29-09-2016, 05:16 PM
Connected the printed coil via a 22pF capacitor to a signal generator. The response of the tuned circuit monitored using an oscilloscope. No external capacitor across the coil. The circuit resonates at 1650Khz. Placing a 90cm aluminium disc close to the coil results in a resonance of 2700Khz.
So we know that the tuning disc concept works. Placing the disc 1cm away from the coil results in a resonance of 1900Khz.
The advertising for the VB4 tells us that the tuning system employs two sets of coil pairs for long waves and short waves. To tune to the shortest waveband a pair of coils are connected in parallel. For the next waveband the same coils are connected in series. It's the for the long wave coils, the HF end of the long waveband the coils are in parallel and series for the LF end of the waveband.
The receiver was designed to tune between 300 to 3000 metres in four stages.
I'm not entirely convinced if this is correct, it could be that the two coil assemblies for long and short waves were in fact single coils with taps for the two tuning stages.
Geordie McBoyne.
So we know that the tuning disc concept works. Placing the disc 1cm away from the coil results in a resonance of 1900Khz.
The advertising for the VB4 tells us that the tuning system employs two sets of coil pairs for long waves and short waves. To tune to the shortest waveband a pair of coils are connected in parallel. For the next waveband the same coils are connected in series. It's the for the long wave coils, the HF end of the long waveband the coils are in parallel and series for the LF end of the waveband.
The receiver was designed to tune between 300 to 3000 metres in four stages.
I'm not entirely convinced if this is correct, it could be that the two coil assemblies for long and short waves were in fact single coils with taps for the two tuning stages.
Geordie McBoyne.
