EMRFD Message Archive 774

Message Date From Subject
774 2007-05-20 13:44:12 Hari G POS-200 question
All,
 
  I was looking into the POS-200 gain or Mhz/volt spec its around 8Mhz, does this mean that there is no way i can control this with a DAC with 1mv switching ?.In this case also the freqency step will be high ?
 
Any ideas on controlling the POS-200 with a DAC of 12bit or 16bit resolution and not using a PLL to get 100Hz or better resolution.

--
De Hari
 
778 2007-05-21 07:00:32 DSNman@comcast.ne... Re: POS-200 question
Hari,
 
Looks like the smallest step would be 8 khz.
 
--
Loren Moline
WA7SKT
 
-------------- Original message --------------
From: "Hari G"

All,
 
  I was looking into the POS-200 gain or Mhz/volt spec its around 8Mhz, does this mean that there is no way i can control this with a DAC with 1mv switching ?.In this case also the freqency step will be high ?
 
Any ideas on controlling the POS-200 with a DAC of 12bit or 16bit resolution and not using a PLL to get 100Hz or better resolution.

--
De Hari
 

789 2007-05-22 21:52:15 Hari G Re: POS-200 question
Loren ,
 
   Thanks ,
 
     Looks like i will have to abandon the idea of controlling it through a DAC and will have to lok for a complex DDS PLL combination !
 
Best Regards
 Hari

 
On 5/21/07, DSNman@comcast.net <DSNman@comcast.net> wrote:

Hari,
 
Looks like the smallest step would be 8 khz.
 
--
Loren Moline
WA7SKT
 
-------------- Original message --------------
From: "Hari G" <vu2ghb@gmail.com>

All,
 
  I was looking into the POS-200 gain or Mhz/volt spec its around 8Mhz, does this mean that there is no way i can control this with a DAC with 1mv switching ?.In this case also the freqency step will be high ?
 
Any ideas on controlling the POS-200 with a DAC of 12bit or 16bit resolution and not using a PLL to get 100Hz or better resolution.

--
De Hari
 




--
De Hari
VU2GHB
794 2007-05-24 07:03:59 Allison Parent Re: POS-200 question
801 2007-05-25 08:24:32 Kenneth Stringham Re: POS-200 question
The PLL tracking filter is fine, but he's not talking
about a DDS. He's talking about a VCO running with a
DAC to tune the frequency. This here is stability.
That VCO has to very stable on its own. I doubt it
will have sufficient stability. It should be used in a
PLL with either a programmable divider in the feed
back loop to make it adjustable or with 1:1 feed back
and a DDS as the reference to make it variable.

Ken - AE1X




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806 2007-05-26 22:25:25 Hari G Re: POS-200 question
Alex /Ken ,
 
   Thanks for the comments , i think i will explain my intention a little more.
Use a freqency counter and DAC plot the freqency steps, then sweep the DAC and using the ADC take the reading for the respective voltage to display.
 
Two things that became clear to me is stablity and the step size i get with a 12bit DAC, looks like i must use a PLL if i want to tune in 10Hz steps.
 
Hari (VU2GHB)
 
On 5/25/07, Kenneth Stringham <ae1x@yahoo.com> wrote:

The PLL tracking filter is fine, but he's not talking
about a DDS. He's talking about a VCO running with a
DAC to tune the frequency. This here is stability.
That VCO has to very stable on its own. I doubt it
will have sufficient stability. It should be used in a
PLL with either a programmable divider in the feed
back loop to make it adjustable or with 1:1 feed back
and a DDS as the reference to make it variable.

Ken - AE1X

__________________________________________________________Need a vacation? Get great deals
to amazing places on Yahoo! Travel.
http://travel.yahoo.com/




--
De Hari
VU2GHB
807 2007-05-27 06:30:16 Ed Almos Re: POS-200 question
Hari

I am sorry but controlling the POS200 VCO with an ADC like this is not
possible if you want 10Hz steps. Math and real life is not
808 2007-05-28 19:09:26 Hari G Re: POS-200 question
Ed ,
 
  Thanks , yes using the POS-200 with a PLL kind of arrangement seems to be the only option.
 
The plan is to use 1MHZ as reference and then use a DDS as the programmable divider and  POS-200 as the VCO.
 
Regards
  Hari
 
On 5/27/07, Ed Almos <edwardalmos@gmail.com> wrote:

Hari

I am sorry but controlling the POS200 VCO with an ADC like this is not
possible if you want 10Hz steps. Math and real life is not