26-10-2016, 10:18 PM
Here is possible AM TX based on Wolfgang Holtmann / 12V Car Radio RF to IF converter
The oscillator coil can be the MW ferrite aerial off a small transistor radio. On older ones there is a separate smaller winding you can use for the grid, otherwise separate the coils at the tap. Or add about 50 turns of overwinding for the tap. You can use the polycon off the transistor radio too. The Hexode anode load / loop I expect to be about 20 turns on about 40cm square frame made of two crossed batons.
Anyway ... probably I'll build it next week.
The 68nF and 100nF are not critical. You can use 2 x 100nF or 2 x 220nF, again parts for a transistor set will do.
If the RF out is too little, or the audio sensitivity is too poor, then I will replace Hexode Anode load with an identical transistor radio coil and use 1/2 of another ECH81 to drive the loop and half as audio preamp. But which section for which function?
The oscillator coil can be the MW ferrite aerial off a small transistor radio. On older ones there is a separate smaller winding you can use for the grid, otherwise separate the coils at the tap. Or add about 50 turns of overwinding for the tap. You can use the polycon off the transistor radio too. The Hexode anode load / loop I expect to be about 20 turns on about 40cm square frame made of two crossed batons.
Anyway ... probably I'll build it next week.
The 68nF and 100nF are not critical. You can use 2 x 100nF or 2 x 220nF, again parts for a transistor set will do.
If the RF out is too little, or the audio sensitivity is too poor, then I will replace Hexode Anode load with an identical transistor radio coil and use 1/2 of another ECH81 to drive the loop and half as audio preamp. But which section for which function?
