AM Single Frequency Network

ID: 206227
AM Single Frequency Network 
26.Nov.09 10:16

Dietmar Rudolph † 6.1.22 (D)
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Dietmar Rudolph † 6.1.22



Single frequency networks (SFN) in the medium wave broadcast band were introduced in Germany in the late 20ies and early 30ies. They were developed by C. Lorenz A.G. So a short presentation of Lorenz transmitter development is given. A complicated problem then was the synchronization of these SFN. Therefore pilot tones of about 2 KHz were used and transmitted via telephone trunk lines. A frequency multiplication was necessary at the transmitter's side. Some solutions used a technique called today PLL. Between the SFN transmitters is a zone of heavy interference, where nonlinear distortion of the received AM signal occurs. Nowadays SFN's use digital modulations, and interference no longer plays a major role. Some principles of single and multi carrier radio systems are presented. In former days jamming transmissions on AM occurred. Optimal AM jammers use DSB modulation. In WW2 a jamming with intelligible text message was used. The modulation usable was SSB.
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