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The AN/URM-25 was part of a series of vacuum tube-based signal generators built for the U.S. military in the early Cold War-era.. Today they are collected and used by vintage amateur radio and antique radio enthusiasts who say they provide reasonably high accuracy and stability for a low cost, with build quality reflecting tough military construction requirements and standards.
Cable length limits the controller-device distance to two meters per device or 20 meters total, whichever is less. This imposes transmission problems on systems spread out in a room or on systems that require remote measurements. Primary addresses limit the system to 30 devices with primary addresses. Modern instruments rarely use secondary ...
The S stands for "Strength". Strength is an assessment of how powerful the received signal is at the receiving location. Although an accurate signal strength meter can determine a quantitative value for signal strength, in practice this portion of the RST code is a qualitative assessment, often made based on the S meter of the radio receiver at the location of signal reception.
An RF switch or microwave switch is a device to route high frequency signals through transmission paths. RF (radio frequency) and microwave switches are used extensively in microwave test systems for signal routing between instruments and devices under test (DUT). Incorporating a switch into a switch matrix system enables you to route signals ...
A dummy load is a device used to simulate an electrical load, usually for testing purposes.In radio a dummy antenna is connected to the output of a radio transmitter and electrically simulates an antenna, to allow the transmitter to be adjusted and tested without radiating radio waves.
RF probes are especially relevant for switches and RF traces in printed circuit boards as well as terminations of RF components. In such systems, like many other RF circuits, there is a higher requirement of matching probe impedance with that of the DUT. Efficient matching avoids reflection which in turn leads to efficient power transfer.
Several countries in ITU Region 1 have access to frequencies in the 70 MHz region, called the 4-meter band. The band shares many propagation characteristics with 6 meters. The preferred location for beacons is 70.000–70.090 MHz; [5] however, in countries where this segment is not allocated to Amateur Radio, beacons may operate elsewhere in ...
An SWR meter does not measure the actual impedance of a load (the resistance and reactance), but only the mismatch ratio. To measure the actual impedance requires an antenna analyzer or other similar RF measuring device. For accurate readings, the SWR meter itself must also match the line's impedance (typically 50 or 75 Ohms).