--- In digitalradio@yahoogroups.com, "Vojtech Bubnik" <bubn...@...> wrote: > > Hi Ralph. > > The second or multiple received streams may be caused by a non-linearity > somewhere between his computer and your computer. It may be his sound card, > his TX, your RX or your sound card. Yes, I experienced it also. The "ghost" > signals are of much lower amplitude though, so they are easily recognized and > ignored. > > If I were you, I would first verify, whether you do not overdrive your sound > card. Secondly I would adjust attenuator to just get some slight atmospheric > noise in your receiver. This way you will maximize your receiver's dynamic > range. If you still get some ghost signals, it may be a good time to upgrade > your sound card. > > 73, Vojtech OK1IAK
I agree with this. Nonlinearities in the audio stages can create multiple copies of the signal in the audio band. Nonlinearities in the RF stages would normally create copies of the signal at multiples of the RF frequency for a single tone signal. I understand that the Collins KWM-2 creates a CW signal by modulating the carrier with an audio tone. The frequency of the audio tone is set around 1700 Hz so harmonics caused by nonlinearity in the audio stages would be outside the audio band. With my TS-2000 many ghost signals can often be seen. Not only are frequency multiples of the signal seen but also a weak signal in the presence of a strong signal can often be seen equally spaced on the opposite side of the strong signal. I suspect this is due to the nonlinearities associated with quantization of the 12-bit A/D conversion. Even when a narrow bandwidth is selected, copies of the signal can be seen well outside the passband of the narrow filter. Ghost signals are seen much less frequently with my radios with analog filtering. Ed WB6YTE
