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The advertised range of my recently bought YIG oscillator is 1.1 - 3.4 GHz.

On my spectrum analyser, I found 2 resonances, spaced at about 1 GHz and 2 GHz from the main peak (see picture below were the first resonance can be seen at about 2GHz).

That means that the resonances fall inside the advertised range.

In the other YIG oscillators I bought, there were resonance only beyond the advertised range. Is it normal or is the oscillator damaged ?

enter image description here

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  • \$\begingroup\$ Resonance or harmonic distortion? \$\endgroup\$ – The Photon Apr 17 at 14:42
  • \$\begingroup\$ Yes, probably one or the other. That's my jargon to qualify that thing. \$\endgroup\$ – MikeTeX Apr 17 at 14:44
  • \$\begingroup\$ Fo you have a datasheet for the part? \$\endgroup\$ – The Photon Apr 17 at 14:44
  • \$\begingroup\$ No. This is this one: ebay.com/itm/… \$\endgroup\$ – MikeTeX Apr 17 at 14:59
  • \$\begingroup\$ Actually, the term resonance is probably unappropriated since it is clear that the peaks are harmonics (as proved by their uniform spacing of about 1 GHz). Harmonic distortion is probably the right term, but I'm not sufficiently acquainted with this domain. \$\endgroup\$ – MikeTeX Apr 17 at 15:57
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That looks pretty close to double the frequency. If that's the case, then this is harmonic distortion, and it is common for this type of oscillator to produce that, especially if the output power is high. In fact, it is common for spectrum analyzers to use these harmonics to receive frequencies above the range of the YTO.

Besides, the spec on the YTO refers to the tuning range of the fundamental output of the YTO. It is certainly possible for harmonics to fall in this range when the YTO is tuned near the low end of the range.

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  • \$\begingroup\$ So, you think it's normal. Yet I don't understand how a spectrum analyser can properly heterodyne if there are more than one frequency at once. \$\endgroup\$ – MikeTeX Apr 17 at 19:08
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    \$\begingroup\$ The thing to keep in mind is that any nonlinearity anywhere will generate harmonics, not just the LO itself, so systems are usually designed with that in mind - image filters, preselection filters, multiple conversions, etc. can be set up to ensure that images from any unwanted mixing products are removed. \$\endgroup\$ – alex.forencich Apr 17 at 20:31

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