[hpsdr] Janus Alpha #2 - TBD part values

[Bill Tracey]

The values Phil H and I had come up with (actually Phil came up with them 
and I ordered) are:

R13,14 39k 1% - yields an attenuation of 1/5

R27: 3.3k

R35,36, C66,72:  10k and 470pf -- these were picked as these values were 
already on the BOM -- 1k and 500 pf should do as well

The notes chain on picking these values is below.

Cheers,

Bill

--- Original notes chain follows ----

Those values will be fine - since we are clocking the PWM at 6MHz we have
plenty of  tolerance for this 3dB frequency.

Phil...


----- Original Message -----
From: "Bill Tracey" <bill at ewjt.com>
To: "Phil Harman" <pvharman at arach.net.au>
Sent: Friday, June 09, 2006 7:36 PM
Subject: Re: TBD Values on Janus


 > Hi Phil,
 >
 > Safe to assume 10k and 470pf would work for the PWVM (R35,36 and
 > 66,72)  -- 10k and 470 pF parts are  already on the BOM - would be nice to
 > keep the unique values of these things down if we can.   As I recall the
 > values on these were not terribly critical.
 >
 > Regards,
 >
 > Bill
 >
 > At 07:29 AM 6/8/2006, Phil Harman wrote:
 >>Hi Bill,
 >>
 >>Sure,
 >>
 >>R13,14 = 39k 1%  which gives an attenuation of 1/5.
 >>
 >>R27 I've not used an electret mic before but values between  1-5k seem to
 >>be used in other circuits, how about 3.3k.
 >>
 >>The cut off for the LPF  R13/C66  needs to be high enough above the
 >>highest freq so that any phase shift does not have any effect.  So if Bob
 >>moves I/Q to 11kHz and allowing 5kHz max modulation we get 16kHz. Lets put
 >>the 3dB point a 2x this so  CxR = 1/(2 x PI x 32,000) so 10k and 500pf
 >>would work as would 1k and 5000pf.
 >>
 >>73's Phil....
 >>
 >>
 >>
 >>
 >>
 >>
 >>----- Original Message ----- From: "Bill Tracey" <bill at ewjt.com>
 >>To: <pvharman at arach.net.au>
 >>Sent: Thursday, June 08, 2006 2:21 PM
 >>Subject: TBD Values on Janus
 >>
 >>
 >>>Phil,
 >>>
 >>>Any thoughts on values for C66,C72,R13,R14,R27,R35,R36  - they're all
 >>>listed as TBD on the current Janus BOM.
 >>>
 >>>Cheers,
 >>>
 >>>Bill




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