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BARRETT 4050 HF SDR TRANSCEIVER - OPERATING AND INSTALLATION MANUAL
Engine Instru-
mentation
Certain types of oil-pressure sensors and voltage regulators
used in instrument systems contain a vibrating or thermal
cycling contact. These devices can only be suppressed
by isolating and screening or wiring in the same way as
described for the alternator to regulator control wire. Disc
ceramic capacitors with short leads (protected with insulat-
ing sleeving) are frequently useful but to prevent damage
to instrument contacts, where the use of bypass capacitors
is attempted, values larger than 1 nF should not be used.
General Noise Suppression Tips
When searching for sources of noise, some of their characteristics can be help-
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•
Petrol engine ignition noise and contact breaker noise is a sharp staccato
‘plop’ varying with engine speed. It is only with this class of noise that the
impulse noise limiter incorporated within some Transceivers is effective.
•
Noise from other sources generally has a more ‘mushy’ sound. That from
the alternator / generator may only be troublesome over a limited range
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battery.
•
The noise from instrument regulators may depend on the battery voltage,
the reading of the instrument and the length of time the system has been
switched on. For this reason, the search for noise sources must be done
thoroughly to prevent noise from apparently reappearing after the instal-
lation has been completed.
•
Electric motors generate a ‘whining’ sound. Do not forget to check wind-
screen wipers, electric fuel pumps, heater and air conditioning fans and
other motors which operate only on an intermittent basis.
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