Hi Robert "Robert Darlington" <[EMAIL PROTECTED]> wrote:
> Hi Mike, I'll answer the questions in line with your email > message, below. [...] >> 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. That is very interesting. Making things fit can be fun! > 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 Too bad about losing the 1PPS. Maybe you can persuade them to get some spares. > Here's the board: http://www.losalamostech.com/gps_board.jpg Thanks - that gives a good idea how bug the GPS is. But don't the connectors add a lot of weight? > Here's their gadget: >http://www.lanl.gov/orgs/tt/pdf/techs/hands_off_gun.pdf Shades of Star Trek. We can see it happening right before our eyes. >> 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. I wonder about the GPS chips used in cellphones. Would they be suitable for this project? They might save some weight. >> 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. Thanks, I would really appreciate that. >> 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 Great - thanks for the link. > 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). I'm very interested in antennas these days. I know nothing about them, but find they can have a lot to do with time errors. Such as multipath from passing cars. What happens if a pigeon sits on your GPS antenna? > 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. Me too! I just got news that my rubidium has already shipped, which is surprising. PayPal hasn't cleared yet, so I guess he has a lot of confidence in the system. Which Efratom do you have? And who are you dealing with in China? > -Bob >> Thanks for your help! Best Regards, Mike Monett _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
