v1.0 Specification Document: Winrad Modes of Operation and Notes on Using Winrad
Complex spectral displays should not be confused with a spectrum analyzer or a panadapter display. The center of a spectrum analyzer displays the tuned frequency of the receiver or analyzer and the information is valid at all frequencies. A complex spectral display cannot provide any information about signals located at or very near the center ferquency. The reduced accuracy area on the screen is generally from -100Hz to +100Hz of the center frequency, but may even extend further if the phase noise of the receiver is high. Knowing that the center is devoid of any information, one must always choose a center frequency that will move your signals of interest outside of the deaf center band. Therefore, as implemented in Linrad, it is useful to move the local oscillator and receive frequency in large discrete steps. These steps only need to be smaller than the full displayed bandwidth so that an overlap of coverage is provided by adjacent steps. In conclusion, remember that Winrad, Linrad, and similar programs use the mouse to select the signal of interest which is never the center frequency. Winrad Native Mode In this mode, no hardware DLLs are loaded and the only control between Winrad and any hardware is the selection of the soundcards, their modes, and their sampling rates. The center and LO frequency displayed on the Winrad screen are set manually by the operator using the mouse and the keyboard. The operator only needs to set the LO frequency on the screen if he wants to read the true signal frequency that is read by the mouse cursor position. If the LO frequency is left at zero, then the cursor readout will be a positive or a negative number at baseband. Winrad Mode 2 In this mode, a DLL unique to the specific receiver or transceiver is loaded. This hardware has a complex baseband output and if capable of transmit, also has a complex baseband input. Whether the hardware is a synthesized softrock or is a multiple IF superheterodyne such as the WSE hardware, the LO or receive frequency is communicated to Winrad via the loaded DLL. It is then displayed on the Winrad screen. This frequency may be one fixed frequency or may be adjustable in discrete steps. If adjustable, the steps only need to be in 50KHz increments for 96KHz soundcards or 100KHz for 192KHz soundcards. If the hardware is capable of transmit, then a means of controlling and communicating a separate transmit frequency must be provided. When a hardware DLL is loaded, Winrad should disable the operator control of the LO frequency on the Winrad screen. It is thus "read only" and controlled by the DLL interface. If the hardware is capable of frequency control, it should be done from a separate DLL window. Winrad Mode 3 Some hardware such as the SDR-14, SDR-IQ, the HPSDR and Phil Covington projects have wideband general coverage, a built-in digital downconverter, and built-in digital to analog converters, usually with non-standard sampling rates. Thus no soundcard is needed. The custom DLL for that hardware must control the frequency, the sampling rate, and often control RF pre-selectors, attenuators, and pre-amplifiers. These controls are displayed in a DLL created window separate from Winrad. Although all of these general coverage receivers use a DDS for frequency selection, the fine steps do not serve any purpose since Winrad can demodulate any signal displayed on on the screen other than the center. The mouse and its wheel move the Winrad selection cursor in fine steps. Therefore, it is suggested that the DLL be written to set the DDS hardware in large steps as discussed in Mode 2. The chosen receive frequency is set in the separate window created by the DLL but it is also displayed in Winrad if passed by the DLL. Winrad and Transmit Control When appropriate hardware is available, an extended version of Winrad will be developed. In addition to DLL control of the hardware functions, the frequency of the transmitter must be be displayed since most operating is split frequency. The T/R timing will also control which Winrad processes are running. 73, Jeffrey Pawlan WA6KBL _______________________________________________ Winrad mailing list [email protected] http://winrad.org/mailman/listinfo/winrad_winrad.org
