Having the chance to focus RF power has long been an effective way of increasing the range of transmissions and for decades has been put to good use by radio amateurs the world over but now with purpose built directional antennas for CB radio those of us who use 27MHz can enjoy the increased performance that a beam antenna brings.
Types of Directional Antenna
The most common form of directional antenna is the Yagi and this can be seen everyday employed in a range of communications with the most common use being television aerials. The Yagi is an efficient design for use at higher frequencies above 50 MHz where the antenna wavelength means a Yagi can be built in a practical size.
To use the Yagi design at HF much of the actual physical length has to be added by the use of coiled wire to try and keep the antenna size down, this method of coiling the antenna into a smaller size is necessary in many HF radio setups including mobile systems, otherwise installing antennas for these frequencies would require ridiculous amounts of space to work effectively.
Managing Antenna Size at 27 MHz by using Quads
Full wavelength at CB frequencies is 36 foot meaning any sort of directional antenna produced for this band is going to be a little on the large side if you want anywhere near good performance.
Quad antennas have long been successful in delivering this performance while at the same time going some way to dealing with the size issue. Because the whole physical length of the antenna elements are arranged in a four sided square configuration it is possible to produce a 27 MHz directional quad for CB radio that needs much less room than a traditional HF beam.
Of course if you going down the directoianl anttena rooute your going to need addiational hardware (tower and a rotator) to get the most out of the setup.
Rotators can be a big additional cost to setting up a directional system but choosing something that works well and more importantly is going to continue working will save so much maintenance time in the future, the last thing anybody wants is to be constantly working on a antenna once it is set at height.
Most of the cost of a rotator will be in the amount of weight it can support but some considerations must be taken in the actual operation of any potential purchase. The ideal rotator is one that moves in the smallest increments possible allowing for total control over the direction of you transmissions.
A good rotator will cost a bit more but if your going to the trouble of installing this type of antenna it only makes sense to get the absolute best from it. This is going to add a whole new level of cost to running a CB station but provided your aware of the standard of tower needed (based on antenna weight) it can be kept to a minimum.
Choosing a Tower
Some of the smaller quads built for CB radio are light enough to be attached to the outside wall of most buildings but if your thinking about a high gain quad with many directional elements it will have to be mounted on its own tower to operate safely.
The choice of tower comes down to available space with a tilt over type being the easiest and safest to work with but unfortunately requires a lot more space especially when working on the antenna. If the tower is 20 foot high then its going to need that much length clearance on the ground once it is tilted.
A more traditional tower will have to be climbed to preform any maintenance and antenna mounting can be a lot of hard work but will only need just enough ground space to get the thing assembled. Some tower models are like huge Mecharno sets that can be put together one piece at a time making them the perfect choice when space is at a premium.
Any tower is going to need a good base with the ideal situation being a solid area of concrete that tower can be set directly into or bolted on. This can either be a suitable flat roof that will handle the weight or by laying down a concrete base on available ground.
Even though the tower and antennas combined weight will be kept to a minimum by the use of lightweight materials try to economize on the base and the first heavy winds will happily turn the whole setup into scrap metal very quickly.
Using Amateur Beams
HF beam antennas designed for amateur radio enthusiasts will work at CB frequencies but do require some additional equipment to function properly. Because amateur HF antennas are wide band they will need to be used via a antenna tuner to get the best possible match to your CB radio and help keep that dreaded SWR (Standing Wave Ratio) at a reasonable level and give maximum RF power transfer.
The other problem with using a full HF beam is there is a lot of extra material in the construction of the beam that a typical CB user will never need, this adds to the cost not only of the antenna itself but might push the rotator needed into a higher weight class which is also going to seriously push the price of installing a directional system higher again.
Whole directional setups including antenna, rotator and tower can often by purchased at good prices if you have or can arrange a method of transporting it.
The Price of Serious CB use
A quality constructed basic two element CB radio quad can be bought new for under 300 USD but that is the quad alone without a rotator or the other bits and pieces needed when installing a new antenna system.
The same quality higher gain 8 element beast isn’t going to leave you much change from 1000 USD and that’s before you even start mixing concrete for the tower, throw in everything else you need including the time needed to get the whole system up and running and its going to take one dedicated CB radio user to justify it all.
Quad Antenna photo courtesy Wikipedia