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M0VGA's picture
Fri, 09/12/2016 - 09:56 -- M0VGA

Introduction

K1JT’s superb WSPR protocol has kept me busy/addicted for months, but until recently I was RX only, relying on the global network of other Ham’s WSPR transmitters so that I could spot and report them to the central WSPR database using my station to get an idea of propagation conditions, my antenna performance and just for fun!

I’ve been wanting to TX for a while but didn’t quite got round to configuring a PC and rig for that. What I really wanted was a simple & cheap standalone unit, negating the need for a PC and rig being tied up 24x7. Then Sotabeams came along and produced a USB powered WSPR beacon for small money and simple operation which sounded perfect.

What is it?

Description from the Sotabeams website: “WSPRlite is a self-contained propagation beacon transmitter. Once configured using a special Windows app, WSPRlite only needs a USB power supply to operate (no need to tie up your computer). WSPRlite operates on 160-80-40-30-20m. The unit contains filters for 30m and 20m operation. Operation on other bands requires a simple low-pass filter. WSPRlite is a low power device at only 200 mW but because of the clever encoding of the WSPR signal it has the DX capability of a 1 KW SSB transmitter (80W CW).”

Evaluation

In addition to the small beacon unit (a tiny 55x50x20mm), Sotabeams also provides access to their bespoke website www.dxplorer.net which takes a data feed from the main www.wsprnet.org site allowing you to see performance on a map, table or graph, or against another WSPRlite user on the same band in these formats. This is really useful and adds value to the existing WSPR proposition. Let’s say a station only a few miles away is doing better or worse than your station over time for example, then why might that be and what might you choose to do about it? See the photos attached for an antenna performance comparison recently on www.dxplorer.net between me M0VGA and G4JVF as an example. Naturally you still have access to the main WSPR website for their standard features.

WSPRlite has really low power consumption – even when transmitting on full power (200mW) the current draw is tiny. I measured the USB current in idle (54mA) and during a 200mW transmit on 40m (138mA). A small USB power bank could keep it running for days for example, really handy if you’re taking WSPRlite /P or just want to avoid mains PSU ripple. For some low quality USB adaptors this can be important to avoid harmonics, but in the absence of scientific equipment you can just use your rig and your ears to check for a clean WSPR tone on TX.

How much DX does 200mW using the WSPR protocol get you? Lots is the answer – with my modest OCFD wire antenna in IO93fx I’ve already got round most of Europe on 40m, Australia (albeit only once) and reached USA on 20m. All praise to K1JT’s efficient protocol where less really is more! QRPp :)

I’ve been mostly TX on 40m, as such I’ve needed to fit an external Low Pass Filter (LPF) to avoid stray harmonics as the WSPRlite built-in filter covers 20 & 30m only. As of December 2016 Sotabeams are developing a LPF kit specifically for the WSPRlite which may be of interest, or you could buy / build your own.

I’ve also been pleased to experiment with both TX and RX at the same time using two antennas on the same band – my standard Aerial-51 OCFD mounted externally in an inverted V formation for TX using WSPRlite and one in the loft space mounted in a fairly compromised position for RX using my KX3 with Win10 laptop. This has worked well but even with only 200mW the WSPRlite completely overloads my transceiver on TX of course! The 20% spacing of TX I’ve selected means this is only of limited impact though, allowing RX & TX operation from my station simultaneously – see spots/spotted map attached. Even with only 200mW I get more spots of my signal than I manage to spot other stations, probably due to limitations of a compromised loft mounted antenna for RX.

Setup & Support

Setup is easy – you do need to “RTFM” of course but this represents only a few simple steps: install the user-friendly Windows software, connect a USB lead which provides the power and data connection, add a few configuration details (call sign, band, TX power etc) and then you’re ready to connect an antenna (SMA adaptor/lead required!), power (eg USB charger or USB power bank) and set the timing which just involves pressing the button on an even minute using a synchronized clock as a reference. Timing is sensitive with WSPR (sub second) so getting this right is absolutely key to success. Try an MSF radio controlled clock or a web-based service such as www.time.is

In terms of support (not that you should need much), there’s an active support group on Facebook WSPRlite for DXplorer and of course direct support from Richard G3CWI at Sotabeams.

Most of the support issues I’ve seen in the Facebook group relate to people not RTFM, but an understanding of how WSPR works before getting going also helps to get the most out of it.

Summary

If you already use WSPR or just want to get started then I’d highly recommend the Sotabeams WSPRlite beacon for QRPp WSPR TX – small, good value and simple! WSPRlite costs £59.95 from Sotabeams.

73,
David, M0VGA
@M0VGA

Websites - WSPRlite Specific

www.sotabeams.co.uk/wsprlite

www.dxplorer.net

www.youtube.com/watch?v=ky64QG8dL64

Websites - General WSPR

www.wsprnet.org

https://physics.princeton.edu/pulsar/k1jt/wspr.html

https://itunes.apple.com/gb/app/wspr-watch/id532487317?mt=8

https://play.google.com/store/apps/details?id=com.glandorf1.joe.wsprnetviewer.app&hl=en