Modem

DRO stations already use TV amateurs some time and modulate these with the video-signal with a level of 1 Vsses directly. Instead of a video-signal, of course also data can become aufmodulierts. With the usual DF9IC / G3RUH modems lies the frequency-spectrum at the lowermost end of the possible modulation-frequencies, sends and virtually still can become transfer 0 Hzes reception-page. That manages unnecessary problems. The modulation-spectrum should be transferred by 0 Hzes upward therefore preferably far. From Gerald Ruscher DL7VGN came the suggestion, Manchester, to enforce coding of the data-signal. With this procedure, the spectrum builds itself about the frequency of the throughput around, doesn't start with zero therefore. The higher one chooses the throughput, umso further removes itself one from the deep frequencies. The paddock-condensers can be reduced with it, what that accelerates send reception-switch. The high throughput is more a " by-product " therefore. It passed no necessity to transfer actually big data-mixing on the route. That was realized coding Manchester by a rebuilt DF9IC-Modem of Landolt, that was driven on 76k8 gejumperts and with double bar-frequency. This yields a Bitrate of 153k6. Through them/her/it Manchester coding decreases the data-transfer-installment on the half, therefore 76k8, however. Henning Rech DF9IC burned us the GALs for Manchester coding, that we put instead of the G3RUH-GALs into the modem. Also the Tiefpassfilters had to of course be modified in the sends and reception-branch of the modem for the high Bitrate, for which we also got valuable hints from Henning. The modem delivers the Ausgangsspannung of 1 Vsses required to the modulation, that is cared over a Emitterfolger ausgekoppelt for the entrance of the station laid out for 75 ohms. also the business-tension, that is switched over the PTT and a PNP transistor, is supplied over this entrance. The Betriebsspanung (>15 VS) can the Sat. receiver is taken. Polarization to it on horizontally that with it for the LNC put and generate 17 or 18V in the Receiver draws off and leads out (for example at a free Scart pin puts).