Vectronics VEC-821K - Manual (Page 19)

VEC-821K Instruction Manual Super CW Filter kit
s o l d e r e d -in parts is a " solder sucker". This consists of a suction bulb or a
spring loaded vacuum pump that draws molten solder away from the pad and
lead. Alternatively, you may use a special copper braid called "solder wick"
(solder suckers and solder wick are both available at your local Radio Shack or
electronics supply house). If you suspect you've damaged a component during
removal, better to replace it than risk reusing it!
Finally, rosin flux can absorb moisture, which may cause a problem for some
electronic equipment. To remove flux, use isopropyl alcohol (or 95% grain
alcohol) and an old toothbrush. Apply a generous amount of alcohol with the
toothbrush and scrub gently. Once the flux has fully dissolved, blot the bottom of
t h e b o a r d d r y w i t h a n u n t r e a t e d t i s s u e . G i v e i t a final alcohol wash, and allow
to dry thoroughly.
CAUTION: ALCOHOL IS HIGHLY FLAMMABLE AND MUST BE USED WITH
ADEQUATE VENTILATION! USE SAFETY GOGGLES, AND AVOID
PROLONGED SKIN CONTACT. IT
' S ALSO BEST TO DO THIS
OUTDOORS.
N o w t h a t a s s e m b l y a n d i n s p e c t i o n is completed, you're ready to begin the
testing and alignment phase of construction.
TESTING AND ALIGNMENT
The best way to test the VEC-821K is with a calibrated audio signal generator
and oscilloscope. However, VEC-821K does not require any alignment. If all
c o m p o n e n t s a r e i n s t a l l e d c o r r e c t l y a n d i n t h e p r o p e r p l a c e s , t h e c e n t e r
frequency of the filter will be between 750-800 hertz. The filter has three
switch selectable selectivity cutoff points, 80, 110, and 180 hertz. The switch
positions on SW1 from le ft to right are BYPASS, 180, 110, and 80. The 80
hertz cutoff is the fourth switch position from the left and is the narrowest filter
cutoff, while the 180 hertz cutoff is the second position from the left and is the
widest filter cutoff.
Probably the best method of seeing if the VEC-821K is working, or not, is to
listen to some "on the air" CW signals. Then using SW1, select the filter cutoff
position that best cleans up the signal being received.
If you are trying the pick out one signal out of a very tig ht band pile up, then
try using the 80 hertz cutoff. The 80 hertz cutoff provides the highest selectivity
and will greatly help you in "pulling out" those hard to get signals.
If the CW signal you are receiving is noisy with some static, then try either the
110 or 180 filter cutoffs. However, in these positions the filter will let slightly
more noise through, but in some cases this may be desirable. The best way to