The AUSCB.AU Page is here to help with common hints and tips for CB use’s on 27MHz HF CB or 476/477MHz UHF CB. These tips will hopefully help new uses enjoy and get the most out of CB Radio.

Citizen band radio stations class licence

The class licence lets you use citizen band (CB) radios to communicate over short distances. 

What this class licence lets you do

You can use CB radio to communicate over short distances via the Citizen Band Radio Service (CBRS).

You can use the CBRS for:

• any voice communications
• telemetry and telecommand

All users operate on shared frequencies.

Licence rules

You don’t need to apply for a class licence or pay any fees with the ACMA.

But you must follow all the rules in the:

• Citizen Band Radio Stations Class Licence 2015
• Radiocommunications Act 1992

Power output

Your equipment cannot exceed the maximum power stated in the class licence.

• HF AM – 4 watts
• HF SSB – 12 watts
• UHF FM – 5 watts

Frequencies for CB radios

You can find the frequencies for CB radios in schedule 1 of the class licence.

You can only use CB radios on designated channels in these frequencies:

• HF – 26.965 MHz to 27.405 MHz (inclusive)
• UHF – 476.4125 to 477.4125 MHz (inclusive)

You can only use telemetry and telecommand on UHF channels 22 and 23. You cannot speak on these channels.

Packet radio and other types of data operation are not allowed on CB bands.

If you want to use other frequencies, you must apply for an apparatus licence.

UHF CB repeater stations

To operate a CB repeater station, you need an apparatus licence.

If you are near a repeater station, you can operate a CB radio station through the CB repeater station but only:

• In the UHF band
• on the repeater’s assigned channels

Channels 1 to 8 and 41 to 48 are repeater output channels. Channels 31 to 38 and 71 to 78 are the matching repeater input channels.

For example, a repeater that transmits on Channel 1 will always receive on Channel 31.

If you operate your CB radio in duplex or repeater mode, it will automatically select the matching frequency.

Please note that if there is a repeater station in the area, you should not use the repeater channels to communicate on a single frequency. Be aware that these can interfere with a repeater station, even if it’s a long way away.

Contacting other CB users for the first time

There are 2 channels you can use to contact other CB users for the first time.

These are:

• Channel 11 (AM) (27.085 MHz) and Channel 16 (SSB) (27.155 MHz) in the HF band
• Channel 11(FM) (476.675 MHz) in the UHF band

After you’ve made contact, you should move to another channel that’s not in use. This leaves the channel available for other users to contact each other.

Call channels are legislated assignment

Emergencies

ACMA has set aside 2 channels that are only for emergency messages:

• Channel 9 (27.065 MHz) in the HF band
• Channels 5/35 (476.525/477.275 MHz) in the UHF band

But you can use any CB frequency to attract attention in an emergency. If you have mobile phone service Dial 000 or 112 for Police, Fire and Ambulance

Emergency channels are legislated assignment

Telemetry and Telecommand Channels

On UHF Channels 22 (476.950 MHz) & 23 (476.975 MHz) are dedicated telemetry and telecommand channels, no voice communications are allowed. Used mostly by farmers.

Examples include:

• Monitoring water levels in dams
• Controlling equipment such as irrigation pumps
• Opening and closing gates
• Radio ID
• GPS information

Miscellaneous Channels by convention

• HF Channel 8 AM (27.055 MHz) highway/Road
• HF Channel 35 LSB (27,355 MHz) unofficial LSB calling channel
• UHF Channel 10 FM (476.650 MHz) used 4×4 convoy & national parks
• UHF Channel 18 FM (476.850 MHz) used by caravan and motorhomes in convoy
• UHF Channel 29 FM (477.125 MHz) Pacific Hwy (NSW) & Bruce Hwy (QLD)
• UHF Channel 30 FM (477.150 MHz) Local Alert & Broadcasts Channel
• UHF Channel 40 FM (477.400 MHz) Highway/Road

Selective Calling methods

If you want to use selective calling, you can only use these methods:

• Selective calling (Selcall) allows a radio to call another radio using a sequence of tones, usually presented to the user as a series of 5 numbers. UHF CB radios can be set to be completely silent until they receive a series of tones matching a pre-programmed sequence. Radios which have this feature usually indicate that a call has been received by emitting a number of beeps and by opening the squelch. The popularity of selcall has dropped since the introduction of CTCSS. SelCall may be used on UHF.

HF Selcall uses CCIR 493-4, 4-digital or 6-digit numbering system. The calling radio emits a data steam while the receiving radio being called will indicate a call has been received by emitting a number of beeps and by opening the squelch. If you would like to use selcall on HF CB you could use a Jannel SC2 Selcall/Telcall Microphone or a SC51 – Selcall/Telcall/GPS internal module.

• Continuous tone coded squelch system (CTCSS) allows a group of radios set with the same tone to converse on a channel without hearing other radios using that channel. CTCSS can be used to silence a radio until another radio with the same tone transmits. This allows monitoring of a channel for transmissions from radios set with the same tone without hearing other conversations that use different or even no tone. May be used on UHF CB.

• CDCSS or Digital Code Squelch (DCS) is a further development of the continuous tone-coded squelch system or CTCSS that uses a slow-speed, binary data stream passed as sub-audible data along with the transmission. Motorola calls this Digital Private Line or DPL. It consists of a 23-bit telegram sent repeatedly on the channel at 134 bits per second along with the voice transmission. This allows for over 100 possible fleet codes to be used. This gives it an advantage over the CTCSS tones in that there are more possible codes to use; however, it does use more bandwidth and can be affected by voice tones below 300 Hz if not properly filtered by the radio circuitry. May be used on UHF CB.

The use of CTCSS & DCS are not permitted on UHF CB repeaters or the designated emergency channels.

Call signs

Call signs are a unique series of letters and numbers. They make it easy to identify a station.

You do not need to use a call sign for class licences. But it’s recommend that you identify yourself when you communicate by CB radio.

UHF CB Channel List

Channel Name:	Frequency:	Purpose:	*Frequency Spacing:
Channel 1	476.4250	Repeater Output	12.5 kHz / 25 KHz
Channel 2	476.4500	Repeater Output	12.5 kHz / 25 KHz
Channel 3	476.4750	Repeater Output	12.5 kHz / 25 KHz
Channel 4	476.5000	Repeater Output	12.5 kHz / 25 KHz
Channel 5	476.5250	Emergency Repeater Output / Simplex	12.5 kHz / 25 KHz
Channel 6	476.5500	Repeater Output	12.5 kHz / 25 KHz
Channel 7	476.5750	Repeater Output	12.5 kHz / 25 KHz
Channel 8	476.6000	Repeater Output	12.5 kHz / 25 KHz
Channel 9	476.6250	General Channel	12.5 kHz / 25 KHz
Channel 10	476.6500	4WD Clubs or Convoys and National Parks.	12.5 kHz / 25 KHz
Channel 11	476.6750	Call Channel	12.5 kHz / 25 KHz
Channel 12	476.7000	General Channel	12.5 kHz / 25 KHz
Channel 13	476.7250	General Channel	12.5 kHz / 25 KHz
Channel 14	476.7500	General Channel	12.5 kHz / 25 KHz
Channel 15	476.7750	General Channel	12.5 kHz / 25 KHz
Channel 16	476.8000	General Channel	12.5 kHz / 25 KHz
Channel 17	476.8250	General Channel	12.5 kHz / 25 KHz
Channel 18	476.8500	Caravanners and Campers Convoy Channel	12.5 kHz / 25 KHz
Channel 19	476.8750	General Channel	12.5 kHz / 25 KHz
Channel 20	476.9000	General Channel	12.5 kHz / 25 KHz
Channel 21	476.9250	General Channel	12.5 kHz / 25 KHz
Channel 22	476.9500	Telemetry and Telecommand Only (No Voice)	25 kHz
Channel 23	476.9750	Telemetry and Telecommand Only (No Voice)	25 kHz
Channel 24	477.0000	General Channel	12.5 kHz / 25 KHz
Channel 25	477.0250	General Channel	12.5 kHz / 25 KHz
Channel 26	477.0500	General Channel	12.5 kHz / 25 KHz
Channel 27	477.0750	General Channel	12.5 kHz / 25 KHz
Channel 28	477.1000	General Channel	12.5 kHz / 25 KHz
Channel 29	477.1250	Highway Channel, Pacific Hwy (NSW) & Bruce Hwy (QLD)	12.5 kHz / 25 KHz
Channel 30	477.1500	Local Alert & Broadcasts Channel	12.5 kHz / 25 KHz
Channel 31	477.1750	Repeater Input	12.5 kHz / 25 KHz
Channel 32	477.2000	Repeater Input	12.5 kHz / 25 KHz
Channel 33	477.2250	Repeater Input	12.5 kHz / 25 KHz
Channel 34	477.2500	Repeater Input	12.5 kHz / 25 KHz
Channel 35	477.2750	Emergency Repeater Input / Simplex	12.5 kHz / 25 KHz
Channel 36	477.3000	Repeater Input	12.5 kHz / 25 KHz
Channel 37	477.3250	Repeater Input	12.5 kHz / 25 KHz
Channel 38	477.3500	Repeater Input	12.5 kHz / 25 KHz
Channel 39	477.3750	General Channel	12.5 kHz / 25 KHz
Channel 40	477.4000	Highway/Road Channel Australia Wide	12.5 kHz / 25 KHz
Channel 41	476.4375	Repeater Output	12.5 kHz
Channel 42	476.4625	Repeater Output	12.5 kHz
Channel 43	476.4875	Repeater Output	12.5 kHz
Channel 44	476.5125	Repeater Output	12.5 kHz
Channel 45	476.5375	Repeater Output	12.5 kHz
Channel 46	476.5625	Repeater Output	12.5 kHz
Channel 47	476.5875	Repeater Output	12.5 kHz
Channel 48	476.6125	Repeater Output	12.5 kHz
Channel 49	476.6375	General Channel	12.5 kHz
Channel 50	476.6625	General Channel	12.5 kHz
Channel 51	476.6875	General Channel	12.5 kHz
Channel 52	476.7125	General Channel	12.5 kHz
Channel 53	476.7375	General Channel	12.5 kHz
Channel 54	476.7625	General Channel	12.5 kHz
Channel 55	476.7875	General Channel	12.5 kHz
Channel 56	476.8125	General Channel	12.5 kHz
Channel 57	476.8375	General Channel	12.5 kHz
Channel 58	476.8625	General Channel	12.5 kHz
Channel 59	476.8875	General Channel	12.5 kHz
Channel 60	476.9125	General Channel	12.5 kHz
Channel 61	476.9375	Reserved, Guard channel for 22 & 23	–
Channel 62	476.9625	Reserved, Guard channel for 22 & 23	–
Channel 63	476.9875	Reserved, Guard channel for 22 & 23	–
Channel 64	477.0125	General Channel	12.5 kHz
Channel 65	477.0375	General Channel	12.5 kHz
Channel 66	477.0625	General Channel	12.5 kHz
Channel 67	477.0875	General Channel	12.5 kHz
Channel 68	477.1125	General Channel	12.5 kHz
Channel 69	477.1375	General Channel	12.5 kHz
Channel 70	477.1625	General Channel	12.5 kHz
Channel 71	477.1875	Repeater Input	12.5 kHz
Channel 72	477.2125	Repeater Input	12.5 kHz
Channel 73	477.2375	Repeater Input	12.5 kHz
Channel 74	477.2625	Repeater Input	12.5 kHz
Channel 75	477.2875	Repeater Input	12.5 kHz
Channel 76	477.3125	Repeater Input	12.5 kHz
Channel 77	477.3375	Repeater Input	12.5 kHz
Channel 78	477.3625	Repeater Input	12.5 kHz
Channel 79	477.3875	General Channel	12.5 kHz
Channel 80	477.4125	General Channel	12.5 kHz

* Channel bandwidth 25KHz is only used by older UHF CB 40 channel sets, while 12.5KHz is used by all new 80 Channel sets.

You should not use repeater input channels 31 – 38 & 71- 78 for simplex operation (radio to radio), interference to repeaters is possible. If you intend on using repeater inputs for simplex (radio to radio), make sure you check for a repeater in the area you intend to operate in.

HF CB Channel List

Did you know in Australia we have a 27MHz marine band?

The Australian 27MHz marine band is in the upper portion of the band. 10 channels have been allocated, mods used on this band are AM and USB and the power output is the same as 27MHz CB 4w AM and 12w SSB.

The use of the channels are for Australian water ways. They come under a class license like CB radio no marine radio qualification needed unlike VHF. The use of 27MHz marine has reduced over time as equipment is harder to purchase. Unlike VHF marine that uses FM the AM/USB sets are susceptible to noise from engines on the vessel.

The early radio sets had the 10 channels marked from 1 to 10. later set’s then used channels marked from 68 to 98, this was formed from the frequency used, i.e. 27.8800 is channel 88.

 Distress & Calling Channels

Like CB radio Marine also has emergency channels (Distress and Calling) these are allocated under law from the Australian Communications and Media Authority (ACMA). Channels allocated for are:

• Channel 88 used as the Maine Distress and calling.
• Channel 86 used as a secondary to 88.

A majority coast station monitor 27MHz Marine channels 88 & 86. In recent times some coast stations have stopped monitoring 27MHz marine. Please check with your local Coast Gaude before heading out!!

It’s recommended that vessels are equip with a VHF marine transceiver and a qualified person on board (most likely the Skipper). For more information see ACMA at https://acma.gov.au

Calling on 88 and 86 used to log in and out from the Coast Guard. you can call other station as well, once you have made contact with the other vessel or land station you need to move to the appropriate channel I.e. Channel 94.

27MHz Marine Antennas

Like 27MHz CB there are lots of antennas for use with 27MHz marine from the helical, 9-foot stainless steel, and base station antennas. Base station antennas like the Shockwave Station master or pre-tuned types from ZCG scalar range. As for Vessel mount type antennas there are of course the Helical with the 5/16 base and 9′ stainless steel antennas, this type of antenna works well on Steel or Aluminum decks as this is used for a ground plane much like on a car. Ground independent deck mount antennas typically use a marine antenna mount, plastic or metal and can be used on fiberglass vessels. Most antennas come pre-tuned and don’t need adjustment, but you should check your SWR after installation is finished.

Current Radios available

Uniden UM255, AM Marine and AM 40 Channel CB.

GME GX400W/B AM Marine.

HF 27MHz Marine Channel List

Channel	Frequency	Purpose & Mode
68	27.6800	Commercial calling and working – AM/USB
72	27.7200	Professional fishing calling and working (Ship-Shore/Ship-Ship) – AM/USB
82	27.8200	Professional fishing calling and working (Vessel-Shore/Ship-Ship) – AM/USB
86	27.8600	Supplementary distress, safety and calling. – AM/USB
88	27.8800	Maine distress, safety and calling. – AM/USB
90	27.9000	Non-commercial calling, public use and working (Vessel-Shore) – AM/USB
91	27.9100	Non-commercial calling, public use and working (Vessel-Shore) – AM/USB
94	27.9400	Non-commercial calling, public use, club events and working. (Vessel-Vessel/Vessel-Shore) – AM/USB
96	27.9600	Non-commercial calling, public use (Vessel-Vessel) – AM/USB
98	27.9700	Rescue organizations, e.g. surf rescue, volunteer coast guard. (Vessel-Vessel/Vessel-Shore) – AM/USB

Did You Know We 27MHz Handphone?

This class license lets you use a 27 MHz handphone station equipment (Handhelds) to communicate by radio. 

What this class license lets you do

This class licence lets you use a 27 MHz handphone (Handheld) station.  

Handphones have a built-in antenna and you can carry them by hand. They make it easy to talk to another person who is a short distance away.

They are often used for or:

• by bushwalkers and firefighters
• during sporting events and group activities
• to communicate with someone who is less than 1km away

All users operate on shared frequencies.

Licence rules

You don’t need to apply for a class licence or pay any fees.

But you must follow all the rules in the:

• 27 MHz Handphone Station Class Licence 2015
• Radiocommunications Act 1992

Power output

Your equipment cannot exceed the maximum power stated in the class license of

700mW pZ, 4W pZ and 12 Px. See table below.

Frequencies for 27 MHz handphones

Frequency in MHz	Mode / Power / Bandwidth	Purpose / Note’s
27.230	AM / 700mW pZ / 6Khz	General Use ** Refer to note.
27.240	AM / 700mW pZ / 6Khz	General Use ** Refer to note.
27.250	AM / 700mw pZ / 6Khz	General Use ** Refer to note.
27.260	AM / 700mW pZ / 6Khz	General Use ** Refer to note.
27.270	AM / 700mW pZ / 6Khz	General Use ** Refer to note.
27.280	AM /700mW pZ / 6Khz	General Use ** Refer to note.
27.550	AM / 4W pZ / 6Khz – USB / 12w Px /3KHz	General Use.
27.560	AM / 4W pZ / 6Khz – USB / 12w Px /3KHz	General Use.
27.580	AM / 4W pZ / 6Khz – USB / 12w Px /3KHz	Bushfire fighting purposes only.
27.590	AM / 4W pZ / 6Khz – USB / 12w Px /3KHz	General Use.
27.620	AM / 4W pZ / 6Khz – USB / 12w Px /3KHz	General Use.
27.660	AM / 4W pZ / 6Khz – USB / 12w Px /3KHz	General Use.
27.760	AM / 4W pZ / 6Khz – USB / 12w Px /3KHz	General Use.

NOTE: If you use the frequencies with notation ** you:

• must not interfere with citizen band (CB) HF radio stations.
• may get interference from CB equipment that uses the industrial, scientific and medical (ISM) frequency band.

Problems with interference or reception-

You may get interference if you use 2 handphones near each other or class to other services in the band on or around same frequency.

If this happens, try changing to another frequency.

You can use selective calling under this class licence.

Antennas, cable and Placement

Choosing the right antenna for you home base or mobile will depend on a few factors.

Type of antenna, gain, height above grand, purpose base or mobile, HF or UHF and the type of feedline required.

• Vertical Antenna base
• Vertical Mobile Antenna
• Yagi (Beam) Directional Antenna

Feedline-

Most people know co-ax cable for their TV set RG6 and RG59 75 Ohm type although similar the co-ax cable used for CB has an impedance of 50 Ohms common cables are RG213, RG58U and RG58C/U.

RG58 is commonly used in mobile installations as it’s small and we only have a short run of normally 10m or less. while in a base station we would tend to use RG213 for runs greater then 10m to 30m as RG213 has less loss per meter than RG58. There are better cables out there like LMR400 (LL400) recommended for use with UHF CB, but for basics we will stick to RG213, RG58U and RG58C/U.

RG213 and RG58C/U have a multi core centre conductor, RG58U has a solid centre conductor. other cable s like LMR400 (LL400) that also have a foil shield have less loss and are used for UHF and higher. The foil also helps to reduce noise that may be induced by local equipment.

Connectors–

There are many types of connectors used for CB radio from the humble PL259 (UHF), N type, BNC, FME & SMA. Same cables come with an FME/PL259 adapter so you can pass the cable though the firewall of your vehicle.

Did you know the SO239 comes in two flavours?

SO239 (UHF): Connectors in the UHF connector family mate using the ⁵⁄₈ inch 24 tpi threaded shell for the shield connection and an approximately 0.156 inch-diameter (4 mm) pin and socket for the inner conductor.

M Connector: Similar connector to the SO239 (M connectors) has an incompatible 16mm diameter, 1mm metric thread, but these are not standard SO239 connectors and do not play well with the older SO239. M connector commonly used by Diamond Antenna Corporation in Japan.

Before fitting your connector cut a piece of dual wall heat shrink and slide it over your cable, fit your connector use the heat shrink to cover the entry point of the cable and connector. This dose too things, seal the connector at the cable entry point and provides some strain relief.

Sealing connectors is a must when out in the weather. It will reduce the risk of antenna system failure. Using some self-amalgamating tape like 3M SCOTCH 23 wrapping the connector and cable, finely wrapping with a layer of PVC tape like 3M SCOTCH 33+ or Nito tape to protect it from UV.

Mobile Antenna Placement

When installing your antenna there are some factors you may wish to consider, I.e., In a mobile installation if you have a ground dependent antenna the more metal surface you have for the ground plane the better, but with the length of a lot of them it may not be practical to center roof mount antenna. see the picture below that shows the antenna radiating pattern in different locations.

After selecting your mounting location for your antenna base you make need to prepare the surface. If mounting to a painted surface, it’s a good idea to remove any paint from under neath so the earth of the antenna base can clean connection to the metal surface. This is particularly important when installing ground dependent antennas like the Mobileone Bush Bandit 27Mhz Antenna DX160RW, this will help SWR and the antenna performance.

Fitting Antenna’s to a Vehicles–

With so many different types of two-way radio antenna’s installing them need to be practical and efficient. This also means installing them so that you meet the requirements of your state and territory.

Rules and guidelines:

• Victoria – Download
• New South Wales – Download (General rule for fitting options) Don’t install antennas in drivers view. left as practical keeping antenna separation.
• Australin Capital Territory – Download
• Tasmania – Download
• South Australia – TBA
• Westen Australia – TBA
• Northen Territory – Download
• Queensland – Download

We are trying to compile the information for each state and territory. And where we can have highlighted the appropriate section in yellow. It’s very important to know that in same states and territories mounting on the front can be very gray, in the front of the driver. It is recommended that the installation of any antenna be mounted as close to the left as practical. The information provided is a guide only, If not sure contact your local roads authority.

Practical Mounting of Antennas–

Ok we will need to look at a few different types of antennas and their mountings options. They are

UHF CB ground independent antennas, 3G/4G/5G LTE antennas HF antennas.

• Starting off with the most common the UHF CB antenna. Most UHF CB antennas used today are ground independent they come mainly the raised feed type and the larger heavy duty 4×4 style antenna. with the smaller type of antenna like the raised feed you can mount this ether on a roof bar, bracket, fender mount or bull bar. the primary position would be on the roof bar or backet if practical secondary location would be fender, then bull bar. The heavy-duty UHF CB antennas are designed to be mounted on a bull bar and should have the mount (spring mount) on the top loop as to have the antenna clear of the bonnet. because they are very large in size and diameter it is recommended the mount to the left side of the vehicle as not to block the drivers view of the road.
• 3G/4G/5G LTE antennas are for the most come in a few different types of small low gain (3.5dBi) for roof mount application and the larger 6.5 to 7.5dBi antennas that can be mounted on fender or bull bars. Agine when mounting them on a bull bar it’s a good idea to keep them as far left as practical. Because of the frequencies use for this service in the 700 to 3500MHz rage it’s best to keep them well away from other metallic objects.
• HF Autotune and ground dependent antennas are one of the hardest to mount on cars 4×4’s we will start with the good old 27MHz CB antenna these come is a few flavors from the 9′ 1/4 wave to the 5′ helical antenna. This type of antenna needs a good ground plane for maximum performance, as they are quite large placing the smaller 6′ one on a gutter or roof mount is a good place to start, while the longer heaver antennas like the 9′ stainless steel or Skipwhip from Mobileone antennas are best mounted on a bull bare because of the wight and sine of the spring and base. Keep in mind you may need to bond the bull bare to the body of the vehicle with a 12mm or 20mm braided strap, this will help with antenna performance and tunning for the best possible SWR. Other HF antennas like the multi band tap antennas that cover from 2 to 30MHz also would be suited to bull bar mounting or on the back of some vehicles, again grounding with a strap will be needed. HF autotune antennas are very handy and convent because at the touch of a button you can tune the antenna for the desired frequency. They come in a few models I.e the taller Codan 9350 and the smaller 3040, the 9350 is very large antenna and need to mount about 100mm (10cm) away from any meatal substrate. As the tunning section of the antenna con be affected by the body most people mount this on the left of the bull bar and on the back. keep in mind this antenna can create blind spot in the drivers view. this is much the same for the 3040 the lower section can create a blind spot closer to the vehicle. with all autotune antennas good grounding is a must.
• Antenna separation is another very important issue to look at. You will see from time to time mostly 4×4 with antennas mounted to the left witch is great for the driver but not so good for the antenna and equipment connected to it. It’s good practice to keep antennas as far apart and away from any metallic objects as possible. Antennas are part of a tuned system this help your equipment work at it best.

Somes problems with antenna installed to close to one another may cause the following:

1. Detuning of antenna system which could damage the transceiver.
2. RF energy from the transmitter could damage the receiver on the send radio.
3. Diminish the performance and distance (range) your setup.
4. It’s looks stupid!!

To help stop rust and corrosion use some electrical contact grease, a light film on the bear surface is all that is needed.

Mobile bases commonly used in Australia

The 5/15 TPI base are quite common and are used for antennas from small to 160cm CB antenna’s the difference between the two types of 5/16 bases is the way the co-ax is terminated. The VHF/UHF version was used on a lot a of Taxi’s with a 4.5dbi antenna. these bases may also be panel mounted in a roof of a vehicle.

The 1/2″ BSW base (also known as the SAM base) is used by some lager HF and 27MHz CB antennas like taped multi band, Mobileone Skip Whip and the classic 9′ stainless steel antenna. These antennas will also have a spring to help with shock, vibration and allows for the antenna to bend to reduce damage.

SO239 Also known as M base is used by a lot of commercial users in the VHF and UHF bands, some the antennas used are RFI antennas VHF and UHF, 27MHz CB base loaded, UHF CB and amateur radio dual band antennas like the SG-7900.

Base Used in the USA and abroad.

3/8 x 24 Stud mount, Used mostly in the USA for 27MHz CB and Amateur radio mobile antennas. Can come with SO239 (UHF) and eyelet styles termination.

3/8 x 24 Stud ball mount. The ball mount is designed to filled onto the vertical fender or other panel. The ball is adjustable to allow for radiator to be set vertically. this mount is very common with the 9-foot stainless steel whip and spring & other HF antennas.

Used mostly in the USA the NMO or “New Motorola Mount” is a mobile mount used for mobile VHF/UHF PMR, LMR, cellular phone, EMS, 27MHz CB, GRMS & amateur radio. The NMO mount is low profile making it ideal for panel fitment on the boot lid and roof. When installed correctly and a good quality antenna attached it makes for a watertight seal.

Light Reading

HF Propagation

Here is a splendid video that shows and explains HF propagation aka Skip from Rohde Schwarz.

information brought to you by BNCom Australia / Australian Communications & Media Authority ,wikipedia and other sources.