PLL Question


M0ZHN
 

Hi everyone,

I am new here, just joined today. I would like to ask a question if I may. I am looking to build the versatile PLL that was published by Brian in RadCom Plus some time back. The circuit seems to require a VCO that is designed for 0-5V tuning. Is there a way I can use a wideband VCO, say 0-20V tuning, with this circuit and if so what do I need to add/change/modify?

Any advice and help is greatly appreciated.

73 Elia, M0ZHN


Andy G4JNT
 

Can you refer the RadCom article - like which issue?
I suspect you could use a non-inverting op-amp stage with a gain of 4 running from a 25V rail to get the swing you need.   
May need a fast opamp - There are suitable ones around




On Tue, 13 Jul 2021 at 22:22, M0ZHN via groups.io <eliamady=yahoo.com@groups.io> wrote:
Hi everyone,

I am new here, just joined today. I would like to ask a question if I may. I am looking to build the versatile PLL that was published by Brian in RadCom Plus some time back. The circuit seems to require a VCO that is designed for 0-5V tuning. Is there a way I can use a wideband VCO, say 0-20V tuning, with this circuit and if so what do I need to add/change/modify?

Any advice and help is greatly appreciated.

73 Elia, M0ZHN


M0ZHN
 

Hi Andy,

Thanks for your reply, it was in RadCom Plus Volume 1, No.1 but it is also on Brian's website:

Versatile PLL

Elia, M0ZHN


Andy G4JNT
 

Looks back though archives ...
Brian being GM8BJF

Yes, use an OPAMP gain stage.   I use the LM6211 which is a 20MHz bandwidth chip that can operate up to 24V, and have used it with LMX2470 and LMX2487 synth chips to drive VCOs that take a tuning voltage greater than 5V.

Rather than a buffer / gain stage though, the complete loop filter is built around the LM6211 which end up as an inverting stage so the appropriate config bit in the synth chip to ser negative phase detector polarity needs to be set.   http://g4jnt.com/LMX2470_DevModule.pdf  gives more details.
  


On Tue, 13 Jul 2021 at 22:36, M0ZHN via groups.io <eliamady=yahoo.com@groups.io> wrote:
Hi Andy,

Thanks for your reply, it was in RadCom Plus Volume 1, No.1 but it is also on Brian's website:

Versatile PLL

Elia, M0ZHN


M0ZHN
 

Thanks Andy, will give that a try and see how it goes.

Elia, M0ZHN