VCXO as a local oscillator

[aloishis89]

I need to be able to adjust the local oscillator frequency going into my mixer, but only by a relatively small amount (from about 100 MHz to 200 MHz). I don't want to use a VCO because I can't find any that will go that low, and they're overkill since the ones I've seen give you a range from like 300 MHz to 2.3 GHz. A voltage controlled crystal oscillator has the correct range, however the one I'm looking at is about ±50 ppm accuracy. Is it considered bad practice to use a VCXO as a local oscillator like that? I've only really seen them used before in PLLs.

 

[pstuckey]

What is the part# of the VCXO you are looking at?

VCXOs typically have very narrow tuning ranges. Are you sure the +-50 ppm isn't the tuning range?

 

[aloishis89]

It's this one: https://www.foxonline.com/pdfs/FVXO_HC53.pdf

It says "Freq: 0.75 MHz to 250MHz", so I was assuming that was the range. I think I may be misunderstanding how a VCXO is used though.

 

[pstuckey]

It's this one: https://www.foxonline.com/pdfs/FVXO_HC53.pdf

This family of parts covers that frequency range, but each individual part must be specified for just one center frequency. Then they can be tuned +-50 ppm around that one frequency. So for a 100 MHz VCXO, the tuning range is +-5 kHz.

I've attached is a datasheet of a VCO that tunes over 100-200 MHz, see if this will meet your needs.

 

[aloishis89]

Oh ok, I get it. Thanks for recommending that part, that should work great!