggle switch to ground one decoder output With ihe switch in the low position, the tone alert can be activated by a DTMF 7, 8, or 9. We recommend the use ol the figure 7 for low-level alerts and reservation of the figure 9 for high-level alerts.

Generally, the amateurs leave the tone alert on low level when they are around the shack and switch to high level when they go to bed 1 hus, their alert device would awaken them only for high-level general emergencies.

Several other groups are planning to use the 9 for their alerts Thus, a number of hams are now using the tone alert with scanners monitoring these several repeaters The scanners are being modified so that they will scan silently even if there is routme activity on the frequency, but i! the 9 signal is given, the scanner will lock onto that frequen cy and activate the audio

The Texas DX Society is considering using the tone alert on their repeater to alert members when rare DX is heard on the HI bands I hey anticipate us ing a set of tones other than the 9 so that their signal will not activate scanners that are monitoring the repeaters for emergencies.

Another modification of the tone alert will be for use with weather radios to de code the 1050-Hz tone of the National Weather Service alerts and activate weather receivers not previously provided with tone aiert Since the NWS alert is only a single tone, such use will require only one decoder of the tone alert The tone alert used for NV\ S cannot be used at the same time for the DTMF emergency tones.

Why were the 9 and 7 tones chosen? We thought that sjnce 911 is used on the telephone to dial emergencies to fire and police, use of a 9 would be easy to remember as the alert sig-

F/g, / Schemai/c diagram fSee Paris JL/si.J

nal. The low-level alert is a good-neighbor service for individual or personal emergencies; therefore, it was considered appropriate to use the 7 or 73 for this alert tone

Whether a large area such as the Galveston-Houston area is involved in emergencies or smaller local areas only, there is a way to alert only one or the other If a general alert is involved, then the alerting operator goes from repeater to repeater giving the alert and announcing the emergency. If oniy a local area is involved, then only the repeater covering that area is alerted

Because of the seriousness of emergencies that can occur in this region of the Gulf Coast and the potential for abuse, it was earls decided to establish the following Galveston County general guidelines for use of the tone alert.

High-Level Alert

1. The tone alert will be activated only by duly-authorized operators acting on behalf of emergencies declared by Civil Defense or other official agencies, or on behalf of the repeater organization.

2 Alert will be sounded:

a) in the event of a civil emergenc\;

b) for a regularly scheduled test or drill, c) to call attention to bulletins of general jn-terest during an emergency.

3 Initially, the alert will be sounded on the repeater (14775/15 MHz) covering the area affected by the emergency and on 145.5* MHz simplex.

4, Alert will be sounded by transmitting the digit 9 for 15 seconds The station transmitting the tone will a) identify;

b) transmit tone for 15 seconds;

c) call CQ or QST, d) state the nature of the emergency or that a test or drill is in progress;

e) give instructions concerning action to be taken and or frequencies to be mom tored.

Individual testing and tune-up of the tone-alert circuit will be done on a simplex frequency other than 145.53 MHz and will not be done on repeaters Use low power if possible when testing or tuning circuit

6 High-level tone alert will not be used for routine personal emergencies such as tlat tire, out of gas, etc

Low-Level Alert

1, This alert may be sounded by any amateur having a personal or individual emergency for which he needs help (It is recommended that a direct call on the repeater or simplex frequency be tried first before using the tone alert.)

2, tow-level alerts will be sounded only on the local area simplex or repeater frequency Low-level alerts are not to be used ior general alerts covering more than one repeater

3, Alert will be sounded b\ transmitting the digit 7 tor 15 seconds The station transmitting the tone w:||

a) identify;

b) transmit the 7 tone for 15 seconds, c) call CQ or QST;

d) state the nature of the emergency and request the necessary assistance.

This plan lias been operational since August, l<i7c.*J is

gaining adherents, and the idea is spreading. Based upon our experience, we would recommend this or a similar system to other amateurs participating in emergency at tivities.

Circuit Description

The schematic is shown in Fig. 1. The components listed in the Parts List are standard items which are readily available Advantages and disadvantages of the 567 PLL tone decoder have been discussed previously m the amateur literature M

I he circuit is powered from a 12 volt dc source Zener diode D4 provides 6.2 volts dc for U1 and U2<

When the circuit is armed by bringing pin 12 of U3c to logic one briefly, audio is routed through the normally-dosed contact of the relay to loading resistor R1 and to the input of the decoder circuits through R1 Germanium diodes D1 and D2 conduct at 300 mV to protect the circuit from audio overload, C2 and C3 pass the audio tones but block dc from entering U1 and U2 along with the audio signal

U1 and U2 decode the high and low tones, respectively. R3, R13, and C4 set the center frequent y of U1; R4, R14, and C5 set the center frequent y of U2 (bandwidth is about 5% of the center frequency).

When a decoder locks on an incoming tone, pin 8 goes to logic zero When both U1 and U2 are locked, pin 4 of NOR gate Lr3a goes to logic one. C10 then charges through R7 to provide a delay before pin 8 of U3b reaches logtc one. U3d inverts the output ot U3b. The sequence is now complete, the rela\ and LED are activated by Qi, and audio is now routed to the speaker until the circuit is again armed.

A total delay of three to four seconds is introduced between initial reception of the tone and activation ot the relay to prevent false activation of the circuit

D3 and R8 provide a discharge path for CIO when no lone is present.. This prevents a buildup of charge over a period of time from intermittent fake signals which might cause activatton of the circuit 05 protects Q1 from the transient voltage present when the relay is deactivated.

Momentarily closing the normally-open ARM (RH-St I ) switch will deactivate the relay (open the audio circuit to the speaker} and will arm the decoders so that they tan responti to an incoming tone signal

Momentarily closing the normally-open SET switch will activate the relay so that audio goes to the speaker This mode will continue until the ARM (RESET) switch is activated. (A momentary DPD I toggle switch with center off can be used in place of two separate momentary switches.)


The circuit was assembled on a WB5PRD circuit board (Drilled printed circuit boards are available from WR5PRD for an SASE and $4.00*) The foil side of the board is shown in Fig 2> which is suitable for use in reproducing the board An assembled PC board and a completed tone alert are shown in the photographs.

Parts layout is shown in Fig. 3 Assembly can be facilitated if one starts with those components at the center of the board and works outward toward the edge. Diodes, capacitors, trimpots, <md quarter-Watt resistors are mounted ver tic a 11 y The two one-Watt resistors are mounted horizontally If proper care js taken as to which end of the vertically-mounted resistors is upmost then that pomt of the resistor can be used as a test-point contact for testing other parts of the circuit. (See Table 1.)

The usual precautions should be observed when handling the 4001 CMOS integrated circuit. For temperature stability, C4 and C5 must be high-quality mylar™ or metallized film capacitors.

The switches and LED are installed on the front panel or speaker enclosure. The I.ED should be near the SI T switch, 1 he LED lights when the tone-alert unit is in the SET activation The relay 'S installed off the circuit board with epoxy glue or silicone rubber A multi-pole relay may be substituted if other devicesr in addition to the speaker, are to be controlled. (Remember that when other devices such as bells or buzzers are on the relay, they will be activatec! when the SET switch is activated.)

The twelve-volt dc supply is connected between points marked + and -(ground). One side of the relay coil and the LED anode are connected to point K&L and the other side of the relay coil goes to K. The cathode oi the LED goes to L. The ARM (RESET) swttch is connected to the points marked A. The SET switch is connected to the two points marked S. Audio is connected between INPUT and ground Points Er B. and C indicate the emitter, base, and collector of


The tone alert may be adjusted for the DTMF tone 9 using either of two procedures—either a frequency counter or a voltmeter may be used. With the ire quency counter method, the counter is connected to U1 at pin S (for a square wave) or pin b (for a triangle wave), and R13 is adjusted until the counter shows 1477 Hz Take care not to load the circuit with the test equipment Next, connect the counter to pin 5 or 6 ot U2 and adjust R14 until the counter shows 852 Hz.

Fig. 2. PC board foil side. This is suitable for reproducing the board for those who would like to do so

a leo anode

Fig. 3. Parts layout a leo anode

Fig. 3. Parts layout

Alternatively, a voltmeter or logic probe may be used. Star! with R13 and R14 fully counterclockwise, Apply an alert tone with the probe on pin 8 of Ul or pin 5 ot U3 and slowly turn R13 clockwise. Note the position of R13 when the voltage drops and continue turning R13 clot k^ise until the voltage goes back iup; note this point lurn R13 counterclockwise to a point midway between the two voltage change settings. Do the same with the probe on pin 8 of U2 or pin 6 of U3 whiie adjusting R14.


Apply 12 volts dc to the unit Momentarily close the St 1 switch; the relay should activate. Provide an audio input from the two-meter rig. The circuit will not function properly with a high noise signal or with too little audio drive. Turn the audio gain up to ensure proper drive level. The loading resistor is rated at one Watt. ARM the circuit and have another operator transmit an alert lone on a simplex frequency for fifteen seconds, The unit should activate in less than ten seconds.

Circuit Alternatives

I he circuit can be tuned for tones other than the digit 9. The standard tone pairs are listed in lable 2.

Component Connection

R4 Pin 5t U2

R12 Pin 3, U3d

Table 1, The end ot the component connected to the listed test point is placed in the up position.

Low Tone 697 Hz 770 Hz 852 Hz 941 Hz

1209 Hz 1 4

0 0

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