Spectrum Analyzer Repair Trick

[sherlock]

Hi All....   I recently bought a non-working Advantest 2.6GHz spectrum analyzer on eBay.  Turns out the front attenuator diodes were fried along with the first mixer diode.  I bought the resistors from Digikey and found a suitable replacement diode again on eBay.  Still no signal display.  The analyzer uses a mixer with the local oscillator running 2.6 GHz higher than the input signal, so the LO runs at 2.6-5.2 GHz.  Since that was a possibility of no signal display, the manual says to check the frequency and amplitude.  Well, nothing in my basement workshop, or at my work either, will measure anything that high.  I thought of trying to make some kind of detector circuit from one of the mixer diodes I bought, just to see if the LO was present.  I was guseeing that if its there, its probably correct.  Then it suddenly dawned on me...  I HAVE a microwave detector already!  Went out to the garage and found my old radar detector that I used to use in the car.  I fired that up with a 12VDC supply and put the antenna side directly over the mixer coupler.  Viola' !  The radar detector sang like a bird!  Now again I couldn't measure the frequency, but it was there!  I managed to find out the remaining problem and now the analyzer seems to work fine.  Just thought I'd pass that on in case anyone else could use it.

sherlock   

[saturation]

... great idea for a quick microwave detector from K and up.