Difference between revisions of "Instruments required"

Revision as of 20:23, 3 November 2009

1. Two (3) Signal generators
2. Hybird combiner
3. Audio AC voltmeter
4. Distortion meter (FM Only)
5. Noise figure meter (for noise figure measurements only)
6. Two (2) step attenuators with 10dB and 1dB steps

Top to bottom, HP 3406A Broadband Sampling voltmeter, Tektronics TAS 465 Two Channel 100MHz Oscilloscope, HP 3586B Selective Level Meter, and HP 8656B Signal Generator

The signal generators at the W9KFB lab are as follows:

1. 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)
2. HP 8656B Signal Generator 0.1-990 MHz (dBm measurements are calibrated for 50 Ohm characteristic impedance)
3. HP 10544A Crystal Oscillator

Formulas and Values for a 45 Ohm Hybrid Combiner

Homebrew 45 Ohm Hybrid Combiner

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.