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These are
global settings and are set by the
[ATT] and
[RF
GAIN] keys |
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ATT |
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Sometimes you can have just
way too much signal. The R20 is a sensitive radio and is optimised to work
as a portable handset with a small inefficient antenna. |
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If you plug the R20 into an
external antenna and operate in a strong signal area, you will sometimes
find the radio becomes overloaded. This does not damage the radio except
under extreme conditions but you will find that performance suffers.
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The overpoweringly strong
signal may not be the actual signal you are trying to listen to, it's more
likely to be one nearby in the band and it will cause an effect known as
blocking or de-sensitisation |
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When the Attenuator is
activated the R20 is forced to become far less sensitive and so blocking is reduced. You
may think that this sounds like a counterproductive measure but it is a very
worthwhile feature indeed. It's useful for dealing with pager interference
on VHF and very useful in crowded HF bands. |
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The Attenuator lowers the
gain of the front end, that's the very first part of the radio that the
signal goes through just after the BNC socket. |
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To activate the Attenuator,
press the
[ATT]
Button (bottom left on the keypad). A flag saying
ATT
appears bottom left on the display. If you are in
dual receive mode, it appears as a letter A in inverse. |
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 The
attenuator function has no effect if either the the
internal bar antenna or headphone lead are in
use as an antenna. |
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RF
GAIN |
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This is a similar function
to the attenuator but is variable in ten stages and affects a different part
of the receivers circuits. |
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Often a signal,
particularly on HF appears weak and noisy but you can wind the RF gain down
and gradually the signal appears out of the noise. |
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An RF gain control affects
the gain at the IF stage and as there are two of these line-ups, you can
adjust the RF gain of each side independently when in dual receive mode.
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To change the settings of
the RF gain, hold down the
[RF
GAIN] key until
SET RF GAIN: x
appears on the screen. Adjust the value with a
dial button.
When in dual receive mode, again press and hold he
[RF
GAIN] key and use the
dial for the row of your main side to adjust. |
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