Unfortunately many Medium Wave radio stations have closed down over the past couple of years and very little remains to test our beloved radios.
This little module allows you to hear what AM radio really sounded like back in the 50's and 60's. The few remaining signals on AM are heavily compressed and limited in bandwidth.
The board runs from 12V dc at 60mA and takes a line level input from a computer or smartphone, The modulation frequency response is very flat and is only -3dB down at 20KHz. Thanks to the Class E transmitter design the modulation characteristics are very good indeed. The carrier frequency is crystal controlled.
The output is fed through a pi attenuator so that the modulator can feed into any load without affecting the modulation characteristics.
The output power is nominally 5 milliwatts into 50 ohms. The range is generally only a few feet depending on what is used as an antenna. This is not intended to be a long range radio transmitter. It is a high quality modulator to allow you to use your vintage equipment and feed whatever audio you desire to it.
The audio level required for 90% modulation is approximately 1 Volt peak to Peak (350mV RMS). The audio input is connected via a 3.5mm Stereo Jack Socket. Both left and right audio inputs are available and these are summed together to give mono transmitted audio.
The listing is for the PCB only (built and tested).
These are hand made and tested using brand new components. The board measures 6.5 x 4 cm.
Please see my other listings for different frequencies and also a version with a Bluetooth input.
Thanks for looking!
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