Low cost weak signal work from VLF to light

Well, I do get about a bit - in the spectrum that is!

1. At the moment I am running a test transmission on 8.977188kHz (precisely) to G3WCD who is trying to detect my VLF beacon in a 22uHz (yes micro-Hertz) bandwidth over several days. Chris is 32km away.
2. I am running WSPR on 28MHz with 200mW and, for the second day running, my QRP signals have reached Australia.
3. In 2 weeks time (when the grandchildren have gone home) I will be resuming my over-the-horizon QRSS tests on 481THz (red light) using my high power beacon and more sensitive detector. The signal is too weak to see by eye, yet the sensitive kit can detect it.

All three of these have one thing in common: the circuitry to do them all is very very simple and the kit cost just a few pounds to build.

Over-the-horizon 481THz optical signal from G4HJW last winter

In each case though the processing power of a PC is used to help extract weak signals from deep in the noise. Luckily the software in each case is absolutely free: Spectran and Spectrum Lab for VLF and optical frequency detection and WSPR software for the WSPR tests.

Homebase-10 28MHz wire halo antenna

Homebase-10 antenna on the back of my house.

28MHz (10m) is excellent at the moment. If you are looking for a small, simple, horizontally polarised, omni-directional antenna for 28MHz, you may want to build a copy of my Homebase-10 halo which was published in Practical Wireless a few years ago. This antenna takes hardly any space, is simple and inexpensive to make and works extremely well. All the parts apart from the wire can be obtained from your local hardware store (wood, brackets, screws etc). You should easily have change from a £10 note.

The results on WSPR today (see previous post) give some indication of how well it performs. Mine currently has a second halo nested inside the first giving me coverage on 50MHz too.

WISPY spans the globe

Today WISPY, my little 10m 200mW WSPR beacon, excelled itself getting spots from 5 continents with the best being a spot from Australia late this morning. 

Conditions in the last few days have been excellent. I keep reminding myself that if, as some are now saying, cycle 24 has already peaked and we are on the way down, conditions in my lifetime (and probably most of those reading this) are unlikely EVER to be as good again.  It is just possible there may be a second peak next year which is stronger, but I somehow doubt this now.

Unique 10m WSPR reports with 200mW and a halo today

10m QRP (2W) AM DX QSO

The excellent conditions on HF today

Just worked K1IED in Connecticut when using 2W AM to my halo antenna. The 10m AM segment is busy with some good signals from the US and Canada. When 10m AM is like this you just know 10m is wide open.

Although K1KW was an excellent AM signal I was unable to get through the pileup on AM to work him.

The very poor quality video below shows K1IED's 10m AM signal a few minutes after I worked him.

Simple 10m AM transceiver?

Yesterday, someone suggested that I build a simple 10m AM rig. Now clearly the best option would be a DSB transceiver for which I have many of the ideas clear in my head and implemented in my WISPY transceiver for WSPR.

However, I think it would be fun to make a 10m version of my Fredbox and Sixbox QRP AM transceivers. These are to be described in an article in Practical Wireless. For local nattering I think more output is needed on 10m, probably 1-2W AM. A low level series modulator followed by a single stage linear amplifier is a simple way to go on TX. For receive, a super-regen receiver would be fine for local use when the band is not busy. This is 75% of the time at least and almost 100% of the time in the evenings, most times of the year. It would be unsuitable when the band is very active, as currently during the day. A better AM receiver could be built, but nothing beats a super-regen for elegant simplicity, as long as it has an RF amp to isolate it from the antenna.

Maybe this is a quick project for a few autumn afternoons. A few watts of AM on 10m should span several miles locally with a vertical or a dipole.

472kHz Transverter Updated

A few people have now successfully copied the transverter design. I have just updated the webpage describing it and corrected a few errors on the schematic. Also, I have shown an additional low pass filter on the output which is prudent. It should not be necessary with a sharply tuned short Marconi or loop antenna.

See https://sites.google.com/site/g3xbmqrp/Home/472khz-transverter for the updates.

Rev H 472/500kHz Transverter Schematic (click to enlarge)

Petrol from air and water???

The BBC Business page carried a story this week about a company in NE England that is developing a technique to produce petrol from air and water. This sounds like something too good to be true, but if scaled up to production levels could be something remarkable.

"A British firm based on Teesside says it's designed revolutionary new technology that can produce petrol using air and water. Air Fuel Synthesis in Stockton-on-Tees has produced five litres of petrol since August, but hopes to be in production by 2015 making synthetic fuel targeted at the motor sports sector. The company believes the technique could help solve energy supply problems and curb global warming."

See http://www.bbc.co.uk/news/business-20003704 .

Another 472kHz transverter copy

LA5VNA's version of the G3XBM 472/500kHz transverter

Steinar LA5VNA has built a copy of my 472/500kHz 10W transverter and showed a copy of the design on the RSGB LF reflector today. Like G3ZJO, Steinar's is giving over 10W (more like 15W) output. To my knowledge there are now 3 copies of this design built and working. I recommend the addition of a second low pass filter to improve the harmonic content. The one from GW3UEP's QTX transmitter would be ideal (2 x 6n8 caps and a 15uH inductor).

IC7100

As yet, I have not heard any more firm news on price and availability of the IC7100.  There was a rumour that the US price was going to be around $1875, but I have no idea where this figure came from. If correct, it sounds far far too much.

Although I am a QRP person, this rig does appeal to me: the very comprehensive band coverage (including 4m) would make it a good main station radio. With the IC7000 being just over £1100 I would expect the IC7100 to be somewhat more than this, at least at first, but not as high as the figure above which would translate to around £1875 with import duties, VAT and dealer mark-ups.

IC7100 - will there be a QRP version available in the USA and Europe?

What would be really nice would be an "IC703 version" of the IC7100 i.e. a 10W pep version. Now if Icom  produced one of these a lot of QRP enthusiasts would sit up.

10m comes to life big time

This afternoon I took a look on 28/29MHz and the band was WIDE open. We are close to the sunspot peak - some would argue just past it - and at this time of the year conditions on the higher HF bands are at their very best. If you have never worked on 10m get on now (especially for the CQWW DX SSB contest next weekend!) and enjoy it whilst it is so very good. In 5 years from now the band will be very very different with just the occasional African and South American openings and Es propagation.

K1IED who worked many QRP AM stations on 10m today

When conditions really are this good, I recommend listening 29.0-29.1MHz for DX AM stations. Today there were some excellent AM amateur signals to be heard from the USA and Russia. K1IED was S9+ with his 250W to a big beam and he managed to work several QRP stations from Europe. In the past I have worked the USA with a few watts of AM but time prevented me having a decent try today. Andy G0FTD managed to work him with just 1W. You can see his video here.

Listening to 29.0-29.1MHz AM when the band is in good shape is like entering a time warp taking you back to how amateur radio sounded in the 1950s and early 60s. Wonderful.