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From: Chris on 23 Feb 2010 13:51
The data sheet just gives some ancient reference for finding the
values for R1, R2, and C1.

Is the RC network for the VCO is (R1, R2, C1)? Would I just use the
cutoff frequency for the R1 and C2 RC filter (i.e. fc=1/(2*Pi*R1*C1)).

Thanks,
Chris KQ6UP
From: Tim Wescott on 23 Feb 2010 14:06
Chris wrote:
> The data sheet just gives some ancient reference for finding the
> values for R1, R2, and C1.
>
> Is the RC network for the VCO is (R1, R2, C1)? Would I just use the
> cutoff frequency for the R1 and C2 RC filter (i.e. fc=1/(2*Pi*R1*C1)).
>
> Thanks,
> Chris KQ6UP

Find some other data sheet?

Some of them are more informative than others. I don't know who still
makes 'em, but I'd look to TI, ON Semiconductor, and Fairchild to start.

The 74HC4046 is very similar (it has one more phase comparator, IIRC,
and may delete some other function) -- if you can't find what you want
in a 4046 data sheet a 74HC4046, or other 74xx4046 data sheet, may help.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com
From: Chris on 23 Feb 2010 14:22
On 23 Feb, 18:51, Chris <christopher.man...(a)gmail.com> wrote:
> The data sheet just gives some ancient reference for finding the
> values for R1, R2, and C1.
>
> Is the RC network for the VCO is (R1, R2, C1)?  Would I just use the
> cutoff frequency for the R1 and C2 RC filter (i.e. fc=1/(2*Pi*R1*C1)).
>
> Thanks,
> Chris KQ6UP


The Texas Instruments data sheet at
http://www.datasheetcatalog.org/datasheet2/6/0rs2lxolj6lew0llx95wkfal45yy.pdf,
which is more-or-less a photocopy of the relevant pages in the
original RCA handbook, doesn't refer to an 'ancient reference' but to
"Deisgn information" which is a section of the same data sheet ... the
clue is the title of the section "Design information". There, a
number of graphs are provided illustrating how the centre frequency
varies with R1 and C1, how the frequency offset varies with R2 and C1,
and how the fmax/fmin ratio varies with R2/R1. I've found in the past
that these usually provide sufficient information!

Chris (another one)
From: Ban on 23 Feb 2010 14:40
Chris wrote:
> The data sheet just gives some ancient reference for finding the
> values for R1, R2, and C1.
>
> Is the RC network for the VCO is (R1, R2, C1)? Would I just use the
> cutoff frequency for the R1 and C2 RC filter (i.e. fc=1/(2*Pi*R1*C1)).
>
> Thanks,
> Chris KQ6UP

hmm, you will need also a loop-filter, so it is better to study the data
sheet until you understand what you are doing.
ciao Ban


From: Chris on 23 Feb 2010 14:48
On Feb 23, 11:22 am, Chris <christof...(a)talktalk.net> wrote:
> On 23 Feb, 18:51, Chris <christopher.man...(a)gmail.com> wrote:
>
> > The data sheet just gives some ancient reference for finding the
> > values for R1, R2, and C1.
>
> > Is the RC network for the VCO is (R1, R2, C1)?  Would I just use the
> > cutoff frequency for the R1 and C2 RC filter (i.e. fc=1/(2*Pi*R1*C1))..
>
> > Thanks,
> > Chris KQ6UP
>
> The Texas Instruments data sheet athttp://www.datasheetcatalog.org/datasheet2/6/0rs2lxolj6lew0llx95wkfal...,
> which is more-or-less a photocopy of the relevant pages in the
> original RCA handbook, doesn't refer to an 'ancient reference' but to
> "Deisgn information" which is a section of the same data sheet ... the
> clue is the title of the section "Design information".  There, a
> number of graphs are provided illustrating how the centre frequency
> varies with R1 and C1, how the frequency offset varies with R2 and C1,
> and how the fmax/fmin ratio varies with R2/R1.  I've found in the past
> that these usually provide sufficient information!
>
> Chris (another one)

Got it 1MOhm, and .002uF ~400Hz I didn't notice the table.

Thanks,
Chris
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