31 Jul 2010

136kHz QRP QRSS3 beacon video

This is a video showing the 2W QRP beacon for QRSS3 on 136.93kHz. Using a 20m spaced earth electrode transmit "antenna" it has been copied 8.6km away using an E-field probe antenna.

30 Jul 2010

2696km on 10GHz - new record

A new DX record for terrestrial (non EME) communication has been set with a QSO between D44 and CT on July 10th over an incredible 2696km. See http://www.hyperatlantica.ch/ for more information.

136kHz with QRP and earth electrode antenna

Today I increased the power from my QRSS3 136.93kHz beacon to 2W out of the PA into the 20m spaced earth electrodes. Another "ride about" test locally with the deaf FT817 and E-field probe RX antenna gave the following results:

At 2.4km good copy on the Spectran display
At 4.6km clear copy on the Spectran display.
At 8.6km the signal was detectable, but weak (see picture attached from Spectran screen).

These reports are roughly "end on" to the electrodes and I've yet to try other directions such as orthogonal to them. No attempt was made to match the PA output to the impedance presented by the earth electrodes which are around 40-60 ohms below 10kHz; I've not measured it at 136kHz yet.

Even with true QRP it looks like a range of at least 10km should be possible on QRSS3 (and probably WSPR) with a half decent receiver (better than my crude set-up) using just a 20m earth electrode TX antenna on 136kHz.  I'll leave the QRSS3 beacon running over the weekend on 136.93kHz from my QTH in Burwell, Cambs (JO02dg) and any reports and screen shots would be much appreciated.

Class E MOSFET PA for 136kHz

I'm trying to optimise an IRF510 MOSFET PA for use in the 136kHz beacon and later transverter design. Alan Melia G3NYK has a very useful page on practical approaches to class E designs for 136kHz at his page http://www.alan.melia.btinternet.co.uk/classepa.htm together with a useful Excel worksheet to come up with practical values for the output network. Class E using square wave drive on the input can produce very good efficiencies, thereby reducing heatsink requirements.

29 Jul 2010

136kHz PA progress

Today I started to modify my 136kHz QRP beacon to increase the power from 250mW to around 5W using an IRF510 MOSFET PA. I've still work to do to optimise the design but hope to complete this tomorrow.

More on time travel

A rather long, but fascinating article on the possibilities and issues with time travel is on Wikipedia.

28 Jul 2010

Quantum time machine?

Researchers at MIT may have come up with a way of travelling through time (and space) using quantum closed timeline curves or CTCs. It has always fascinated me that in quantum mechanics one can describe things as wave functions that have existed in all space and all time, past present and future. It takes a leap of imagination to consider the possibilities. For an explanation see http://www.telegraph.co.uk/science/7904712/Quantum-time-machine-allows-paradox-free-time-travel.html

This is the abstract of the original MIT paper:
"This paper discusses the quantum mechanics of closed timelike curves (CTC) and of other potential methods for time travel. We analyze a specific proposal for such quantum time travel, the quantum description of CTCs based on post-selected teleportation (P-CTCs). We compare the theory of P-CTCs to previously proposed quantum theories of time travel: the theory is physically inequivalent to Deutsch's theory of CTCs, but it is consistent with path-integral approaches (which are the best suited for analyzing quantum field theory in curved spacetime). We derive the dynamical equations that a chronology-respecting system interacting with a CTC will experience. We discuss the possibility of time travel in the absence of general relativistic closed timelike curves, and investigate the implications of P-CTCs for enhancing the power of computation."
Simple ??? See http://arxiv.org/abs/1007.2615

25 Jul 2010

136khz transverter

I'm getting ideas, and parts, together to allow me to build a small transverter for 136kHz. For the TX low pass filter I'll use either T68-2 or T157-2 (or something on between) toroids as these seem most suitable at up to 30W.  For the RX input tuned circuit I still need to find a suitable inductor, preferably tunable. Any ideas?

24 Jul 2010

Further 136kHz earth electrode tests

Later today I hope to do some more tests on 136kHz using 250mW QRP to the earth electrode "antenna". Last night I went out to look for the QRSS3 signal locally but realised the battery in my E-field probe was flat, so heard and saw nothing!  I expect to see the signal to well beyond 5km.

UPDATE: Well a repeat of the test on July 19th gave less encouraging results. Reasonable copy on QRSS3 at 1.5km but no copy visible at the same spot 4.6km away from the QTH (within 20m). Not sure what has changed as the earth electrodes are the same. Maybe the soil is slightly more damp?

PW author Gordon King G4VFV now silent key

Practical Wireless author Gordon King G4VFV died yesterday from stomach cancer. Gordon wrote many radio and TV related books and contributed regularly to PW. He lived in Brixham, Devon.

20 Jul 2010

Parts from Farnell - good service

For the first time I ordered parts from Farnell on-line yesterday. In the order were some 3C90 toroids (16mm and 42mm) to use in my 136kHz transverter.  I cannot fault the service: parts were here the next morning with free delivery. Just remember the prices on the internet are shown less VAT. For on-line orders there is no minimum order quantity.

19 Jul 2010

4.6kms with earth electrode "antenna" and 250mW on 136kHz

Today I tried some more experiments with my 20m spaced earth electrode "antenna" and small QRP beacon TX on 136kHz. I switched over to QRSS3 and  used the FT817, E-field probe and PC with Spectran to see where copy stopped. 1.5km from home and solid copy on QRSS3 when holding the E-field probe box as high as possible above the car roof. Then I drove on to a spot 4.6km from home and copy was again achieved, albeit not as strongly.  I'm certainly getting a signal radiated beyond the near field.  I'd like to check "antenna" directionality by looking for signal levels with the QRSS3 beacon at all compass points some 4-5kms away from the QTH.

In the meantime, if anyone near Burwell, Cambs wants to look for the QRSS3 signal near 136.93kHz I'll leave it running until about 8pm tonight when I have to switch off as my grandson is sleeping in the shack bedroom. Any reports would be amazing.

18 Jul 2010

Simple 136kHz beacon TX

Francis F6HSI very kindly sent me a "divide by 26" module based on a small micro-controller. With this I've built a small beacon transmitter for 136kHz (QRSS3 or 10wpm CW) by dividing down from 3560kHz, the QRP calling frequency on 80m. At the moment it only puts out 250mW and, with the earth electrode "antenna" used, the ERP probably considerably below 1uW.

Using my 20m spaced earth electrode "antenna" on TX and with a PA0RDT designed active antenna with a 19 inch whip antenna feeding into the (deaf) FT817 I could copy the 10wpm CW at 0.4km across the fields.

17 Jul 2010

New VLF DX record today: 5.6km on 838Hz earth mode

Today I resumed my VLF earth mode tests using 4W into 20m spaced earth electrodes. The aim of the test today was to determine the absolute maximum range possible by utilities assisted earth mode. Best result was 5.6km along Commissioner's Fen to the west of Burwell. Signals were just copied at this distance using the 80cm 30 turn loop and preamp into the PC running Spectran. A test a 6km resulted in no detectable signal.

An amateur solar plane "satellite"?

Recently, Qinetic managed to keep a solar power plane aloft for 7 days using its onboard navigation to keep it over a fixed location and using solar cells to top up batteries to keep it flying at night. Could such solar powered flying devices could be used as "satellites" flying a few miles above the earth to support amateur VHF/UHF repeaters and experiments i.e. a more sophisticated version of balloon experiments?  See http://www.bbc.co.uk/news/science-environment-10664362 .

16 Jul 2010

More 8.97kHz operation from Germany

Just seen this post on the LF reflector from Horst DO1KHS/DI2AN :
"As you know I am planning tests on Dreamers Band from 24. July 2010 on our fieldday at Erpeler Ley, JO30ON.  I will install a 800m earth base. Possibly there is a chance for me to leave the near field. So watch out for my signal.  Beside that there is much space for near field test. So I can compare my vertical antenna with the tv transformer to the big earth base. I will be online there via UMTS so I can give you the details here in the reflector."
So, some further 8.97kHz operation from Germany next week. More details of power, mode etc expected next week but he is expecting to run 100W with QRSS600 and plain carrier.

70MHz, Icom and Yaesu

There are now approaching 40 DXCC countries granting access to the 70MHz (4m) band and further countries are granting access every few months it appears. See  http://www.70mhz.org/bands.htm.  I do hope that some of the commercial "big boys" such as Yaesu and Icom start to make VHF multimode rigs that include 4m in future. It can't be too difficult to add this band. Apart from the latest ChineseWouxun FM handportables (see  www.wouxun.co.uk) and ex-PMR units, only the FT847 has 70MHz coverage. Imagine how operation on 4m SSB/CW would take off if Yaesu's FT817 successor has 4m coverage as well.

Technology Page

The Tech the Future page has an interesting mix of articles on new technology and is worth a read from time to time. See http://www.techthefuture.com/

13 Jul 2010

6m northern Es opening

Just took a look on 6m this evening and heard several northern beacons (GB3RMK, GB3LER, OY6BEC) and worked GM8IEM in IO78 square way up on the north of Scotland followed by GM4DZX in IO88 on CW.  Nothing else about, but this sort of opening to more northern areas is common at this time in the Es season.

12 Jul 2010

Fabulous noctilucent cloud image

Check out this image of a noctilucent cloud formation. See http://www.spaceweather.com/swpod2010/10jul10/CROISIER-Alexandre1.jpg

Soundcard based VLF receiver

SM6LKM has a very neat sound card based VLF receiver ideal for listening to sub-9kHz ham signals and SAQ on 17.2kHz. On his website you can download the files and instructions.

11 Jul 2010

Noctilucent Cloud storm

Recent nights have been good for these high altitude night-time visible mesospheric clouds which return strong microwave echoes, so should be good for 10GHz super-DX. See www.spaceweather.com
NOCTILUCENT STORM: Last night, sky watchers in Europe witnessed the finest display of noctilucent clouds (NLCs) so far this year. Electric-blue tendrils spread as far south as France:"I could see the NLCs from my window," says photographer Alexandre Croisier of Brittany, France. "So I rushed down to the beach to take this picture--a 6 second exposure with my Canon 350D.  

In England, the same display stretched from horizon to horizon. "There was quite a lot of detail visible, including swirls and tiger stripes," reports Mark Jones of Leamington Spa, UK. Even city lights did not overwhelm the NLCs. "I had no trouble seeing them from southwest London," says onlooker Maurice Gavin.
July is often the best month of the year to see these mysterious clouds. High-latitude sky watchers should be alert for electric blue in the nights ahead.

9 Jul 2010

iPhone electronics toolbox app

http://www.iphone.roskosch.de/electronictoolbox.php has a useful app for the iPhone (and Touch?) which allows you to carry out lots of useful electronics calculations.

Tour de France - live action

On our way through Burgundy today we got diverted because of a roadblock at St Fargeau which turned out to be because the Tour de France was coming through. We were able to watch the whole "circus" coming through over about 2 hours and took some great pictures and video clips from about 10m from the  racing cycles. I'd no idea that, before the riders came through, there are loads of vehicles throwing goodies to the waiting crowds. I managed to catch a Frisbee that my grandson will have when he next comes to stay. Great fun and an opportunity to be part of the real French experience, purely by chance.

7 Jul 2010

French food

Being in France currently it gives me a chance to try some good, and inexpensive food. This evening we've enjoyed a first class 4 course meal with wine that was superb. Carpaccio (marinated raw beef with a pear sorbet - tastes wonderful) followed by Loire fish, cheeses, and a delicious sorbet and tart and good coffee to follow. Tomorrow there are a few more chateau visits. I can recommend Logis de France as good value places to stay and eat.

Miracle Whip Yahoo group

Many years ago now I started a Yahoo group for people interested in the Miracle Whip and similar antennas. Amazingly the group now has over 1200 members.  Opinions vary about the effectiveness of the MW - in my opinion it is a compromise antenna that is inferior to many simple whip antennas - but it is easy to tune and with a counterpoise or reasonable ground does allow DX contacts on all modes when conditions are decent. See http://groups.yahoo.com/group/miraclewhip/ .

5 Jul 2010

French wedding

These last few days we've been enjoying our son's wedding in Brittany, France where the weather, company, food and wine have been great. Unlike an English wedding, this one has taken 3 days to get through! Great fun though with a day dedicated to eating crepes (pancakes) yesterday followed by a siesta in a meadow under the oak trees!