31 Aug 2010

Solar activity progress

See http://solarscience.msfc.nasa.gov/images/ssn_predict_l.gif
Sunspot cycle 24 does, at last, show signs of gathering some momentum. Despite the ups and downs in the sunspot count, there is an inexorable climb now towards the next maximum, probably on 2012 or 2013. This autumn we should start to get the regular 10m transatlantic openings again which, to me, are a sign that the new cycle is here and "good" for several years. In the press there's been some alarmist headlines about solar storms around the sunspot maximum knocking out swathes of the power systems and satellites around the world. Certainly the danger exists, but surely it is a manageable risk with planning and contingencies in place? See news.com.au on this subject.

LF/MF antenna change

Today I changed the earth electrode antenna by raising the height of the connecting wires to form a (part) loop in the air as well as in the ground. The loop part in the air has an area of >100 sq metres.  This should increase the effective loop area by a factor of at least 2, thereby improving the ERP. Later I'll repeat the tests with just the loop in the air only, so I have 3 different sets of results to compare. On 500kHz WSPR my signal with M0BMU (69km) was 6dB stronger than before with the earth electrode antenna. At the moment I am QRSS3 beaconing on 137.675kHz and seeking reports.

29 Aug 2010

136kHz WSPR - first report received

Well, it is no great DX at 3km away in the next village, but I've now received my first WSPR report on 136kHz from G6ALB. He gave me -21dB S/N when I was running 20uW ERP from the earth electrode antenna.

28 Aug 2010

WSPRing on 137.5kHz at last

136kHz TX transverter
Having got the TX part of the 136kHz transverter going today I am, for the first time, putting out a WSPR signal on 137.5kHz. Power from the PA is around 4W and the ERP from the earth electrode antenna is around 20uW. I am hopeful that Chris G3XIZ in Biggleswade may be able to decode the signal, possibly others not too far away. In the picture the transverting bit (from the 10MHz band) is on the right and the PA in the top left with low pass filter visible using the T106-2 toroid. Note the heatsink for the IRF510 - a couple of crock clips being all I could find in the junk box!

My 20uW ERP QRSS3 signal as received by G3XIZ
This was the signal G3XIZ got today 48km away on QRSS3 from me on 137.675kHz.  It is somewhat stronger than earlier in the week, confirming the few dB extra ERP.

27 Aug 2010

136kHz TX transverter almost ready (5W from PA)

Today I should complete the first breadboard version of my QRP TX transverter for 136kHz. It mixes down from 10MHz in a similar arrangement to my 500kHz unit, which transverted down from 28MHz. ERP on the original 137.675kHz QRSS3 beacon has been increased by 3dB to 20uW. The ERP from the transverter into the earth electrode "antenna" will be about the same level initially. I'll run WSPR tests for the first time on 136kHz this weekend.

25 Aug 2010

Another report on the 136kHz QRPp beacon

G3XIZ has sent me a nice screenshot of my 10uW ERP 136kHz beacon as received in Biggleswade, about 35km away. Chris believes I'd be perfect copy with QRSS10 (10 second dots).

24 Aug 2010

62km with QRPp and earth electrodes on 137.675kHz

Today I ran an earth electrode transmission test with Mike G3XDV in Welwyn Garden City 62km away. I put my QRSS3 8-10uW ERP beacon on and Mike took regular screen shots through the day until mid afternoon. Although unable to copy the message in QRSS3, when using QRSS30 speed for reception the start and end of the message sequences (9 mins 7 seconds apart) could clearly be seen. He was able to precisely detect when the beacon was turned off. Mike estimates another 6-10dB should allow him to read the message properly. Signals were weaker later, possibly because of rain here altering the effective loop size within the ground.

22 Aug 2010

136kHz RX loop calibration

Today I attempted to calibrate my 136kHz 80cm loop antenna by measuring the signal strength of DCF39 in Germany on 138.83kHz. I'm told that the field strength of this signal in daytime in this area is around 1mV/m. The level of DCF39 was -4.5dB on the Spectran screen with the settings I used. So, by extrapolation 0dB on the screen should be close to 1.7mV/m.

I then measured the signal level of my QRSS3 beacon on 137.675kHz  to see how much lower the level was at the same point about 1.5km away from the home QTH. My QRSS3 beacon was measuring -42dB approximately, corresponding to a field strength level of 12uV/m at 1.5km.

To work back to my ERP from the earth electrode antenna I used the formula ERP = (E * d)^2 /49 and this gives a result of 6.3uW and an antenna "loss" factor of 56dB (power in to RF out).

There are several sources of error:
  • loop orientation +/-3dB
  • loop Q/tuning +/-3dB
  • measurement accuracy +/-2dB
So, the ERP could be as high as 40uW or as low as 1uW.

17 Aug 2010

Chinese SSB and CW transceiver kits/built

YouKits of China is advertising a new 6 band HF SSB transceiver, the TJ6A that is available both in kit form and ready built. Prices look very attractive for a 10W transceiver. Well worth a look at their website.  This last year we have begun to see Chinese ham products appearing. It is only a matter of time before a Chinese manufacturer will produce quality transceivers to seriously rival Icom and Yaesu, and at unbelievable prices.

Pakistan Floods

This map appeared on the Oxfam site today and gives a graphic indication of how much land is affected by the floods in Pakistan when overlaid on a map of the UK.  It must be truly awful for the poor people there affected by this with crops, homes and businesses in ruin. Just imagine if this happened here (see map) and think how we would like the rest of the world's governments and peoples to help.

Help here: http://www.oxfam.org.uk/get_involved/campaign/actions/pakistan_response.html

ICQ Podcast: LF/VLF and QRP stuff

Last week Martin M1MRB interviewed me by Skype for an ICQ Podcast mainly about LF/VLF and QRP . My contribution starts about half way through the podcast. Thankfully Martin edited out many of the "ums" and "errs" that littered the piece!

16 Aug 2010

Resonating the earth electrode antenna on 136kHz

The 20m spaced earth electrodes "antenna" has about 30m of wire coming back ato low height to the feedpoint upstairs. I wondered if I could increase the current flowing into this structure by tuning out the small inductance presented by the wire. Using a small capacitance switching box I selected the value that gave most current with the 2W beacon TX. It was 100nF although because of the resistance of the ground return path the Q is low and the peak small. This suggests the inductance of the feed wire is only 13.5uH. I also tried matching the loop using a 3C90 transformer with various secondary taps but this made little difference. So, conclusion is that resonating the loop and matching it makes very little difference to the current (and ERP) because of the low Q.

15 Aug 2010

136kHz with a vertical antenna ....8uW ERP

Having simply tuned and matched my 5m coax feed to the 28MHz halo (the halo is used as a top capacity hat) I'm now putting out the grand level of 8uW (+/-3dB) on 137.675kHz in QRSS3 from my 2W out beacon TX.  Tuning was with 1.2mH wound on a small piece of ferrite in parallel with some fixed and variable capacitance. Matching was via a 3C90 toroid transformer. Field strength tests a few km away from the QTH suggest that the ERP from the earth electrode antenna is higher than this vertical, which is a bit disappointing as it suggests the vertical is, well, poor.

14 Aug 2010

Old UK radio and TV clips

If you were young in the UK in the 1950s you may be interested in these two sites dealing with radio and TV in the 1950s. There are many old clips that take you back nearly 60 years.


13 Aug 2010

Back on the vertical on 500kHz

WSPR Reports today
This afternoon I fired up the 5m long feeder (inner and outer strapped together) running up the pole to the 28MHz halo (used as a top loaded vertical) on 500kHz. Tuning was with a tapped inductor on a ferrite rod and matching using a 3C90 toroid with multiple tapped secondary winding. This works well and the signal reports on WSPR from M0BMU are 18dB stronger than on the earth electrode antenna. Also had reports from GW3UCJ, PA0A, OR7T and M0LMH so far this evening. If I can create a suitable loading coil (4-6mH needed I think) I will try this vertical with the 136kHz QRSS3 beacon as see what the signal is like.

300% more efficient wind turbine?

Japanese professor Yuji Ohya and his team have investgated the design of wind turbines and suggested a honeycomb-like structure could triple the amount of wind energy that can be produced by offshore turbines. See Tech Future site for more information.

12 Aug 2010

Perseids meteor shower tonight

The Perseids meteor shower is supposed to be a strong one peaking this evening. I may run the WSPR software overnight on 10m to see if any bursts are long enough to support a 2 minute WSPR transmission.

LATER: Overnight I copied PA0PSY at 0044z by what looked like MS: quite strong signal, seen once only, with Doppler, over a 300km path, although it could also have been aircraft reflection. Unfortunately I didn't see the WSPR screen to examine the actual screen trace.

Sunspots - high 60s

Have you noticed how high the sunspot count is climbing? Today it is 66 or 70 depending on which measure you take. This is not far off the sunspot count predicted at the peak of cycle 24 in about 3 years' time. If this trend continues, we could be in for a bigger peak than some were predicting. It could by just a blip.

10m halo re-erected

Today I rebuilt my Homebase10 10m wire halo and put it back up on the pole. I was going to erect a spiral top hat vertical for LF but decided instead to go HF. VSWR was good from 28-29MHz and WSPR reports from G4IKZ (18km west) good with just 1W out. I can use this antenna, with feeder strapped, as a vertical on 500kHz. For 136kHz I've decided to erect a wire loop rather than a Marconi and will support this from the 10m antenna mast.

10 Aug 2010

417km on 500kHz QRP ....with just earth electrode antenna!

Just been received in Holland by PA0A on 500kHz WSPR when using just the 20m spaced earth electrodes! The ERP is around 250uW and I am amazed that this non-antenna is able to work so well. I've also been emailed by Victor PA3FNY to say he also copied me at -27dB S/N.

500kHz WSPR with 20m spaced earth electrode antenna

The effectiveness of the 20m spaced earth electrode "antenna" (virtually nothing is in the air) continues to amaze me. Last night I copied PA0O on 500kHz WSPR and this morning I've got 4 reports of my sub-1mW ERP signal from M0BMU around -19dB S/N at a distance of 69km. This level suggests the (non) antenna is only around 6-8dB down on my best top loaded  short vertical used to get reports from OK2BVG 1232kms away last winter and the ERP is around 200-250uW.

9 Aug 2010

160m WSPR receive with earth electrodes

Although I've not matched the 20m spaced earth electrodes yet on 160m, it makes a fine RX antenna. See the logs on WSPR in just the last hour.

500kHz WSPR

This afternoon I restarted 500kHz WSPR transmissions using about 250uW ERP from the earth electrode "antenna" in the ground. Two reports received from M0BMU at 69km received so far (-24/-25dB S/N). In the next few days I'm hoping to erect a vertical top loaded Marconi antenna to use on both 136 and 500kHz, so it will be interesting to see how reports compare with those obtained on the earth electrode antenna.

8 Aug 2010

500kHz with the Elecraft K3

On the Elecraft website I see there is an article showing how to use the K3 transceiver on 500kHz. The K3 will receive on 500kHz but needs an external PA (described) to get around 25W output. See http://www.elecraft.com/TechNotes/k3qtx_v2_pa3cw.pdf

5 Aug 2010

FT818 - a "what if" radio that does not exist....

The FT818 handheld:
  • All mode, all bands 1.8-1296MHz with 5MHz and 70MHz
  • 5W RF (2W 1296MHz)
  • 3.5AHr Li-Ion battery pack (2hr charging)
  • Built in random wire and whip auto-ATU
  • Full colour OLED display
  • Multi-function DSP noise reduction
  • RF Speech processor
.....wouldn't that be nice for Christmas 2010? Sadly, it doesn't exist except in our dreams.

3 Aug 2010

US and Canadian East Coast Loran closed today

Apparently the very last Loran TX on the east coast of the USA and Canada closed at 0500 today. This will make reception on 136kHz much easier in this part of the world. At one time Loran was one of the most popular navigation systems in the world but now made obsolete by GPS units costing a few dollars and fitting in your pocket.

2 Aug 2010

14.9km on 136kHz QRP (earth electrode antenna)

This morning I did some more tests using my little 136.93kHz 2W QRSS3 beacon feeding into the 20m spaced earth electrodes. The TX end was unchanged, but this time on receive I used my 30t 80cm loop resonated with about 700pF and fed straight into the high impedance input of my E-field probe. Results were as follows:
  • At 2.4km good copy by ear (12wpm CW would have been very solid)
  • At 8.6km good copy using Spectran
  • At 14.9km clear copy of my callsign and locator in QRSS3 with Spectran on the Gog Megog Hills near Cambridge (see screenshot)
All these locations are more or less in the line of the earth electrodes that run NE-SW from the home QTH (JO02dg).  Another RX test some 11km to the south of the QTH  resulted in no visible trace, suggesting the TX earth electrodes are behaving as a loop antenna with some directionality. This was not the case when the same earth electrodes were used at 0.838kHz some weeks ago and when the mode was mainly conduction through buried utilities. Remember, this is ultra simple stuff:
  • 2W out crystal controlled QRP 136kHz beacon TX on a 5 x 5cm board (see picture)
  • Invisible ground "antenna" that can't be seen, even when a few metres away from it.
  • No attempt to match the TX to the earth electrodes.
  • Simple loop + FET impedance matching circuit and deaf FT817 at the receiver end.
It would be interesting to work out what the ERP must be and interesting to speculate what would happen with such a system at 73kHz. Pity there is no allocation there today.

1 Aug 2010

DK7FC's 6th VLF kite TX experiment

Stefan DK7FC is testing his 600W VLF transmitter into a 200m high kite supported vertical today (Aug 1st). He expects to radiate about 10dB more than in his last test (on 8.97kHz) and may transmit at a slightly lower frequency today (around 6.5kHz) depending on where the antenna is best matched. You can check progress on his grabber at http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html .  Results from his last tests were amazing with reception across Europe in DFCW600 mode (dual frequency slow CW). For a summary of the reports (screen grabs) see http://abelian.org/vlf/ss100321/.  To copy his signal you will need a decent low noise/high dynamic range receiver (E-field probe or loop with preamp and filters) at VLF feeding into a PC running a package like Spectrum Lab, Argo or Spectran using narrow 3...5 mHz FFT settings and about 1 minute per pixel running speed. You also need to know precisely where to look, so calibration will be very important.