Comments by "Mike H" (@Mike-H_UK) on "Inside The Shortwave Russian Woodpecker Killer" video.

  1. I concluded that there is much more to this circuit than a simple audio blanker when I saw that both SO239 and phono sockets were on the back. Why are the RF sockets needed for a pure audio blanker? I think the problem with 'only' an audio blanker is that the RF front-end will overload , produce intermodulation distortion and create a period of poor reception in the radio for a number of milliseconds as the AGC recovers. So I strongly suspect that this box is a two stage solution that blanks (gates out) the strong pulses from the RF by using a threshold comparator to create a dead zone in the RF and a final 'mopping up' stage in the AF. This slightly more complicated approach explains the larger number of components than a single audio notch filter and also the requirement of an external power supply.and the SO239 sockets. After the time that the Datong product was developed, single-chip, two-stage blanker solutions came out, for example the Allegro Microsystems 3845.
    5
  2. Yes, I asked myself the same question when I saw that both SO239 and phono sockets were on the back. I think the problem with 'only' an audio blanker is that the RF front end will overload , roduce intermodulation distortion and create a period of poor reception in teh radio as the AGC recovers. So I strongly suspect that this is a two stage solution that removes the strong pulses from the RF by using a threshold comparator to create a dead zone in both the RF and AF. The dead zone length following the comparator triggering is set by the 10Hz or 16Hz button. This slightly more complicated approach explains the larger number of components than a single notch filter and also the requirement of an external power supply.
    2