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Is this IMD?

K5ESS All Messages By This Member #57988 Just looking for some insight.? See attachment for details. Mike K5ESS Is this IMD.pdf Is this IMD.pdf
Warren Allgyer #58002 Mike I don't think this is IMD per se. It looks to me like harmonics of the modulating tone. Those harmonics could be present in the tone itself or they could be generated by non-linearities in the audio chain. For IMD measurements you need two tones with the pair centered in your filter passband and the tones must not be harmonically related. The difference between one of the tones and its adjacent product tone is the figure of merit for IMD. Your span and RBW are ok although if you have a lower RBW, 30 or 10 Hz, you will get better resolution and may see some close in products that are covered up at 100 Hz. W
K5ESS All Messages By This Member #58013 开云体育 Warren, Guess I now agree that it’s audio distortion creeping in somewhere.? I’ll have to try tracing it down.? Mike K5ESS ? toggle quoted message Show quoted text From: [email protected] [mailto:[email protected]] On Behalf Of Warren Allgyer Sent: Tuesday, August 28, 2018 5:01 AM To: [email protected] Subject: Re: [BITX20] Is this IMD? ? Mike I don't think this is IMD per se. It looks to me like harmonics of the modulating tone. Those harmonics could be present in the tone itself or they could be generated by non-linearities in the audio chain. For IMD measurements you need two tones with the pair centered in your filter passband and the tones must not be harmonically related. The difference between one of the tones and its adjacent product tone is the figure of merit for IMD. Your span and RBW are ok although if you have a lower RBW, 30 or 10 Hz, you will get better resolution and may see some close in products that are covered up at 100 Hz. W
ajparent1/kb1gmx All Messages By This Member #58030 Distortion is the likely animal.? If its more than 40db down that is not bad and not to worry about it. To see IMD you need two equal tones inside the filter pass band with non harmonic relationship. I use a 750hz and 1750hz as thse are in the typical voice bandwidth. IF the IMD were perfect you see two tones in the sideband and much weaker ones (more than 40-50db down) in the apposing sideband.? IF the IMD were poor you see a flock of new tones (750+1750 and 750-1750 and harmonics of those) with varying amplitude inside the filter pass band and outside of it. Allison
Warren Allgyer #58040 Allison If the IMD were "perfect" you would see two tones, period. :-) WA8TOD
ajparent1/kb1gmx All Messages By This Member #58049 Yes, but we know this is not perfect.? Wrong word should been reasonable.

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