Κόλπα και tips

This month's column is a selection of hints and tips that I trust will be found useful around the shack and workshop.

Vertical dipoles from coax cable

With a Stanley knife make a cut around the coaxial feedline approximately one quarter wavelength from the end of the cable (length in metres = 71.5/frequency).   Then slit the cable to remove the outer jacket from the cut to the end of the cable.  With a small screwdriver make a hole in the braid near the start of the outer jacket.    With the screwdriver, lever the inner conductor out through the hole.  Solder an eye terminal or washer to the end of the inner conductor to provide a support for hanging from a tree branch or curtain rail.

Uses for scrap circuit board material

These include small boxes, dividers where shielding is important, small nameplates (if etched) and square pads for 'paddyboard' construction.  For the latter, tin snips or multipurpose shears will cut the material nicely.

Soldering two wires together without an iron

Wrap join with solder.  Then wrap with aluminium foil.  Hold a lighted match to joint until solder melts.  Remove foil when solder sets.

Illuminated dummy load

A 12-volt 300mA light globe soldered into a PL259 plug makes a useful dummy load for HF QRP equipment running up to a few watts.

Cutting ferrite rods to size

Saw groove around rod with hacksaw.  Hold rod in two hands and apply force.

The rod should snap cleanly.

Determining loss of coil formers for antenna traps, etc

Place material in microwave oven with glass of water.   High loss material will get very hot or melt.  Material that stays cold or warms only slightly is suitable for use.  Remember to remove all metal traces (eg wire or mounting screws) before doing the test!

Portable antenna mast

An eight or nine metre giant squid pole forms an excellent mast for portable operation.  These lightweight poles (also called roach poles or telescopic poles) are available from fishing shops and collapse down to about 1.1 metres.  Squid poles can support lightweight wire antennas for HF and VHF/UHF groundplanes.    The poles will not support coaxial feedline unless it is supported by taping it to the pole.

 

Handheld antennas

Antennas that a quarter wavelength or less on handheld transceivers often benefit from the addition of a counterpoise.  Clip a quarter wavelength of wire onto the earth connection of the radio's antenna socket.

Holding nuts in tight places

1. Blu-tac or small dab of glue on end of screwdriver

2. Rubber band across handles of long-nose pliers

Easy connectors

Terminal blocks cut up into strips make handy barrel connectors.

Insulators for wire antennas

For temporary portable antennas, use toothbrush handles.  Otherwise use sections of plastic conduit.

Pedestrian mobile HF station

 

A case to hold a transceiver, gel battery and antenna can be made from pieces of 10mm-thick chipboard.   Thread old coaxial cable through holes in the box to make carry handles.  To prevent rubbing against the operator if the station is used whilst walking, glue carpet to the side of the box closest to the operator.  For the transceiver, use a converted CB for 10 metres or Yaesu FT-817 for HF/VHF/UHF coverage.

 

Spreaders for open wire feedlines

If you have a few more toothbrush handles, you can use them as spreaders in home-made open wire feedline.   Alternatives include hair curlers, or my favourite, plastic irrigation tube about 6mm in diameter as sold by garden suppliers.

Doing well in contests

If you use a good antenna from a good location and consider yourself to be a 'strong station', spend most of your time calling CQ – others will find and work you.  If your signal is weaker than others, spend most time tuning the band and calling other stations.  Once all stations heard have been worked, find a clear frequency and call CQ for a while.

 

Cheap VHF/UHF signal generator

An HF rig fed into a dummy load makes a crude signal generator for doing tests on VHF/UHF receivers or as a BFO for receiving SSB on an AM receiver.  Set the transceiver to just above 28.8 MHz for harmonics in the 144 and 432 MHz bands.

Projecting sound forward from top-mounted speakers

Transceivers with top-mounted speakers can benefit from a yoghurt container (with a forward facing cutout) placed over the speaker grille.  The container projects the sound forward towards the operator.

 

Improving access to station equipment

When you next renovate the shack, consider placing the operating desk about a metre from the wall.  This will make it easier to access power and antenna connections and add new equipment.

Labelling leads

 

Cables should be labelled to minimise the risk of equipment damage, for example when transmitted power is applied to the antenna socket of a receiver.  A good way is to write (with a ballpoint pen) labels onto strips of paper 5mm wide and as long as the label requires. Clear adhesive tape is placed over the front of the label and around the cable. The tape is then continued so that it sticks to the back of the paper and around to the front of the label, where it is cut with scissors. The result is a descriptive 'flag' at the end of the cable near the connector. A refinement could be to write on both sides of the paper strip instead of one.

Solder dispenser

Pierce hole in 35 mm film container.  Wrap solder around pipe or tube to form coil.  Thread one end of solder through hole, and place coil inside container.    Replace cap.

Antenna accessories at fishing shops

Apart from squid poles (see previously) several other items useful to the amateur can be procured at fishing shops.  Fishing reels are ideal for storing wire antennas.  Depending on the length and thickness of the antenna wire, diameters between 10 and 25 centimetres are suitable.  Sinkers and fishing line are also useful for raising antenna wires over tree branches.

Uses for octal valve bases and film containers

Octal valve bases screwed to 35 mm film containers form useful plug-in coils for receivers, dip oscillators and antenna coupling units covering the low HF bands.  Octal plugs and bases are still stocked by major parts outlets.  For coverage of higher frequencies, use 5-pin DIN plugs and formers approximately 12mm in diameter, such as conduit.

Use for old coax

Lossy or water-damaged coax can still be used for ground radials. The braid can also be used for earth connections.

Calling on repeaters

When putting out a call, press the PTT button, wait 5 seconds and then call. This gives time for people's scanning transceivers to stop on your frequency, for your call to be heard and increases the chance of getting a response.

On indicator

To add an on indicator for projects that operate from 12 volts, wire an LED in series with a 560 ohm resistor.

Polarity protected projects

 

Simply wire the positive and negative power leads to the positive and negative connections of a diode bridge rectifier.  The polarity applied to the two AC inputs is not critical.  This technique is only recommended for low-powered projects with plastic or non-earthed metal cases and in situations where the voltage drop across the bridge will not impair operation.

Learning about Spread Spectrum

An excellent web page about spread spectrum communication can be found at  http://sss-mag.com/    The site includes an amateur section.

BFO for SSB

Cheap one or two band shortwave receivers seldom have a beat frequency oscillator required for amateur SSB reception.  A portable AM broadcast radio placed near the receiver can be used as a BFO, with no connections required.  Setting the radio near 1.3 MHz should cause a carrier to be heard near 3.5 MHz or 7 MHz.  To use, tune for maximum 'duck talk', and carefully adjust the broadcast receiver until the signal becomes intelligible.  Move the receivers closer together for strong signals and further apart for weak signals.   It's fiddly, but it works!

Estimating thickness of enamelled wire

Wind 10 turns onto a pencil, measure in millimetres with a ruler and divide result by ten.

Tuning indicator for base loaded HF antennas

Attach one side of a neon bulb to the top of the loading coil.  Leave the other side of the bulb floating.  Use 5-10 watts and aim for maximum brightness.

Use for computer power supplies

Many articles have described how two disused computer power supplies can be made into a high-current 13.8 volt supply for transceivers, etc.  Not all constructors have found this project straightforward, and only competent builders should attempt it.  However if you are willing to accept a reduced voltage (11.5 to 12 volts) and reduced current (up to a few amps), the 12-volt output from a single, unmodified supply will adequately power CB and low power amateur equipment.

 

Using small bits in large drill chucks

Wrap a few turns of solder around the bit, insert in chuck and tighten.  The technique can also be used to salvage drill bits that have been broken.

Preventing components being lost

When assembling kits or constructional projects, place the parts in a shallow dish to prevent them rolling off the table or bench.

SO239 antenna mount

A square-type SO239 chassis mount socket makes a handy base for quarter wave ground plane antennas for two metres or seventy centimetres.  The feedline can be fed up a tube (with an inside diameter larger than the PL259 diameter) or taped to a squid pole for a quick home station antenna.

Emergency supply of solder

Wrap solder around cord of soldering iron to form emergency supply of solder to use when your reel runs out.

Quick six metre antenna

It's worth a reminder that a 5/8 wavelength whip for two metres will operate effectively on six metres as a ¼ wavelength whip.

Cases from component stereo systems

1970s stereo equipment is now available cheaply from garage sales and car boot sales.  The boxes from amplifiers, tape decks, graphic equalisers make fine enclosures for large projects, such as homebrew transceivers, antenna couplers and power supplies.  Use printed circuit board scraps to cover holes if necessary.

Λειτουργώντας έναν σταθμό στα βραχέα, μέρος Β'

Part One of this series covered basic HF operating procedure. This month, we take a more detailed look at specific operating activities enjoyed by amateurs. There is also a chance to put what you have learned to practical use in contests such as the annual WIA Remembrance Day Contest held mid-August.

DXing

In amateur parlance, DX means long distance, normally defined by HF operators as being outside one's continent. There are many amateurs who, after establishing a station, enjoy talking around the world. DX operators have a variety of motives; some like experimenting with antennas, while others prefer to chase various operating awards.

As well as having an efficient station, good operating skills are important for the successful DX-er. These include a knowledge of radio propagation, being able to discern weak signals, a habit of listening around the band before transmitting, and a sense of timing when calling another station. Clear pronunciation, the use of standard phonetics on SSB, and steady sending on Morse are the hallmarks of the good operator.

Active DXers place great importance on contacting remote, obscure islands. Sometimes, groups of DXers may organise special voyages (called DXpeditions) to such islands, so that other amateurs may work them. These DX peditions are very costly, and organisers often solicit donations from amateurs and commercial sponsors.

When a signal from a DX-pedition is heard, there are often many stations trying to make contact. Quite appropriately, this wall of QRM is called a 'dogpile'. DXpedition stations may operate 'split-frequency'. This means that you listen on one frequency and transmit on another. For this reason, serious DXers use transceivers with dual VFOs.

Being able to be heard by a DX station is a matter of strategy and timing; the station might have a particular pattern of operating that you can exploit. When called by a DX station, make the contact brief, as you would in a contest, as many others may be waiting for their turn.

The impression gained so far is that the DXer is a rather competitive, solitary operator. This is not always so; some DXers hunt in packs. Several nets for amateurs who enjoy working DX, exist on the bands. In addition, groups of DXers in some cities have set up early-warning systems called DX clusters. This is essentially a special packet radio link between DXers. Their function is to alert all suitably equipped stations that a sought after station has appeared on the band. Thus, instead of spending time tuning around, one can switch off, watch TV, and only fire up the rig when a rare station comes on.

CONTESTS

A contest is an organised event where the aim is to make the most number of contacts within a given period. Apart from being an exciting and absorbing activity in its own right, contesting allows you to test the efficiency of your station, together with operating skills. With there being many stations on the air at the one time, a contest is an ideal opportunity to have contacts with various countries or call areas so that you can work towards many of the awards on offer.

While most major contests run for 24 hours, some short contests ('sprints' or 'scrambles') run for only an hour or two. These short contests have simple rules, and are good fun.

Contest contacts are much shorter than most other amateur radio contacts; all you need to exchange with the other station is a five or six digit number, consisting of a signal report followed by a serial number starting at 001. This serial number increases by one for every contact you make, thus you might send 57003 to the third station you work in a contest. The object is to make as many contacts as possible within the contest period.

The following is a typical example of an SSB contest exchange between VK1AA and VK6AA.

(VK1AA): CQ CQ CQ RD CONTEST, THIS IS VK1AA.

{VK1AA seeking a contest contact}

(VK6AA): VK6AA

{VK6AA responds}

(VK1AA): VK6AA, THIS IS VK1AA. My NUMBER TO YOU IS 57011

{VK6AA's signal is 5/7, VK6AA is VK1AA's eleventh contact in the contest}

(VK6AA): THANK YOU FOR THE 57011. MY NUMBER TO YOU IS 58001 {

{VK1AA's signal is 5/8, this contact is VK6AA's first in the contest}

(VK1AA): 58001 RECEIVED. 73 AND GOOD LUCK IN THE CONTEST.

{Contest contact ended successfully and both stations enter the contact in their logs. VK1AA continues calling CQ, while VK6AA looks for other stations calling CQ}

On CW, the procedure is similar, except there is a heavy use of abbreviations to save time (see Part One). Very often, nines are sent as 'N', and zeroes as 'T'. Thus, the first station you work might receive a '5NNTT1' number from you, which is the equivalent of a 59001 report on phone.

To formally enter a contest, a log of all contacts must be submitted. A sample log sheet, suitable for most contests, is shown in Figure 1. Normally, a front summary sheet, which shows your name, callsign, total score and declaration that you operated ethically is stapled to the front of the log - the format for this is generally specified in the contest rules. The major WIA-sponsored Australian contests are as follows:-

• Remembrance Day Contest (August)
• VK-ZL-Oceania DX Contest (October)
• Ross Hull VHF/UHF Contest (December/January)
• VHF/UHF Field Day (January)
• John Moyle Field Day (March)
• VK Novice Contest (June)

Certificates are awarded to contest placegetters. Up-to-date information on these and other contests can be found in AR magazine. On the Internet, contest rules can be found at http://www.uq.edu.au/radiosport/Rules/index.htm

FIGURE 1 - SAMPLE CONTEST LOG SHEET

Name---------------------------Callsign----------------------Contest---------------------

Date----UTC----Band---Mode---Callsign------RST/no. sent----RST/no. rec--------Points

______________________________________________________________________

______________________________________________________________________

______________________________________________________________________

______________________________________________________________________

______________________________________________________________________

______________________________________________________________________

______________________________________________________________________

This log sheet is typical only, but should be acceptable for most contests. Read the rules applicable to the particular contest for more information.

AWARDS

An award is a certificate received for having contacted a specified number of stations in a certain geographic area, or on a particular mode. They range from the local club award to the internationally-recognised, and from the easy to the almost impossible.

The most well-known international award is the DXCC (DX Century Club), issued to those amateurs who have proved that they have contacted at least 100 countries. Another award gaining prominence is the 'Islands of The Air' (IOTA) award for contacting a specified number of islands.

The WIA has its own awards program, with certificates issued free to members.

WIA awards available include:-

• WIA DXCC
• Worked All VK Call Areas (WAVCA) Awards (VHF and HF)
• Worked All States (VHF)
• Australian VHF Century Club
• WIA Antarctic Award
• WIA Grid Square Award

Refer to the 1995 Australian Callbook for further information on the above awards. Those interested in collecting awards should maintain a log of stations worked. Note that QSL cards are required to show proof of having worked a station; log entries alone are not sufficient.

QSLing

A long-standing tradition has been to exchange QSL cards after the completion of a contact. The practice comes from the days when working DX (usually with low power and home made equipment) was much more of an achievement than it is today. Many overseas stations tend to be almost obsessed with QSLing, to the point that they ask for a card even if filling in and sending the card takes longer than the original two-minute contact. In contrast, many VKs are more laid back, only sending cards for the more memorable contacts. It may be for this reason that we have the reputation of being bad QSLers.

Nevertheless, QSLing is almost mandatory for those who aspire to collect awards, which normally require cards to show evidence of contacts claimed. Also, the new amateur will often want to decorate the shack with cards received from distant countries. After a wall has been 'wallpapered', the novelty often wears off, with many an amateur storing cards in shoe boxes in a seldom-opened cupboard.

Every amateur should have a stack of their own QSL cards, even if they are only sent infrequently. Cards should be of postcard size, and include your callsign, address and (preferably) your Maidenhead grid square locator number. It should include spaces for the callsign worked, UTC date and time, signal report, band, and mode used. Spaces on the card for your equipment, antenna and power output are also desirable. Figure 2 shows a typical commercially-printed QSL card.

There are two ways of sending cards. They may be posted via the normal mail system. While fast, it is expensive. Fortunately, the WIA and its sister societies have established QSL bureaus for use by members. These bureaus send and receive QSL cards in bulk, so postage costs are reduced. Though sending cards 'via the bureau' is slower than QSLing 'direct', the money saved is considerable, particularly if you are an avid DXer.

QSL Bureaus consist of two sections; Inwards and Outwards. The Inwards section receives cards from overseas and interstate, and distributes them to members, while Outwards accepts cards from you and forwards them to bureaus in other states/countries.

You can collect cards that have arrived for you from your Divisional Office, or WIA or club meetings. Alternatively, you can have your cards mailed to you by sending a SASE to the QSL Bureau Manager. QSL Bureau procedures vary slightly between states; some Divisions may charge a nominal sum per card sent, while others charge nothing. Addresses for QSL bureaus are listed periodically in this magazine, and in the WIA Callbook (Reference Two).

QRP

QRP operation is the use of low transmit powers. Its adherents gain a special pleasure from working across the country or across the world with a couple watts of power. QRP, defined as the use of five watts or less on CW, and ten or less on SSB, is ideal for portable operation, where lightweight transmitting equipment must be used. In addition, the low-cost and simplicity of QRP equipment makes building one's own transceiver a practical proposition, particularly for CW operation.

Practically the full range of operating activities, such as DXing, contesting and VHF operation can be done with QRP. An efficient antenna and good operating skills are required for maximum success. Ownership of special equipment is not required; QRP can be obtained from many 100 watt transceivers that have an external ALC socket.

QRP in Australia is promoted by the CW Operators' QRP Club, which publishes a quarterly magazine, runs nets and sponsors contests for QRP operators. Those seeking further information on QRP are referred elsewhere on this site.

CONCLUSION

This short series has, I hope, given you a better knowledge of HF operation. As well as reading about it, the best way to learn is by listening and operating yourself. The appearance of this column has been timed to coincide with the Remembrance Day Contest, to maximise this opportunity.

REFERENCES

1. Lewis M, QRP- The Crest of the Radio Wave, Amateur Radio, April 1995,

2. 1996 WIA Callbook

Λειτουργώντας έναν σταθμό στα βραχέα, μέρος Α'

Having obtained a callsign, established a station and erected an antenna, the next step is to learn how to operate it. This requires an ability to adjust equipment to transmit a clean signal, as well as a knowledge of basic operating procedures. Part One will focus on the latter, while Part Two looks at some of the specialised operating activities, such as DXing, awards and contests, enjoyed by amateurs. this series concentrates on SSB (voice) and CW (morse), both of which can be used by Foundation licensees.

WHICH BAND?

Amateurs have a range of bands from which to choose. Thus, at any one time, a well-equipped amateur station can contact stations over various distances by selecting the right band. Band conditions vary according to the season, time of day and sunspot activity. Foundation licensees can use the following HF segments:-

3.500 - 3.700 MHz (80 metres)

7.000 - 7.300 MHz (40 metres)

21.000 - 21.450 MHz (15 metres)

28.000 - 29.700 MHz (10 metres)

In very general terms, the lower frequency bands (such as eighty metres) are most used at night, while the higher bands 10 and 15 metres) are more active during the day. 40 metres is an in-between band, permitting short and medium distance coverage during the day and long distance contacts at night. 10 and 15 metres are greatly affected by sunspot numbers, with the ability to make DX (overseas) contacts on them peaking in years of high solar activity. At the moment, we are in the trough of the eleven-year sunspot cycle, so we can look forward to improving conditions in the next few years. At this phase of the sunspot cycle, 15 metres is likely to yield more DX contacts than 10 metres for the Foundation operator, though ten metres can still be productive, particularly during major contests.

Around mid-winter and mid-summer, ten and six metres come alive due to a phenomenon known as 'sporadic-E'. Sporadic-E occurs during all phases of the sunspot cycle and permits distances of approximately 500 to 2000 kilometres to be covered, even with just a few watts and simple antennas. It can occur at any time, but is more prevalent during the day.

The time of day is an important determinant of band conditions. While local contacts are possible on eighty metres during daylight hours (particularly in winter), it is during the evening that the band finds most use, with distances of up to 3000 kilometres being typical when conditions are good. More typically, a 10 watt Foundation licence station can expect regular contacts up to 500 to 1000 kilometres in the evening. An important advantage of eighty metres is the almost blanket coverage that is obtainable; this is in contrast to the higher bands where a 'skip-zone' exists between the limit of ground-wave coverage, and where the sky-wave, reflected from the ionosphere, returns to earth.

40 metres during the day permits the sort of contacts you can get on 80 metres at night, though it's easier to have longer distance contacts (eg 1000 - 3000 km) with low power. At night overseas stations can sometimes be contacted but there can be a lot of interference and 80 metres can be better for contacts within Australia.

For cross-town communication (say up to 20-30 kilometres), any HF band will provide results, though ten metres is preferred, because of its lack of crowding, low band noise, and relative efficiency of mobile antennas. Somewhat longer distances can be spanned on eighty metres, or else on the higher bands when sporadic-E propagation is apparent. DX contacts are most prevalent on 15 and 10 metres (mainly during the daytime), but could be possible on eighty metres if you possess an antenna whose radiation pattern is concentrated at low angles.

Which band is best to start on first? My pick would be 40 metres, since it is capable of short, medium and long distance contacts at various times of the day. Its antenna requirements are also less onerous than 80 metres, and many good contacts can be made with 10 watts. My second preference would be 80 metres. However (a) if you have very little room, (b) you are more interested in overseas contacts, or (c) it's a high sunspot year, 15 metres might be chosen instead. 10 metres also has its moments and is made more accessible as many 27 MHz CB antennas can be converted for use on this band.

THE ANTENNA

It is assumed that an antenna has already been erected. The typical Foundation station may include a dipole or inverted vee for 80 and or 40 metres, a trap vertical or small beam for 10 and 15 metres, and a groundplane, discone, J-pole or similar antenna for VHF/UHF, with different capabilities on different bands in line with the operator's interests. All these antennas can be constructed at home; details are provided in magazine articles and in the standard antenna handbooks.

MAKING CONTACTS

There are more similarities between HF SSB and CW operating procedures than there are differences. In both cases, it is wise to tune across the band you intend to use prior to transmitting. This provides a general impression of band conditions.

Assuming the transceiver and/or antenna tuning unit are properly tuned up (a process which, if performed on-air at all, should be done on a clear frequency at low transmit powers), the process of seeking contacts can begin. There are three main ways of obtaining contacts. These are as follows.

Responding to a CQ call: Tuning across the band may reveal one or more stations calling CQ. A CQ, which is a general call to all amateur stations, is your invitation to respond. Such a response takes the form of sending the other station's callsign, followed by your own, perhaps sent several times if signals are weak.

If the calling station is VK6AA, and your callsign is VK1AA, your response on SSB could be:-

VK6AA, THIS IS VICTOR KILO ONE ALPHA ALPHA, VK1AA.

On CW, you would send:-

VK6AA de VK1AA VK1AA VK1AA K

In this case, 'de' means from, while 'K' is an invitation to transmit (or 'over' on voice)

If the station replies to another station, you may wait until the contact finishes, or move to another frequency. On the other hand, the calling station may ask 'QRZ?'. This indicates that the station heard a signal, but was not able to decipher the callsign. The correct procedure in this case is to repeat your call, possibly speaking (or sending) a little slower this time.

Calling CQ: If no other stations are calling CQ, it is a good idea to issue a call yourself, especially if you have reason to suspect that the band may be open (eg hearing beacons on 10 and 15 metres). After selecting a clear frequency, it is polite to ask if it is in use. On SSB, this is accomplished by announcing your callsign and asking if the frequency is occupied, while CW operators simply send 'QRL?'. If no response is received, the frequency is yours to use.

The length of CQ calls depends on band activity and conditions; if band occupancy is sparse, a longer CQ call is suggested to attract the attention of the casual listener tuning across the band. In order to maximise the chance of obtaining contacts, and to minimise interference with other operators, the Amateur Radio bandplans should be adhered to at all times. Essentially this means not operating SSB on frequencies reserved for CW or digital modes. Bandplans are published annually in the WIA Callbook (Reference One).

On SSB, a typical CQ call is as follows:-

CQ CQ CQ CQ CQ CQ CQ CQ CQ THIS IS VK1AA, VICTOR KILO ONE ALPHA ALPHA, VK1AA, CALLING CQ AND LISTENING

(before calling, make sure you are on the right sideband - LSB for 80m, USB for 15/10m)

A CQ call on CW may be:-

CQ CQ CQ DE VK1AA VK1AA VK1AA K

Higher speed operators may choose to make their calls longer, to increase the chance of the call being heard. However, this should not be overdone; hearing 20 CQs before a callsign is sent will cause most listeners to seek contacts elsewhere.

'Tail-ending': An effective means of obtaining contacts (especially if using low power) is by the use of 'tail-ending'. This means listening in to a conversation, and calling one of the stations involved immediately after the contact ends. Timing is important here, particularly if unable to hear all stations on frequency.

When 'tail-ending', the call made can be just as if one was answering a CQ. If used with care, 'tail-ending' is probably the best way to make contacts on the HF bands.

DURING THE CONTACT

Once contact has been established, the first few exchanges normally entail a swapping of RST signal reports, names and locations ('QTHs') with the other station. From this point, the conversation may extend to the antenna and equipment, and (unfortunately) the seemingly ubiquitous weather report. Discussion beyond this point is a matter for those concerned, though amateur regulations and ethics mean that there are some topics best left alone.

The purpose of signal reports (see Table Four) is to give your contact some idea of how their signals are being received. Signal reports on phone consist of two digits. The first of these is readability (R), on a scale of 1 to 5. The second figure given is the strength (S) of a signal, this time on a scale of 1 to 9. The third digit, used by CW operators to indicate the purity of the received tone, is also on a scale of 1 to 9. Because of the quality of most modern equipment, reports of less than T9 are rare.

Some tend to accept the S-meter as gospel, without realising that S-meter calibrations vary between transceivers. Cases of people refusing to give signal reports if a signal (though perfectly readable) is not moving their meter's needle are not uncommon. If in doubt as to what report you should give, it is best to ignore the meter on your transceiver entirely.

ENDING A CONTACT

If the time that it can take is any guide, many people have trouble ending contacts. On CW, this manifests itself in the endless repetition of 73, BCNU, CUL, CUAGN and other solecisms, while on SSB, many a fictitious saucepan must have boiled over! Try to end contacts cleanly and keep the number of 'final-finals' to a minimum; this makes it easier for other stations who might want to call one of those about to depart.

CONCLUSION

This article, has provided some pointers on basic operating techniques. Join me in August for Part Two, which includes more detailed information on DXing, contests and award hunting.

AMATEUR RADIO ABBREVIATIONS AND PROSIGNS

Table One: CW Procedural Signals (Prosigns)

CQ A general call to all amateur stations

AR end of message, full stop

K "over", invite any station to transmit

KN A specific station only to transmit

BK invite receiving station to transmit

R all received OK

SK end of contact

CL going off the air (clear, switching off)

Note that all two-letter prosigns are sent with the letters merged together (except CQ).

Table Two: Commonly used Q signals for CW work

QRL?: Is this frequency in use? (use this just before calling CQ).

QRM: Man-made interference (eg other stations on/near your frequency).

QRN: Natural interference (eg thunderstorm activity)

QRO: High(er) power.

QRP: Low(er) power - normally 5 watts or less.

QRQ: Send faster (eg QRQ 12: please send faster at 12wpm).

QRS: Send slower (eg QRS 8: please slow down to 8wpm).

QRT: Stop transmitting.

QRX: Please wait (eg QRX 1: please wait one minute).

QRZ? Please call again (used when a station has responded to your CQ call, but you missed their callsign).

QSB: fading signals.

QSK: 'break-in mode' - your equipment allows listening while sending.

QSL?: Can you acknowledge receipt (of message)?

QSO: conversation.

QSY: move to another frequency (eg QSY 3530 means QSY 3.530 MHz).

QTH: transmitting location.

Note: The above lists the most commonly used Q-codes for amateur CW operation. The meanings shown are those that are most used on-air, and vary slightly from the definitions in the standard handbooks. To ask a question, simply attach a question mark (?) to the Q-signal; for instance, QRQ? means 'Shall I send faster?'. While Q-signals are sometimes used on SSB, plain English is probably as effective in most cases.

Table Three: Common abbreviations for CW work

ABT About

AGN Again

AS (please) wait

CQ Calling any station

CUL See you later (similar to BCNU, HP CU AGN, etc)

ES And

FB Fine Business, excellent

GM(N) Good morning (night)

GUD Good

HR Here; Hear

HW How

NR Number (used in contests)

PSE Please

RST Signal report (see later)

SIG Signal

SRI Sorry

TKS, TNX, TU Thank you

UR Your; You're

VY Very

WKD Worked

WL Well; Will

WX Weather

Abbreviations for other words exist, but their use is less prevalent than those in the list presented here. Their use can make CW communication faster and more pleasurable, particularly at slower speeds.

Table Four: Standard Readability and Strength Scale (source: ARRL Handbook)

Readability

1 unreadable

2 barely readable, occasional words distinguishable

3 readable with considerable difficulty

4 readable with practically no difficulty

5 perfectly readable

Strength

1 faint signals, barely perceptible

2 very weak signals

3 weak signals

4 fair signals

5 fairly good signals

6 good signals

7 moderately strong signals

8 strong signals

9 extremely strong signals

Tone

Scale of 1 to 9. Nearly all signals today are T9.

REFERENCE

1. WIA Radio Amateur's Callbook (any year)
Note: This article was written in 1996 but has been adapted to reflect subsequent licensing changes.

Ο πρώτος σας πομποδέκτης βραχέων

There are several choices when it comes to procuring your first HF transceiver. This article provides guidance to help you make the right decision.

Buy new

New HF amateur rigs start from under $1500. While these prices may seem high,.amateur transcveiver prices have fallen sharply relative to real wages since the 1960s. When buying new, you also get the manufacturer's warranty and a better availability of optional accessories and spare parts. For details of new rigs, see the advertisements and reviews in magazines such as Amateur Radio.

You will notice significant price differences between new and secondhand HF rigs. When choosing a rig, consider bands and modes you may wish to use in the future. A $400 used transceiver may appear cheap, but will not have much of the following:

• 160 metres
• 30, 17, 12 metres
• AM and FM modes
• Digital frequency display
• Dual VFOs (required for much DXing and 10 metre FM repeater operation)
• AM and/or FM facilities
• General coverage receiver
• Narrow CW filter
• Inbuilt antenna tuning unit
• Digital signal processing

A Foundation Licensee needs none of these frills to make contacts, but they are nice to have later on. Even if you just need several, a basic new transceiver with all or most of them included (such as a Yaesu FT-817 or Icom 703) starts to look a better proposition. You also get the benefit of the supplier's warranty (2 years typical) and the better availability of optional accessories as mentioned above. Don't fall in to the trap of buying an older cheaper second hand rig thinking that you'll get the extras later - some accessories are much harder to find on the secondhand market than the transceivers themselves.
Similar comments apply for Standard and Advanced Licensees, except with their higher power limits there is a wider range of equipment to choose from. A popular no-nonsense 100 watt HF-only transceiver is the Icom 718. In contrast the Yaesu FT-847 or Kenwood TS-2000 appeal to those who want 'all bands in the one box'.
Apart from the top range home station transceivers (eg FT-1000 MK5), most new equipment runs off 13.8 volts DC. Home operation with these rigs require a power supply that can deliver at least 20 amps continuous. Suitable supplies are available new, second hand or in kit form. If you plan on buying a 100 watt rig, you should obtain a 20 amp unit. Any supply you buy or build should be regulated and include over voltage and over current protection. The Dick Smith D3800 is an example of a high-current supply suitable for any 100 watt solid state transceiver. This reasonably priced supply (under $300) includes voltage and current metering which is very useful.

Buy secondhand

A basic used rig can be picked up for between about $300 and $500. Generally older gear is the cheapest. If buying second hand, avoid the older all valve transceivers; these rigs may be over 30 years old and replacement valves, transformers and high voltage components may be hard to come by. As well, they are not as sensitive as more modern rigs, particularly on 10 and 15 metres. Portable and mobile operation with valve transceivers is much more difficult than with newer equipment.

Transceivers that are solid state except for the finals are a better proposition, but again they may not include all HF amateur bands. Examples include the Yaesu FT101 series and the Kenwood TS520/530/820/830 series. These can perform well for home station operation, but are too bulky for mobile and portable operating. Final valves for them are becoming harder to obtain and more expensive. You may be lucky and buy a rig that gives you twenty years service with the one set of finals, on the other hand you may not. If buying a set with valve finals, it is probably an advantage to buy one where the seller is offering one or more set of spare finals along with the transceiver.

For about 20 years all HF tranceivers from the major manufacturers put out around 100 watts. In recent years the growth of QRP, portable operation, and more recently the Foundation Licence encouraged manufacturers to make lower power equipment.
Going back, many lower powered sets were imported into Australia during the late 1970s/early 1980s when the old Novice licence permitted only 30 watts on SSB. Examples include the Yaesu FT-7, FT-77S and the Kenwood TS-120V. Though these sets do not cover all bands available to Advanced licensees, they make good starter rigs for the Foundation Licensee on a budget.
Possible bugs include dry joints, bad earthing, erratic internal sockets, display problems and frequency drift so test before buying. Expect to pay $200-350 for these older rigs.

Second hand gear is available from some amateur radio dealers or privately. Note that used rigs bought from a dealer may have a short warranty, whereas if you buy from an individual, you’re on your own if something goes wrong. When buying a rig privately, see it operating and insist on receiving the manual for it.

You can find out about equipment being offered for sale in your area by scanning the classified advertisements in both of Australia's amateur magazines, or listening to weekly broadcasts in some states. Many of these include 'buy and sell' or 'Disposals' segments. If there is no suitable equipment advertised, try putting an 'Equipment Wanted' notice in one of the magazines, on the club notice board or the VKHAM website.

Another place from which you can obtain used equipment is at amateur radio hamfests and junk sales. Details of these are normally given in the weekly broadcast and the amateur magazines. Radio clubs are good places to start when looking for used equipment. It is quite likely that at least one member will have gear for sale, and you will not need to travel far to collect the rig. You may even know the seller and the history of the particular piece of equipment being offered for sale. As well, if your club has its own station, you may be able to use it to test equipment that you are considering purchasing. Club members are also valuable sources of information on new equipment that you may be considering purchasing.

Convert equipment to the amateur bands (Standard & Advanced licensees only)

Another option is to convert a commercial Royal Flying Doctor or similar SSB transceiver to the amateur bands. These radios deliver good performance, are rugged and are great for portable and mobile operation, especially if you want coverage of only a single band, such as 80 metres. However, converting these radios has many pitfalls for the newcomer. These include:

• Price - second-hand RFDS-type transceivers can be much more expensive than a brand new fully-featured HF amateur transceiver.
• Availability of information - Unless you are an experienced amateur, you will need a technical manual to do conversions. This may not always be easy or cheap to obtain.
• Correct sideband - Some sets transmit on upper sideband only. This severely limits their usefulness on 160, 80 and 40 metres where 99% of SSB activity is lower sideband.  Also older rigs do AM only.
• Crystal control - The older sets that are available cheaply are crystal-controlled. However frequency agility is essential for amateur operation. A variable frequency oscillator (VFO) can be built in to some transcievers, but this is not a task for the raw beginner.

Unless you can get a set for a good price (less than $100), and can work under guidance of a more experienced amateur, I would suggest giving these transceivers a miss and buying or building instead.

Build your own (Standard & Advanced Licensees only)

Introduction

One of the unique aspects of amateur radio is being allowed to build your own transmitting equipment. Though it is unrealistic for the newcomer to be able to build their own multiband HF transceiver, building simple single band direct conversion receivers and low powered (QRP) transmitters is not unreasonable.

If you are on a very limited budget, building your own is the cheapest way to get on the air - an eighty metre Morse Code (CW) transmitter capable of covering distances of up to several hundred kilometres or more costs less than $30 to construct if all new components are used. Voice transmitters are a little more complicated to build and adjust, but can be rewarding projects.

The basic components for homebrew transceivers can be obtained from suppliers such as Jaycar and Dick Smith. However you will need to obtain more specialised parts such as variable capacitors, dial drives, toriods, crystals, RF transistors and ICs elsewhere. These can be found at amateur hamfests and junk sales or purchased by mail from the CW Operators' QRP Club. Some Australian and overseas companies put out transmitter, transceiver and receiver kits from time to time. If you can get one, a kit is a good idea for the constructor just starting out as there are no esoteric parts to seek. The main disadvantage of kits is that they are harder to customise to your requirements, especially if they are constructed on printed circuit boards.

Choosing a design

What type of homebrew transmitter should you start with? Sure, it's very easy to build a simple 80 metre Morse Code rig. Just one or two transistors and a 3.58 MHz TV colourburst crystal, and you're on the air. But will the rig sound OK? Will you get contacts? Or will the rig lead you to give up amateur radio because you are not getting responses to your CQ calls?

Gateway to Amateur Radio is about practical amateur radio. Radio that works. Radio that's fun. And to get the most enjoyment from your hobby, you need to know something about the capability of your equipment so that you don't expect too much and become disappointed when your hopes do not materialise.

That's why you have to be selective about the type of transmitting equipment you build. Firstly it must be fairly simple and not require too many hard to get parts. Secondly, it must be put out enough power to be heard on the air. Thirdly, it should be frequency agile over at least a segment of the band.

Power

What is sufficient power? Though this depends on the distances you wish to work, I would say that an inexperienced amateur aiming to make regular contacts with powers of less than one or two watts on 80 metres is going to be disappointed. Sure those milliwatt rigs you see described in foreign magazines do work, but remember that Europe and the USA have far more amateurs per square kilometre than we have in Australia. As it's so easy to build one or two watt transmitters that there is little sense in settling for less unless you specifically want to do experiments in milliwatt communications. I would recommend powers of 1-2 watts as a practical minimum assuming you are using a reasonably efficient antenna (eg a full-sized dipole on 80 metres). Though there will be times when more power than this will be required (eg when static is bad), you should be rewarded by reasonably frequent contacts up to several hundred kilometres, and the occasional two or three thousand kilometre contact with 1-2 watts.

Frequency agility

Then there's frequency agility - being able to move around the band, rather than being stuck on a single frequency. Most home brew transmitters are crystal-controlled. Most of them also sit on the shelf gathering dust and are seldom used. Why? Being locked on one frequency severely hampers your operating success. You could be calling CQ, but not be getting any replies. Then 5 kHz up the band, you hear another station also calling CQ. If you were frequency agile, you could move to the other station's frequency and most likely obtain a contact. Instead, you remain on your frequency, hoping that the other station will not get a reply, stop calling, tune around and eventually find you. A lot of people build simple rigs, have one or two contacts, and do not use them again for this reason.

The disadvantages of crystal control are greatest with low powered (QRP) equipment. Unless someone happens to start calling on 'your' frequency, the only way to get contacts is to call CQ yourself. As many people tend to reply to CQs from stronger stations only, your chances of getting a reply are reduced if your signal is weaker. A much more successful way of getting contacts is to reply to CQ calls from other stations (you know that at someone is at least listening for your call), or 'tail-end' contacts that are concluding. Both of these techniques are only possible if you can move frequency. And, if there is not much activity around, and you do want to call CQ, your chances are better if you can make the call on a clear frequency. The probability of this is of course much greater if you are able to vary your own transmitting frequency.

Another aspect of crystal control is that your crystal may not be in the most active part of the band. For example, 3.58 MHz TV colourburst crystals are conveniently in the middle of a busy part of 80 metres. However, most CW activity is below 3.550 MHz. Operators seeking CW contacts will not be tuning across 3.58 MHz. So, the chances of getting a response are reduced as you are not calling where most of your potential contacts will be listening. Of course, if you're on voice, 3.58 MHz is a good frequency on which to call. However, frequency agility is desirable for reasons mentioned previously.

Mode

If you are building a voice rig, should you choose AM, double sideband suppressed carrier (DSB) or SSB? Though some newcomers have successfully built SSB transceivers, an SSB rig is a challenging project for the average constructor. So, the choices boil down to AM and DSB. AM was used prior to the advent of SSB, and still has a small following on some HF bands. However, many SSB rigs do not have AM and it may not always be easy to resolve a weak AM signal on an SSB transceiver. Because AM signals include a carrier that does not contribute to the intelligibility of the signal, AM is less efficient than SSB, and more transmitting power is required to make oneself heard. DSB has an equivalent bandwidth to AM, but has no carrier. Thus it is a more efficient mode. As well, DSB is fully compatible with modern SSB equipment, and unless you tell them, many SSB stations will not know that you are using DSB. The combination of a direct conversion receiver and DSB transmitter is highly recommended for the Standard or Advanced licensee wanting to build an HF voice station, and because of the similarity of DSB and SSB, DSB transmitters can later be upgraded to SSB by adding extra circuitry. Such rigs are particularly effective on eighty metres. However, AM still has its uses. The speech quality of AM is generally better than DSB or SSB. Where you have a small group interested in local contacts only (such as within a country town or small city), a homebrew AM rig would be a fun project, particularly on ten metres where there is plenty of band space. Ranges of up to about 5km can be achieved with powers of under a watt.

VK3YE's minimum standards for homebrew rigs

Taking into account the above observations based on years of practical experience, I am now in a position to lay down some minimum standards for practical homebrew rigs. These are:-

• Power output at least 1-2 watts
• At least some degree of frequency agility in a popular part of the band
• CW and/or DSB operation.

If you see any design or kit that does not meet the above, you should have second thought about building it, even if it is cheap and simple to build. Don't laugh - kits of rigs that would be almost unusable on the air have been sold in the past in Australia. In my view, the presence of such kits does practical amateur radio no good at all in that they raise expectations and then fail to deliver.

Meeting VK3YE's minimum standards for homebrew rigs

1. Power output

Look for a design with a reasonable power output transistor. A BFY51, 2N3053, 2N3866 or 2N4427 in the transmit final stage should have an output close to 1 watt. 2N3553, BD139, IRF510 or IRF511s are all capable of power outputs between 2 and 4 watts. Two lower power transistors can be wired in parallel (with suitable emitter resistors) to produce more output. A 2N2222 or BC548 as the final amplifier is a sure sign that the rig is nowhere near powerful enough.

2. Frequency agility

A free-running VFO or synthesised VFO can provide full band coverage, but can be difficult for the beginner to get going properly. It is not always easy to obtain good frequency stability in a free-running VFO on the higher HF bands, and synthesisers tend to be somewhat complex to build. Nevertheless, a free-running VFO is a good choice for an 80 metre rig provided that care is exercised in its construction. Cheap 3.58 MHz ceramic resonators are also good for use on 80 metres - stability is acceptable, and the pulling range can be as much as 100 kHz, neatly covering a useful section of 80 metres. Ceramic resonators are excellent for 80m CW or DSB direct conversion receiver and transmitter projects. Quartz crystals are not recommended on 80 metres as they cannot be shifted very far in frequency. However, at 7 MHz and above, crystal oscillators (VXOs) can be pulled to provide worthwhile coverage of frequencies immediately below the crystal's nominal frequency. Ranges of 5 to 30 kilohertz can be achieved, depending on the crystal type and the operating frequency. VXOs particularly useful for CW/DSB equipment on 40, 30, 20, 17 and 15 metres.

3. Mode

DSB transmitters require a balanced modulator stage to null out the carrier signal. Devices such as the NE602 (also used in direct conversion receivers) can be used. Many older published designs use other ICs (CA3028 and MC1496) or two or four diode balanced mixers). Like in an SSB rig, power amplifiers used in DSB rigs have to be linear. This means that a power amplifier circuit used in a CW transmitter is normally unsuitable for DSB unless its operation is made linear.

Συχνότητες QRP

QRP clubs around the world have agreed (with some local variations) for the following frequencies to be centres of CW QRP activity:
160m: 1.815 MHz 80m: 3.560 MHz (US 3.540 MHz, Australia 3.530 MHz)
40m: 7.028 MHz
30m: 10.106 MHz
20m: 14.060 MHz
15m: 21.060 MHz
10m: 28.060 MHz
In Australia the majority of QRP activity takes place away from these frequencies, for two reasons. The first is that QRP operators are a minority and the vast bulk of contacts made will be made throughout the band with stations running 100 watts. Secondly most Australian QRPers use the 'search and pounce' technique to get contacts (answering calls and 'tail-ending') as this is more effective than calling CQ if your signal is weak. Hence these frequencies are not widely used, except during QRP contests, such as the annual QRP Day and various scrambles throughout the year. 
However it's worth knowing them if two-way QRP contacts with DX stations are desired.  14.060 MHz is particularly popular overseas when conditions are favourable. Also homebrew QRP activity may occasionally be found on 1.843 MHz and 3.580 MHz due to the easy availability of crystals for these frequencies.
When tuning around the higher HF bands, it is worthwhile to listen for the International Beacon Project beacons. These operate on 20, 17, 15, 12 and 10 metres and are located around the world.  IBP beacons are particularly useful for QRPers as their output power is varied over four steps – 100 watts, 10 watts, 1 watt, 0.1 watt.  It is often possible to hear the 1 watt transmissions, and sometimes even the 0.1 watt signals.  IBP beacons operate on the following frequencies:
20m: 14.100 MHz
17m: 18.110 MHz
15m: 21.150 MHz
12m: 24.930 MHz
10m: 28.200 MHz

Τι μπορούμε να κάνουμε με QRP

The following are examples of what QRP can do:
600km spanned with 2 watts DSB and Australia to US with 5 watts CW on 160 metres.
VK3 to ZL with 5 watts SSB with a 1.5m indoor magnetic loop antenna on 80 metres.
Australia to US with 5 watts on 40 metres with a simple wire antenna.
Newcastle (VK2) to Nauru Island on 40 metres with 1 watt CW to quarter wavelength wire antenna.
Pedestrian mobile VK1 to VK7 with 4 watts AM on 28 MHz.
Australia to Japan with 500 milliwatts CW on 6 metres (antenna G5RV, SWR unknown!).
Regular 144 MHz SSB Sydney to Canberra contacts with 2.5 watts to a 2 el yagi (operating portable)
Of course some of these require good locations, favourable conditions and/or other stations with good antennas and low noise levels.
Even without these advantages 'full-time' QRP can be quite satisfying and provide many comfortable contacts. Routine contacts with QRP to simple antennas are quite achieveable up to distance of about 500km on 80 metres, 1000 kilometres on 40 metres and 3000 kilometres on 20 metres (subject to conditions). This applies to a range of modes such as SSB, SSTV, PSK31 and CW. On VHF/UHF QRP SSB to a small yagi will reach 100 - 150km or more, with even better results with weak-signal digital modes.

Γεννήτρια σήματος 3 - 12 MHz HF

Ταλαντωτής δοκιμών

The dip oscillator is a useful piece of test equipment for the radio amateur. For further information on its uses, see August 2000's Novice Notes.

The circuit below is an example of a dip oscillator. The basic circuit has been described by Drew Diamond VK3XU in Amateur Radio magazine. The circuit presented here is my version of this design.

The unit features four plug-in coils for frequencies between 2.6 and 55 MHz. The coils are mounted on 12mm formers glued to 5-pin DIN plugs. A two gang, air dielectric variable capacitor (salvaged from an old radio) is used as the tuning control. The use of the smaller gang provides better bandspread at higher frequencies. The larger gang is connected when needed (lowest frequency band only). A vernier reduction drive on the variable capacitor makes the instrument easier and more pleasant to use. Wires should be kept short to ensure correct operation at higher frequencies.

In use the variable resistor is set so that the meter needle is near two-thirds scale. Bringing the coil close to a tuned circuit and adjusting the variable capacitor should result in a dip of the meter needle when the dip oscillator's tuned circuit and the tuned circuit under test resonate at the same frequency.

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Απλός εξοπλισμός ελέγχου

This month we plug in our soldering irons and put together some pieces of basic test equipment. Though inexpensive, the projects described will prove useful in the radio shack. Any one of them can be assembled in an afternoon. They are described in order of complexity, so that the reader can find a project suitable for their expertise.

FIELD STRENGTH METER

A field strength meter is perhaps the simplest piece of RF test equipment that can be built. Used for checking transmitters, antenna experimentation, and testing RF oscillators, field strength meters provide an indication of the presence of RF energy. They are not frequency sensitive and are useful where indication of a change in level is more important than the actual strength of the signal indicated.

Figure One shows a schematic of an RF field strength meter. Like a crystal set, it requires no power source. However, unlike a crystal set, the meter has no tuned circuit. It responds to signals of any frequency.

The meter works by converting any RF signal present at the antenna to a DC voltage. This voltage drives a meter movement to give an indication of relative RF. The meter includes a control to reduce its sensitivity where required.

Because it uses few parts, a printed circuit board is not necessary; components can simply be soldered to one another. However, a box is desirable for operating convenience. The case and aerial from a discarded toy walkie-talkie was used in the prototype (see photograph), though any small plastic case will suffice. The meter movement need not be large; we are only detecting the presence of RF, and not making precise measurements.

A meter from an old radio or tape recorder should work fine. The diodes can be any germanium type; the actual part number is not important. Germanium diodes can be recognised by their 6mm-long clear glass case with two coloured bands towards the cathode end. None of the component values shown are critical; a 50 percent variation would have little effect on circuit operation.

To test the operation of the meter, a transmitter is required to provide a source of RF. Placing the field strength meter's extended antenna near a handheld VHF rig should produce an indication on the meter, assuming that the sensitivity control has been set to maximum. No indication means that the meter is not working. Common construction errors include connecting the diodes or the meter wrongly and using silicon diodes in place of the germanium diodes specified. In this case, the meter will still work, but with reduced sensitivity. The earth wire is optional; when working with low-powered oscillators, it is useful to clip it to ground (of the circuit under test) to ensure a better indication on the meter.

Those without a transmitter can use an RF signal generator or crystal oscillator (such as that described later) for testing purposes. In this case, place the meter's antenna directly on the output terminal to verify operation. However, only attempt this with transistorised circuitry; component ratings and safety considerations make the meter described here unsuitable for poking around valve equipment.

The field strength meter is a useful instrument in its own right, but it can be made more versatile. Modifications include adding an amplifier (for greater sensitivity), including a tuned circuit (so it only detects signals in a particular band), or converting it into an RF wattmeter and dummy load. Circuits for such instruments are found in the standard handbooks.

Figure One

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CRYSTAL TESTER

Figure Two shows the circuit of a simple crystal tester. It switches on a light emitting diode (LED) if the crystal is working.

The crystal under test is placed in an oscillator circuit. If it is working, an RF voltage will be present at the collector. This is rectified (converted to DC) and made to drive a transistor switch. Applying current to the base causes current to be drawn through the collector, thus lighting the LED.

If an indication of frequency is required, simply use a general coverage receiver to locate the crystal oscillator's output. Note however that when testing overtone crystals (mostly those above 20 MHz) the output will be on the crystal's fundamental frequency, and not the frequency marked on the crystal's case. Fundamental frequencies are approximately one-third, one-fifth or one-seventh the overtone frequency, depending on the cut of the crystal.

The circuit may be built on a small piece of matrix board and housed in a plastic box. Alternatively, a case made from scrap printed circuit board material may be used. Either a selection of crystal sockets or two leads with crocodile clips will make it easier to test many crystals quickly. The RF choke is ten turns of very thin insulated wire (such as from receiver IF transformers) passed through a cylindrical ferrite bead. Its value does not seem to be particularly critical, and a commercially-available choke could probably be substituted.

The circuit can be tested by connecting a crystal known to work, and checking for any indcation on the LED. A shortwave transistor radio tuned near the crystal's fundamental frequency can be used to verify the oscillator stage's operation. Note however that this circuit may be unreliable for crystals under 3 MHz, and some experimentation with oscillator component values may be required.

The crystal checker also tests ceramic resonators. Other applications include use as a marker generator for homebrew HF receivers (use a 3.58 MHz crystal) and as a test oscillator for aligning equipment.

Figure Two:

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CAPACITANCE METER

This project is more complex than the others described earlier. However, when finished, you will have an instrument capable of measuring all but the largest capacitors used in radio circuits. Unlike variable resistors, most variable capacitors are not marked with their values. As well, the markings of capacitors from salvaged equipment often rub off. By being able to measure these unmarked components, this project will prove useful to the constructor, vintage radio enthusiast or antenna experimenter.

The common 555 timer IC forms the heart of the circuit (Figure Three). Its function is to charge the unknown capacitor (Cx) to a fixed voltage. The capacitor is then discharged into the meter circuit. The meter measures the current being drawn through the 47 ohm resistor. The 555 repeats the process several times a second, so that the meter needle remains steady.

The deflection on the meter is directly proportional to the value of the unknown capacitor. This means that the scale is linear, like the voltage and current ranges on an analogue multimeter.

The meter has five ranges, from 100pF to 1uF, selected by a five position two pole switch. In addition, there is a x10 switch for measuring higher values and a divide-by-two facility to allow a better indication on the meter where the capacitor being measured is just above 100, 1000pF, 0.01, 0.1 or 1 uF.

Component values are critical. For best accuracy, it is desirable that the nine resistors wired to the Range switch have a 2% tolerance. If 0A47 diodes are not available, try OA91 or OA95 germanium diodes instead. Construct the meter in a plastic box; one that is about the size of your multimeter but deeper is ideal. The meter movement should as large as your budget allows; you will be using it to indicate exact values. A round 70mm-diameter movement salvaged from a piece of electronic equipment was used in the prototype. The meter you buy will have a scale of 0 to 50 microamps. This scale needs to be converted to read 0 to 100 (ie 20, 40, 60, 80, 100 instead of 10, 20, 30, 40, 50). Use of white correction fluid or small pieces of paper will help here.

The components can be mounted on a piece of matrix board or printed circuit board. Use a socket for the IC should replacement ever be needed. Keep wires short to minimise stray capacitance; stray capacitance reduces accuracy.

Calibrating the completed meter can be done in conjunction with a ready-built capacitance meter. Failing this, a selection of capacitors of known value, as measured on a laboratory meter, could be used. If neither of these options are available, simply buy several capacitors of the same value and use the one which is nearest the average as your standard reference. Use several standards to verify accuracy on all ranges.

To calibrate, disable both the x10 and divide-by-two functions (ie both switches open). Then connect one of your reference capacitors and switch to an appropriate range. Vary the setting of the 47k trimpot until the meter is reading the exact value of the capacitor. Then switch in the divide-by-two function. This should change the reading on the meter. Adjust the 10k trimpot so that the needle shows exactly twice the original reading. For example, if you used a 0.01 uF reference, and the meter read 10 on the 0.1 uF range, it should now read 20. Now switch out the divide-by-two function.

If you are not doing so already, change to a reference with a value equal to one of the ranges (eg 1000pF, 0.01uF, 0.1uF etc). Switch to the range equal to that value (ie the meter reads full-scale (100) when that capacitor is being measured. Switching in the x10 function should cause the meter indication to drop significantly. Adjust the 470 ohm trimpot so that the meter reads 10. Move down one range (eg from 0.01uF to 1000pF). The meter should read 100 again. If it does not, vary the 470 ohm trimpot until it does. That completes the calibration of the capacitance meter. Now try measuring other components to confirm that the measurements are reasonable.

With care, an accuracy of five percent or better should be possible on most ranges.

Figure Three: