Monday, 27 February 2017

LoRa

200km from a low power 868MHz device?

https://www.youtube.com/watch?v=adhWIo-7gr4

See this video for very long range experiment using LoRa modules. LoRa is a spread spectrum (125KHz bandwidth) data mode which can be received at very low signal levels, and its main use will be for the Internet Of Things - smart meters and other stuff which only needs to transfer a small amount of data. This is all done in licence free bands that are normally used for low power data such as remote controls.

https://www.thethingsnetwork.org/

There is also The Things Network, connecting LoRa gateways around the world which anyone can access (it's a bit like the amateur radio APRS gateway system but for LoRa devices). There are already a few set up in the Liverpool, Manchester and Lancaster area.

The YouTube channel above has instructions on how to build both a node and a gateway for LoRa. 
You can get LoRa modules for the 433(in the amateur band but low power devices are used here), 868(main band in Europe) and 915MHz (USA) bands.

It's interesting to see that there's so much experimenting with radio going on outside of the usual amateur radio bands and organisations. To me, anything that could possibly get more than a few hundred metres is worth trying (further than your average indoor Wi-Fi access point).

Monday, 6 February 2017

WSPRlite

My WSPRlite arrived on Friday, from SOTABeams. A 200mW WSPR transmitter, needing no PC or any cables except power (micro USB) and antenna (SMA).



And while I'm taking photos in the kitchen, here's Friday's tea


One button, one LED. Press the button once at 2 seconds past an even minute to begin the first transmission. I use the Clock Sync app on my phone to get an accurate time via the internet.

I've no permanent HF antennas at home so I tried it in the car, with a Watson Multi Ranger antenna. The mag mount is a bit small for the HF bands but I found it worked OK on 14MHz, with 20 reports in the first hour of use. I powered it from a TP-Link power bank, and at 180mA on transmit and under 50mA waiting, it will last for days on that. My USB power monitor won't measure below 50mA so read zero except when transmitting.
At that low power, most SWR meters won't let you calibrate to full scale, but as long as they have a separate reverse power reading, you can see when the SWR is OK (3:1 would be 25% reflected power, 2:1 9% etc.).
 No connection at all to the car electrics

 The next time I tried it in the car on 14MHz, I got 2 reports from the USA.
Compared to the usual 5 watts I'd been using for years on WSPR when I had a proper HF radio, 200mW (14dB down) needs a bit more effort - 5 watts will work into just about anything with WSPR, especially with an auto tuner. At 200mW an auto tuner might not even start to tune on transmit. I think the mobile whip is just as efficient as a random length of wire.

On Saturday I made my first SOTA chaser contact on DMR (or any digital voice mode). I've made QSOs from summits on both D-Star and DMR before though. When I was scanning round, I heard some activity on 438.6125, so quickly changed over to the DMR radio and spoke to 2W0SEY/P on Moel Famau (G/NW-044).

For tea on Saturday we went out to One Restaurant in Barrow. The last time I'd been there was 3 years ago for my birthday and tried The Challenge of eating a massive burger, hotdog and fries in 45 minutes (and failed). This time I settled for the normal menu
 "Alligator Cooler"
 Piri Piri Burger
Chips, Cheese and Gravy
"The Black Hole"


Wednesday, 1 February 2017

RF Explorer

Some channel power measurements (all in a 5MHz bandwidth) on my RF Explorer on the tri-band colinear.
I've had the RF Explorer for over 5 years but only just tried the PC software for it.

930 - 935MHz: O2 (3G) base stations


 390 - 395MHz: Airwave TETRA base stations

955 - 960 MHz: O2 (2G) base stations



452.5 - 457.5 MHz: Various business radio users, mostly continuous trunking data and DMR



 950 - 955 MHz: Vodafone (2G) base stations - a lot lower than O2's sites here

I've ordered a WSPRlite to get myself back on HF, if only at very low power.