30 Apr 2010

Shack repainting

Just got back from a few days in Brittany and straight into DIY! The small bedroom used as the operating shack, and a bedroom for my little grandson when he comes to stay, was in need of a repaint, so everything was removed and the whole room is being repainted. All being well, the radio gear should be operational again by Sunday.

25 Apr 2010

8.97kHz RX started

Today I made the loop antenna for the front-end of my 8.97kHz receiver. This consists of 24 turns on an 80cms square frame (the most I could wind with the 0.2mm PVC covered wire I had). Next stage is to resonate the loop and add some gain and selectivity so it can be used with a PC based SDR such as SpectrumLab or with a stand-alone direct conversion receiver.

24 Apr 2010

My 2 year old grandson's CW

My grandson trying his hand at CW - despite being only 2yrs 5 months old!

Further 8.97kHz earth-mode tests

All being well, I'll be carrying out some more earth-mode (through ground conduction current) WSPR and QRSS tests on around 1kHz and 8.97kHz in about 10 days time. My aim is to achieve a new personal DX record for the mode using about 4W. My previous best distance is 0.3kms, but I'm pretty certain that with QRSS or WSPR this can be bettered. Remembering an earlier post, 18dB more system gain is needed to double distance using this mode of propagation.  This can be achieved by raising TX power or effectively improving the RX sensitivity, in this case mostly by better filtering and signal processing.

Got my shack back

For the last 9 days my little grandson has been sleeping in the single bed in my shack, so amateur radio activity was on  hold, especially in the evenings. Today he went back to London so the shack was free again. I went on 500kHz WSPR again with 1mW ERP this evening and managed 4 unique reports so far with best DX 306kms to PA3ABK. At the end of next week I'm planning on repainting the room, so will again be unable to operate for a few days.

G3RJV QRP lecture on the BATC streaming site

A talk called "QRP Why and How" by G3RJV is available now on the BATC website. Go to http://www.batc.tv/ and click on the 'Film Archive' icon and select "G3RJV QRP Lecture" from the drop-down list on the left hand side. The BATC site has a wide choice of videos available to view on-line as well as streamed outputs of amateur TV stations and repeaters.

23 Apr 2010

Sporadic-E season

As we approach the end of April, the first signs of the summer sporadic-E season will be appearing with decent, strong openings to Europe from the UK on the higher HF bands plus 6m, 4m and occasionally 2m. Every year there are also multi-hop openings to much greater distances such as the USA, Middle East, Caribbean and South America. This year, more stations will be using WSPR beaconing on these bands, so even fleeting openings will be noticed. My plan is to WSPR beacon on 6m whenever around and not working stations using QRP on 10m or 6m. It will be good to see some remarkable 6m DX on the WSPR database.

20 Apr 2010

Volcanic ash and propagation

My son, his wife and 1 year old son are currently stuck in Los Angeles: all came down with a virus and were unable to travel back to the UK after a 2 week holiday. Not that they could have flown anyway, because all the planes were cancelled as a result of the Icelandic volanic ash. They are now stuck there until May 1st, the next available flight, and that is assuming the volcanic ash is not an issue then.

An upside of the flight ban are the beautifully clear blue skies in the UK completely devoid of vapour trails for days now. Not sure what effect, if any, this has on VHF/UHF tropo or even sporadic-E conditions.

19 Apr 2010

DX birds: swallows have arrived

This morning I saw that the first swallows of the spring had arrived in our village. The swallows fly from Southern Africa all the way to Europe every spring arriving between late March and the end of April. Many nest in the same nest for years and years. The returning swallows, house martins and swifts remind me that this magical journey has been done for thousands of years and that we humans are just one small part of the Earth's diversity.

18 Apr 2010

New 80m AM transceiver kit from Small Wonder Labs

Dave Benson K1SWL has produced a QRP 80m AM rig with a crystal controlled TX and 50kHz tunable receiver. Full details at http://smallwonderlabs.com/Retro-75.htm including a PDF builders guide. There is also a Yahoo Group at: http://groups.yahoo.com/group/SWLRetro75/

17 Apr 2010

VLF amateur DX in Poland (290kms) on 9.6kHz

Marcin SQ2BXI has sent me this message today (April 17th 2010):
In last night we have VLF eksperiment in 9,6kHz in SP2KDS Club.Club signal copied Jacek SQ5BPF -distance 290km.
Movie tranmiter: http://www.youtube.com/watch?v=2sn6AmpkwlU&feature=player_embedded
and Polish page: http://www.sp2kds.pl/136khz/298-pierwsze-proby-nadajnika-w-pamie-marzycieli.html

Next experiments will soon have to 8.970kHz...
73! Marcin SQ2BXI

16 Apr 2010

Next 8.97kHz German test delayed 2 weeks

Stefan DK7FC says it will be a couple of weeks before his next VLF test transmission on 8.97kHz. This gives me more time to get the RX ready.

Icelandic fireworks - lots more to come?

Volcanic activity on Iceland appears to be getting worse with more activity recently. Disruption to air flights in the N.Atlantic may become more common. See this article in New Scientist.

15 Apr 2010

Ham and other books on eBay - still time to grab a bargain

My ham and other books including some magazines about the remote island of Tristan da Cunha (ZD9) selling on eBay still have a few days to run, so you still have time to get a bargain. Check out http://myworld.ebay.co.uk/rlapthorn

Even greater DX on 8.97kHz?

Stefan DK7FC has now got his 600W 8.97kHz VLF PA working and is waiting for a windy day to get his kite supported antenna up in the air. With a few dBs more power and more well-equipped stations listening/watching on 8.97kHz (33kms band) Stefan is hoping that >1000kms can be spanned in the next test transmission.

14 Apr 2010

Rockmite 20m kit (unbuilt)

For some time now I've had an unbuilt Rockmite 20m QRP transceiver kit waiting to be put together. The problem is I have so many other things on the go that a 20m QRP kit is way down the list and 20m was never my favorite band: I'd wanted a 40m kit but they only had 20m ones in stock when I bought it over a year ago. The kit has never been opened and I'm thinking about putting it on eBay. The current price for the kit in Europe is 45 euros plus shipping.

What would be a fair price?

Free power transmitters

Mike AA1TJ has sent me an interesting letter about using thermoelectric modules to generate a few milliwatts of power from body heat. This got me thinking about the other ways of "harvesting" free energy from vibration, movement, heat, mains hum fog, RF from radio stations etc. One bizarre idea from a few years back was a leg-brace that powered a mobile phone by leg movement (see left). There are ICs coming onto the market that scavenge energy from various sources allowing low powered devices to be powered for free. The challenge for us QRPers is to think of creative new ways to generate a few milliwatts to get signals across oceans. Who will be the first to work DX using RF rectified "off-air" from the local FM radio or TV transmitter?

13 Apr 2010

Talk request from Peterborough CLub

Having given a talk about "kitchen sink" simple radio last year, the good folks at Peterborough have kindly invited me back to talk about sub-9kHz radio. Date confirmed as Wednesday Aug 25th 2010.

11 Apr 2010

Some ham books of mine on eBay

Today I've put a few of my books for sale on eBay. They include RSGB and ARRL handbooks. If you are interested do take a look. If you live in the Cambridge area and want to pick them up locally then there will be no postage to pay. See http://myworld.ebay.co.uk/rlapthorn

Thoughts on VLF Earth-Mode and Induction DX

Earth-mode (through the ground conduction) and induction communication (mutually coupled coils) have an inverse cubed attenuation with distance. Think about this: I reached 0.3km with earth mode for an audible CW signal with around 4W RF and a simple 5m base receiver and 10m base transmitter. To double this range, all other things being equal, means increasing power by 18dB to 250W. To double range again means raising the power to kWs. Conversely, improving the detectable sensitivity threshold by 18dB (increasing the electrode spacings at each end, using WSPR or QRSS, etc) reduces in power needed for a given range dramatically: my 4W signal could be detected at 0.6kms or a just a 63mW signal could be detected by earth mode at 0.3km. In reality, especially in urban areas, water pipes and cabling may help "propagation" and achievable ranges may be greater. DX is relative, especially with conduction and induction at VLF.

10 Apr 2010

Still being heard on 500kHz

This evening the reports on 500kHz WSPR have been quite reasonable, despite the smaller antenna than a few months ago. Three unique reports from PA and from the UK so far this evening.

Blog visitor DXCC

Just noticed that this blog has been visited by people from 102 different countries this year so far.

Another new WSPR report on 500kHz

Last night I got another new 500kHz WSPR report, this time from PA0O in the north of the Netherlands at 440kms. This brings the total of unique WSPR reports on the band (via the internet database) to 83 stations plus a couple of others who reported by email. Overall the total number of unique reports on 500kHz including CW is 86 stations in 11 countries. Not bad for 1mW ERP. The most recent reports have been with my "degraded" antenna consisting of the 5m feeder to my 28MHz halo as a top capacity hat.

9 Apr 2010

W1VLF's page about 8.97kHz experiments

Paul W1VLF is getting operational on the 33kms band (8.97kHz) and has already been received 5kms away running 50W into a base loaded vertical. He has created a website to detail the progress as he goes along. At the moment the website only has details of his HUGE loading coil. See http://rescueelectronics.com/9-Kilohertz.html .

7 Apr 2010

82nd unique 500kHz WSPR report

This evening I got a new unique WSPR report, the first in 3 weeks, from Chris G3XIZ. This is my 82nd on the band. Chris has just started on WSPR and is likely to come on WSPR TX shortly. He is a very experienced 500kHz CW operator.

Auroral Chorus Recording (Paul Nicholson)

If you missed the streamed natural VLF auroral chorus emissions the other morning here is a nice recording made by Paul Nicholson in Todmorden UK.  It is a truly unbelievable sound, produced not by birds but by the auroral electromagnetic activity at VLF.

Moonbounce from Aricibo

The Arecibo Observatory Amateur Radio Club KP4AOwill be putting the 1000-foot radio telescope on the air for 432 MHz EME from April 16-18. It can be heard with a small hand-held yagi pointed at the moon. A 15 dBi antenna and 100 W will be enough to work us on CW.

Times of operation are:

April 16: 1645 - 1930 UTC,
April 17: 1740 - 2020 UTC,
April 18: 1840 - 2125 UTC

Tx Frequency: 432.045 MHz,
Rx Frequency: 432.050 to 432.060+
Tx power: 400 W,
Antenna gain: 60 dBi

Antenna feeders

Today I have to move my two main antenna feeders which wind their way untidily through the house from the back of the house, where they enter the building, to my shack in a front bedroom. This means getting up into the small loft space to run the cables across and down. Some years ago I had a bent end fed antenna on 10m squeezed up there and it managed to get to South America on QRP SSB. A small ground plane for 10m (with a capacity top hat to shorten the vertical section) would probably perform quite effectively.

UPDATE: Job done. It took about 1 hour and everything is fine.

6 Apr 2010

VLF Chorus audible in UK this morning

Auroral Chorus, a natural VLF emission that sounds like birdsong is audible in the UK this (early) morning. It is still audible at 0650z. Check out the VLF natural radio receiver at http://abelian.org/vlf/test.html as soon as possible, as it will soon be gone.

5 Apr 2010

Operating on 40m

This evening, as my wife was busy watching the TV, I decided to go onto 40m SSB with 10W pep and see what was about, not chasing DX. I worked a special event station OZ2SPACE  and a couple of other stations in Europe. Actually I must confess that this sort of rag-chew operating rather bores me these days: I'd far rather be building something or experimenting with WSPR. Working DX with QRP is fine on the other hand.

3 Apr 2010

G3XBM's 500kHz article in May's Practical Wireless

The follow-up article on my 500kHz transverter and WSPR experiments appeared in the May edition of Practical Wireless today. I hope it encourages a few others to give 500kHz a go, especially as my approach is a simple and easy one.

DF6NM and DK7FC active on 8.97kHz today

Not one, but 2 stations were active on 8.97kHz today in DFCW mode. Part of DK7FC's transmission was copied at 902kms away in Warsaw and DF6NM, running a much smaller station and antenna, was copied 21kms away. A first QSO on the 33kms band cannot be too far away now!

2 Apr 2010

4th Amateur VLF test transmission on 8.97kHz this weekend

Stefan DK7FC is planning to transmit again on 8.97 kHz VLF if the wind is able to support his kite antenna. The tests start Saturday April 3rd, at around 1000 UTC. The mode used will be DFCW-600 (dual frequency very slow CW). Several stations across Europe will be listening some using tiny E-field probe antennas.

1 Apr 2010

Temporarily QRT - shack becomes grandson's bedroom!

It had to happen sooner or later: our elder grandson, now 2.5yrs old, is staying with us a couple of times in the next few weeks as his mum and dad pack to move flat. Tonight he moved from the usual travel cot to a real bed for the first time .....in my radio shack. So, I shall be unable to operate evenings for a while so no 500kHz WSPR I'm afraid. Daytime operation may be possible, but apart from 10m WSPR I doubt I'll be able to do any serious operating. In the meantime he is fast asleep and looking very cosy.