28 Oct 2012

More DX on 10m today

This must rank as one of the most fun CQWW DX contests I've taken part in. Plenty of DX could be worked with just 5W SSB from the FT817 and my small Homebase-10 halo today and yesterday. If anything conditions were better on 28MHz today than yesterday.
HK1NA (worked today) operating CQWW
 ...and in contrast G3XBM operating CQWW today!
Stations worked include LR3M, LP1H (Argentina), C5A (The Gambia), HK1NA (Colombia), CR2X, CR3A, CT3HF (Azores), CN3A (Morocco), ER3AU (Moldova), A65BB (UAE), 3V8BB (Tunisia), ZW5B, ZZ2T, PY1NX, PS2T (Brazil), EY8MM (Tajikistan) plus loads of US, Canadian and other stations. My ears are sore with SSB signals! I have now filled my third page of contacts in the logbook.

Some of the operating skills were amazing: PJ4X was working stations at a rate of one every 5 seconds. He spoke so crisply and quickly that by the time I'd called he'd already worked another station! 

First signals seen on JT9-2 mode

On 500kHz this morning PA0A and G3ZJO were testing with the new JT9-2 weak signal mode. Not yet copied Eddie, but PA0A was coming through well. This is a screenshot with his decoded signal overlaid.
500kHz first JT9-2 signal received

Choice DX on 10m SSB today

The CQWW DX Contest continues to brighten up things on 28MHz SSB, although the competition is fierce for some of the rarer stations.

XV1X QSL card
Some DX is surprisingly easy to work though, responding after just a couple of calls with QRP.  My 5W QRP SSB got through to EY8MM and A65BB but failed (so far) to work XV1X (Vietnam) or JT1BV (Mongolia).

27 Oct 2012

JT9: a new digital mode for MF and LF

Hot news from Joe Taylor K1JT on the RSGB LF Yahoo group this evening about a new 9-FSK digital communications mode (for 2-way QSOs rather than beaconing) optimised for MF and LF bands. With winter approaching and better LF conditions, this is an exciting development.
The wide graph display for JT9
"I invite you to try a new digital mode called JT9, designed especially for making amateur QSOs at MF and LF. JT9 uses the structured messages introduced in 2003 for the JT65 mode, now widely used for EME and for QRP operations at HF. JT9 can operate at signal levels as low as -27 dB (in a 2500 Hz reference bandwidth), with one-minute timed transmissions. It also offers slower transmissions of 2, 5, 10 and 30 minutes duration, and the slowest mode can decode signals as weak as -40 dB. With one-minute transmissions, submode JT9-1 has a total bandwidth of just 15.6 Hz -- less than one-tenth the bandwidth of a JT65A signal. The other submodes are narrower still: a JT9-30 signal occupies about 0.4 Hz total bandwidth.

Note that these JT9 sensitivity levels are comparable to or better than those of WSPR, which uses simpler messages and is not intended for making 2-way QSOs.  JT9 has much higher throughput and reliability than QRSS CW, including DFCW modes.

JT9 is implemented in an experimental version of WSJT called WSJT-X. Some further details can be found at http://www.physics.princeton.edu/pulsar/K1JT/WSJT-X_Quick_Start_Guide.pdf , and an early version of WSJT-X can be downloaded from

Please note: WSJT-X is in an early development stage. A number of improvements and enhancements are already in the works, and others will surely be added. 
Your feedback will be much appreciated!

-- 73, Joe, K1JT"

CQWW SSB DX contest 2012 (28MHz) - a recording

Well, Oct 27th 2012 and the CQWW DX contest is in full swing. 28MHz is filled with SSB stations all the way from about 28.25MHz right through to 29MHz, with even a few SSB stations on top of the AM users around 29.05MHz. Conditions appear to be excellent for the contest and they are likely to hold up for tomorrow too.  I was able to work 5 continents in 50 minutes this morning with 5W SSB and a halo.
In 5 years or so, this day will seem like a dream with 10m probably dead and devoid of activity. So, for posterity, I made a sound recording late this morning of the 10m band as I tuned across it and later this video at around 1630z.

Here is an earlier sound recording CQWW SSB DX contest 1125z October 27th 2012. Recorded near Cambridge, UK.  Feel free to share/use this recording and video. I only made them for posterity so I can remember, in years to come, what 10m was like at a sunspot peak.


This week saw the launch of Windows 8. Also, Google launched a new Chromebook 11.6 inch PC manufactured by Samsung which is getting rave reviews. Chromebooks use Google's Chrome OS which is very much linked to Cloud based operation.  The new series 3 Chromebook is only £229 from John Lewis complete with a 2 year warranty. In the USA it is available for $249. Now, when I looked I could not see any amateur radio apps for this OS. They will surely come though.
UK retailers include PC World, Amazon and John Lewis. They seem to be selling FAST.

Although I am not sure why, this PC really appeals to me: it is simple, small and effective. The local machine remains uncluttered and safe to use as most of the applications work remotely "in the cloud" although Gmail, Goodle Docs and lots of other apps will work without an internet connection too.

Has any reader used a Chromebook? What were your impressions?

26 Oct 2012

VLF DX radiated test results

My days long, continuous carrier test with G3WCD (32km) and G3ZJO (around 50km) around 8.977188kHz ended yesterday. I was using my 20m spaced earth electrodes with 5W out of the PA. The test was to see if anything at all could be detected well beyond the 6km I can repeatably obtain with QRSS3 earth-mode (through the ground) communications.  Despite the hint of a signal a couple of times on the G3WCD 45uHz and 22uHz grabbers, these proved to be false signals and nothing was detected.

Using Spectrum Lab, locked to a VLF MSK signal I am able to measure my TX frequency with VERY great accuracy, in fact to an accuracy of less than 1mHz. What this showed up was that my crystal controlled TX drifted (very slightly by HF VFO standards) about 13mHz over the 4 days of the test. Starting frequency was around 8.977177kHz and the final frequency 8.977190kHz. With shack temperature variations it may have moved slightly higher or lower too.

When the RX stations are looking for a very very weak signal in a bandwidth of 22uHz this means the signal is only "within band" for the FFT software to analyse for a brief period before drifting out of the measuring "bucket".  To have ANY chance it will be essential for me to lock the TX frequency so that it stays within a few uHz over a period of days. This could be done using a GPS reference signal or using Spectrum Lab. It is the latter that I shall be trying - receiving a VLF MSK signal on one antenna as the reference, then using SL to synthesise the continous TX carrier which is transmitted on a second antenna.

In reality to get 32km on VLF with my set-up was always a "long shot", but all parties agreed it was worth trying and we have all learned a lot in the process. Experimentation is the name of the game and failure is as important as success.

It may be some time before I try the long range VLF tests again: I hope to have over 100W next time and a super-stable TX signal. Who knows, we might just succeed next time.

For information on these software packages (all free) that I use at VLF see https://sites.google.com/site/sub9khz/software .

25 Oct 2012

My 10m halo - soon time for an overhaul

After the CQWW DX contest this weekend I plan to take down my Homebase-10 halo and rebuild it. The birds have managed to tear away at  the nylon rope supporting the nested 6m halo and the wooden supports now look a bit weather beaten.

So, I plan to replace the wooden cross frame supports with PVC pipe or fibre glass rods and re-do the wire elements. These have been up in all weathers for around 4 years now, so a few pounds on a remake is justified. The antenna works so well and is so small that I cannot think of a better antenna for the 10m band short of going to a beam which would be huge by comparison and need a rotator. The neighbours are quite used to it too, which is good.

Ten-Tec Argonaut VI latest

Ten-Tec is working on a new Argonaut transceiver called the Argonaut VI.  Details remain sketchy but at K4SWL's website http://qrper.com/tag/model-539/ there is some news that 25 units are going through a pilot run currently with production likely towards the end of the year.

A photo of the Argonaut VI on the K4SWL website (linked)
There are not enough details available to make any judgement on this new QRP transceiver. As far as I can find there is nothing at all about it on the Ten-Tec website. Some rumours are that it will NOT cover 12m and 6m and neither will it support 10m FM. Who would produce a brand new HF radio without at least all 80-10m inclusive bands and modes?

Unless the price is very attractive and the unique features substantial, then I just cannot see it competing well against the 11 year old FT817 and the new Elecraft KX3. The pictures seen so far show a simple looking radio, some would say plain, but with what is supposed to be a very decent receiver along the lines of the Ten-Tec Eagle.

What's cooking Ten-Tec? Are you still going ahead with this transceiver? If so, please can we have some firmed-up specs and prices?

24 Oct 2012

CQWW DX SSB contest this weekend

Although not a serious HF contester - I have never submitted a log -  I do enjoy a fling in the CQWW DX SSB contest at the end of October each year, usually on 28MHz.

The most I can run is 5W pep but, if conditions hold up, there should be little problem in working stacks of US and Canadian stations as well as loads of others worldwide.  This year I have a speech processor which appears to make a good 1-2 S-points difference and makes working DX much easier.

Especially towards the end of the contest there are plenty of big contest stations looking for new contacts. If you want to work some good DX plus new US states and Canadian provinces, then this coming weekend will be your best chance.  In my experience running QRP SSB is no barrier at all to working LOTS of DX in this contest.

Some people love contests on HF and VHF and others hate them. Personally, I am happy to enjoy the DX opportunities they provide and tolerate the heavy band usage they bring, albeit for 48 hours in the case of the CQWW.
CQ zones map
Exchange is report and CQ zone. In the UK we are zone 14, so a typical report would be "5914"

23 Oct 2012

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.

22 Oct 2012

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

21 Oct 2012

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)

20 Oct 2012

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).


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.

Just maybe DX on 8.9755kHz?

Last week G3WCD, who is 32km from me, monitored my very long carrier VLF transmission to see if he could detect anything. I transmitted a continuous carrier for a day with a 1 hour break during the period. On his 45uHz bandwidth VLF grabber he noticed a signal (me?) very close to my stated frequency that disappeared the day after, when I was not transmitting. So, starting late tonight, I am repeating the test with an even longer continuous transmission (days if need be) to see if the carrier re-appears on his screen. Should the signal appear, I will drop carrier for a day or so and then re-key the TX to see if the signal re-appears.  At this distance I would be very surprised if anything would be detectable, but this is certainly worth this second, longer, try. Chris G3WCD has a VLF grabber at http://g3wcd.bplaced.net/.

16 Oct 2012

Mixed result on 8.9775kHz today

Earth-mode test results. Distance to "best DX" location 6km NW of TX
Today I tried a few new things:

(a) A larger coil for RX: 12 turns on a loop with a diameter of approximately 3m, that could be placed on the ground.
(b) Transmitting a callsign in 10wpm CW followed by a 60 second carrier.
(c) Trying to pick up the signal at new locations.

Results were mixed:

The larger coil is really no better than the 80cm 30t coil placed on the ground. I was hoping it might be better. Failure!

Although I tried several locations in a new direction (SW) I only managed to copy my beacon signal at one new test location 4.4km away in the village of Swaffham Bulbeck. Tests at a closer location in that direction gave no copy at all. Also tests at 3 more distant locations (max 7.5km) were complete failures with not the slightest hint of anything there.
Much weaker signal copied at 4.4km SW today (nowhere near strong enough for QRSS3)
The trick of sending 10wpm CW followed by a long carrier worked: when the signal was weak it could be copied on Spectrum Lab in narrower bandwidths than I use for QRSS3 as the dash is 20 times longer. This helped me positively ID the signal in Swaffham Bulbeck. On QRSS3 the signal would have been lost in the noise. Best signals appear to be out in the Fens to the NW and to the south (on the chalk hills). I have still to try NE with sensitive kit.

I am still totally puzzled by how the signal propagates through the ground. Placing the loop right over water pipes in the road failed to detect anything where I expected copy at about 4km SW, and the one successful location at 4.4km  SW was on a corner of a road close to some overhead (11kV?) lines but not near water pipes as far as I know. So, I tried other places close to these overhead cables and copied nothing! There must be something that is common to all successful places that is not there helping the signal at other places. I am still trying to think how to find what this is!

I am extremely doubtful of success on these DX tests we are running over the next 24 hours judging by the mixed bag of result very locally. Certainly it will require the very narrow bandwidths to see anything at all from the miniscule radiated component.

15 Oct 2012

KX3 in stock at Waters and Stanton

I read that W&S now has the Elecraft KX3 in stock for immediate delivery. This is a far cry from the 8 month lead-time when deliveries first started.  The supplier is  taking a profit from selling the units, but at least you know the price. My experience when importing kits and parts from the USA into the UK is that the import duty and VAT and Parcel Force "handling charge" (a rip off!) can add a significant amount to the final price, and a degree of uncertainty.

I am still tempted by the KX3. It is many years since I last bought a commercial rig and this one, although expensive, does tick all the boxes: small, 10W, excellent SDR receiver, coverage to 6m (soon 2m), auto ATU, speech processor., etc.


Workmans Broadcast Radio

When I had my kitchen refitted recently, the workmen had one of these radios on the go all the time. I guess they are designed to be rugged and stand a lot of abuse. Theirs was covered in plaster and dried on dust but it still managed to work! They are not cheap and not that small, but I guess it is "horses for courses" as they say.  Any readers used one of these?

Makita BMR-101 Job Site Radio with DAB + AC Power Adaptor (Blue) (Google Affiliate Ad)

32km test on 8.9775kHz VLF

Tomorrow evening, Oct 16th, at 1700z I'm starting a 24 hour continuous carrier transmission on 8.9775kHz using my earth-mode system and 5W beacon TX. The carrier will be dropped for a few hours at some time (not previously disclosed) during the transmission to help later ID.

Chris G3WCD, who is 32km west of me, is trying to see if anything at all is detectable from my earth-mode set-up at that distance. We both do not realistically expect success, but with the ability to look in uHz bandwidths using Spectrum Lab it is worth a go.

If there is anyone else closer to Burwell, Cambs JO02DG85VD who wants to try looking as well, please let me know ASAP. Ideally stations in the 10-20km range.

14 Oct 2012

MF WSPR activity at an all-time high

MF WSPR activity this evening
This evening the 472 and 500kHz bands are humming with WSPR signals and those monitoring for them. At the last count there were 40 stations either on RX or TX WSPR. No great DX so far this evening here with the best report being from an SWL F59706 who is 560km south of me.

Best DX yet on 8.97kHz earth-mode: 6km QRSS3

Today I went out to my usual test sites to check the performance of my latest VLF earth-mode system. For the first time, my RX loop and preamp could be optimally tuned in the field. At 1.6km the 8.978kHz QRSS3 beacon signal was rock solid (see first image).
5W 8.978kHz QRSS3 earth-mode signal at 1.6km (STRONG)
5W 8.978kHz QRSS3 earth-mode signal at 6.0km (10dB S/N in 0.67Hz BW)
I then moved on to a number of other locations eventually arriving at a spot 6km from the 5W TX where previously I'd only ever managed copy with a constant carrier or QRSS30 (30 second dot CW). This time the signal was about 10dB over noise in 0.67Hz bandwidth on QRSS3, my best ever result at this range (second image).

In the coming week I'll be looking for a new RX test location around 7km or further from the home QTH in the hope of increasing my through-the-ground DX record.

13 Oct 2012

500kHz WSPR Spots

Conditions on HF appear to be very disturbed (according to the propagation forecasts) yet I'm getting plenty of WSPR spots on 500kHz. It will be much better when we all get access to 472-479kHz as, currently, activity on MF is split between this band and 500kHz.

SAQ (17.2kHz) transmission Oct 24th

SAQ, the historic alternator transmitter on 17.2kHz CW VLF will be making a special transmission on United Nations Day next Wednesday Oct 24th 2012 starting at 1010 UTC with the message being sent at 1030 UTC.   Reports from this transmission will not be confirmed by QSL card (some test transmissions are  QSLed).  The transmission is a part of the celebration of the United Nations Day in Grimeton, see http://undayorg.files.wordpress.com/2012/09/unday-english1.pdf.

IC7100 for 1 penny??

Amused to see the Nevada advert for the Icom IC7100 on their website. At this price I would expect this high end mobile/home station multimode to be sold out!

Nice price for the IC7100 !

Earth-mode VLF RX kit updated

Today I've been updating my VLF receiving kit ahead of doing some further field tests, probably on Monday. I've now changed my RX loop so that the resonance can be adjusted in the field using a capacitance switch box to bring it to resonance.  The capacitance to bring it to resonance is around 240nF. The loop was about 1kHz off-tune so that the signal was around 4-6dB weaker than it should have been. Now I can tune the loop for maximum S/N in the field and can adjust the loop to a variety of test frequencies.  I've also peaked the 8.97kHz tuned circuit on my earth-electrode receiver input and fixed a faulty connection cable.

Whether these changes will allow me to get any further through the ground remains to be seen.

What a 500kHz WSPR signal looks like

G6AVK has his temporary grabber running on 500kHz this evening. See http://www.qsl.net/g6avk/ . It was interesting to see what my WSPR signal looks like on a grabber at around 80km away. My report was -24dB S/N but, as you can see, it is clearly visible FSK keying around 6Hz.

12 Oct 2012

G3ZJO builds the G3XBM MF transverter

Over the last few days Eddie G3ZJO has been building a near carbon copy of my 10W transverter for 472/500kHz. I am pleased to hear that the build went well and Eddie is getting well over 10W RF from the unit.
G3ZJO's (very neat) version of my 472/500kHz transverter
Eddie found a couple of errors on my schematic (values shown on my photo are wrong on the circuit) and these I must correct. Once these had been sorted - my fault - the transverter worked fine. I see Eddie is getting some good reports on 500kHz WSPR this evening.

If anyone else builds a copy, please let me know and send me a photo.

11 Oct 2012

Earth-mode 8.97kHz VLF tests

Today I did the first tests using my new 5W 8.97kHz beacon looking for signals at my usual "close" test site 1.6km from the home QTH. Good copy on QRSS3 and even solid copy on 10wpm CW. Copy was using my 30t 80cm loop on RX although results were similar using a 5m spaced earth electrode pair. Tests at greater range over the weekend. This is a recording of the 10wpm 8.97kHz CW signal at 1.6km .
QRSS3 signal at 1.6km using a 30t 80cm loop on RX
10wpm signal at 1.6km using a 30t 80cm loop on RX
As the traces show, there are a lot of strong interfering signals around in this part of the spectrum. With an E-field probe there were lots of telemetry like signals audible which I think are being carried over the national grid overhead cables. These were about 0.5km away from the test site.

9 Oct 2012

Ten-Tec Argonaut VI

Ten-Tec is working on a new QRP radio that is a little larger than the FT817 but with a more conventional styling than the KX3. At the moment I understand price has not been fixed. 25 pre-production units are being field tested.  First shipments are not expected until later this year and there are hints that this may slip.

I am ambivalent about this new design: with limited HF band coverage and no VHF/UHF coverage and a styling that is "plain Jane" how many people will opt for it compared with (a) a new KX3 or even (b) an FT817 despite it being a 10 year old design? It needs to have some pretty strong unique selling features I think.

Interestingly, the Ten-Tec website makes no mention of this radio as far as I can see. Elecraft were forward selling the KX3 nearly a year before it made it out to first customers. Why is Ten-Tec not already seriously warming up the market? Surely if it is to be worth buying they should be encouraging potential customers not to buy a KX3?

The image above is linked from the www.qrper.com website.

Improved Software VLF Receiver

SWL Roland's enhanced SM6LKM software VLF receiver
An SWL called Roland from Germany has produced an enhanced version of SM6KLM's software VLF receiver, originally designed to allow reception of SAQ on 17.2kHz CW. The new version has:
  •  44.1k/48k/88.2k/96k/176.4k/192k sample rate support
  • More CW filters, SSB filter and AM filter added
  • Spectrum display for audio frequency
  • File-I/O for *.wav format (16bit)
  • Left/Right channel select
  • RMS signal level bar for audio level
  • Muting (M) key
  • Time+Date display, UTC or local time
This now makes the "enhanced" SM6KLM software receiver a superb tool for VLF use. Information and downloads are available at Roland's website https://sites.google.com/site/swljo30tb/

To use the receiver all that is needed is a VLF signal feeding into the mic input of the PC. Be sure you know what you are doing: the usual safe thing to do is to put a couple of back-to-back diodes across the DC isolated VLF input to prevent damage to the sound card. With an E-field probe antenna this receiver is capable of receiving many VLF transmitters from around the world. I shall be using it in future to monitor my 8.97kHz earth-mode CW beacon when out in the field testing.  

New VLF Beacon TX

Today I completed the build of my new VLF beacon transmitter. The beacon puts out 5W into a 50 ohm load, which is very close to the resistance of my 20m spaced earth electrodes. The beacon operates at either 8.970kHz or 4.485kHz with (a) continuous carrier, (b) 10wpm CW or (c) QRSS3.
VLF Earth-mode Beacon Transmitter
The main changes were to separate the keyer and the PA, mount the whole unit in a larger metal box and to use a 3C90 matching transformer with a fixed turns ratio having measured the ground resistance, which does not change greatly. On a continuous carrier soak test the case temperature only rises about 10 deg C, so frequency drift in the oscillator divider frequency source should be only around 0.1Hz at final frequency.

Having got the beacon finished, the next stage is to start work on some improved receiving kit and to see what sort of range can be achieved through the ground. My best DX so far with the original beacon was 6km, but this is certainly not the limit.

8 Oct 2012

iPod Touch 4g - resetting

This evening I decided to do a "return to factory reset" on my Apple iPod Touch 4g as I'd run out of storage space on the 8GB machine and the battery life, despite regularly closing open apps, was getting very poor. I'd put this down to the age (2 years) and almost daily use draining the LiIon batteries.

So, I backed up the photos and videos, ensured the apps were safe on the main PC and pressed the "reset". Then I loaded iOS6.0 and all the apps back on the iPod. First impressions are that the battery life has just about doubled and appears to be almost back to what it was 2 years ago. I wasn't expecting this. To be honest, it feels like a brand new machine.

Although I don't buy that many modern gadgets the purchase of the iPod Touch 4g 2 years ago was one of my best ever purchases. It allows me to keep in touch with my emails, BBC, family by Skype and FaceTime video, WSPR spots monitoring, take photos and videos, Facebook, etc wherever there is a WiFi connection.  It slips in my pocket and is an almost constant companion.

My whole family are Apple converts!

6 Oct 2012

Latest sunspot news

The latest from NASA:
The current prediction for Sunspot Cycle 24 gives a smoothed sunspot number maximum of about 75 in the Fall of 2013. The smoothed sunspot number (for 2012/02) is already nearly 67 due to the strong peak in late 2011 so the official maximum will be at least this high. We are currently well over three years into Cycle 24. The current predicted and observed size makes this the smallest sunspot cycle since Cycle 14 which had a maximum of 64.2 in February of 1906.
 The latest prediction graph from http://solarscience.msfc.nasa.gov/images/ssn_predict_l.gif

Charity jazz concert, Oxford Sunday Oct 7th

Final reminder: Tim Lapthorn Trio (jazz) at the Jacqueline du Pre Music Building, St Hilda's College, Oxford this Sunday at 1pm. Concert is raising funds for multiple sclerosis research.  Tickets from http://www.oxfordplayhouse.com/ticketsoxford/index.aspx?catid=24
or on the door. Good music, good cause. Please come if you can to support it.
Tim in one of his many appearances at Ronnie Scott's in London
My son Tim is a world class professional jazz pianist - see www.timlapthorn.com/ - and he is launching his new CD called "Transport" available later this month. Proceeds from the concert will got to the MS Society. 
If you cannot attend and want to make a donation to MS, please email me. Samples of his music available on his website.

Over-the-horizon on 480THz

My order for 3 off 12W red LEDs known as PT54 Phlatlights has arrived. These are VERY VERY bright LEDs mounted onto substantial heatsinks which emit a strong signal on 480THz. They were originally intended for portable projection systems. One of mine is going into my QRO optical beacon running continuous carrier, CW, DFCW, QRSS3 or QRSS30 to use in further over the horizon (non line-of-sight) beaconing tests using the scatter from particles in clear air and the reflection off the base of clouds. Last winter my own simple beacon running at around 300mW was detected several km over the horizon using QRSS3. G4HJW's optical beacon using a Phlatlight LED was detectable in my village some 8-9km over the horizon. In neither case could the red glow from the TX be detected by eye.  This week I also received some SFH213 10 degree half angle PIN photodiodes which should be considerably more sensitive than my BPW34 detectors currently in use. Estimates suggest at least 6dB more sensitivity.

Together, the QRO optical beacon running from home, focussed with a 100mm lens (gain about 24-30dB), and a portable high sensitivity 100mm lens based detector should allow plenty of scope for innovative NLOS tests on dark winter evenings.

Just realised: 5W out (for example) into a 30dB gain lens "antenna" is equivalent to 5kW of light power in the beam. That is SOME bright light. Clearly great care is needed in siting and aiming such a system to ensure safety.

4 Oct 2012

New soldering iron needed

My old Weller soldering iron station (an old Pye Telecom chuck-out from about 1980) is on its very last legs - it is physically cracked and really does need replacing. You can tell how old it is by the mains wire colours! It was possibly the one I had on my bench when I started work in 1970.

I'm looking at the Maplin soldering iron range for a replacement, which look good value. Most of my work is with discrete parts but increasingly some SMA parts are being used too. Up to now I have been using up my stock of tin-lead solder, but am happy to move to lead free.

So, please may I have your recommendation on what soldering iron to go for?

I don't mind spending a bit more if by doing so I get a more reliable soldering station. Clearly replacement tips must be available inexpensively.

3C90 cores at 8.97kHz

The output of my TDA2003 based VLF earth-mode transmitter is around 5W into 4 ohms. The new semi-permanent earth mode "antenna" just installed measured at around 50-60 ohms resistive at 8.97kHz.  I used an AC potential divider technique to check this. Today I wound a small 3C90 based transformer using the advice I got from various people yesterday and it works very well, matching the TDA2003 perfectly to the earth electrode pair. I managed to destroy my K1EL message keyer's 5V regulator (and the keyer IC too!) so a rebuild is required before I go out into the field again to do some RX measurements. All being well these new tests will start in the next few days.

My SFH213 PIN photodiodes arrived today and my 12W Phlatlight LEDs are due next week. I'd better crack on with the new VLF earth-mode tests before these arrive as I will want to try some over-the-horizon 481THz tests with the more powerful optical transmitter and more sensitive detectors.

More on LF transformers

Following on from the earlier blog entry about using a 3C90 core for a VLF and LF transformer, I got this reply from Jim M0BMU last night on the RSGB LF Yahoo group. I post it here as it contains some useful additional information. See also the mini-Ring Core Calculator from DL5SWB at http://dl5swb.de/ .
"Dear Roger, Andy, LF Group,

>> Four turns minimum for 137kHz 25 Watts. 60 or so for 9kHz

> Yes these values look quite practical ones.

...But now the inductance of the winding and AL value of the core do become
important. (BTW, the value of 2000 is the relative permeability of the 3C90 material. The "inductance factor" AL, the "inductance per turn-squared", is a different number which depends on the shape and size of the core as well as the permeability.) AL for this core is given as 2690nH nominally. With a four turn winding, the resulting L is about 43uH, with a reactance of only 37ohms at 137k. In a 50 ohm circuit, this will cetainly mess things up a bit. As a general rule, you would probably like the reactance of the 50ohm winding to be at least 250ohms at the operating frequency. This requires an inductance of more than 290uH, so a winding of 11 turns minimum will be needed for a 50ohm impedance level.

This is a typical result when using a core that is much larger than what is
  required by power handling considerations - the number of turns needed to keep the flux down to an acceptable level becomes so small that the inductance becomes the deciding factor. It also obviously makes it tricky to match to low impedances, which is often what you are trying to do in a PA or
loop-matching transformer - you may well find that you end up with windings of less than 1 turn! In these cases the inductance or the required turns ratio becomes the determining factors. In the more normal situation where you are trying to design a transformer with an economically-sized core for a given power level, the inductance is usually large enough not to be an issue, as Andy stated.

At 9kHz however, the 60turn winding is quite reasonable from the inductance
point of view, giving 9.7mH and about 550ohm reactance. Also, the core losses would be lower at 9kHz, so you could allow a higher flux density and reduce the number of turns (or increase the power level, which might be better!)

Cheers, Jim Moritz

73 de M0BMU"

Azores Islands

This evening I switched on the FT817 not expecting to work anyone on 10m when I heard CU7AA, Faial Island in the Azores archipelago, calling CQ on 28.520MHz. A quick single call and he came back to me with a 57 report on SSB. Although I've worked the Azores several times, including on 6m QRP, this is the first time I've worked Faial Island I think

3 Oct 2012

On-line LF toroid transformer design tool?

I have some 42mm diameter 3C90 toroids and want to use these in output transformers in 3 applications:

(1) in the output of a 137kHz (up to) 25W transmitter
(2) in the output of an 8.97kHz (up to) 25W transmitter
(3) as an impedance transformer for a TX loop antenna at 8.97, 137 and 500kHz.

I was looking for an on-line calculator to help me work out secondary turns needed, but could not find one.  Andy G4JNT helped with this input:
"The magic equation is Vrms = 4.44.F.N.A.B    all in SI units.   
rearranged  Nmin = V / (4.44 . F . A . B)
Al is irrelevant for transformers.
Use a Bmax of 0.1 Tesla for Ferrites, allowing a decent safety margin.
Your A  (of 25 mm^2)   = 25*10^-6    ,   F = 137000, 
25W in 50 ohms is 35V"
To aid calculations in future I have produced a small spreadsheet to work out the secondary turns from the input data (freq, cross sectional area and RF power out).

As an aside, I use http://www.66pacific.com/calculators/toroid_calc.aspx very often to work out the turns needed for the common HF toroids such as T37-x and T50-x.

2 Oct 2012

A return to earth-mode VLF experiments

This afternoon I installed a more permanent earth-mode ground system to use in forthcoming tests at VLF through to 500kHz. Instead of bringing the 2 earth connections into my upstairs shack, as I had done previously, I have now installed a couple of grounds and wires that come into my "designing" shack downstairs. This means I can now run a lot more tests using the test equipment at my disposal. It also means I do not tie up equipment in my "operating" shack upstairs when doing earth mode beaconing.

The diagram shows the current arrangement of the grounds and wire. At its highest point the wire is 1.5m above ground, running along the back garden fence. It is invisible.

Tomorrow I hope to get the ULF/VLF earth-mode beacon TX on-air initially on 8.97kHz and 1.147kHz in QRSS3 and QRSS30 and carry out my usual reception test at a point 1.6km from home where the signal is usually strong. Subject to satisfactory results with the new TX "antenna" I then intend to do a series of RX tests using new equipment out to around 10km from home.

The OXO QRP transmitter

OXO schematic on the G3PTO website

One of the most simple and popular HF transmitters is the OXO, originally design by GM3OXX. The circuit appeared in the GQRP club's SPRAT magazine about 30 years ago. It is essentially a 2 transistor QRP transmitter (plus another for keying) capable of working as a fundamental crystal controlled or VXO controlled transmitter on an HF band. I used this design as the TX part of my Pipit 800mW transceiver for 15m and later the Tenner transceiver for 10m. On the higher bands there is more chance of a little chirp, but perfectly usable. On the lower HF bands the OXO is capable of over 1W. It is a very easy transmitter to build, is almost guaranteed to work first time, and is great fun to use.

As it is some time since I've built one, I might just knock one up this afternoon and see how I get on, perhaps on 80m or 40m CW.