[time-nuts] LTE-Lite module

[SAIDJACK at aol.com]

Hi there,
 
I don't know how much the Wenzel units are, but if someone is not able  to, 
or willing to build one on their own then this could be a  viable 
alternative.
 
I will look into writing a short appnote describing how a low-noise  
div-by-2 can be built at home with minimal components using a surface mount '74  
chip and a couple of passives.
 
Lastly the 20MHz LTE-Lite boards do generate a 10MHz output of course, and  
if you feed that into a standard counter (5370B, 53132A etc etc) I  think 
the noise floor of the counter would be higher than the  noise floor of the 
synthesized 10MHz output, so you would not see any difference  between using 
the noisier synthesized output and the low-noise 10MHz TCXO  divided output..
 
Bye,
Said
 
 
In a message dated 10/17/2014 13:19:08 Pacific Daylight Time,  
gigneil at gmail.com writes:

How much would we guess that Wenzel blue-top would run you?


Relative to the low cost GPSDO,  my understanding is the Wenzel  parts are 
priced appropriately to their quality.






On Fri, Oct 17, 2014 at 11:32 AM, S. Jackson via  time-nuts 
<_time-nuts at febo.com_ (mailto:time-nuts at febo.com) > wrote:


Hello  Jim,
let me answer through Time Nuts as this may interest  other  parties as
well.
Yes, using a fast flip flop to generate 10MHz out  of  the 20MHz TCXO 3.0V
CMOS output from the LTE-Lite module will  preserve the phase  noise 
(actually
improve it by up to 6dB due to  the 20log(n/m) noise improvement)  and will
not add any spurs if you  use the clean 3.0V output from the LTE-Lite  
module
or an external  clean power supply (please note the LTE-Lite TCXO RF  output
is 3.0V  due to the internal 3.3V to 3.0V Low Noise regulator feeding the
TCXO and  buffer).
Use fast logic such as 74AC74, 74FCT74, or the like.  We do  exactly that on
our ULN-2550 boards to generate 50MHz and 25MHz out of  the  100MHz, and
using a fast CMOS divider will result in additive  phase noise  that will be
below the crystal oscillator phase noise  floor.
That will result in significantly better phase noise and   much lower spurs
than using the synthesized 10MHz output from the board,  and one  74' chip
can generate both 10MHz and 5MHz out of the 20MHz  LTE-Lite output. This  is
exactly what we would do here if we needed  a clean 10MHz from the 20MHz
LTE-Lite board.
I believe you can order  low-noise divide-by-2  blue-top boxes from Wenzel
already  packaged-up and connectorized as  well.
Hope that  helps,
Said
Hi Said
I was one of those looking for 10Mhz but I just  thought  again now that it
might be just as well to divide the  standard 20Mhz output by 2  using a FF.
I think that would preserve  all the desirable characteristics of the  20Mhz
signal which I  understand to just be square wave at CMOS 3.3v levels
anyway. Is that  correct?
Thanks
Jim
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