Notes on HPSDR Calibration
Receiver Frequency and Amplitude Calibration
The source I use for calibrating the HPSDR receiver frequency and amplitude is an HP 8642A signal generator with its external reference connected to my house standard (normally an HP5065A Rubidium standard that is kept within 1 part in 10e11.
I use 14.200 MHz with an output level of -50dBm for calibration.
To verify the amplitude, I use an HP 438A power meter with 8484A power sensor that can read down to -70dBm. When the power sensor is connected directly to the 8642A's RF output connector with no cables or adapters, a -50dBm setting on the generator results in a reading of about -50.4dBm. Measuring at the end of an ~18 foot N to BNC RG-316 cable, the signal is about -50.75dBm.
I adjust the signal generator output level until the power at the BNC end of the cable is -50.0dBm. That provides the most accurate signal possible at the RX input jack of the radio.
Transmitter Amplititidue Calibration
To make measurements at the 100W level, I use a Bird 30dB power attenuator. Here is its measured loss from 0.3 to 60 MHz, as measured with an HP 8753C network analyzer:
