[Wswss] 10MHz GPS Diciplined Oscillators

[Greg Stahlman]

I know most of you are on the SBMS page and probably saw these, but I still
have some so I am posting here.

 

These are very similar to a Trimble, but not exactly the same

 

If you forgot already, go here for the basic board info on the True Position
boards.

http://www.packratvhf.com/A%20Packrat%20GPS%20Receiver%20Project.pdf



These are just the GPS boards shown on the website, not the entire rack unit
they built out of one!  Although a nice job!



These are NOT plug and play.  As they describe, after initial power up, you
have to send two commands to get them started via the built in RS232 port(or
TTL Ports).  Once done, they stay locked as long as they have power.



  I have tested every board for lock, RS232 coms, number of satellites and
clock quality. 



They come with a jumper for the GPS to SMA-F connector, Power jumper, very
short jumper for the 10MHz out you can customize with your own connector,
and a 6 pin connector you can customize for your RS232 interface, or the TTL
interface if you wish.

 
What I have seen testing..

  These will operate down to around 13V although designed for 15.

  Current draw is about 250ma once warmed up.  About 400ma for a short time
when cold power up.

  They are very stable after an hour, very useable after just a few minutes!
I can only see freq down to 10^10th and after an hour, they are all well
within that!

  Looking at the 100th harmonic (1GHz), they were all < + or - 1Hz
according to another GPS locked analyzer.  Again, not the best test bench
for NBS standards, but best I could do.

  Output @ 10MHz is +12DBm

 

  They also have a 1PPS output

  They use a 5V bias for the GPS antenna.  Those little 1" square
"thumbnail" GPS antennas are usually 3V and will NOT work!

  There is a "$RESET" command that will restart the unit without a power
cycle.  That wasn't listed on the PackRats page.

  The unit needs the $PROCEED command (case sensitive) to start the OCXO to
lock to the GPS and it needs the $SURVEY 1 command so it knows where it's
at!  For whatever reason, it will not automatically learn where it is at on
its own and needs that to "reposition" itself.  At first, I couldn't figure
out why the accuracy was only +or- 0.3Hz @ 10MHz, then was told about the
$SURVEY 1 command and that drastically increased the accuracy!  The "1" is
in hours, how long you want it to survey its own location.  1 is min.  48
max.  If you leave it blank, it will survey for 8hrs.  After that command
was done, the clock quality number decreased (better) and the status went to
"Locked" or "Acquiring."   So, if you are roving around, you need to do the
$SURVEY when you stop at your next location.



Working tested boards will be $35 shipped via USPS.  Two for $60.  Paypal
preferred



Any other questions, let me know! 



73

 



Greg Stahlman  KJ6KO

kj6ko.com

Trustee Northern California 900 Repeater System

NC9RS

nc9rs.com





 

Greg Stahlman  KJ6KO

kj6ko.com

Trustee Northern California 900 Repeater System

NC9RS

nc9rs.com

 

 



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