WSPR - how long to get a decode?

A question for my esteemed readers please.

Using WSPR (WSPR2 that is) the transmission burst is nearly 2 minutes long, but I believe strong signals can be decoded when only a part of the burst is received. My question is, how short a burst can be decoded?  Presumably it depends on how strong the signal is.

LB9YE was coming through quite well this morning but there was no decode of a very strong (I assume MS) burst at 1048 which lasted about 30 seconds. Of course with MS there may also be some Doppler shift which can mess things up a bit.

If you know about WSPR and can help with the answer, I'd appreciate it. I am particularly curious to know how WSPR might do with short MS bursts which can be strong but only last a few seconds. It also begs another question: there is now a longer version of WSPR (WSPR15) with better decode S/N levels. I wonder if a shorter version of WSPR has been considered? Then again I think there may be better modes for MS.

Night watch on 10m

Overnight, I ran WSPR on 10m just for fun. Although my 2W wasn't spotted until 0600, a couple of Germans were spotted here around 0400 presumably by Es or MS. Without modes like WSPR such brief night time openings would go unnoticed.

One Laptop Per Child project

When I left paid work in 2008, the One Laptop Per Child project was in its infancy. At that time the idea of a low cost PC or netbook was not really on the horizon, although the Linux 7 inch Asus EEE PC was a sign of the future.  As far as I can tell, the availability of low cost netbooks and tablet PCs has rather overtaken this project: low cost computing is now available from many sources.

The idea of making low cost computing and internet access available to under-privileged children and others worldwide is a noble one and one I fully support: knowledge is power and knowledge and education are  rights for all citizens of the world.

However, there seems to be some doubt about the success of the OLPC project 5 years on. It was a "good idea" but maybe market forces overtook it?

One of the reasons I like QRP projects is because they have the potential to make useful radio technology accessible to all at low cost.  Like the OLPC project, my dream is a simple, low cost, easily reproducible, HF transceiver design that really can produce useful results. There is something beautiful is "elegant simplicity" don't you think?

The £20 decent HF transceiver thoughts

I never fail to be impressed by what other people know and that I don't.  Several people have responded to my post about the "£20 decent HF transceiver challenge" with ideas that use PICs and similar micro-controllers in novel ways to generate SSB signals. In all honesty I wouldn't have a clue about how to start doing this, so I am VERY impressed.

My own approach to the £20 transceiver would be very low tech indeed: not an IC in sight probably and certainly no processors. Having said that, I would be very interested to see how such novel approaches could help to realise a low cost decent HF transceiver. As an example of this look at the HF WSPR transmitters produced entirely using a Rasperry Pi PC.

One thing that life has taught me is that it is impossible to know about everything: some of us know lots about RF (I am only a surface scratcher) whereas others know lots about software or something else. Some very talented people have a wide span of knowledge.

We should be grateful for the unique knowledge WE have and gracefully accept that others know lots more than us about something else. It never does any good to be stressed about what we don't know. In my work days I always told my staff never to be afraid to ask the dumb questions as there are lots of others waiting for someone to ask them!

Incidentally I have done nothing yet towards this design. Weather has been too nice to be inside engineering, HI.

Solar activity - a second peak?

Looking at the sunspot and solar flux levels in the last month, it looks like we are seeing evidence of a second peak to cycle 24.  Whether it exceeds the peak of November 2011 remains to be seen.  As the slide down from the peak(s) is slower than the rise towards the peak(s), we can expect reasonable HF conditions for several more years yet before we return to the quiet years when activity on 12 and 10m is very low indeed.

10m WSPR

My 10m WSPR system has been running most of the day with powers between 500mW and 2W. The only reports were from 4X1RF at 3519km. Best DX station copied here was DU1MGA at 10710km.

One of the reasons I like WSPR is that you can do other things at the same time whilst checking on how propagation is changing.  I am really looking forward to running WSPR in the quiet sunspot years on 10m and expect far more openings that might be found by calling CQ on CW or SSB with 5W.

New QTH work

New QTH rear garden - with the "roof tile feature"!

The work on our new (to us) QTH in Burwell is progressing steadily and if things go to plan we should be in later this summer. Today I was at the new location sorting out the garden - as much as I could - in the beautiful sunshine. There is still a great deal of builders rubbish and mess around and it will be some months before the garden can be properly worked on: for example, we have a row of roof tiles neatly stacked down the middle of the rear lawn and the front of the house has a pile or 2 of sand and bricks! The drive has a skip in it which is rapidly filling with neighbours rubbish too.

I am still thinking about ideas for antennas. At least in the new QTH I will have a dedicated shack where I can both build and operate: in 37 years at the current QTH this has not been possible. Currently I have called off the plans for VHF/UHF SSB/CW/data operation as I don't think there will be enough activity.  So, an effective, neighbour friendly stealth antenna for the higher HF bands and 6m will be the immediate priority.  

ISWL

Back in the 1960s, when in its heyday, I was a keen member of the International Shortwave League (ISWL). In those days its membership was measured in thousands from all over the world.

A few years ago I rejoined and enjoyed the monthly magazine called Monitor. I contributed a few articles too. Sadly, membership has been declining steadily and now, I believe, the membership numbers fewer than 300 people. The club keeps going as a result of the dedicated hard work by its voluntary staff who put together the magazine each month.

This last year I have started to take the magazine as a .pdf copy. It really isn't the same as a paper magazine you can take to bed and flick through. I find the pdf version much less satisfying.

After some thought, I've decided not to renew my subs this time as it is surely now only a matter of time before the ISWL folds. It served its purpose in its day, but those days have passed. This last month a final coffin nail was the closure of the ISWL QSL bureau, one of the last to process broadcast QSLs as well as amateur ones. 

The £20 DECENT HF transceiver challenge

Ideas for the £20 (or less) new HF transceiver so far, based on past experiences:

• VXO controlled, single band- GQRP crystals are inexpensive, but will allow around 10-15kHz easy pulling on 14MHz, more on 21 or 28MHz.
• Single balanced diode RX mixer - homebrew with low cost diode and toroid matching
• 2N3904s everywhere - these low cost (5p or less), ubiquitous transistors work well as oscillators, PAs (if several paralleled up) and are OK in audio stages. Maybe an IRF510 PA if a lower HF band chosen,
• Deadbug build - on  a small piece of copper laminate and low cost using a few MeSquares to help ease construction
• Low cost metal box - e.g. Maplin Aluminium box or a diecast enclosure. A mint box would be less expensive but too small.
• Few controls - a 1k pot for RF gain is all that's needed on RX
• Capable of running from a PP3 9V supply or external 12v - rechargeable 9V packs are low cost from 7dayshop.  69p each non rechargeable and £2.60 for a rechargeable one.
• Low-Z stereo headphones will be less expensive than a crystal earpiece these days - may need an extra audio stage but at around 10p for this, this is a price worth paying.
• Probably CW, although DSB not out of the question.
• No ICs at all - these are too expensive (maybe an NE602 might be cost effective and I'm not sure about a low cost IC for the RX audio).
• TX-RX offset essential - so that listening on the actual TX frequency is possible
• Does not have to be pretty - the aim is a transceiver that can be thrown in a rucksack and survive reasonable abuse levels.
• Wire antenna - a simple dipole or end fed half wave.
• At least 2W RF out, ideally 5W - so that the rig has a reasonably good chance of being heard on a busy band

Is anyone else up for this challenge? The target is a really credible HF transceiver with decent, not compromised, performance that can be made with all new parts for less than £20.

GQRP club sales offer some very good prices for components if you are a GQRP Club member. If you are not a member then you are missing out on the very best magazine (SPRAT) available. I cannot recommend SPRAT and the GQRP club highly enough.

Back home again

Well, the week long holiday in South Devon is over and we are back home in Burwell again. The portable HF operation was very successful and enjoyable, operating from a mix of locations, mainly clifftop sites with excellent take-offs across the sea to the USA, Africa and S.America.  Average QSO distance with 2.5W SSB was over 3000km, with several QSOs with the USA and Canada on the higher HF bands using just 2W and a short base loaded whip.

In all, not that many hours of actual operation in between just relaxing and enjoying the very best part of England. I say this as this is my "promised land", where I was born and brought up. Out of season, when there are few tourists around and in weather like we had last week - perfect wall-to-wall sunshine - there is honestly no better place on this planet, but then I am biased.

My video, taken yesterday, shows the town of Salcombe in South Devon where I lived until I was 10 years old. In those far off days I took all this for granted: I knew nowhere else really. The view from my junior school window was up the beautiful estuary and the sunlight playing on the water would reflect on the classroom wall. Sunny days indeed, long before ham radio and the worries of adulthood.

Now I'm back home my challenge is that £20 (all new) portable backpack transceiver with decent performance that I've been challenged to design. In between cutting grass, weeding and paying the bills!