Thursday, April 25, 2013
Looking for the Square Law region (III)
Last weekend I assisted to a small ham radio flea market surprisingly with a lot of microwave hardware. Thanks to Andrés EB4FJV, I was able to get a DC to 18GHz Narda crystal detector. My idea was to use it as a relative measurement device, just to peak circuits at maximum output.
But the surprise came when I arrived home and looked for it in Internet. I found its datasheet and I could see it was a zero bias Schottky detector with a sensitivity of 0.5mV/µW and ±0.6dB flatness. Quickly I took my tested W1GHZ's power source reference (from QST, April 2007 and available in eBay from time to time) who gives -10dBm at 50MHz, and applied it to the crystal detector. The DC output was 54.5 millivolts.
Applying the 0.5mV/µW factor, it is converted to 109µW which equals to -9.6dBm. Pretty close!
I tested also the insertion of some SMA attenuators, and in all cases readings where really close to the theoretical values.
I think I can conclude that I have a device to measure RF power with some accuracy. After the experiences I had here and here this device amazes me. Maybe the secret is the zero bias Schottky diode, or maybe the secret is it's a professional device, or maybe both.
Thank you Andrés!