MSF 60kHz off air until April 6th

If you use the 60kHz LF signal from MSF Anthorn to lock your frequency reference or digital watch you may have a problem for a couple of weeks: it is off the air!  It is scheduled to be off air until 20:00 UTC on April 6th. See http://www.npl.co.uk/science-technology/time-frequency/time/products-and-services/msf-outages.

PA1B's QRPp website

Bert PA1B has an excellent website describing his experiments with very low power on HF. Using his FT817 with various simple attenuators he has been able to work some remarkable DX with powers ranging from 1mW to 500mW. His website explains how he has achieved this. It is an inspiring page showing just what is possible.

QRP JT65 to HB9 on 160m with indoor antenna

Just seen that HB9FX has copied my 160m QRP JT65 signal at -24dB S/N. Still finding it hard to make 2-way QSOs with this mode on 160m, but it proves the tiny indoor loft vertical antenna is radiating OK. Best DX report on JT65 is still the SP station about 10 days ago at over 1000km.

10m DX

This evening there were some interesting west African stations coming through on 10m.  6V7Z in Senegal on SSB and J52HF in Guinea Bissau on CW. I did not try to break pile-ups with my QRP and instead worked CT9/DL3KWR on QRP CW. Following this I moved down to 12m and worked N1WPU on CW also with QRP.

First ever 2-way international ham QSO on VLF

From Marcus DF6NM via the RSGB LF reflector earlier today:

"Today between 7:30 and 14:00, Lubos OK2BVG and I successfully completed a two-way contact on 8.97 kHz. We believe that this is the first international QSO ever on VLF.

The distance between Breclav (JN88KS) and Nuernberg (JN59NJ 69es) is approximately 424 km. The weekend before, Lubos and I had found that we could see each other's VLF transmissions from our small home antennas in a slow spectrogram, using about 0.45 millihertz FFT resolution ("DFCW-6000"). This long integration requires about 2000 seconds of continuous non-interrupted carrier to reach full sensitivity.

We decided to use absolute frequency encoding of characters ("MFSK-37" mode), which has a simple structure but is significantly more efficient than two-frequency DFCW. The software signal generators in SpecLab were used to create 30 minute dashes by editing the frequency in 1 mHz steps every half hour. This can be automated by opening a textfile which is read by the "periodic actions" function. Between transmissions, additional half-hour gaps were inserted to let the FFT ring down, and allow for TX-RX reconnections.

Characters are identified by reading the frequencies above 8970.000 Hz, with 8970.000 to .009 assigned to the numbers, .010 idle or space, and .011 to .036 the letters A-Z. Lubos used a Rubidium standard to lock his transmit samplerate, while both receivers and my TX were synchronized by military MSK signals from GQD (22.1 kHz) and DHO (23.4 kHz).

With about 80 watts from an audio amplifier, I could get up to 0.38 A antenna current into my top-loaded vertical 9 m above the roof, radiating on the order of 10 to 15 microwatts. I believe that Lubos is using similar equipment, perhaps a couple of dB stronger. For receive, my soundcard was connected straight to the loading coil and antenna, whereas Lubos has an active probe at a quiet site remote from his TX location.

We wanted to go for a "full QSO" format with reports and confirmations, beyond the rudimentary three-dash "micro-QSO" format which was used in June 2009 between DJ2LF and myself. With single-letter suffixes, we ended up proceeding as follows:

07:30-08:30 "NB" ;Lubos' call: df6Nm de ok2Bvg
09:00-10:30 "BNM" ;my reply and report: Bvg Nm M
11:00-12:00 "RO" ;his confirmation and report
12:30-14:00 "RTU" ;my confirmation and thank you

Although today the noise was not as low as it had been before, we managed to exchange the essential information in 5.5 hours until 13 UT, after which QRN from lightning in southeast Europe became strong enough to obliterate further copy.

Attached image contains captures from Lubos' grabber at Apollons temple (top) and my receiver (bottom), with screenshots from the DK7FC and OE3GHB grabbers pasted inbetween. The original captures are at http://df6nm.bplaced.net/VLF/ok2bvg_df6nm_120325/. All spectrograms were stretched to the same timescale (5 min/pixel). On the left hand side, you can see a MFSK pre-test from Lubos, sending his call to hs own grabber at very low power. There was also a long dash from OE3GHB on 8970.030, and a carrier from DJ8WX on 8970.022 is visible at DK7FC.

The rightmost part of the captures shows the essential eight dashes from our QSO. You can see that I had almost lost Lubos' "B" when my noise blanker triggered heavily on local QRM, inducing me to give an "M" rather than "O" report. But hovering the cursor to 8:15 UT does show the peak at 8970.012 Hz in the spectrum graph. My final "R" is just barely visible at .028, whereas the following "TU" at .030 and .031 ended up drowning in the increasing noise.

During the lowest noise period (9 - 12 UT), the dashes were visible (though not decodable) in 4.5 mHz "600" spectrograms. At that time, our symbols also appeared on Paul Nicholson's spectrogram http://abelian.org/vlf/fbins.shtml#p=1332712800&b=110&s=sp

Thanks again to Lubos for the effort and patience! Although exchanging half-hour symbols is tedious and may sound boring to some, both of us enjoyed it and actually found it quite exciting.

Best 73,
Markus (DF6NM)"

DX reports with JT65 on 10m QRP

This evening I called CQ on JT65 on 10m as the band was closing (I thought) and was surprised to see a couple of reports appear from LW9DC (Argentina) at 11272km. No QSO resulted, but a report of -16dB was quite good with the 5W and halo antenna. A little later I got reports from LU2XPK (13419km) and LU2XPL (13426km). Again no QSOs, just reports from these stations on http://jt65.w6cqz.org/freceptions.html.

VLF activity this last week

Whilst I was away on holiday there was considerable activity around 8.970kHz from Europe with Henny PA3CPM now putting a consistant signal from his small home station antenna on the G3ZJO grabber. Activity is continuing this weekend.

One of my priorities in the next 2 weeks is to get my VLF receive set-up back in full working order as this has been off-air for a couple of months. I will try a new E-field probe this time around and see how results compare with my 80m square wire loop. The PA0RDT or DK7FC E-field probes are well proven designs that work well if mounted high and in a low noise environment. See https://sites.google.com/site/sub9khz/antennas for details. Antenna size is less important than S/N and dynamic range on VLF RX. This is why tiny voltage probe antennas can work so well.

160m WSPR

Just back from a week away on holiday and sorting out things like washing, post etc. So, whilst this is going on I have set the WSPR beacon running with my 5W into the short loft vertical to see what is about.  In the next couple of weeks I have some work to do on antennas in the garden.

Holidays and light

Starehole Bay near Salcombe today

Being on holiday in South Devon at the moment it is a good time to do some walking on the cliff tops in the spring sunshine. Now, most people looking at the beautiful coastal scenes will think, "this is a beautiful view" or "aren't we lucky having such good weather".

So do I, but I find myself looking out to sea and thinking how would a 481THz light signal scatter off waves in the sea? Would my beacon be copyable around the coast by aiming a few miles out to sea and aiming a receiver (located down the coast) at the same spot in the sea? How would my QRSS3 light beam beacon signal scatter off those metamorphic schist cliff formations? 

I need a holiday .....oh, I'm on one!

All for the want of an SMA-BNC adaptor

This week my wife and I are on holiday at my brother's home in South Devon. I don't bring much ham gear with me these days, but I packed my VX2 dual bander and a small mag-mount to erect when static on the car roof.  Packed the rig, charger, several whips, mag mount  ......but I forgot to put in the essential SMA-BNC adapter.

Never mind, there are plenty of things to do instead of amateur radio including seeing the house in Island Street, Salcombe where my dad used to live in back in the 1920s now on sale as a second home for rich bankers at £325k. The house has no views, is tiny, has nowhere to park the Rolls and floods when there is a very high Spring tide.