2016-05-07 (2)

I have run the experiment with better resolution on the Spectrum Analyzer. The settings are as follows:

Signal Generator    
Freq Step 0500.000 MHz
Start Freq. 2300.000 MHz
Stop Freq. 2500.000 MHz
Step Delay 00.100 s
Attenuator Off  
Power +3 dBm
Spectrum Analyzer    
Freq Span 002.000 MHz
Start Freq. 2403.000 MHz
Stop Freq. 2405.000 MHz
Module 2.3 - 2.5 G  
Top dBm -065 dBm
Bottom dBm -107 dBm
Iterations 016  
Offset dB +000  
Units dBm  

The results are stored in RFExplorer_SweepData_2016_05_07_17_04_04.rfe. The samples at the edge of the peak around 2404 GHz were:

  • 2403.956 MHz@-99dBm
  • 2404.036 MHz@-100.41 dBm

This implies a Q factor of 26,710. I was skeptical of such a high rating on my first attempt, so I verified my approach with a physicist/engineer Richard Driver. He couldn't comment on my approach or experiment, but he believed I was calculating Q correctly.

I am also seeing a resonant mode at 2351.999 that I wasn't expecting,, and one at 2507.967 MHz, and maybe another at 2534.063 MHz. The analyzer doesn't got beyond that apparently. At least, I can't make it do so.

The wavelength in air of 2403.991 MHz (the average of the peak) is 124.7925 mm (according to www.wavelengthcalculator.com), so the half-wavelength is 62.3962 mm. The measured height of the cavity is 62.70 mm - 1.36 mm = 61.34 mm (the plunge depth from teh calipers from the top of the base plate, minus the thickness of the base plate). I'm off by about 1 mm from matching the half-wavelength, and I can't tell if the that's close. Neither of the other nearly peaks (59.8094 mm and 63.7755) are any closer.

The cut-off radius of the target frequency is:

fc(mn) = X'mn/(2 * pi * a *sqrt(mu * epsilon)) c = 3 * 108
ac = X'mnc/(2 * pi * f) X'mn = 1.8412
ac = 0.03656870 m f = 2403.991 GHz
dc = 73.14 mm  

At the lower frequency:

ac = X'mn * c /(2 * pi * f) c = 3 * 108
ac = 0.03737707 m X'mn = 1.8412
dc = 74.75 mm f = 2351.999