The antenna is the most important part of the transmission system and must be correctly installed before proceeding further and before any transmission equipment is connected.
Under no circumstances should the antenna be mounted and used at ground level or within a few meters of personnel.
Ideally this antenna should be mounted at least 20 meters high and clear of any surrounding objects to get maximum range and more importantly to reduce risk of radio frequency radiation to personnel. When mounted at least 20 meters in height off ground and using 400 watts of transmitter power, power flux density measurements made at ground level directly under the antenna show less than 1 W/m2. Several European countries use a value for the power flux density of 10 W/m2 as a basis for considering whether or not an area is safe. The issue of radio frequency radiation limits is a contentious one and work in this field is continuing worldwide.
You are responsible for selecting the correct antenna for your application, installing it properly and ensuring the system maintenance.
This antenna is intended for use with an FM broadcasting transmitter up to 800 watts at a permanently pre-defined location with a license or authorisation from the radio spectrum regulator of your country.
|PVC insulation tape and/or Self Amalgamating Tape|
|Tape Measure with mm|
|A secure mounting mast or pole with a diameter of 45-50mm and a vertical space or length of at least 8m|
|Antenna 50 ohm feeder cable, normally this is LMR400|
Following is a list of precautions to follow when installing the antenna if placement of antenna and cables is anywhere near power lines.
|Erect antenna on side of house or building as far away as possible from the power line.|
|Avoid crossing antenna cables under electrical power lines.|
|Do not attach antennas to towers, poles or similar structures carrying electrical power lines.|
|If you are not experienced in installation of antennas, have experienced persons assist you.|
|During installation, tie off antenna with rope so if it falls it can be diverted away from power lines.|
|Avoid fastening antennas, especially self-supporting types, to old chimneys or to any chimney not designed to take such stress. Forces created by a strong wind may be sufficient to topple both chimney and antenna.|
|Make sure antennas have been properly grounded and provided with other necessary lightning protection.|
|2||A Dipole (YELLOW marked cable + 0.63 cm RG11)|
|2||B Dipole (RED marked cable + 0.63 cm RG11)|
|8||C 65.5cm radiator rods|
|8||D Bolt, wing nut and plastic spacer|
|2||E LMR400 3.0m BLUE / 0.63m RG11 GREEN (Total 3.63m)|
|3||F Splitter box|
|4||G Mast fixing clamp|
|20||H Cable ties|
1. Mount the tuned dipoles to the mast using the clamps provided. The RED must be at the bottom, then next up YELLOW, the next up RED and finally YELLOW at the top. IMPORTANT! for correct operation the dipoles must be mounted in this order with RED at the bottom and YELLOW at the top and the dimensions on the diagram are followed as closely as possible. All dipoles must be directly above each other and all 'terminal boxes' must be facing the same way for the system to work properly and give full tuned bandwidth from 88-108MHz.
2. Mount the splitter boxes using the tie wraps provided on the mast between the dipoles as shown on the diagram. The splitter boxes are marked top and bottom, make sure top is facing upwards. This shelters the connections from rain and water.
3. Connect the two red and two yellow marked dipole antenna cables as shown in the diagram to the outer sockets of top and bottom splitter boxes. There will be excess cable, simply coil this neatly and tape or tie it to the mast (DO NOT CUT IT BACK AND REFIT THE PLUG). The cables marked with YELLOW, RED, BLUE and GREEN are critical phased lengths and must never be altered in length.
4. Using the first of the two (E) 4.17 meter cable lengths, connect the BLUE MARKED end to the centre connecter on the top splitter box and GREEN MARKED end to one of the outer connectors on middle/center splitter box. There will be excess cable, this is okay, simply coil this neatly and tape or tie it to the mast (DO NOT CUT IT BACK AND REFIT THE PLUG). The cables marked with YELLOW, RED, BLUE and GREEN are critical phased lengths and must never be altered in length..
5. Using the second of the two (E) 4.17 meter cable lengths, connect the BLUE MARKED end to the centre connecter on the bottom splitter box and GREEN MARKED end to one of the outer connectors on middle/centre splitter box. There will be excess cable, this is okay, simply coil this neatly and tape or tie it to the mast (DO NOT CUT IT BACK AND REFIT THE PLUG). The cables marked with YELLOW, RED, BLUE and GREEN are critical phased lengths and must never be altered in length.
6. Connect the one end of the main feeder cable to the centre connector on the middle centre splitter box on the mast. The other end will go down the tower and connect to the transmitter later.
7. Wrap PVC or self amalgamating tape tightly around and all over the plugs on the splitter boxes to waterproof them.
8. Securely fix the cables using PVC tape or large cable ties to the mast as shown in the diagram opposite. Make sure the cables are not going to flap around in the wind.
9. Make sure none of the cables are not loose in the wind
10.Make sure that all fixings are tight and are not going to work loose over time with wind
When writing this manual there was no EU directive regarding the EMC (Electro Magnetic Compatibility) of Band II VHF broadcast antennas, however in our view there are some potential EMC compatibility issues that need to be addressed when installing this antenna system. On completion of the antenna installation check;
1.All the cables entering the connectors are tight and properly crimped or soldered
2.All the connectors are screwed in tight and sound.
3.PVC insulation tape and/or self amalgamating tape are wrapped around all the connectors to stop water entering the connector and the inside of the body of the cable.
If any cables are loose or there are bad connections this can cause some non-linear resistance, diode action or some small arcing. When this happens it creates EMC disturbance (arcing and crackling sound) across a wide frequency spectrum.
The diagram above is the E-Plane radiation pattern. To obtain this pattern of 6dB over a dipole and 8.1dBi the design uses four separate dipoles. Each dipole is tuned to give 50 ohms at band centre of 97.5 MHz. The four 50 ohm dipoles are combined together using 3 sets of two ¼ wavelength 75 ohm cables, this configuration is known as the Wilkinson combiner. At the point where they are all combined the impedance is also 50 ohms (SWR 1.6 maximum at the feed point)
|Frequency Range||87.5 to 108 MHz with SWR < 1.6|
|RF Connectors||N type|
|Impedance||50 ohm (+/-1.5 SWR) unbalanced input|
|Antenna Gain (Isotropic)||+7.8 dBi|
|Antenna Gain (Rel. Dipole)||+5.7 dBd|
|E-Plane Radiation Angle||15 Degrees (see diagram above)|
|H-Plane Radiation Angle||360 Degrees Omni-Directional (depending on the tower or mounting pole used this figure may be modified by 0.5dB)|
|Maximum RF Power||800 Watts|
|Weight of Each Dipole||1.4 Kg|
|Weight of Total Package||7.5 Kg|
|Wind Speed Handling||90 MPH Minimum|
Because antennas are passive devices maintenance requirements are low, however don’t accept low as being none existent, some periodic inspections are required.
Always following a heavy storm or extreme weather condition an inspection should be done and as shown in the table below.
|WEEKS||Building Roof||Light Duty Tower||Heavy Duty Tower|
Antenna Inspection List
1.Check antenna is still rigid and tight on tower, mast or pole and vertical tubes are still exactly vertical as opssoed to twisted and slanted.
2.The PVC tape insulation or self amalgamating tape still covers all the connectors properly and the connectors remain tight.
3.The antenna feeder cable (normally LMR400) continiues to be held rigid to the boom, tower, mast or pole.
We sell this equipment to professionals and organizations in good faith it will be used correctly and legally. Most countries in the world require licensing for this antenna to be used with a transmitter. It is the customer's responsibility to check relevant laws, directives, regulations and licensing requirements before putting this product into service with an antenna system. You, the customer or user agree to defend, indemnify and hold harmless Aareff Systems Limited, its employees and agents, from and against any claims, actions or demands, including without limitation legal and accounting fees, alleging or resulting from improper or unlawful use of this equipment.
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