Cabledog.net

Atlas board assembled and installed in the enclosure for new HPSDR radio.

This weekend I assembled the first of many circuit boards for my new radio project.  I am working on building a SDR based on designs from the HPSDR (High Performance Software Defined Radio) project group.  The parts are named after figures from ancient mythology and are designed by the smart people of the HPSDR project.  Most of the boards are still available from TAPR.

Atlas is the digital backplane for the various radio boards.  It does little by itself, just connects the various boards via data buses and equally important it connects an ATX style power supply to the boards for DC power distribution.

Atlas Backplane

This is my first project involving SMT parts.  One of the advantages to using SMT versus through hole components is you don’t have to constantly flip your board over.  On previous projects it seemed too easy to loose track of where you’re at or just plain loose a part due to flipping the boards over all the time.  The disadvantage of working with SMT parts is that they’re small as all get out (often smaller than grain of rice) and having to use a microscope is not an exaggeration.  However, by using a small tip for my soldering iron, tweezers, and a 4x jewelers loop I was able to get all 40+ parts on the board and apparently did not loose or damage any.

Points to remember are to observe polarity for certain caps, diodes, etc.  I soldered one of the LEDs backwards (I knew which way it went, just could not SEE the darn thing correctly) and using soder wick took the solder pad off the PCB in the process of removing it.  Also, a couple of the 3.3k resisters for the LEDs could not be installed as they were not included with the kit from TAPR.  When I got the kit I did an inventory and saw that they were missing from where they should be taped to the parts sheet, but since they only impact the LEDs and not the workings of the board or power distribution I went ahead and assembled the project anyways.  I’ve had no issues with the few kits I have ordered from TAPR and so do not know what the customer support experience will be like.

P.S.  Each of the white card slots has many dozens of solder points on the reverse side of the board which cannot be seen in the photo, but believe me are there, and after all is said and done it makes for a lot of soldering fun!

My request for a vanity amateur radio callsign was approved by the FCC. My new ham radio callsign is now KS0HAM instead of KC0CGH. I’m still only a Technician Class licensee, so I need to study so I can upgrade my operators privileges.  Many years ago I passed the 5 WPM CW exam and the written test for General Class but never filed the test results.  I thought I would come back and retake the 13 WPM CW test and then qualify for General but never got ‘round to that.

This morning I installed a surplus Thunderbolt GPS Disciplined Clock or GPS DO I bought from eBay.  It’s made by Trimble to be a precision GPS synchronized time and frequency standard.  The beauty of the Thunderbolt is that it has a GPS receiver, ovenized oscillator, and control circuitry all integrated on one board.  I already have a few GPS receivers for timing that provided 1PPS but no 10MHz and the homebrew solutions to integrate any kind of quality oscillator and control circuity were above my abilities to build and way too expensive when all was said and done.  So getting a plug-and-play solution that provided precision time and frequency for little over $100 and no soldering was too much to pass up.

Besides the Thunderbolt unit itself one needs a power supply and GPS antenna.  The power supply should provide +12VCD. -12VDC, and +5VDC at should be rated to at least 15 Watts total.  The GPS antenna can be a high gain unit or a simple magnetic mount one.  I have been using the magnetic mount ones at my house for several years and have had no problems acquiring signal even when the antenna was conveniently stuck to the guttering or sideways on an antenna mast.  Specs for power, GPS antenna, communications, and software utilities are available on Trimble’s website.

After making the power and GPS cable connections I downloaded the GPS monitor utility and connected my laptop (old one that has both RS-232 and USB ports) to the unit via a RS-232 serial cable.  I powered the unit up and the software immediately connected and proceeded to provide enough blinky lights and statistics to prevent me from going crazy with curiosity.  Which is good because it seems like any GPS experimentation is probably not going to work correctly the first few times and even if it is working it’ll take so long that you’ll think it’s broken.

It seemed like it was getting power and at least some sort of satellite signals so I left it to work things out on it’s own for a while.  After about 30 minutes I noticed that It had only locked onto one satellite there were a few alarms.  Specifically the Self-Survey, Stored Position, and Position Questionable lights were yellow.  Also there were several oscillator related alarms present, but expected these until the GPS receiver got squared away.  I verified the the time and date were correct, the lat/long seemed odd, but was populated and noticed that it seems to be having trouble tracking any birds.  From previous experience I knew that the placement of the antenna should provide signal from several satellites so something is up.  Staring at the alarms there seemed to be a positional issue in common and so returning to the lat/long boxes I realized that these are not even close for Kansas City area,  Google showed me the lat/long was from China which is coincidently where the unit was shipped from and probably last used.  After a factory reset of the parameters and a cold restart the unit came up and in seconds was tracking multiple satellites and in a few minutes had the oscillator running and providing 10 MHz and 1 PPS out.  The display was green except for the Stored Position indicator, but I got antsy and took the lat/long displayed and manually entered it in and so that also cleared.