AOR AR8200 Spezifikationen PDF herunterladen (Seite 139)

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DA900 VHF/UHF flexible whip 245mm in length.

TW500 VHF/UHF telescopic which aerial. Comprises of six sections,

extends to 625mm in length.

MA500 VHF/UHF whip aerial on magnetic base with 4m of coaxial cable.

Base is 85mm in diameter, total height is 720mm. Coverage is 25 to 1300 MHz.

DA3000 16 element discone aerial with 15 of coax. Coverage is 30 MHz to 2 GHz.

SA7000 Passive twin element wide band aerial with 15m of coax.

Coverage is 30 kHz to 2 GHz.

LA320 Desktop loop aerial 1.6 MHz to 15 MHz. Optional elements available

for LW & MW. Supplied with BNC lead.

ABF125 VHF airband filter for increased adjacent channel selectivity.

(21) Aerial (antenna), earths & propagation

The subject of aerial choice and earth can be quite complex. There are many advantages and disadvantages to consider before

connecting an external aerial to your receiver. One interesting phenomena is that aerial theory and practice can be surprisingly

different. Keeping common sense in mind it is one of the few remaining areas for listeners to easily experiment and often achieve

fantastic results.

Whip aerial

The supplied semi-flexible whip aerial should give adequate results for general hand-held operation on the VHF and UHF bands.

A longer wire aerial or telescopic whip should be considered for listening to the short wave bands. The AR8200 is supplied with a

ferrite bar aerial for medium wave reception, for best results, rotate the receiver as the bar aerial is directional.

Mounting location

It is important to mount any external aerial as high as possible and in clear space although this is more important at VHF

frequencies than for short wave. If possible the aerial should have a clear path to the horizon. Results are usually disappointing

when an installation is in a loft space.

Long wire aerials

For short wave reception a random length of long wire approximately 10 to 20 metres in length forms a good compromise. The wire

should be connected to the centre pin of a BNC plug then connected to the BNC aerial input on the top of the AR8200. If possible

try to locate the receiver close to a window so that the wire has the shortest and most direct run from the rear of the receiver to the

outside world.

Discone

For wide coverage in the VHF-UHF bands a compromise has to be met and the most popular aerial is a discone (AOR DA3000).

Their appearance is like a large spider or umbrella without the covering material, the better models have about 16 elements.

Typical usable coverage starts from about 25 MHz and extends continuously to 500 MHz 1300 MHz or even 2000 MHz. The

coverage peaks and dips throughout it’s range as the elements interact to provide the widest possible coverage. Due to their

necessary construction discone aerials are a little prone to “wind noise” due to vibration and possible damage in severe gales.

Filters

A VHF civil AIRBAND FILTER is available (ABF125), this will help minimise the possible effects of breakthrough when listening to

VHF airband in Band-II VHF high signal areas or when connected to external aerials.

Earth systems

A separate EARTH connection made to the outer (braid) connector of the BNC plug may improve aerial efficiency and reduce noise.

Suitable earth points include connection to a water pipe, central heating radiator or external earth rod. If fitting a separate external

earth rod, consider the implications carefully if your mains supply uses Protective Multiple Earth (PME) system. If in doubt consult

an experienced electrician. Connecting an external earth wire may greatly reduce the local noise encountered when listening on the

short wave bands. It is very important to provide a good earth should you use an aerial tuning unit.

A short length of thick gauge earth wire may be connected to a nearby central heating radiator or water pipe but never use a gas

pipe for earthing. Ideally a separate earth rod should be used but the length between the receiver and rod becomes restrictive,

if too long the earth system may well “pick up” noise rather than remove it.

Section 21

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