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Both mobile (vehicle, vessel, or aircraft based), and field based operations usually make use of non-mains power sources, and may involve compromise antennas, although a field operating site with large trees can provide some great options for full-scale antennas.
HF can be operated from vehicles, although this can be a little more challenging than VHF or UHF.
Many mobile HF operations operations use a vertical antenna, but the problem is that a there is a limit to the height of antennas, due to low flying tree branches, telephone and pay TV cables, and saggy power lines, not to mention the potentially most "exciting", uninsulated rail and tram overhead supply systems, with between 600 volts DC, and 25 kilovolts AC. In Australia rail and tram power can be 4.3 metres, occasionally less. (Sydney is 750 volts, while the Museum remains at 600 volts).
How does a tram-train level crossing work? Melbourne, Victoria has level crossings between street-running trams and electric trains. Assuming two tracks crossing two tracks, a section of overhead in the shape of a hash # has section breaks from the rest of the two systems, and is switched from 600 volts DC to 1500 volts DC for the passing of trains, no doubt interlocked to the crossing barriers, etc.
One antenna option is the 108" (2.743 metres), or 102" (2.591 metres) stainless steel whip, the latter designed to be used with a spring, bringing the overall length close to the former. These are designed for use with 27 MHz CBs, where they are around a quarter-wave long. They can be trimmed to use on 10 metres, or may work on 12 metres, although them may be 10cm short. Any spring you use should have an internal braid link between the base and top. A tuner of some sort can match these for use on lower frequency bands, with decreasing efficiency, as the frequency drops. SGC has gone out of business, but they sold several Smartuner products designed for use with 4WDs and pick-ups. The also sold whips to use with them, and longer whips for use on larger boats and yachts. Others sell products such as 7.5 metre and 35 foot (402", 10.688 metres) marine antennas.
Not on the exam, the back-stay of a yacht, with appropriate insulators, also makes a great wire antenna, but you MUST also have a whip for use on marine channels if you lose your mast.
Several single-band helically wound antennas of around 1.5 to 1.8 metres are available, on a fibreglass rod or heavy tube. They usually include a short steel rod at the top, which can be adjusted to tune the antenna.
Such antennas typically use a half wavelength of enamelled wire. The tip can be simply be 10-15 cm of wire over a single turn. You can also use something like dried bamboo or timber for a home antenna. Fibreglass "squid-poles" are okay, but not carbon-fibre.
VKs can order from Mobile 1: 160 to 15 metres, 27 MHz - ask about conversion to 10 metres, Custom HF & VHF-Low, and 6 metres and up. They may be able to make up things like 23 cm antennas, for a group order.
Various sellers have "Hamstick" or "Ham Stick" antennas. An Australian seller's MFJ offering for 75 / 80 metres: MFJ-2675T, and their "Shark" HamStick for 40 metres S-F40. Note that MFJ have discontinued manufacturing, so "while stock lasts" very much applies.
AMPRO antennas by Moonraker in the UK are very affordable single band antennas: 30 metres, and 80 metres, as examples. Paying in US Dollars is much less expensive than in GB Pounds, perhaps these are VAT-free prices.
For confusion value, CBG Systems in Tasmania also uses "Moonraker" for marine antennas, including much larger units.
Multiband HF antennas also use a helical winding, but with sockets (usually 4 mm) to allow a "wander lead" to to link the bottom point with the relevant tap. They include taps for all ham bands from 80 to 10 metres, sometimes also 160 metres. Terlin / Outbacker, and FAMPARC are examples. The Terlin ones can be custom made with extra (typically non-ham) channels, if needed.
Lightweight Diamond antennas are wound on a thin rod, with a longer, thin wire whip, and several optional sections for extra bands. This is the HV7A and coils. Like Yaesu HF verticals, these are for black-top roads, not long sections of dirt road use while in motion. The latter may develop a wave pattern called "corrugations" or "washboarding", which can damage fragile antennas and motorised tuning systems.
If you are in Australia you may find FAMPARC tapped vertical antennas, named for a radio club in Melbourne, at flea-markets or "For Sale" listings at clubs. Or you can place a "Wanted" ad in your club's newsletter. Or maybe get some fishing-rod blanks and build your own, or suggest it as a club project. You'll need someone with a lathe to make up ferrules (no, not ferals - they might object to being put on a lathe).
"Screwdriver" antennas, so named because the home-build ones use the motor and gearbox of a battery screwdriver, vary in quality, but most are designed for use on a soft-suspension car on Japan's smooth city roads, and may fail if used on a 4WD and/or on Aussie roads. The ATAS-120 from Yaesu, parts of which are distributed on roads such as the Barkley Highway, are not for rural driving. These work by having a long coil with a strip where a contact (or the coil), is driven up and down by the motor, finding a tune point. There is a thin stainless whip above this. Bullbars apparently amplify vibrations, contributing to ATAS failures.
The heavy-duty Codan and Barrett antennas include tuners in the base. Perhaps the long ones include a long tapped coil, but the shorter quite possibly use relay switched inductors and capacitors, like many auto-tuners. The top element is either a steel whip, or a braid covered fibreglass whip, with heat-shrink.
The more flexible antennas can be pulled back using a cord, to the back of the vehicle, either to reduce the height, or so the antenna acts as an NVIS antenna, for effective shorter range operation on lower HF bands. They can also be pulled forward from a rear mount; either way, and arc is formed above the vehicle. The mount may be designed to better facilitate this.
The auto-tuners should be able to also tune a length of wire thrown into a tree, or even just across shrubs or dry ground.
As well as linear loading provided by helical winding along the antenna, loading can be placed in the base, or in the middle, and a plain rod or tube of metal used for the element. If it is stiff, and possibly guyed with non-conductive line, with or without loading coils, stiff wires radiating to a ring can be added; this, or a similar arrangement; being called a capacitive hat. This increases current flow in the lower parts of the antenna, having it appear to be electrically longer. Centre-mounted coils are termed "Bug-catchers". Antennas with central coils, and many with capacitive hats, would be made from tubing, rather than wire.
Antennas with a hat: CBG 100MF (PDF); and Hat and loading coil from Tom Thompson's Mobile Antenna page
Any antenna with an open end (that is, not a loop) can suffer from corona discharge. This increases with both voltage, related to the power level; and to the thinness of the air, increasing with altitude. Closed loop antennas are one answer, often not practical on vehicles. The alternative is to ensure that the end of the antenna is either a metallic ball, or has a non-conductive bead on the end. This is not an absolute preventative, but does limit the likelihood at sensible power levels, and normal altitudes.
As you move down in frequency an antenna of a certain, restricted length becomes both less efficient, and narrower in bandwidth. I have been told that if the blank a helical antenna is wound on is thicker, then the bandwidth is greater.
Certain ex-military antennas can be used, such as tank antennas. This is to introduce a story: A member of a club I am in was driving through an inner western Sydney suburb, with one on his Morris, or similar car, in the days of (real) trams. While 600 volts DC on the antenna sliding along the wire was not a problem, contacting the grounded over-road railway bridge and the wire at the same time resulted in a section of antenna being welded between the two, and no doubt a loud bang!
If your antenna obstructs your number-plate, in this age of camera based revenue raising, with additional revenue raising applying for even a fine whip which which causes no lack of readability, you need to either move the plate and light to the mount or the side, or fit a small bicycle rack plate. (Many areas without the 5th Amendment right to not incriminate yourself (or your spouse), even despite similar Common Law rights, allow revenue to be raised based only on a photo of the rear plate, with no evidence as to who the driver was, and some even extort much larger amounts of revenue if the owner refuses to self-incriminate, or incriminate their spouse). That said, a wealthy driver can preserve their licence by paying extra, while a worker losses theirs.
There is also the option of using the vehicle as power source and shelter while operating using a larger antenna while stationary, just don't flatten your battery! Oversized stainless telescopic anennas, reaching 6 metres when extended, are now available.
As a reminder, many amateur radio "rigs" can operate on a range of DC voltages, typically between 11 and 15 volts. This is a low 12 volt auto battery without the engine running, while the on-charge voltage has increased from 13.8 to 14.4 with the inclusion of calcium in the chemistry of lead-acid liquid electrolyte batteries. Spiral Cell AGM batteries have a similar voltage, ditto marine batteries. Many marine batteries have a dual deep-cycle and engine cranking function, and can be used in cars where they can power radios for a period. EVs have traditionally included a 12 volt lead acid battery of some kind - swapping to a Optima Spiral Cell AGM may be a good idea, as not all manage this battery well (looking at you, older BYDs). Tesla is moving cars and SUVs to "16 volt" lithium batteries for low voltage loads. I expect this in 4 cells in series, meaning something like 14.8 to 16.8 volts in real life. This may be a bit high for some radios, so something like a few large diodes in series might be needed, although these will get hot on transmit. For 48 volt Cybertrucks either a 120 VAC to 13.8 volts supply, or a 48 to 13.8 volt step-down device is required, such as these. Similar devices are required for 24 volt trucks and "28 volt" light aircraft (one being named for the off charge voltage, the other on-charge), although in the latter case they should be aviation grade. Small devices such as chargers for hand-helds, and radar detectors (where legal), can be run on a USB-C PD to lighter socket adaptor.
One of the things which needs attention is the connection to the vehicle's battery. 100 watt Amateur transceivers can draw up to 22 amps, depending on the band and mode used. This can cause a high voltage drop, causing the radio to operate poorly, and this can apply to field operations too.
The efficiency of the radio may drop off as frequency increases, so more current is drawn as you move up the bands, with 10 metres FM likely to cause the greatest draw.
To reduce the voltage drop, heavy cable should be used. For this current, cable of at least 6 mm² should be used for the normal front battery to dash-board distances. This just fits in the yellow crimp terminals. You need to avoid both scuffing and high temperature points. You should use an existing penetration of the firewall. If you wish to place the radio in the boot / trunk of a car with a front-mounted battery, or in the cabin of one with a rear-mounted battery (some BMWs do this), then heavier cable should be used. The best option in the latter case would be to mount the radio in the rear too (but not where battery fumes can damage the radio, although you'd hope they had properly vented it to the exterior), and use a "separation kit" to place the control head, a speaker, and the microphone in the front.
The connections should be to the two terminals of the battery. Fusing must be used in the positive line, as close as practical to the battery. Many auto shops sell holders crimped onto a short loop of heavy wire, the options being for standard sized ATO / ATC automotive plastic "blade" fuses, or glass or ceramic 3AG barrel fuses. Replacement auto fuses are available at any petrol / gas station for very little. so these are probably the best choice. The battery end might have a eye to go under a stud on the clamp around post, and the other end crimped to the cable to the cabin, using a yellow crimp butt joiner. The first fuse is for the cable, perhaps 35 amps, and a second one is placed close to the radio, rated for the radio itself. Some cars used a thick lead tab, through which a bolt was passed, and there are other screw-down arrangements; in these cases an appropriate sized eye is used.
The lighter socket, termed an "auxiliary socket" in the exam, generally has inadequate wiring to operate a 100 watt Amateur transceiver. While lighters may draw high current, they are designed to function at something like 8 volts, due the voltage drop, although if a higher voltage is available they pop out sooner. With the decline in smoking, these are being replaced with outlets which are designed to supply things like in-car fridges, and these may supply a radio with adequate voltage, or the cabling to these can be tapped. Should you use such an outlet, ensure you don't then have metres of additional cable between this point and the radio, adding to the voltage drop. You may wish to cut the supplied cable short, or to make a short jumper to the radio's inlet.
You should use finely stranded, flexible copper wires, termed "Class 5" in IEC 60228. Courser Class 2 can be used if necessary, but Class 1, with a single, stiff cores should be avoided, as being subject to vibrations, it may eventually fail. Tinned wire is perfectly fine.
Note that the wires suggested are not merely about current carrying capacity or "ampacity" (now forget you ever saw that non-word), but having a low voltage drop. In Australia and NZ, for some not adequately explained reason Jaycar sells finely stranded 8 gauge single wire, 8 gauge figure-8, and stranded 10 G single wire. 8G is 7.78 mm², and 10G is 5.26 mm². Their "25 amp cable" is too light, except for the shortest sections. They also have a sheathed "70 amp" single wire solar cable. Altronics has 8 G in 105°C rating.
Automotive shops term AWG "B&S" after Brown & Sharpe, which helped define the system; they also sell wire by overall diameter instead of cross-sectional area. They do however sell in metres - the depth of the doo-doo for selling in feet would be far greater than this use of non-metric measures in wire size. Leisure boat part suppliers also have wire, using the same tricks as above, often with no marine approvals. They are also claiming currents which would only be applicable for short horn blasts (they are used to communicate with other vessels in the area, such as three blasts meaning "going astern").
As an example, 8 AWG may be written as № 8, No. 8, No. 8 AWG, #8, or 8 ga; or in Oz as 8 B&S, the ugly 8B&S, or 8 G. British SWG is different, with 10 SWG being similar to 8 AWG, and 12 SWG similar to 10 AWG; it appears to be now restricted to fine enamelled wire used to wind coils.
LAPP Australia is a reliable supplier. LAPP from Germany also has distributors in the US, and across the world. They sell approved vehicle cables under the "TRUCK" name, and DNV and German Lloyds approved marine wires and cables. They have various "SOLAR" cables, such as 2 x 6mm² at a good price, along with 6 mm² single; 4 mm² pair and single; and 10 mm² single. If you are elsewhere search for: LAPP SOLAR YourCountry
On the site, cables can be searched by configuration, 2X6 for 2 cores of 6 mm² (without ground). 3G1.5 for 3 core 1.5 mm² mains cable including a green/yellow Ground. Something like 6X1 or 8X1 might be useful for rotators (these may have numbered wires). US distributors also have US colour coded cable, including black, white, red, and green, for powering amplifiers from 240 volt split phase; some with numbers as well as the colours. The ÖLFLEX name comes from oil resistant flexible cable, and presumably coincided with the move from rubber to plastic insulation and sheathing, although rubber is still used in some cases, including mining. Their modern plastic 1.5 mm² has a similar overal diameter to generic 1 mm² at Bunnings.
Beware of direct sales from China, etc, as these cables can be either underweight, or made from things like copper clad aluminium strands, which has a strange dead feeling, or perhaps strangely stiff copper clad iron strands. Also avoid aluminium, such as old used house wiring, or scrap overhead cable, as reliable connections are difficult.
For Americans, "mains" is a reference to utility power, typically around 120 or 230 volts AC. Rotating generators or inverters generate similar power.
Going beyond the exam for a while, these are a range of handy connectors suitable for 12 volts. They consist of square housings, and contacts which can be crimped to wires, then inserted into them. They can be configured into multi-way connectors, and be used at significantly greater AC or DC voltages, if enclosed within equipment: Don't assume PP = 12 volts.
The smallest size of Powerpole housing houses 15, 30, or 45 amp crimp terminals, named for capacity of the wire they can be crimped onto. 25 amp PCB mounted pins are also sold, along with a 45 amp version, which requires a slot in the board. Ultrasonically welded or glued red and black housing pairs, made up in the standard format for 12 volts are also available. The next sizes are 75 and 120 amps.
Multiple fused and unfused distribution units are available, which accept power from a single small or 75 amp PP, and allow power top be drawn from the others. You should however avoid any product which goes red-black-red-black with no gap between the red and black, as in would be too easy to accidentally connect with reversed polarity. Always be careful, as it is still may be possible to short a supply line to ground via a radio's case or antenna connection.
If you come across a "Red-Dee-2 Connect", or the even better 75 to 45 amp version, at a field day, flea market, etc, grab it - they are, like many useful things, a discontinued product. Thankfully, West Mountain Radio now sells the "PWRnode 4 Pole Temporary Power Node" either directly, or via the likes of DX Engineering.
Ebay seller "bd7-maple" sells duplicates. However, this seller's wire-based ones use wire insufficient for full sized rigs, but OK for accessories, LED lights, HT chargers, and maybe CBs (at legal power).
One way to step from cable larger than 6mm to the wire to the radio is to use an Anderson SB connector, or a 75 or 120 amp Anderson Powerpole (PP) connector, with appropriate terminals inserted in to each housing. Note SB connectors are colour coded and keyed, so only blue mates with blue, and grey with grey, as examples. Terminals of various wire sizes are available for SB and PP housings.
A rough looking but perfectly fine way to split out or distribute power is to make tails with Powerpoles one one end, and to join them is you require by "choc-block" connectors popular in the UK and Down-Under, named for their somewhat chocolate-tablet like appearance. Fold wires over the top, and zip-tie together. If using a mains power supply with banana / screw-down sockets, use spade type terminals under the nuts, with tail(s) and Powepoles, so as that you are not relying on getting the bananas right every time.
Anderson Power Products' patent has expired, and various copies, probably of varying quality and compatibility, are sold online.
Powerwerx in the US is a company specialising in radio and related low voltage power accessories. This includes a wide range Anderson connectors and pre-built cables. This includes short cables with the HF6 or HF4 connectors used on many HF radios. They also sell 10 AWG PP to PP cables, and cables with ring terminals for batteries at one end, a Powerpole connector on the other. See: powerwerx.com
Some of their wires appear to use thick strands, between Class 2 and 5, and others to be similar to Class 5. They als have approved marine wires which they term "Type 3".
There are Anderson / Powerpole distributors around the world. Meanwhile, clubs or emergency communications groups may do a bulk order, in order to then sell the connectors at a far more reasonable price than some retailers (eg Jaycar - A$6.25) sell a single set of red + black + contacts. Based on Powerwerx pricing, larger orders of 30 amp bonded connectors should should get the price under A$2.50 each; add some 15 and 45 amp contacts, and a mix of coloured housings, perhaps a few related tools. This will vary over time with the exchange rate.
I've used pink to indicate the output side of diodes, low current sources or devices, etc; a yellow one on the removable charge lead for a yellow cased battery, blue on a blue strobe, and so on. These are good value: DX Engineering multicolour housing set
Finally, there are a range of projects involving an arrangement of PPs on a PCB, or otherwise connected; mounted in a typically 3D printed enclosure. Available in kit form, Waverly Amateur Radio Society has produced a unit which allows distribution to 6 devices, via individual automotive fuses. It is available on the VK2BV store.
WAGO [vay-go] or similar lever based joiners or "lever nuts" can also be handy for making ad-hoc connections to stripped wires. Use genuine for mains voltages.
Modern cars use high pressure injection systems, and the high current pulses in the electrically operated injectors can generate interference to HF radios used in the car. High pressure gives finer droplets in the fuel spray, giving cleaner emissions, and greater power, including in diesel vehicles. The vehicle's alternator, which charges the battery can also generate whine, usually conducted into the audio stages, and thus audible in the speaker and/or transmitted audio. The question also mentions the vehicle's computer as a source of interference. I have noticed that LED tail-lights and brake-lights flicker, and perhaps these pulsed current also cause either RF interference, or impulses on the power input which may make clicks or buzzes in the audio. I am unsure if this flickering is just brightness control, or directly related to the CAN-Bus system, there instead of a wire going to each lamp to control it, just a lower line and a signal line runs to all lamp clusters, and they are controlled by serial data. Various control modules (computers) may also cause interference.
Off the exam, current pulses in spark plug leads in spark-ignition systems, including petrol (gasoline), ethanol, LPG (propane), and CNG (compressed natural gas) also cause interference, as any systems which include arcing can lead to RF interference. If parked by the road with a radio with the squelch open, as you tend to with SSB, you can also hear the ignition of passing cars, even listening on 2 metres. Given many mains voltage generators are spark ignition, they also can generate RF noise.
Also not yet on the exam, there is the potential for the variable frequency 3-phase AC drives used in electric vehicle to be electrically noisy - they certainly were hoping to save a few bucks, and use a module capable of FM and DAB+ only, and/or cellular Internet connections, for in-car entertainment and news reception, potentially due to the need for better (read as "more expensive") filtering to avoid interference to the AM broadcast band.
For various reasons, be they emergency communications, "Field Day" competitions, JOTA (Scout and Guide events), publicity events, SOTA / IOTA / National Parks / DXpedition events, or to operate in a park to avoid (surely unconstitutional) "Home-Owner Associations" rules against antennas (and thus free speech via radio), Amateurs set up stations, often away from sources of mains power. While a battery of adequate size might be lugged along for a short operation, there are options to charge batteries on site.
The process of converting solar (light) energy to electricity is called photovoltaic conversion, and the cells, photovoltaic cells. Photon striking the cell causes electrons to be released. Each cell typically generates just 0.5 volts, so significant numbers must be placed in series within the panel; to obtain the necessary current they are also placed in parallel. This combination is termed "series-parallel". For simple charging of lead-acid battery, a diode is placed in series, between the panel and the battery. This prevents the battery discharging through the panel with it falls into darkness. In this case you need to manually watch the voltage.
Now added to the exam, a controller is used to prevent the battery being overcharged. These often use FETs with a low RDS, and therefore often a voltage drop less than the diode, which is typically then not needed. While overcharging can damage a lead-acid battery, and an cause gassing, much more "exciting" things can happen when Lithium cells are overcharged. The military supplier euphemism is "vent with flame". Maximum power point tracking (MPPT) units are often considered the best option.
Solar may not need to be able to keep the battery fully charged, just supply enough to extend your operations.
Another option is to use a pole-mounted wind generator, charging batteries. The downside is that you may need a large battery, or as the now removed question called it, an "energy storage system", as there may be extended periods without wind. The benefit is that they may work at night. Some can be audibly noisy, and could potentially be electrically noisy.
A well looked after 7 AH 12 volt AGM or "gel" battery, as used as a backup in alarm cabinets (and some NBN services in Oz) can run a radio for an hour long club net. These weigh* around 2 kilograms. These put out a little above 12 volts when well charged, and off charge, and drop a little below with use. These can supply peaks of current for an SSB transmission just fine. (They will even help kick a small petrol engine, if the vehicle battery is low, but not seriously flat). An 18 AH unit will extend operating time, but it has a mass approaching 6 kg, with 10 AH also availabe. Powerwerx, et al, sell short fused cables with approprirate terminals, and a PowerPole, or you can make one. Reducing power output if you are being received well will also extend operating time. Radio Parts in Melbourne have a good range of such batteries: SLA Batteries. Power sonic is the affordable brand; YUASA is the premium one, and I note the 7.2 AH is heavier, but with greater current capability. Ensure you get 12 volts, not 6. Get into the habit of putting these on charge after you walk in the door.
A lithium version of the alarm battery, typically marked "LiFePO4 12.8 volts 8 AH" is available, at a greater cost. The mass is around 1 kg. These have 4 cells in series, at full charge, with the charger disconnected, these output 13.2 to 13.3 volts. These include a Battery Management System (BMS) to ensure they are not overly discharged. Note that these smaller units have discharge limits between 5 and 15 amps; and even that the 100 AH version are NOT suitable for starting a vehicle, but will run a larger radio and accessories.
There are a bunch of 12 volt "power packs" and "jump start" boxes, from under $50 to over $1000. These pretty much all claim exagerated starting current capabilities. Some contain small lithium batteries with a high current output for a few moments, but little capacity; others have decent capacity (what you need), and some include mains voltage inverters, LED lams, and even compressors for tyres. Note some jump boxes use a supercapacitor which slowly charges from a tired battery, then dumps it back into the starter motor; these are clearly not useful for powering a radio.
Various "4S" lithium batteries are available for remote control models, meaning 4 cells in series. These need chargers or battery management systems, which are able to manage each cell. Care needs to be taken not to overly discharge them, and to avoid shorts.
*OK, they have a mass of 2 kg, or aided by gravity, generate a force of around 20 Newetons towards the centre of the earth.
Generators, powered by petrol (gasoline), bottled gas (Propane / LPG / CNG), or diesel engines can be used. As these are often noisy, a long lead can be used, and ideally an earth bank or a wall helps mitigate this. Note that they generate carbon monoxide (CO), a deadly yet odourless gas, and also large amounts of particulates and other nasty emissions (and yes, smoking causes CO poisoning too). More expensive "Inverter" models generate more stable voltages. It is generally better to use the 120 or 240 volt output to run a power supply to generate the 13.8 volts needed by most radios, than to use any 12 volt "battery charging" output on the unit. These are often mechanically commutated generators with two nasty glitches, with "bonus" spikes, on each rotation, as with the "dynamo" in an old car.
A benefit of these is that an appropriately sized unit can power a large amplifier, although in this case an exclusion zone around antennas may be needed. Fluctuating loads caused by some modes can upset some generators, and/or cause significant fluctuations of the output voltage. They can also power lighting, and potentially cooking equipment.
About a decade or two ago there was some excitement about using hydrogen fuel cells for the US Field Day event, these directly generating DC power from hydrocarbon fuels or alcohol, both containing hydrogen. There was also a plan to replace the vehicle's alternator with a fuel cell, the size of a folding umbrella, with the benefit that loads such as air-conditioning could operate with the engine off, as presumably could Ham gear, without the risk of depleting the cranking battery. Hydrogen cars with limited capacity and range would probably be an expensive way to power a station, due to the high cost of this gas.
Both 4WDs, and some cars, support dual batteries, with added charging control circuitry. A deep-cycle battery (sometimes sold for marine uses) is used for this, and if putting it in the boot, a marine battery housing, vented outside the vehicle is needed. Charge controllers are also available for vehicles without this facility.
Some, especially Chinese, electric cars and SUVs, and some hybrid pick-ups could be used to power both power supplies for transceivers, and large amplifiers. These are powered by the higher voltage traction battery. Note that adding such a system to an existing EV or hybrid requires great care, and the batteries can deliver lethal voltages, and extremely high fault currents.
These are actual questions from the General exam pool.
G4E01
What is the purpose of a capacitance hat on a mobile antenna?
A. To increase the power handling capacity of a whip antenna
B. To reduce radiation resistance
C. To electrically lengthen a physically short antenna
D. To lower the radiation angle
This is to electrically lengthen the short antenna, answer C.
This arrangement is also used on MF and perhaps LF broadcast towers where there is a limitation to the height of the antenna.
G4E02
What is the purpose of a corona ball on a HF mobile antenna?
A. To narrow the operating bandwidth of the antenna
B. To increase the "Q" of the antenna
C. To reduce the chance of damage if the antenna should strike an object
D. To reduce high voltage discharge from the tip of the antenna
A plain or sharp wire end has a tendency to have corona discharge off the end, and a ball prevents this, answer D.
G4E03
Which of the following direct, fused power connections would be the best for a 100 watt HF mobile installation?
A. To the battery using heavy-gauge wire
B. To the alternator or generator using heavy-gauge wire
C. To the battery using insulated heavy duty balanced transmission line
D. To the alternator or generator using insulated heavy duty balanced transmission line
Use heavy cable to the battery, answer A.
G4E04
Why should DC power for a 100-watt HF transceiver not be supplied by a vehicle's auxiliary power socket?
A. The socket is not wired with an RF-shielded power cable
B. The socket's wiring may be inadequate for the current drawn by the transceiver
C. The DC polarity of the socket is reversed from the polarity of modern HF transceivers
D. Drawing more than 50 watts from this socket could cause the engine to overheat
The wiring for the socket may be inadequate, meaning they could overheat, or more usually, the voltage drop would be excessive, meaning the transmitted signal would be distorted, answer B.
Modern power sockets, designed to actually power accessories MAY be acceptable, but the old ones designed to ignite cancer-sticks have inadequate wiring.
While C is wrong in 99.995% of cases, if you were to connect a radio to car with "positive ground", then the radio will be subject to reverse polarity power. However, it appears that this polarity was (largely?) discontinued with the move from 6 to 12 volt systems, during the 1950s. Note that lighter sockets on heavy vehicles are likely 24 volts, and in very historical vehicles this may be reversed in polarity.
G4E05
Which of the following most limits an HF mobile installation?
A. "Picket Fencing"
B. The wire gauge of the DC power line to the transceiver
C. Efficiency of the electrically short antenna
D. FCC rules limiting mobile output power on the 75-meter band
An antenna which can be safely mounted on a moving vehicle can only be a small fraction of a wavelength long (around one twenty-fifth, at best, for the 75 metre band mentioned in the previous version of this question). Even with a helically wound antenna the efficiency is only a few percent. Thus the antenna is the limiting factor, answer C.
If it is necessary to communicate, stopping and rolling out around 20 metres of wire is probably a better idea.
G4E06
What is one disadvantage of using a shortened mobile antenna as opposed to a full-size antenna?
A. Short antennas are more likely to cause distortion of transmitted signals
B. Q of the antenna will be very low
C. Operating bandwidth may be very limited
D. Harmonic radiation may increase
These antennas typically have a very narrow bandwidth, answer C.
G4E07
Which of the following may cause receive interference in a radio installed in a vehicle?
A. The battery charging system
B. The fuel delivery system
C. The vehicle control computer
D. All of these choices are correct
All of these may apply, answer D.
G4E08
In what configuration are the individual cells in a solar panel connected together?
A. Series-parallel
B. Shunt
C. Bypass
D. Full-wave bridge
Photovoltaic cells are typically in series-parallel to form a large panel, answer A.
This is because each cell has both a low voltage output, and a limited current output.
G4E09
What is the approximate open-circuit voltage from a fully illuminated silicon photovoltaic cell?
A. 0.02 VDC
B. 0.5 VDC
C. 0.2 VDC
D. 1.38 VDC
It is 0.5 volts, answer B.
Thus tens or hundreds of cells are included in a panel.
G4E10
Why should a series diode be connected between a solar panel and a storage battery that is being charged by the panel?
A. To prevent overload by regulating the charging voltage
B. To prevent discharge of the battery through the panel during times of low or no illumination
C. To limit the current flowing from the panel to a safe value
D. To prevent damage to the battery due to excessive voltage at high illumination levels
This is been corrected to indicate that this diode prevents discharge via the panel when it is not illuminated, answer B.
It was incorrectly called "self discharge" previously, which is a process internal to the cells of the battery. However, if using a proper charge controller, the diode is likely unnecessary; consult its manual. Without a charge controller, monitor the battery voltage, to ensure that it is not overcharged.
G4E11
What precaution should be taken when connecting a solar panel to a lithium iron phosphate battery?
A. Ground the solar panel outer metal framework
B. Ensure the battery is placed terminals-up
C. A series resistor must be in place
D. The solar panel must have a charge controller
A solar charge controller is necessary to prevent fire or other negative outcomes, answer D.
If you are using these you should probably locate them so that they can't burn your shelter down during field operation!
This is the biggest section done, and also about half of this question pool completed.
On to: Electrical Principles 1 - Impedance and Calculations
You can find links to lots more on the Learning Material page.
Written by Julian Sortland, VK2YJS & AG6LE, June 2024.
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