The creation of the new Novice-Limited licence, and the expansion of novice privileges to include digital modes and 70cm operation means that there will be more activity than ever before on the frequencies above 50 megahertz. This article seeks to answer the questions that many newcomers may have on amateur VHF/UHF operation. Although the VHF/UHF bands support a wide range of operating interests, such as amateur television, satellite activity, long-distance SSB operation, moonbounce (EME) and packet radio, this article focuses on FM voice operation (Endnote 1).
PROPAGATION
Unlike shortwave (HF) bands, which are good for world-wide radio communication, the VHF frequencies are best at providing reliable coverage of local areas. Depending on factors such as your location and antenna height, distances of between about 25 and 100 kilometres can be readily covered with modest power and simple antennas. While not quite 'line-of-sight', VHF/UHF signals are attenuated (reduced in strength) by obstructions such as city buildings and hills. This means that stations operating at higher altitudes are likely to have stronger signals than those transmitting from valleys. You will find that seventy centimetres provides similar coverage to UHF CB equipment while two metres often permits slightly longer distances to be covered.
While there are some differences between daytime and nightime radio conditions on VHF/UHF, they are far less marked than the variations experienced on HF bands such as 80 metres. The furthest distances on VHF/UHF are usually covered either early in the morning, or after dusk. At these times (particularly in the summer), tropospheric ducting can extend your transmitting range to several hundred kilometres. This means that you will be able to talk beyond your local area, and reach distant repeaters. VHF/UHF propagation is influenced by weather conditions; inversions in the troposphere give rise to long distance VHF/UHF contacts. During these occasions, the difference between VHF and UHF can be quite marked, and there are times when long distances can be spanned on 70cm, but not on 2 metres.
EQUIPMENT
A wide range of equipment is available for the VHF/UHF FM operator. Because of the popularity of two metres there is more VHF equipment around. In some areas, seventy centimetre activity is sparse, and few repeaters exist. If you live in the country, or are on a limited budget, I'd suggest that two metres be chosen as your first band.
The cheapest way to get on air is to purchase second-hand equipment. Solid-state equipment is preferred; the old transceivers with valve finals are heavy, bulky and consume a lot of power. Used VHF/UHF gear falls into two main categories; crystal controlled or frequency synthesised. Older crystal-controlled amateur or modified commercial rigs can be had from anywhere between a few dollars and $100-150 at hamfests and radio junk sales. Depending on your operating habits, the purchase of such equipment, restrictred to a few frequencies, can represent false economy - for the price of a few pairs of crystals, a second-hand synthesised transceiver may be a wiser choice. However, if a set that you are considering is in good order, cheap and includes the repeater and simplex frequencies used in your area, it may represent a sound buy, especially if you seldom travel.
The more technically inclined could obtain a used VHF high band or UHF ex-commercial FM two way radio, and convert it to the amateur bands. The crystals are the main cost of such projects; suitable transceivers can be bought for a song at hamfests and junk sales. Ensure that any set you buy operates adjacent to the amateur band to which you wish to convert it; converting a 70 - 85 MHz VHF low-band radio to two metres is possible, but not simple. Because the commercial VHF high band (148 - 174 MHz) is so close to 146 MHz, conversion of these sets is simple; all one needs to do is to plug in appropriate crystals, and adjust several tuned circuits inside the transceiver. Radios suitable for conversion to two metres include the Philips FM828, FM1680, and the STC151. All of these are crystal-locked, but newer synthesised sets (such as the Philips FM92) can also be converted. Those intending to modify sets should know what they are doing, possess a schematic diagram, and have suitable test equipment when performing the operation. This is because excessive twiddling of internal trimmer capacitors and coil slugs can break them. Replacements are sometimes hard to come by.
Assuming you have a little spare cash, you may choose gear made especially for the amateur market. Most of this is synthesised, and you can choose between a hand-held or mobile unit. Several models cover both the two metre and seventy centimetre bands. Apart from this difference, most radios do pretty much the same thing, and many features are not really necessary. If travelling overseas, resist the temptation to buy amateur gear there; it may not cover Australian frequencies, and after-sales service may not be available.
Whether to buy a hand-held or mobile transceiver is up to you. Hand-held equipment may have poor receivers (particularly apparent in inner-city areas near pager transmitters) and the in-built ni-cad battery packs often flatten mid-QSO. The small antennas supplied with hand-held transceivers are normally quite inefficient. On the other hand, various accessories such as speaker-microphones, larger battery packs and antennas can make the hand-held suitable for both home and mobile operation.
Mobile transceivers are capable of greater power output, and are good for home station operation in conjunction with a 13.8 volt power supply and outdoor antenna. While most operate FM only, some include SSB and CW cababilities. If you wish to use amateur satellites, or experiment with long-distance SSB operation, a multi-mode transceiver should be seriously considered.
PURCHASING EQUIPMENT
A look through Amateur Radio's Hamads section for the first seven months of this year revealed the following figures on second-hand VHF/UHF FM transceiver prices and availability.
TRANSCEIVER TYPE --NUMBER FOR SALE-- RANGE OF PRICES--AVG. PRICE
2 metre mobile------------------7------------------------ $150 - 450 -------------$290
2 metre handheld--------------18------------------------ $195 - 450------------- $300
70 cm mobile -------------------1------------------------------- - ------------------ $280
70 cm handheld---------------- 2------------------------- $215 - 350--------------$280
Dual band mobile-------------- 3------------------------- $650 - 900------------- $820
Dual band handheld---------- 2------------------------- $500 - 850-------------- $680
These prices are a guide only, as the sample taken was not large enough to be statistically significant. They refer to synthesised transceivers only. Only those advertisements specifying a price for the equipment on offer were included in this survey. When buying second hand gear, insist on receiving the manual with your purchase, and, where possible, ask for it to be demonstrated. The WIA maintains a stolen equipment register. This register lists the serial numbers of stolen amateur equipment, and is published periodically. It should be consulted if you have any doubts about equipment you are intending to purchase. New transceivers are typically 50 to 100 percent dearer than the prices quoted above.
New and used amateur equipment is obtainable from AR advertisers, private sellers (see Hamads), and from junk sales or hamfests. Your weekly Divisional broadcast may include 'Buy and Sell' or 'Disposals' segments for secondhand gear. Membership of a local radio club is another way you can get to know about equipment for sale in your area.
ANTENNAS
The quality and performance of your antenna system is critical if you wish to do other than talk through local repeaters (which can get a bit boring after a while). It is not hard to build an antenna, and experimentation with them is highly recommended. As VHF/UHF antennas are much smaller than those for 27 MHz CB, they are cheaper and easier to erect. Like with UHF CB, vertical antenna polarisation is the norm for amateur FM operations.
While many operate hand-held transceivers inside vehicles with no external antenna, operating range will improve with an antenna on the car roof. The most popular mobile antennas for two metres are 1/4 and 5/8 wavelength whips, preferably mounted in the centre of the roof. The longer antenna will normally deliver the better performance, but this may be short-lived; the low clearance of garage doors and multi-storey car parks are very good at damaging them! Seventy centimetre antennas are shorter, and some provide appreciable gain over a dipole. It is not necessary to drill holes to mount a mobile antenna; a wide range of mounting hardware and magnetic bases is available. Mobile antennas may either be purchased or home made.
The performance of handheld transceivers can also be enhanced by adding a better antenna. A range of proprietry types are available, but they tend to be dearer than home-made devices. An example of an antenna able to be used with a hand-held transceiver when extended range is required appeared in AR a few months ago (footnote 2).
For most home stations, a 1/4 or 5/8 wave groundplane antenna will provide adequate onmidirectional coverage for both repeater and simplex operation. While it should be mounted as high as possible, attention should be paid to feedline losses, which increase with frequency. A loss of 3 decibels means that half the transmitter's power output never makes it to the antenna. Thinner coaxial cable (such as RG58) is lossier than thicker cables (RG8, RG213). While RG58 is acceptable for short cable runs on two metres, its use on 70 centimetres would be unwise unless you are prepared to live with substantial losses and reduced station performance.
Constructional information on VHF/UHF antennas can be found in the ARRL Handbook. A simple groundplane for two metres was described in a previous issue of AR (Endnote 3). When building antennas, observe safety precautions, such as not erecting them near power lines. To prevent corrosion at the antenna, dissimilar metals must not be in contact with each other. This is to ensure antenna longevity, and to reduce the risk of harmonics being radiated. Moisture should be prevented from entering the coaxial feedline. Waterproofing at the antenna feedpoint is essential, and various tapes and sealants are available for the job.
REPEATERS
A lot of amateur (and CB) VHF/UHF communication takes place through repeater stations. Amateur repeaters consist of a receiver, transmitter, filters, and antenna. They are normally on hill tops. Repeaters receive a signal (often from a mobile or hand-held transceiver), and retransmit it on an adjacent frequency, so it can be heard over a much wider area. This means that with low power and compact antennas it is possible to communicate with people up to 100 to 150km away, provided that you are within the service area of your local repeater. Figure One shows a case where two stations, unable to hear each other directly, can communicate, thanks to the existence of a repeater.
Repeaters are constructed and maintained by volunteers. If you intend using them, consider joining the local radio club, repeater group or WIA Division. The WIA Callbook provides a listing of all amateur repeaters in Australia, the clubs/groups that erect them and their frequencies. It is a useful reference, and every active amateur should have one.
BANDPLANS
To promote orderly usage of amateur bands, bandplans which set aside frequencies for various modes and uses have been developed. They are important to the novice, as contacts will not be made if you are transmitting on the wrong frequencies. Amateur bandplans can be found here.
Both two metres and seventy centimetres are divided into channels. These are at 25 kilohertz intervals, again like UHF CB. To make things confusing, several different channel numbering systems are in use; for instance, a repeater transmitting on 146.900 MHz could be referred to as '6900' or 'channel 6'. The former convention is more common in most areas.
OPERATING
Conversations (QSOs) can be initiated either directly, on a simplex frequency (eg 146.500, 439.000 MHz), or via a repeater. In most places, you have a better chance of success by calling on a repeater. Do check that the frequency offset is switched in and correct for the repeater you intend using; some use offsets different to those specified in the Bandplan.
Assuming that the repeater is free, you may either call CQ, or announce that you are listening. Though procedures vary between states, the former is suggested as it corresponds to standard practice on other bands, and more clearly announces your intention (ie you want a contact!).
An effective means of making contacts is to call people immediately after a conversation has ended. Alternatively, you could break in to a QSO still in progress. This is permissible if you have something to contribute to the discussion, or just want a quick signal report, but it is probably wise not to make it a frequent habit.
Once contact has been established on a repeater, it is courteous to move to a simplex frequency if possible; this makes the repeater available to those unable to do so. Another reason why simplex operation is preferred is that repeaters have time-outs, so you could find yourself cut off if you enjoy long overs on repeaters.
During the contact, bear in mind that there are topics that should not be discussed on air. These include religion, politics and matters involving financial gain. Those with more than one amateur in the family should take special care; announcing on the local repeater that 'the key is just under the doormat' is asking for trouble. Criminals have scanners, and your address is in the callbook!
Don't be too disheartened if few respond to your calls. Although many monitor repeaters, comparatively few actually talk. A lot of amateurs do nothing other than talk to their narrow circle of mates; you will notice many little groups congregating on various frequencies, particularly in the larger cities. In the country, there are fewer amateurs, so this tendency is less apparent. Though there are still a few pockets of anti-novice sentiment around, those who harbour such feelings are gradually dying off.
Despite the preceding comments, you will find that most amateurs you contact are courteous and helpful, though many are initially reticent in coming forward and picking up the microphone to talk to a new callsign. To get to know some of these people, it is recommended that you join a local radio club and participate in some of their activities.
After an intitial flurry of activity, one's enthusiasm for local FM operating (particularly through repeaters) can quickly dissipate. Fortunately, even within the conditions of the Limited-Novice licence, there is scope for a range of activities including packet radio, antenna construction, repeater DXing, contesting, QRP, foxhunting, portable operation and homebrewing. Books on most of these topics are available from your local Division. Participation in one or more of these facets of our hobby can be highly rewarding. The practical experience gained will also make it much easier to move to a higher grade of licence, as your interest develops.
That's all for this month. See you in two months for another Novice Notes. In the meantime, any questions can be sent to me at parkerp@NOSPAMalphalink.com.au.
NOTES:
1. Information on other VHF/UHF activities appear in the following AR columns: VHF/UHF - An Expanding World, Repeater Link, AMSAT Australia and Packet World.
2. See AR July 1995, page 10.
3. Amateur Radio, July 1988 'Two Metres for the Novice', Ron Cook, VK3AFW.