[time-nuts] FE-5680A Mechanical Question

John Ackermann N8UR jra at febo.com
Sat Jan 14 14:48:38 EST 2012


Didier, check the HPSDR Janus baseband interface and related bits.  It's a very good ADC on a board designed with time-nuttish care and can do up 192ksps.  The downside is that it doesn't have a soundcard interface; the upside is that the hardware and SDR software that alkmto it are all open source.

http://openhpsdr.org/janus.php

John

On Jan 14, 2012, at 2:13 PM, shalimr9 at gmail.com wrote:

> Here is a common misconception. Most consumer grade "24bit" sound cards only have 16 bit ADCs but 24 bit equivalent DACs (most of them are actually 1bit DAC with oversampling.)
> 
> You have to spend a pretty penny to get a 24 bit ADC running at multiples of 44ks/s.
> 
> Further, the very poor DC performance of the typically sound card 16 bit ADC is hidden by the analog and digital filtering of the card and the driver.
> 
> If anyone has an inexpensive (<$100) sound card with true 24 bit ADC (if they are capable of DC, so much the better), please let me know because I have been looking for one.
> 
> Didier KO4BB
> 
> PS: to remain on topic, I agree with the principle of using a PC to breadboard something, as long as the hardware interface remains simpler than a cheap microcontroller, bit it is easy to get carried away and build PC-based hardware for the purpose of running a test, and having to redo all from scratch to convert it to a uC solution for the final application.
> 
> 
> Sent from my BlackBerry Wireless thingy while I do other things...
> 
> -----Original Message-----
> From: Chris Albertson <albertson.chris at gmail.com>
> Sender: time-nuts-bounces at febo.com
> Date: Fri, 13 Jan 2012 08:15:42 
> To: Discussion of precise time and frequency measurement<time-nuts at febo.com>
> Reply-To: Discussion of precise time and frequency measurement
>    <time-nuts at febo.com>
> Subject: Re: [time-nuts] FE-5680A Mechanical Question
> 
> On Fri, Jan 13, 2012 at 3:19 AM,  <EWKehren at aol.com> wrote:
>> What we know is that you can set the Rb in 7 E-13. Dithering would allow
>> even closer setting, the question is what rate will the Rb accept with out
>> loosing lock or deterioration of the performance. Some one should explore
>> that.  I am still waiting to se some aging. Taking the 10 MHz output and than
>> use an  analog loop and something like a Morion OCXO and you have the best of
>> all.
>> Digitally controlling the Rb will cut the cost of the control loop in half.
>>  For $10 in parts and a PC board for less than $10 using Shera like
>> controller  can be realized. What is needed is some one able to do the PIC.
>> If some one is interested and able, please contact me off list. A low cost
>> GPS or a 1 pps output of a Tbolt be perfect source.
>> Bert Kehren
> 
> Don't use a PIC for the prototype.  A desktop PC could work as well
> and everyone here already has one.   Connect the FE5680 to the PC's
> serial port and send commands to adjust it.  The PC also needs to be
> able to read a voltage.   Many already have audio input with 24-bit
> ADC chips.
> 
> Later you can move the C code from the PC pretty much directly to an
> AVR.  PICs typically use assembly language, that is harder and limits
> the number of people who can contribute changes to the code.  But you
> can start with a PC, maybe running Linux or BSD.
> Chris Albertson
> Redondo Beach, California
> 
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