Many modern amateur radio transceivers provide easy access to the Intermediate Frequency (IF) signal, or In-phase/Quadrature (I/Q) signals, generated by the radios internally. Using either IF or I/Q it is possible to utilize your Apple device running iSDR to function as a touchscreen color-display panadapter!
A panadapter is a device that allows you to see the RF spectrum being received by a radio receiver. There are commercial (often expensive) panadapters available, but if you already own an Apple iOS device then iSDR can provide you with a less expensive and more flexible option.
Panadapter Using I/Q
Using iSDR as a panadapter by direct access to buffered I/Q signals was first accomplished with a commercial radio product using the Elecraft KX3 transceiver. The process is relatively simple and has been documented in an iSDR FAQ page blog entry. The simplified diagram below illustrates the setup.
NOTE: Be sure to consult the radio manufacturer’s documentation to determine whether external I/Q signal access is provided, and how to properly access it.
Panadapter Using IF
In rigs that do not provide I/Q signal access it might be feasible to implement a panadapter using the IF signal. Some modern radios provide access to a buffered IF signal that can be readily used as illustrated in the diagram below. You will notice in the diagram that it is necessary to add a direct-sampling RF detector (with its sampling frequency set at or near the IF frequency) to convert the IF signal to I/Q baseband signals that can be demodulated and displayed by iSDR.
NOTE: Be sure to consult the radio manufacturer’s documentation to determine whether external IF signal access is provided, and how to properly access it.