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Noise at resonance frequency - RF Cafe Forums

Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views. It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if you would like to post something on RF Cafe's Facebook page, please do.

Below are all of the forum threads, including all the responses to the original posts.


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Post subject: Noise at resonance frequency Posted: Mon Sep 26, 2005 11:27 am
I have build a VCO for a mixer IC. When i am viewing the output power of VCO with Spectrum analyzer then there is a lot of noise at and around desired resonance frequency. I am using a DC supply of +- 5V and a regulated supply from 0V to 1.5V to check the response of VCO resonance frequency. Noise is less when i am operating with 0V or 1.5V regulated voltage, but if i give around 0.7V of regulated supply then noise gets worse. I have also tried connecting capacitors with my regulated supply but to no improvement. Can anybody please suggest that how can i get rid of the noise ?


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Post subject: VCO noisePosted: Wed Sep 28, 2005 3:13 pm
I'm a bit confused. Do I understand that you are running the oscillator proper from +/- 5V regulated, and that you're changing the control voltage (from a different supply?) from 0 to 1.5V?

If your VCO uses a varactor diode, you need to make sure that it's never forward biased. That means avoiding the range of 0 to at least 0.7 V

Good Luck!



Posted  11/12/2012
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