[Elecraft] XG3 output above 200-MHz

[Alan Bloom]

Since the output is a square wave, I assume they are using only odd
harmonics.  Probably the fundamental is 222.2 / 3 = 74.07 MHz.

Theoretically, the harmonics are inversely proportional to the harmonic
number.  So the third harmonic should be 20 * log (1/3) = -9.54 dB.
However it might be weaker than that, especially on the higher
frequencies, depending on the circuitry.

I would measure mine, but my spectrum analyzer is currently on loan.

Alan N1AL


On Mon, 2012-01-02 at 23:23 -0900, Edward R. Cole wrote:
> I finished building my 222-28 transverter and decided to test the Rx 
> using the XG3 on 222.200 MHz.  I am not seeing a very strong signal 
> (had to use the -73 dBm level) so questioning if my transceiver 
> sensitivity is off.
> 
> I understand that the output of the XG3 is calibrated up to 200-MHz 
> and above that harmonics are used (up to 1420 MHz).  I would assume 
> then when I entered a freq = 222.200 that the XG3 is really running 
> at 111.100 + harmonics.  I wonder if one can use the rule of 1/n for 
> predicting the nth harmonic output level?  Been too long since I 
> studied Fourier series to remember the coefficients for a square wave.
> 
> I measured the XG3 output on my HP432A microwave power meter (10-MHz 
> - 18GHz) which can read from -20 to +10 dBm.  I see an output of -3 
> dBm when running either 222.200 or 144.200 MHz.  I am assuming I am 
> measuring the total harmonic energy since I have no filters in use.
> 
> I wonder if Elecraft might have done an output curve for the 0 dBm 
> output for the whole operating freq. range?  I am also assuming the 
> XG3 attenuators for -33, -73, and -107 dBm are wideband over the full 
> operating range.
> 
> I don't have a spectrum analyzer to measure power lower than -20 dBm.
> 
> 
> 73, Ed - KL7UW, WD2XSH/45
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