Sunday, 19 February 2017

GPS, Arduino,WSPR... and dirt

As I type this, the fingers of my right hand are absolutely filthy. This is because it is nearly spring, and time to get the veg plots dug over ready. Soon, it will be time to sow the veg seeds. It will also be time for long distance walks, SOTA, and playing radio in the field!

Im only at the PC since ive been working on an Arduino based GPS logger. Those readers with a very long memory might recall that in the dim and distant past I was playing with a low cost GPS module and PICs, but didnt get it to function. Well, this time im running it with an Arduino Uno, and some 'test' code for the TinyGPS library.

Serial Monitor data from Arduino GPS tests

After several false starts because other peoples code didnt quite work (I never claimed to have written any code!) I came across a sketch using the TinyGPS library, and specifically the exact same GPS module as mine. Apart from having to swap a couple of wires over, it works just fine.

Cheap VKEL GPS module and Arduino Uno
The next stage with this is to work out how to select just the data I want, and instead feed that to an LCD. Eventually, and after a bit of work to port it to a much smaller Arduino such as a Nano, I intend to add an SD card module, and write the GPS data to a .txt file on an SD card, for later analysis in Google Earth. But that I think will require Sams coding skills!

Another aspect of the shack that might need Sams code help, is the Ultimate 3S. This is working very nicely, but I want to get just a smidge more power! But, crucially, I also want to automatically switch antenna connections! The purpose of this will be to allow me to use one of my station receivers to receive WSPR signals, without having to manually throw the antenna switch when its time to transmit!

Hans Summers informs me that his latest firmware for the U3S, v3.12, can provide me with a pre- and post-delayed PTT signal. This is ideal. It also has an LCD backlight timeout function, which will be very useful for field use to conserve battery power. How exactly im going to flash the microcontroller I dont yet know!

Bernard ON7AN has emailed me with tables of results for a 3x BS170 PA using various supply voltages. It seems it will be very much worth the effort of adding a second voltage regulator to give me a higher supply voltage for the PA, and adding the other two MOSFETs. I also intend to change L1 (the PA choke) for a 10t bifilar transformer, as detailed on the QRPlabs website, as this also much improves the output, both in power and spectral purity.

So the plan for the U3S then is - upgrade firmware to v3.12; add all three BS170s; change L1 for 10t bifilar transformer; add regulator for higher PA voltage; add either a pair of 'dry' contacts for switching an external antenna relay, or add a relay internally plus an extra RF connector for the receiver.

Following my last post, which was a bit of a rant over the number of times I see questions from people who have huge monies tied up in shiney radios but nothing in basic test gear, Steve G7TAO has been Tweeting me, he says I should offer basic equipment kits for sale! It has to be said, if one of the first things anyone getting their license bought was a kit containing  a dummy load, digital multimeter, SWR meter etc, along with a simple to understand fault finding guide, there would be far fewer silly questions asked. Now, im not saying its silly to ask, of course it isnt, as its said there are no 'stupid' questions, but it is silly to ask for help when you havent even done the simplest tests to check your equipment yourself! Now, I would love to be able to offer such kits, but sadly I dont have the sort of ready cash that would allow me to invest in such a thing!

Whilst were on the subject of basic tests, whatever happened to people having wavemeters???

No comments: