Free power QRPp transceiver or beacon?

The idea of powering a low power receiver, or even a transceiver or QRPp beacon, from free, otherwise wasted, RF energy that is all around us appeals to me. A few people have been toying with this idea and there are even some commercial ICs likely to appear which "harvest" energy from stray RF and even vibrations. The circuit shown here is from the excellent site by KE3IJ (R.Andersen) and shows how to use 50 or 60Hz mains "fog" and stray RF to power a simple receiver. See http://www.tricountyi.net/~randerse/nopower.htm .

See also Ben Tongue's crystal set pages for a circuit using a supercap to store harvested energy which is then used to power a micropower op-amp.

A "harvester" QRPp transceiver or beacon which derives its energy from stray RF, storing this is in a supercap and allowing brief periods of transmission at very low power is worth developing I think. I have not seen such "harvesting" circuits used to power a transceiver or beacon before but for a uW level beacon this should be feasible.

GQRP Club SPRAT 140

The latest copy of GQRP's quarterly magazine SPRAT arrived here today and it was nice to see my little Sixbox 6m AM transceiver featured on the front cover, alongside my car keys! Also in this edition was my article about WSPR weak signal beaconing. Since the article was written back in the summer I have been using WSPR almost daily on all bands from 500kHz up to 50MHz.

Just £6 annually gives you GQRP Club membership with 4 article-packed issues of SPRAT magazine a year, as well as access to the GQRP QSL bureau and club sales items such as toroids, QRP frequency crystals, transistors and ICs at good prices. As a GQRP club member, you can get a CD with all 140 editions of SPRAT magazine for just £4. It's worth joining just for this alone. If all other magazines had to go then SPRAT would be the one I'd still get as it is the best.

Rybakov Wideband Vertical Antenna

For those looking for a simple vertical antenna that can cover a wide range of HF bands you might want to try the Rybakov antenna. This is what IV3SBE says about it:

"Multiband NO TRAP NO GAP Antenna. This Antenna is a small wonder, easy to build and allow you to work all HF spectrum with your TRX and it's internal ATU. It consist of a matching device at it's feed point to enable lowering the impedance of a randow wire. Winding 14-18 turns of twin insulated wire 1.75mm over an AMIDON T-200-2 RED Toroid type and wiring as the image on your right will enable you to perfectly feed the radiating element . Once finished, place it in a waterproof plastic casing used for electrical wiring suitable for UV radiations. Complete it utilizing a SO 239 socket and two Stainless Steel Bolt to ensure long life under external condition. Connect, to the Wire Terminal, a lenght of wire ranging from 7,6m onwards depending the frequency range we would like to obtain. With 7,6m we can easily cover from 7Mhz upwards, for better performance we suggest to leghten the wire up to 8,6 > 12m so to have a better performance staring from 3.5 Mhz. The Antenna will perform well in vertical position utilizing a retractable fiberglass pole ( we use a 9m fiberglass fishing rod ) so to deploy the Antenna in seconds just hook the wire to the top part and extend the elements fully. You are now ready to operate ALL BAND NO GAP making use also of the internal ATU of your TRX for portion of band where SWR is above 2:1. See Below the Antenna fully extended and in Action during a short Portable Expedition."

See http://www.iv3sbe.webfundis.net/html/Rybakov806.htm

IC703 TX failure

After many years of excellent service my IC703 decided to expire on TX last night: power started to drop when running 5W on 30m then 80m (good matched load), then nothing, although I could detect a signal on the FT817, probably at mW levels.

I believe this is a common IC703 issue. Does anyone have data on how to fix this and where I get the spare parts? I believe it is either a driver or PA failure.

Incidentally Martyn Lynch quoted £45/hr plus parts and shipping to do a repair. I don't expect I'd see any change from £100.

This is the first time in 42 years of operating that I have had ANY piece of amateur gear fail, confirming that generally equipment is reliable if used carefully, so I cannot complain.

Genesis Q5 QRP kit from Australia

The Genesis Q5 is a radio transmitter kit designed for novice kit builders and QRP radio enthusiasts. With 40 parts and a professionally manufactured circuit board, the Q5 produces 1W QRP crystal controlled on the international QRP frequencies. Price: US$ 19.95 + postage. For more information visit http://www.genesisradio.com.au/Q5/ . Watch two-minute Q5 promotional "Hook 'em on" video produced by 12 years old Josh, VK2FJDX: http://www.youtube.com/watch?v=5klKvQHqqJ4

Ferrite rods as transmitting antennas?

Assuming one is running very low powers (milliwatts) and use (say) 10 ferrite rods "in parallel" for the core is there any reason why a single thick turn on a ferrite rod, suitably tuned and matched, would not make an effective transmitting loop antenna on the lower HF bands or 500kHz? As long as the core doesn't saturate I cannot think why this would not be feasible.

I have just been told about a Yahoo group for people experimenting with ferrite rods. The owner, John Popelish, experimented some time ago with stacked ferrite toroids to make a ferrite rod.

http://groups.yahoo.com/group/ferriterodantennaexperimenters/

17m WSPR

Just put the WSPR beacon on 17m and received 3 reports from W8LIW at 6105kms when using 5W to the 15m end-fed wire. Activity on 10m WSPR is very low today with no reports of signals.

Sound powered transmitters

A few people are currently experimenting with sound powered RF transmitters, generating the DC power to run a microwatt level oscillator from the human voice or morse key activation. There have been a few such ideas published. What appeals to me is a sound powered TX coupled with a crystal set RX. Such a system might get a mile or two as long as the station at the far end was running a few watts of AM or MCW. This would be the ultimate in QRPp!

There is a patent for this sort of sound powered transmitter - see United States Patent US2981833 dating from 1955 which has some schematics. This is available to view at http://www.freepatentsonline.com/2981833.pdf

DXTV - 1938 style!

There is a fascinating clip on YouTube of 405 line BBC TV being received in New York (from London) presumably by F2 or multi-hop sporadic-E propagation in 1938. This is the only example of a pre-WW2 live 405 line BBC TV transmission known to be recorded. The image shown left is of the female TV announcer. The signal comes and goes as the QSB takes the signal out of sync. Totally fascinating.

See http://www.youtube.com/watch?v=4SniB0JEDGs

Back from holiday - WSPRing soon

Just got back from 2 weeks in Greece visiting the ancient sites. Hope to get back WSPRing on 500kHz within a few days after I've caught up on things at home.