06-12-2013, 11:01 PM
I think the switch is shown in the MW position and in that position the MW and the LW tuning coils are in parallel, the total inductance value of such would be less than the value of the MW coil on it's own.
A possibility is that they have done that to reduce the self resonant frequency effect of the LW coil due to the LW coils relatively high self capacitance. On a lot of receivers the coils not selected were shorted out by the wave change switch to stop self resonance, especially on some shortwave receivers.
If left undamped then any transmission picked up by a self resonating LW coil could well interfere with the MW band as to a certain extent the LW and MW coils are mutually coupled due to the ferrite rod, that's if the self resonant frequency of the LW coil falls within the MW band.
There may be another reason?
Lawrence.
A possibility is that they have done that to reduce the self resonant frequency effect of the LW coil due to the LW coils relatively high self capacitance. On a lot of receivers the coils not selected were shorted out by the wave change switch to stop self resonance, especially on some shortwave receivers.
If left undamped then any transmission picked up by a self resonating LW coil could well interfere with the MW band as to a certain extent the LW and MW coils are mutually coupled due to the ferrite rod, that's if the self resonant frequency of the LW coil falls within the MW band.
There may be another reason?
Lawrence.
