Vectronics VEC-1120K - Manual (Page 30)

VEC-1120K/1130K/1140K/1180K Instruction Manual
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For example, the 30-meter Amateur band is boxed by the 25 and 31 meter SW
broadcast bands. Direct conversion receivers are very simple devices, and by
nature are easily overloaded. There are several things you can try if strong SW
stations are overloading the receiver and “breaking through”.
1. Use the gain control. Simply lowering the gain setting will resolve many
overload problems.
2. Use a preselector. A receiver preselector provides protection from strong
out-of-band signals. They are most effective when the interfering signal is far
from the operating frequency.
3. Use a resonant antenna. A resonant antenna favors signals in the band it
was cut for.
4. Re-position or use a smaller antenna. Changing the direction the dipole
faces may lower unwanted pickup of undesired SW signals. Lowering the
antenna will change its angle of pickup; a low antenna may favor local
stations over the low-angle of distant broadcast signals. A shorter antenna
can also be tried, it will be less efficient and signals will be weaker.
IN CASE OF DIFFICULTY
Only high-quality components and proven circuit designs are used in Vectronics
kits. In very rare instances is a defective component the source of a problem.
Ninety-five percent of the kits returned for factory repair are due to soldering
problems or parts in the wrong locations. We advise repeating the assembly
instructions step-by-step, looking for mistakes or soldering problems. Be
especially wary of electrolytic capacitors and semiconductors. Kit builders
often miss obvious mistakes. What is needed is a “fresh” set of eyes. Enlist a
friend to go over your work.
Always check the obvious! Is the battery dead, or have the battery leads been
accidentally reversed or broken? The speaker and antenna plug should be
carefully checked for shorted or open connections. Check the solder connections
for the antenna and speaker jacks—frequent removal and insertion may have
caused a solder joint to fatigue and open.
Look for clues to help you determine what stages are working, and which ones
may be in trouble. For example, if you can “peak” the RF input tuning for an
increase of background noise, or hiss, in the headphones or speaker with an
antenna connected, you know that the receiver is probably working. The
problem is probably due to the set being aligned for a tuning range covering
inactive frequencies.