Instruments required
- Two (3) Signal generators
- Hybird combiner
- Audio AC voltmeter
- Distortion meter (FM Only)
- Noise figure meter (for noise figure measurements only)
- Two (2) step attenuators with 10dB and 1dB steps
The signal generators at the W9KFB lab are as follows:
- HP 3586B Selective Level Meter (dBm measurements are calibrated for 75 Ohm characteristic impedance, signal is 0 dBm out only at the level measurement frequency)
- HP 8656B Signal Generator 0.1-990 MHz (dBm measurements are calibrated for 50 Ohm characteristic impedance)
- HP 10544A Crystal Oscillator
The Hybird combiner was made from an old PC network splitter. The device was found in an used PC warehouse. It was a four port device with 4 BNC jacks on it. On inspection of the device, we found that it was a resistive splitter with four 39 Ohm resistors connected to each BNC center contact and a common point. These were removed and replaced with 15 Ohm 2 Watt 2% resistors metal film resistors (NTE 2W015 Flameproof Resistors).
To design you own splitter/combiner see this web site for a calculator[1]
Several hams are considering using the new Excalibur board as a test oscillator for SSB Phase Noise measurement. 10 MHz is not the best frequency to use, but the TCXO frequency can be changed to 16 MHz by purchasing a new one. John, N8UR, has done a detailed Allan Variance and phase noise measurement of the TCXO on Excalibur. View his measurement results on this website at:this site. Thanks to John for his testing, and taking time to post the results.
We have found inexpensive used cell-tower 4.800000 MHz OCXOs on eBay recently. They require 12 Volt power and output is +15 dBm. We will test them and evaluate their application as a low phase noise test oscillator.
