We had two talks at the meeting on 23rd May 2014 – “Low Cost Microwaves” by Brian Flynn GM8BJF and “WSPR” by Brian Howie GM4DIJ.
1. Brian Flynn GM8BJF described how Low Cost Microwave reception is possible using consumer electronic devices: a PLL (phase-locked loop) satellite TV Low-Noise Block – LNB (the head unit that is placed at the focal point of a satellite dish), plus a tuner dongle based upon an RTL-2832U chip, allowing reception of the 10GHz (3cm) band. The total cost can be as little as £20. A Raspberry Pi computer can be used if desired.
Brian showed off his LNBs, dongles etc at the meeting.
Click for .pdf file of Brian’s talk. Or see slides following:
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2. Brian Howie GM4DIJ described and then demonstrated WSPR – Weak Signal Reporting System – which is a low-power beacon-like system developed by Nobel Prize – winning amateur Joe Taylor K1JT. It can be used from 136 kHz to 1296 MHz and has a sensitivity of -28 dB. Transmitters can be very low power – QRPP
The system requirements include a suitable antenna for the band(s) in question, an SSB transceiver and a computer with CPU of 1.5GHz or greater and 100MB of RAM and a 48kHz sound card.
The WSPR signal has an FSK speed of 1.4bps (bits per second) and a bandwidth of 6Hz. The length of the transmissions is 110.6 sec.
Using a low 20m dipole slung outside of the meeting room, Brian demonstrated WSPR reception on 14.095 MHz by pulling in signals from DF3KO, HB9RKF, LY2BUS.
Equipment used by Brian for the demo, L-R: 20m ATU, keyboard, FT-847, computer.
A 20m dipole was temporarily installed at quite a low level outside of the meeting room.
A WSPR transmission test with Brian’s FT-847 at its minimum power setting – only 2W – was made using the LRS callsign GM3HAM. Due to problems with the hotel’s WiFi system it was not possible to check the WSPRnet website for reception reports during the meeting. However, when Brian got home he recorded the information and has provided it for this report – see the illustrations below – remember this was with only 2W output. WSPRnet.org/drupal
WSPRnet log of reception reports of the GM3HAM WSPR transmissions from the LRS meeting.
WSPRnet map showing the locations of the GM3HAM WSPR reception reports