User Manual

WiNRADiO G3XX VHF/UHF Receiver

To check this, tune to one of the interfering signals, then switch off the monitor

and see if the signal disappears. If the interference still exists you could

continue using the WiNRADiO receiver, and live with the fact that some useful

frequencies will be obscured by your monitor’s interference, or you can replace

your monitor with a ‘quieter’ one (modern LCD displays are far quieter than old

CRT monitors), or you can try to relocate your antenna further away from your

computer.

A good remedy to try is to wind five to ten turns of the antenna lead-in cable

through a large ferrite core (the doughnut shaped toroid type), near the PC

end of the cable. This suppresses common-mode interference, which is a

typical but curable problem with PC-controlled receivers.

Another type of interference which you may encounter is intermodulation

interference. This is usually caused by strong local stations, whose

frequencies combine to create ‘ghost’ signals on frequencies which are

arithmetic combinations of the stations’ frequencies. These ‘ghost’ signals can

sometimes coincide with useful frequencies, rendering them partially or

completely unusable. They will usually disappear when you switch on the

Attenuator in the receiver control panel. You may also try shortening the

antenna.

If you live very close to a strong local transmitter, these measures may be

insufficient. In such case, you should be able to eliminate intermodulation by

fitting a special filter to your antenna, to reduce the level of the signals causing

the interference. The design and application of such filters falls beyond the

scope of this user’s guide. However, broadcast frequency filters and tunable

preselectors are standard items and can be obtained from good radio

equipment suppliers.