[time-nuts] Lassen IQ receiver

[Robert Darlington]

Hi Mike, I'll answer the questions in line with your email message, below...

On Sat, Oct 11, 2008 at 12:40 AM, Mike Monett <XDE-L2G3 at myamail.com> wrote:

>  "Robert Darlington" <rdarlington at gmail.com> wrote:
>
>  > I use  them  for  non-time keeping things.  You  need  to  use the
>  > configuration tool  to configure the ports so that they  both spit
>  > out NMEA,  and  the particular NMEA strings you want  to  see, and
>  > then save the configuration.
>
>  > Otherwise you  get  NMEA out of one port  and  the  Trimble binary
>  > format out  of the other. Do you have a copy of the  software? You
>  > can find it here:
>
>  >http://www.trimble.com/embeddedsystems/lasseniq.aspx?dtID=support
>
>  > Also, make  sure you have the IQ and not the SQ. The  SQ  only has
>  > one port but is otherwise pin compatible.
>
>   Robert,
>
>  These units look interesting. Do you mind if I ask some questions?
>
>  1. What kind of non-time keeping uses have you found for them?


The first project was an APRS beacon for a high altitude balloon project
which hasn't launched yet, but was tested in my car.  The last project was
for the local laboratory.  They developed a sampling system which had every
gadget but the kitchen sink in it, and every part was made out of
unobtanium.  In this case the gps board had been discontinued for about 4
years so I had to design a new one that would be the same physical size,
same hole spacing, and same pinout.  I figured if I was going to do this and
have a minimum run of 5 boards, I was going to make 2 for me (they needed 3
total).  In the picture you'll see the top half with the GPS module has a
white box around it.  This part I cut off after programming the GPS receiver
modules and installed in their gadget, the rest of the board gave me a
MAX232 (3.3 volt version if I remember right) and broke out both serial
ports to DB9 for easy hookup to a PC.  I should've added a PPS line but was
too concerned with keeping the board working when I cut it in half to really
think about more than what they needed.  What you can't see is the button
cell battery on the back for retaining constellation data

Here's the board: http://www.losalamostech.com/gps_board.jpg
Here's their gadget: http://www.*lanl*
.gov/orgs/tt/pdf/techs/hands_off_gun.pdf


>  2. How  well do they work indoors? Do you have to be near  a window?
>  What about inside a multi-story building?


We only tried it outside.  Their gadget got the short little ceramic patch
antenna.  I used the longer (5 meter I think) mag mount version in my car
when testing the APRS beacon.


>
>
>  3. How well do they handle constellation changes? Is there an abrupt
>  shift in position?
>

No clue!  Sorry.


>
>  4. Have you ever taken the shield off and looked inside? If  so, can
>  you see the crystal oscillator and tell whether it is a bare crystal
>  or a complete oscillator module?
>

No, but it comes off easy enough when not soldered down.  I'll try to pop
mine open and take some pictures of the guts for you later today.



>
>  5. How  much  do  they  cost? Do you know  of  any  others  that are
>  cheaper?
>

We paid somewhere on the order of $50 + the antenna.  Sparkfun sells them
here for $56:
http://www.sparkfun.com/commerce/product_info.php?products_id=163

They also sell the antennas and breakout boards that already have the tiny
little surface mount sockets (I have a few left if you end up buying one of
these).

The really interesting thing is that the manual states that the PPS output
is within 50ns of reality.   I plan on using one to discipline that Efratom
rubidium standard I was asking about earlier in the week.  By the way, the
connector from Mouser electronics came in and I'm ready to go, just waiting
on the part to come in from China.

-Bob



>
>  Thanks for your help!
>
>  Best Regards,
>
>  Mike Monett
>
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