Re: HP11758B Digital Radio Test Set
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Most HP power sensors are made with magic "pixi dust", hence their high price. I have three HP 8484A sensors (10 MHz to 18 GHz, -70 to -20 dBm). Normally they are used with an attenuator because the maximum accurate input power level is -20 dBm. For calibration purposes they were sold with an HP 11708A 30 dB 50 MHz calibration attenuator. With my other well calibrated attenuators, I can accurately measure up to 1000 watts, using a calibrated 80 dB of attenuation.
The maximum safe power into this diode sensor is 200 mW (+23dBm) which is 43 dB above the useful input level. Most other HP sensors use a thermocouple and easily fail when the input power is just above the maximum rated power. I assume that to replace the thermocouple element is a very special procedure and may require some exact RF adjustments. For my purposes, the HP 8484A is more accurate than I need.
I see many defective HP sensors, listed at high prices, as parts units. I wonder if anyone actually buys them and thinks that they will repair them?
Stuart K6YAZ
Los Angeles, California
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