Review of the AOR DA3000 by Chris Lorek

Our recent guide to scanner aerials, published in scanners international a few months ago, must have wetted some appetites! No sooner was it in print, the editorial team had been asked to review a couple of base station types for the benefit of the readers. For this, they chose a pair of very different wideband aerials from those scanner specialists AOR, the DA-3000 discone and the amplified ‘WA’ versions, these arrived at the door within a few days of asking-that service for you!

Following this, AOR were kind enough to lend me there latest AR3000A 100KHz-2036MHz scanner (reviewed in last moth’s issue) which provide a useful ‘test bed’ for comparison with my existing scanner aerial system over a slightly longer period.

The DA3000 has 16 elements in total, these being made from stainless steel to protect against the ravages of the weather. It is, of course, designed for outdoor mounting, and the termination moulding for the disc/cone elements is also well sealed. The coaxial termination is fitted within the 300mm supporting tube supplied, to again protect it from the elements. A pair of supplied mast clamps let you fit the assembly on to the support pole of up to 52mm diameter (see the accompanying photo).

As for the size of the aerial, well its maximum dimensions are given as a height of just over 1m with a diameter of 0.9m, although the different length elements did cause me to give up trying to accurately measure it! The whole assembly is fairly light, weighing in at just over 1Kg which should make installation fairly easy, and to help you further a pre-assembled and terminated 15m length of 50 ohm coax is also supplied. The discone took me around 20 minutes to put together, clear pictorial instructions supplied which made the job easier than I’d first expected.

The usual form of discone you see is made up of a number of rods, simulating a horizontal ‘disc’ above a ‘cone’ of elements, the disc and cone elements being of an individual dimensions. The ratio of disc/cone dimensions, plus the physical size of this in the first place, decided the frequency coverage of the aerial. This usually encompasses around two octaves of frequency i.e. 100-400MHz, or 150-600MHz, and so on. ‘Staggering’ the element dimensions, i.e., by having 50% of these shorter than the other, may be used to achieve a wider overall bandwidth.

However AOR have gone a few steps further, and from the accompanying photograph you may be able to see that the widely differing element lengths are used, with a large maximum/minimum ratio to thus give a wide bandwidth. Inductive loading on one element is even used to attain the lower frequency range, the overall result being a specified 25MHz-2000MHz receiver range.

I connected the DA-3000 to a four-way aerial switch at my ‘listening post’ end, the other switch positions being connected to my 145/435MHz colinear, a ‘normal’ discone, and a wideband 14MHz-30MHz HF dipole system. Careful listening and noting down signal strengths showed the DA3000 to have an excellent all-round performance. Not quite as good as separate ‘dedicated’ aerials for extremes of frequency range, but certainly better all round than any single narrow-band aerial.

In use, I wouldn’t like to think the VSWR (i.e. the impedance match) would be low across the range, for example to allow it to be used with a transmitter. Indeed AOR warn that it is a receiver only aerial (yes their UK-product leaflets speak in English by not calling it an antenna!) so don’t try using your transmitter into it if you value your power amplifier circuit! This is unlike some of the ‘traditional’ discones, which cover a much narrower frequency range band but can be used for transmit reasonably safely.

After a period outdoors, unlike my other discone (where the elements tend to fall off after being used as a handy bird perch for all of the local starlings) it continues to work well, although I’d possibly hate to think what might happen if a large seagull or the like was to take a fancy to it. It provided a good performance across a wide frequency range, and being a ‘passive’ (rather than amplified) aerial it should guard against the possible scanner receiver ‘overloading problems’ of smaller ‘active’ aerial with built in wide-band amplifiers. If you can manage to get one up, I’d certainly recommend it.

Scanners International is a section of Ham Radio Today Magazine published by Nexus Special Interests Limited, Nexus House, Boundary Way, Hemel Hempstead, Herts HP2 7ST, England. Tel: 01442 66551 Fax: 01442 66998, editorial e-mail: editor@qsp73.demon.co.uk editorial web site: http://www.qsp73.demon.co.uk

Due to continuous developments, AOR reserves the right to make design and specification changes for product improvement without prior notice. The performance specification figures indicated are nominal values of production units. There may be some deviation from these values in individual units.

Review - AOR Base Scanning Aerials, DA3000

Chris Lorek reviews a pair of ultra-wideband aerials matching today's super-wideband scanners