SKM52 GPS module

I bought the GPS module for two reasons. One, its a cool device which provides the beacon with accurate data for time-keeping, frequency calibration, and location information (for encoding the Maidenhead locator automatically into WSPR messages).

Two, I don’t possess a vast array of test equipment so calibrating kit is difficult. By having a GPS attached to the beacon you can overcome the need for accurately calibrated frequency counters or receivers.

As such, it seemed the sensible way to go.

After much reading and head scratching I decided just to build a simple Veroboard layout.

http://www.hanssummers.com/ultimategps2.html

is the source of the most reliable information.

You need the 10K pull up resistor and decoupling capacitors on the 3.3V supply as per the data sheet.

http://www.hanssummers.com/images/stories/ultimategps2/skm52.pdf

I’ve emailed a few people who had posted material about their SKM52 builds as their boards don’t resemble the manufacturers data sheet which has got me stumped. Hopefully, someone will come up trumps on the advice.

Anyway, decoupling capacitors. I’m still waiting for them to arrive. eBay is good but the Royal Mail is always the stumbling block.

I’m literally going to add a 10uF and 1uF decoupling capacitor as per the cryptic line on page 2 of the data sheet. I have no idea how it should be done but a bit of blind faith never hurt any one!

With that in mind my board is designed to allow the caps to be added when they land.

IMG_0461

I’ve included the BAT connection as the SKM52 has an onboard lithium cell which when charged gives hot start and warm start ability to the GPS, which cuts down on a lot of time wasting waiting for the GPS to achieve satellite lock. The device “remembers” its last location as a result, so if you haven’t moved . . .

All I’ve done is bridged the BAT to the Vcc line with a short link. When everything’s working I’ll post a wiring diagram so anyone else who has a head scratching moment has got somewhere to look for a few hints.

The board in no bigger than a stick of chewing gum, it could be smaller but I didn’t want to get caught out when the capacitors turn up and won’t fit in the space I’ve left. I can live with it.

Another tip is to use screened cable to place the GPS away from the beacon due to noise. I’ve got some decent grade multi-core screened cable laying around and a 2M length should be sufficient to allow the GPS to sit in the window with a view of the horizon or to be dangled outside when I weatherproof it.

I just wish I hadn’t hacked back the screen so much as I’ve just realised it needs to be connected to the ground on the beacon. In the words of Edmund Blackadder. Bugger!

That said I’ve included a 3.3V supply on my PSU board so we should be good to go when I’ve worked through the setup screens on the beacon.

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