Yaesu FT-767GX, Operating Manual

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As the NB control is set further clockwise the
b l anki ng p u l se beco m es wider.
This is useful
i n b l anking the ' woodpecker ' o n H F i f the
echoes a r e no t too lo ng, but wider b l anking
p u l s e s a l so cause more o f the desired sig n a l
t o be lo s t, so dis tortion is g r e a t e r.
T h e r e ­
fo re, fo r b e s t p e r fo r m ance, a l w ays turn t h e
noi se b l a nk e r o f f when it is no t needed.
4.6. 2
RF Gain C ontrol
The RF g ai n co n t ro l (ou t e r knob on the s a m e
s h a f t as t h e A F co n t ro l, j us t l e f t o f the
tuning knob ) al lows manual setting of the gain
o f the e a r l y s t ages o f the receiver. The gain
of t he s e s t ages is co n t ro l l e d a u to m a tic a l l y by
A G C ( u n l es s switched o f f, see § 4. 6 . 9 ) so the
RF g ai n co n t ro l is usua l l y kept i n the fu l l y
clockwise position ( m aximum gain ) .
When t h e R F gain con t ro l i s t u r n e d cou n t e r ­
clockwise from m aximum, t h e minimum S - meter
i ndic a tio n wi l l ris e, and sig n a l s (or noise )
b e low t h a t l e v e l wi l l be s u p p ressed. This is
u s e f u l fo r e liminating backgro u n d noise when
lis tening to a moder a t e l y s t rong sig n a l .
4.6. 3
NAR ( Narrow ) I F Filter Select
When operating in the CW or AM modes, pressing
t he NA R s wit ch ( l e f t side o f t h e p a n e l, t hird
from the right ) activates the narrow CW or AM
fi l t e rs in t he receiver I F, reducing the re­
ceiver b a n dwidth.
This decreases the noise
l evel, so CW sig n a l s ( a n d so m e ti m e s AM sig ­
n a l s ) m ay b e more readab l e . No t e, ho wever,
that tuning also becomes more critical ( sharp­
e r ) , so e s p eci a l l y fo r CW, i t m ay b e easier to
tune i niti a l l y wi th this swi t c h o f f, and o n l y
turn it on fo r fi ne tuning.
S ee a l so § 4. 1 4
'Tips for C W Operation'.
I n the AM mode, the narrow bandwidth will re ­
duce noi s e and adj acen t c h a n n e l i n t e r feren ce,
but fi d e li t y is a l so reduced when t he NAR
switch is pressed. See also § 4. 15 'Tips for AM
Broadcas t R ec e p tio n ' .
4.6.4
R F AMP Swi tch
This swi t c h ( l e f t side o f the p a n e l, second
f ro m righ t ) a c tiv a t e s the receiver RF a m p li ­
fie r, fo r incre ased sensitivity b e low
30
M H z .
However, the receiver also becomes more sus ­
c e p tib l e to distortio n and in t e r fe r e n c e from
s t rong sig n a l s when the R F A M P is on, so we
recom mend using it only on quiet bands.
On lo w e r frequ encies ( abou t
3
M H z in win t er,
10
MHz in summer) atmospheric noise is gener­
a l l y too high for the RF A M P to be e f fe c tive :
although it will make the S- meter read higher,
t h e read ability o f w e ak signa l s is no t like l y
to b e improved, while interference m ay become
worse. For best performance, always turn this
s wi t c h o f f when lis t e ning to s t ro ng sig n a ls.
4.6.5
ATT ( RF Attenuator ) Switch
P r e s si n g t hi s s wi t c h ( l e f t si d e o f p a n e l ,
rig h t e n d o f the row o f swi t c h e s ) dec reases
t h e suscep tibi li ty o f the receiv e r ( b e low
30
M H z ) to dis tor tio n and i n t e r ference fro m
s t rong sig n a l s, b u t reduces receiver s e n siti v ­
i t y ( t he o p posi t e o f the R F A M P ) . T h e ATT
i n dic a to r ( above and to the left o f t h e tuning
knob ) glows green when the attenuator is on.
W h e n b a n d noise is hig h, such as on lo w fr e ­
quencies during the sum mer, use this switch to
reduce noise when receivi ng s t rong sig n a l s .
A l so u s e t hi s s wi t c h i f s t ro n g sig n a l s o n
o t h e r f r e q u e n cies seem to b e causing i n t e f e r ­
ence o n your receiving band. However, before
p r e s sing t his swi t c h check to ensure t h a t the
R F A MP switch is off ( t he RF AMP a n d A TT
should not both be turned on at the same time,
as they counteract one another ) .
M ake s u r e t h e a t t e n u a tor i s o f f w h e n t u ning
fo r w e ak sig n a l s .
4. 6. 6
A P F ( Audio Peak F i l t e r )
The APF provides a very narrow audio bandwidth
fo r CW recep tion. It is a c tiv a t e d by the
swi t c h of t h e same name to t h e left o f the
tuning knob, and adjusted by the
the middle control at the bottom
a c tiv a t e d,
the indi c a tor n e x t
switch glows green.
outer knob of
right. While
to the A P F
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