Creek Audio T40 Getting Started - Page 7

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signals can far exceed their normal range, and can spill over into adjacent transmitter' s service

areas. This causes Adjacent Channel Interference, which produces whistling or ' twittering' noises at

the receiver (' birdies' ), and can be very irritating. The problem is much increased when listening to

stereo signals, due to the signal/noise and bandwidth requirements for stereo being so much greater

than for mono.

To overcome this problem the T40 allows you to reduce the receiver ' window' to 150kHz by pressing

in the Wide/Narrow switch, which greatly reduces ACI and allows satisfactory reception in

otherwise impossible conditions. Narrow operation will increase distortion of the audio signal quite

significantly, but the ear is much more tolerant of this sort of signal degradation than it is of the high

pitched whistles that ACI normally produces.

The Narrow position can be used if you wish to take advantage of the exceptional sensitivity of the

T40 to receive stations from well outside their normal service area, when ACI would normally

prevent this. The automatic functions in the T40 will try to make any signals as pleasant to listen to

as possible in all situations, but the Wide/Narrow facility will help considerably if you are trying to

receive signals at the limits of the capability of the VHF/FM brodcasting.

DX Local

This switch changes the operating conditions of the automatic functions in the T40 to allow reception

of much weaker signals than are normally useable for high fidelity listening. In the LOCAL position,

although the sensitivity of the tuner remains unchanged, the thresholds of all the monitor signals are

moved, so that only the stronger available stations signals are able to open the muting and become

audible. In this position all the automatic functions are optimised for maximum sound quality.

In the DX position the muting position is held just at the point of release, so that a very quiet

background noise can be heard between stations while tuning. In this position the automatic

functions are optimised for the reception of weak signals with the maximum achievable sound

quality – with very distant stations that achievement may be only just acceptable, but in all cases the

T40 will do its best to extract as much as possible for you to hear the required station satisfactorily.

Mono/Stereo

This switch allows you to force the stereo decoder into Full Mono operation, regardless of the

programme being received. This is sometimes necessary in freak weather conditions to eliminate

' birdies' (adjacent channel interference) if the automatic functions in the T40 are able to cope.

In normal use of your tuner, operation of the Local/DX switch should be adequate to obtain noise-

free listening from any desired station.

AFC

This switch allows you to disable completely the operation of the Automatic Frequency Control

circuits in the T40. This can help when tuning to exceptionally weak stations. Remember that,

without AFC, there is nothing to prevent the tuner from drifting away from the required station.

As mentioned in the Quick Instructions at the beginning of this Handbook, the T40 is designed to be used with the

four function switches in the normally ' out' position, and you will find that you need to over-ride your tuner' s

automatic functions very rarely, if at all.