Energy harvesting wireless bus bell push

The latest edition of Land Mobile Magazine (a magazine for professionals in the mobile radio business) has an interesting column showing how London Eco-Routemaster buses are being fitted with a novel sort of bell push (the kind you push to ask the bus driver to stop) which harvests energy from the action of pushing the bell to send a wireless signal through the bus to the driver. The bell push uses an energy harvesting chip from EnOcean a company that specialises in such devices.

The EnOcean evaluation kit (for professional developers) as shown on their website

This is the first time that I've seen a very practical use for energy harvesting. I assume that the device "harvests" kinetic energy (from the pushing action) and thermal energy (from the finger tips) but it must generate a few uWatts for this to work.  So, no batteries, no wires, wireless comms and good for 300k presses. There has to be a QRP application!

For more on this read the article on line at Land Mobile magazine. 

On with the projects.....

Back home now, so it is on with the autumn projects list.

Several people have been contacting me about the latest 472/500kHz 10W transverter. Someone in OK-land is designing a PCB and I hear a "dead bug" version has been successfully built in the USA - not sure whether an exact copy or "based on" - but it has already been used on MF WSPR with a report from over 2000km up the USA east coast. So, I will continue with refining this design first and then get on with the "WIPSY" 28MHz simple WSPR transceiver next.

The non line-of-sight optical beaconing tests will resume a little later when the evenings start to draw in. I want to set up a more powerful, semi-fixed 481THz optical beacon so that I can do a series of DX tests under various degrees of cloud cover. Tests last winter suggest much further will be possible than the 9km NLOS ranges achieved with clear air scatter when signals were audible by ear. By using much lower sub-carrier frequencies the optical detector sensitivity will be very much greater allowing even weaker signals to be detected on QRSS3 and QRSS30.

DXTV challenge?

Sorry for the absence of postings last week but we've been on holiday. No ham gear with me, but I did spot several nice HF and VHF yagis on my travels.

Several of my blog readers were DXTV enthusiasts (like me a long time ago), so I wonder who will be the first to identify where we were on holiday by this testcard copied at 4am this morning on the hotel TV? No prizes for giving me the country, but interested to know how many out there know the answer and whether or not this card has ever been copied in the UK on Band 1 TV. This was on 625 line UHF.

A plug for my son's MS concert in Oxford, Oct 7th

My son Tim Lapthorn, who is a professional jazz pianist, is holding a concert in Oxford on Sunday Oct 7th to promote his new album. All proceeds will be donated to the MS Society. You are most welcome to attend and enjoy.

Tickets may be obtained from http://www.oxfordplayhouse.com/ticketsoxford/?event=17386. The lunchtime concert is in the Jacqueline du Pre Music Building, Oxford starting at 1pm.

As the publicity says:

"Benefit concert for Multiple Sclerosis Society. Tim Lapthorn and his trio will play material from the forthcoming album, Transport (Pathway Records) which includes brand new original material. The group will also play reworkings of jazz/folk standards. Please come along to this very special event to help support a great cause!"

See also http://www.st-hildas.ox.ac.uk/jdpevent/tim-lapthorn-trio-ms-fundraising-concert

Progress on the WISPY transmitter

This afternoon I managed to do a little more work on the WSPR transceiver for 10m, building the oscillator/x2 multiplier stage and the balanced mixer for the TX part using a couple of 1N4148 diodes and a T50-6 tuned circuit. Carrier suppression is around 30dB without much effort. Next stages will be to add a linear amplifier to bring the DSB output to around 1W (500mW pep SSB carrier). Although I could combine the same mixer on RX and TX, I may stick with the Polyakov RX mixer as this is working so well. 

I should have added that with a linear PA, the WISPY transceiver should also be perfect for PSK31 as the 14.060MHz crystal (when doubled) will certainly pull to the PSK31 10m sub-band.

New ICOM all-band multimode

Icom have announced that they will be introducing a new multi-mode, multi-band radio called the IC7100 which includes 70MHz at 50W on some versions. This is, to my knowledge, the first time one of the big manufacturers has properly included 4m in the design. I know at least one Yaesu rig was capable of working on the band, albeit with some compromises. The new Icom rig has a separated control head with a sloping front, which is ideal for desktop operation and mobile.  It will be interesting to see the price and when it is likely to be launched. Also, whether or not they intend to do a 10W version (like the IC703) which was very popular with QRP enthusiasts.

A bit further with the WISPY RX

Although not in the best of shape today, I spotted CX1BP (11131km) and EA8FF on 10m WSPR today.  Not bad for a handful of cheap parts.

I had a bit of trouble today with the SE602 I was using for the TX part of WISPY (it may have been faulty but I was unable to get a clean DSB signal out of mine), so when I get back on the project after a week of interruptions coming up I'm going to go for the simple 2 diode single balanced mixer instead on TX. I know this works well and is less expensive.  The TX part can be simpler than the RX I believe.

Spots with WISPY RX

FR1GZ and others coming through just fine

This is the PC screen capture using WISPY as the 10m receiver for WSPR in the last hour or so. It is working just fine.

WISPY Schematic (more clearly)

For some reason when I put multiple images on a post it is not easily possible to see them clearly when clicked (at least with Firefox). So here is the schematic again. Clicking this image should bring up the full sized image clearly.

Hum fixed on the 28MHz WISPY WSPR RX

Rev B 28MHz WSPR receiver

Adding more audio decoupling around the oscillator and adding a common base FET RF preamp has totally fixed the common mode hum issues with my Polyakov mixer based DC receiver (WISPY) for 28MHz WSPR. Even running from a mains PSU I am getting good sensitivity and no hum. The board is working on the bench with no attempt at screening and appears totally fine. The oscillator buffer appears redundant, so has been removed.

Wispy Rev B (built using MeSquares)

One possible further mod is to make the input to the RF amp a series tuned circuit. This would be needed when the full transceiver version is made (back-to-back diodes would short the cap to ground on TX).  For now, I will leave the little RX running to see what I spot.