Pushing/Pulling

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YAN-1

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Hello. I was looking at a VCO datasheet and it said that it had good pushing and pulling performance. What does rf pushing and pulling mean exactly? Thanks a lot.

Nichola V Abdo
 
I think pushing and pulling of an oscillator are when the frequency changes when the supply voltage changes and maybe when the load resistance changes.
 
audioguru said:
I think pushing and pulling of an oscillator are when the frequency changes when the supply voltage changes and maybe when the load resistance changes.
Click to expand...

In some systems the osc is p/p by varying the Vbias on a varicap in the osc tuning circuit.

IIRC often used in electronic musical instruments.
 
audioguru said:
I think pushing and pulling of an oscillator are when the frequency changes when the supply voltage changes and maybe when the load resistance changes.
Click to expand...

I agree with you.
Frequency pushing is the sensitivity of the output frequency to the supply voltage.
Frequency pulling is the sensitivity of the output frequency to the load conditions.
 
RadioRon said:
Yes, this is correct. Here is a reference:
https://www.electro-tech-online.com/custompdfs/2007/10/vco15-15-1.pdf
Click to expand...

hi Ron,

IIRC this explains the undesirable 'side effects' that one can get from these sources.

Frequency pushing is the sensitivity of the output frequency to the supply voltage.
Frequency pulling is the sensitivity of the output frequency to the load conditions.

But some applications, musical instruments etc, the VCO is designed so that it can be pulled in a controlled way to produce a desired effect.

 

Hi Eric

My limited understanding of these terms comes from the world of wireless product design and in that industry these terms have the specific meanings referred to in my reference. I'm not surprised that they may have additional meanings in other industries as we often find that the meanings of words and phrases depend on the context of their use. Thanks for the info.
 
I thought pushing and pulling in concerns to a VCO were the intentional effects. I'm guessing it means it has a wide range of frequency responce in the given voltage range. Something that has bad push-pull performance might require more drive voltage for a given frequency shift. That's the way I read it at least in concerns to a VCO.
 
audioguru said:
I think pushing and pulling of an oscillator are when the frequency changes when the supply voltage changes and maybe when the load resistance changes.
Click to expand...

That's it

Lefty
 
That's what I thought until I did a little research. That's why I edited my previous post.
 
**broken link removed**
http://www.freepatentsonline.com/4518930.html
**broken link removed**


In brief
Frequency stability (which should include VCC stability) and pullability are listed as seperate paramaters. But the first link mentions that they're linked, meaning something that is highly pulable is always going to be less stable to circuit conditions. While it obviously refers to both in the context of a VCO I'm certain it refers to the span of frequency variation with a given input signal.

I see it refered to a lot with using different value capacitors to slightly trim the frequency of a crystal oscillator as well.

That's what I found doing a Google search in about 3 minutes. How is the opposite conclusion being reached by other people?
 
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Apparently it depends on your search parameters. As I said, my original thoughts were what you verified here. But try searching for "VCO pushing pulling" and you get mostly the opposite result.
 
I'm surprised that you guys are still going on about this. When it comes to a VCO data sheet, the VCO industry has decided to use Pulling and Pushing to mean those specific things referred to in this link given previously (https://www.electro-tech-online.com/custompdfs/2007/10/vco15-15-2.pdf). If, on the other hand, one is discussing the principles of oscillators in general, then, yes, the pullability of an oscillator is generally its ability (or its weakness, depending on your point of view) to change its frequency of oscillation due to external influences. This is analogous to the use of many words in English that have different meanings depending on their context. The original poster was asking in the context of a VCO data sheet.
 
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