An ad in a recent issue of QST achieved its intended effect and I now have a Siglent SDS-1202X-E oscope available for use any time I need it. The specs (200 MHz, dual channel), the overwhelmingly positive reviews and the low price convinced me that It Was Time.
In the past I have tried "digital oscopes" that are essentially a set of probes and an interfacing box that connect them to a PC and provide a very general, sometimes-accurate presentation of low frequency signals. These are of limited use to the ham who needs to see what is happening at RF frequencies, especially where rise time and accurate shape of a given pulse are needed to be known.
I also like the idea of building and using a ScopeMatch to monitor antenna conditions on 630 meters in real-time. A ScopeMatch provides a way to sample both the current and the voltage in a transmission line. If they are in phase, the antenna is properly matched since no phase shift occurs from a resistive load. During mis-match, an antenna appears either inductive or capacitive, causing a phase shift - that is, current will either lag or lead voltage (remember ELI the ICE man?).
|40 watt output of my G0MRF amp on 475.755 kHz. Note frequency displayed in upper-right corner.|
In the week I've now had the oscope, I've begun to wonder how I ever got along without one - especially having built so many QRP kits over the years with their alignments and (sometimes) troubleshooting. The scope is proving its worth as tinkerings continue with various methods of putting a signal on the new 630 meter band.
|'Measure" function displays rise time, duty cycle and a lot of other data pertaining to the displayed trace|
I particularly like the 'Measure' function that displays most, if not all, of the parameters of a given signal. Variable cursors can also be placed in the X or Y axis to measure parameters manually. A usb port allows data to be saved to a thumb drive.
In the coming weeks I'll do the opposite of what I did in the past - I'll take the Siglent to work and put it up against our frequently calibrated and high-$$$$$ equipment and see how it compares.