Updated 472-479kHz countries list

Following feedback, Rik Strobbe ON7YD updated his list of countries with (or about to get) access to the new MF band as follows:

Monaco (18/05/2012)
Malta (11/06/2012)
Germany (13/06/2012)
Philippines (30/08/2012)
Slovakia (01/09/2012 ?) - special licence(s)
Czech Republic (01/09/2012 ?) - special licence(s)
Sweden (01/10/2012) - special licence(s)
Norway (30/10/2012)
Greece (01/11/2012)
New Zealand (20/12/2012)

Australia (01/01/2013)
Denmark (01/01/2013)
The Netherlands (01/01/2013)
UK (01/01/2013)  - available to full licence holders by NoV
Switzerland (01/01/2013)
Finland (early 2013)
Spain (early 2013)

Countries with access to 472-479kHz

An interesting post on the LF reflector today from Rik Strobbe ON7YD - OR7T about which countries have, or soon will have, access to the new MF band.

This was Rik's list:

Monaco (18/05/2012)
Malta (11/06/2012)
Germany (13/06/2012)
Philippines (30/08/2012)
Slovakia (1/09/2012)
Czechia (1/09/2012)
Sweden (1/10/2012)
Norway (30/10/2012)
Greece (1/11/2012)
 
Denmark (1/01/2013)
Netherlands (1/01/2013)
United Kingdom (1/01/2013)
Switserland (1/01/2013)

UK NoV changes

OFCOM has announced some intended changes to the Notice of Variations issued to some radio amateurs in the UK. See http://licensing.ofcom.org.uk/radiocommunication-licences/amateur-radio/full-licence-jan-2013/ . The main changes are to the 5MHz band (more fixed frequencies), the removal of 501-504kHz NoVs and the release, by new NoV application, to the new 472-479kHz band. Changes are expected to come into force from Jan 1st 2013. Details of how to obtain the new NoVs has not yet (to my knowledge) been made known.

Another 472/500kHz transverter built stateside

Just got this nice email from John WA3ETD/WG2XKA who has successfully built another copy of my 472/500kHz transverter.

"Hi Roger,

I completed your design XVTR Saturday here, on the air on WSPR last evening had eight uniques and flawless operation.

I slightly modified the PA by adding the gate resistor and diode, as well as driving the FET via a cap. I only had surface mount IRF-510, that is the raised, floating copper heatsink that sits on two tiny standoffs at drain potential.

Thanks again for publishing your design!  PIX attached.

73,
John WA3ETD / WG2XKA"

WG2XKA's version on my 472/500kHz transverter

Delay getting 472-479kHz released in the UK?

On the GQRP Yahoo group today Colin, G8FRA/M5FRA, posted this message regarding the release of the new 472-479kHz band in the UK. If his information is correct, there could be some delay in the bulk of UK amateurs gaining access to the new MF band. This would be a great pity.

"Roger,

From what I learned by talking to a couple of people at Newark (RSGB and OFCOM) we will not get the new allocation in Jan 2013. Those with existing SRPs will have them changed to remove 500kHz and add 472-479kHz. I asked when applications would reopen and there was no date for that. Evidently OFCOM have to consult before there can be any changes to the license schedule and have been too busy with the Olympics to make any progress on that. I did suggest that the RSGB should come clean as anybody who has spent time and money on new equipment might just be a bit disappointed.

Colin - G8FRA/M5FRA
m5fra.org.uk"

If this information is correct, then why is our national society, the RSGB, not making this public? I have written to OFCOM and the RSGB asking for more concrete information.

Norway gets 472-479kHz right away

Norway has been granted immediate access to the new MF band with CW and all digital modes permitted. See  https://www.nrrl.no/318-news/latest-news/492-lb1g .  I hope some LA stations come on to WSPR in the new band this evening.

More 474.2kHz WSPR

This evening I am copying 3 stations, so far, on 474.2kHz USB dial WSPR: SM6BHZ and DK7FC are both good signals with QSB but I've also copied DL3ZID at -27dB S/N. QSB is slow and it takes about 12 minutes for DK7FC's signal to go from -27dB S/N to -12dB S/N.

472kHz transverter (rev K)

Several people have now built versions of my 472/500kHz transverter. The latest version is shown below which includes provision for an additional low pass filter when using a fairly long (less sharply tuned) antenna. Although some capacitors could be combined to reduce the component count, I've shown it using readily available high voltage capacitors. The 16uH inductors are 43turns of 0.71mm wire on 22mm white PVC pipe.

In the last few minutes I've been looking on 472kHz WSPR and see that SM6BHZ and DK7FC are coming through OK despite my S8 noise floor.

SM6BHZ and DK7FC this afternoon on 472kHz WSPR

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.

472kHz transverter - real progress

Since reverting to a passive double balanced mixer based design, the circuit is now behaving properly with no signs of oscillation and a good clean signal from the PA. Although I have used an SBL1 mixer, it will work with any similar mixer package. Tomorrow I may try the design with an NE602 as this would allow the separate oscillator to be removed. With an NE602 it should be possible to do the complete TX-RX transverter with 1 IC, 2 transistors and 1 FET.  Now THAT would be neat.

472kHz transverter "progress"?

This afternoon, after a break of a few weeks, I went back to my 10W 472kHz transverter design. The intention was to simply build a second sample to prove repeatability. As is often the case, things didn't quite work out that way: instead I discovered an MF oscillation when drive was removed in some situations. Despite trying all the usual tricks so far, I've not managed to fix it yet. It is not the PA: driving it and the squarer stage directly with a 472kHz signal all is well. It looks like a problem around the oscillator and mixer but so far I have not managed to tame it. Also, and this is probably the same issue, on RX there is a wideband noise resulting in desensitisation. For this evening I have stopped work and will take a fresh look tomorrow. Maybe the double balanced mixer in my original 2010 circuit was not such a bad idea after all.

This is a classic situation when a spectrum analyser would really help as I could see in an instant where the trouble was by poking around with an RF probe and observing the spectrum on the analyser.

On with the projects.....

Back home now, so it is on with the autumn projects list.

Several people have been contacting me about the latest 472/500kHz 10W transverter. Someone in OK-land is designing a PCB and I hear a "dead bug" version has been successfully built in the USA - not sure whether an exact copy or "based on" - but it has already been used on MF WSPR with a report from over 2000km up the USA east coast. So, I will continue with refining this design first and then get on with the "WIPSY" 28MHz simple WSPR transceiver next.

The non line-of-sight optical beaconing tests will resume a little later when the evenings start to draw in. I want to set up a more powerful, semi-fixed 481THz optical beacon so that I can do a series of DX tests under various degrees of cloud cover. Tests last winter suggest much further will be possible than the 9km NLOS ranges achieved with clear air scatter when signals were audible by ear. By using much lower sub-carrier frequencies the optical detector sensitivity will be very much greater allowing even weaker signals to be detected on QRSS3 and QRSS30.

The second 472kHz transverter (with MeSquares)

Partially built 472kHz transverter using MeSquare islands

This afternoon I started the build of my second 472kHz 10W transverter to confirm repeatability of the design. This time I'm using MeSquares from www.qrpme.com as islands to aid construction. The build is about 75% complete so I thought I'd take a photo to show the technique before the board gets too crowded. With some care the results can be almost as neat as a PCB.

LF/MF Loop antennas on transmit

For the last few winters I've used a wire loop antenna on 136 and 500kHz transmit with moderately successful results. Well, considering the extremely low ERP it is better to say excellent results. My wire is not that thick: around 1mm PVC covered multistrand wire and the loop area around 80m square, with the lower part of the wire either very close to, or actually on, the ground.  Using the TX loop calculator at http://www.66pacific.com/calculators/small_tx_loop_calc.aspx the efficiency is around -30dB at 500kHz, so that 5W from the PA would result in around 5mW ERP radiated. My calculations and measurements, with less than ideal loop geometry, suggest the ERP is some 3dB lower at around 2-3mW. At 137kHz the loop is considerably less efficient at around -50dB.

For a small plot with nearby trees I am not sure how well this compares with a small Marconi with a short vertical section (around 6m max) and a horizontal section of around 6m. Anyone know the answer?

Another country on 472-479kHz

Lubos OK2BVG reports that he has been granted access to the new 630m MF band and is already working stations.  Gradually more countries are gaining access although I doubt UK amateurs will be allowed access to the band before January 2013.

A few years ago I was extremely excited when Lubos managed to copy my 2mW ERP 500kHz WSPR beacon at over 1000km for the first time. Since then the beacon has reached Finland at almost 1800km. 

It is good to hear that several German stations are now active in the new band with conventional CW QSOs being quite common.

472/500kHz antenna improvements needed

For the last month whilst testing my 472/500kHz transverter I've been using a highly compromised antenna. Essentially it is a very short Marconi tuned against my central heating system ground. The first 6-7m is a coax cable running next to pipes in the loft horizontally. Eventually the coax runs outside and up 5-6m to my 6m/10m halos. The coax inner and outer are strapped together when used on 500kHz. In the last week we have had a new central heating boiler fitted, this time in the loft, so there are even more copper pipes and wires running close to the coax. Reports appear to be a few dB worse on 500kHz as a result.

The time has now come to design a "no compromise" 500kHz Marconi! Looking at the geometry of my garden I should be able to erect a 5-6m vertical away from the house with some 10m of horizontal top loading. I can add some inductance near the top of the vertical section and tune it all against a reasonably decent ground (4 x 1m long earth spikes, a couple of radials and the central heating copper).  Not sure how soon I can work on this but I would hope the ERP increase could be up to 6dB. At least with WSPR (and OPERA) one can do a series of tests over several days with each antenna and compare results. It will be easy to measure antenna current which gives a good indication of ERP when the antenna effective height is calculable.

New MF transverter ready for testing

472/500kHz transverter built more presentably

Being satisfied with the latest 10W version of my 472/500kHz transverter breadboard, I have now rebuilt it more tidily so it will fit in a small plastic or diecast box. This uses my normal "dead bug" construction using a piece of copper laminate as ground plane with small PCB pad islands to join some components. It will be tested tomorrow, but I am not expecting any issues.

UPDATE 26.7.12
Tested the transverter above on-air this evening and getting reports from several stations on WSPR.

WSPR reports so far this evening on 500kHz

Results with the new 500kHz transverter

WSPR reports received this evening (40mW ERP)

A decent evening testing the new 472/500kHz transverter with WSPR reports from 6 different stations (best DX 440km) and copying 3 different stations on OPERA Op4 mode. There is still a slight PA instability that needs to be fixed (probably decoupling changes), so there is a bit more optimisation to do.

472/500kHz TX transverter - first schematic

10W 472/500kHz TX Transverter (CW, WSPR, OPERA, QRSS)

OK, here is the first schematic (subject to corrections, changes and improvements) of my simple TX transverter for 472 or 500kHz. This one needs no expensive parts and went together painlessly. The PA filter parts used the GW3UEP approach of winding thickish copper wire (1mm in my case) onto 22mm white PVC drain pipe pieces. The mixer, LO and squarer stage all use ubiquitous 2N3904 transistors (my favorite!) and the PA a cheap IRF510 FET that produces 10W RF without even getting warm.

Next stage is to add the RX preamp and filter and sort out RX-TX switching. I also want to try to go for a higher PA output power which will require changes to the output network.

Back home again and the 472kHz transverter

Icefield Parkway, Alberta

After nearly a couple of astounding weeks in British Columbia and Alberta, Canada my wife and I are now back home. The scenery and wildlife were just amazing, especially the bears like the one below seen just a few metres away from us.  Although I only managed about an hour of shallow sleep on the plane back from Calgary last night I decided it was better to fight the jet-lag and get on with some chores rather than crash out and wake at 2am tomorrow.

One of the 8 black bears we encountered - this one VERY closely

Once the lawns have been trimmed and the hedge cut, I've decided to crack on with the design of a new transverter for 472-479kHz as the next project. Already there is activity from Germany and there are a number of NDB beacons to allow the receiver part to be checked. Jan 1st 2013 (the likely date of release in the UK) will arrive far too soon.

I am trying to decide on the choice of IF as I want to use an unmodified FT817. 28MHz will allow 472-479kHz to appear "in-band", but at 28MHz the start-up drift as the LO settles will still be some tens of Hertz. This hasn't proved problematic with WSPR, so guess this is my choice. At least the dial will directly read the "right" frequency e.g. 28.477kHz will correspond to 477kHz.

In view of the picture above, I am not sure what power the transverter will use bear-foot (sorry, weak joke).