Winter MF plans

Well, that was a non-happening! 

One of my plans for now was an E-field probe in a tree for 137kHz and 472kHz RX. We had the tree lopped, but the E-field probe is not up. I replaced my earth-electrode "antenna" in the ground, but my 472kHz transverter does not work, so I am restricted to 472kHz RX only.

Maybe next winter, I shall have more luck!

See https://sites.google.com/site/g3xbmqrp3/mflf/winter .

472kHz tonight

Hopefully, my transverter works. I shall try later.

Whatever happens, I intend to be on 472kHz (630m) this evening. If the transverter works I shall go on TX. Otherwise RX only. 

In both cases, I shall be using the earth-electrode "antenna" in the ground, that gave good results on 160m FT8.

UPDATE 2044z:  I tried my transverter again and still no sign of any 472kHz output, so I decided to go on 472kHz WSPR RX only. Just LA8AV (1012km) spotted so far. If I was fitter I might be able to fault find. With my health as it is, I think this is beyond me sadly.

UPDATE 2130z:  6 unique stations spotted on 472kHz WSPR RX with the earth-electrode "antenna" in the ground. Furthermost is SM6NOC (1056km).

Maybe THIS year?

Looking back over 2018 I see I failed in at least one project aim!  I actually bought the e-field probe, but it has still to be erected. Maybe next season?

See https://sites.google.com/site/g3xbmqrp3/mflf/winter

LF transmissions with ferrite rod TX antenna

A week ago a unique LF test took place in Germany by Marcus, DF6NM.

This morning I attempted to transmit from a small ferrite antenna. It consists of a number of 9 mm diameter ferrite rods, with 7 bundled in parallel. The bundles were stacked with overlap to ~ 35 cm total length, and n=47 turns of litz wire were wound around the middle. Total ferrite cross section is a=4.45 cm^2 and volume V=156 cm^3, weighing 0.77 kg (including the coil). The coil was resonated and matched by several 1 nF high-Q ceramic capacitors.

Under small signal conditions (-17 dBm), the electric parameters at 137.5 kHz were
 L = 0.50 mH, R = 0.62 ohm, Q = 690.

Applying about half a watt significantly increased inductance and losses, and the tuning became sharply hysteretic ("jumpy"). For fine tuning, a small rod was placed at a variable distance beside the antenna.

Then I connected my PA and drove about 25 Watts into the antenna. Losses and inductance increased further:
 I = 1.3 A, U = 867 V (rms), L = 0.77 mH, R = 14.8 ohmn, Q = 45,
with the Q-factor now so low that tuning jumps disappeared again. The central part under the coil became quite hot, so a tiny fan was added which held the steady-state temperature at ~55 °C.

From the induced voltage we can calculate the flux density in the middle of the rod as
 B = U / n / a / omega = 48 mT (rms),
decreasing approximately linearly toward the ends (similar to a small electric dipole). The average Bav=24 mT then results in a dipole moment of
 iA = V Bav / µ0 = 156 cm^3 * 24 mT / µ0 = 3.0 Am^2
which results in a radiated power
 EMRP = 62.34 kohm * iA^2 / lambda^4 = 25 nW.
Thus the efficiency of this transmit antenna is only 1 ppb !

Anyway I attempted to detect the tiny signal on the DL0AO LF grabber, 48 km from here:
https://lf.u01.de
Transmitting on 137.780 kHz (6:29 to 8:22 UT) indeed produced a detectable trace in the QRSS-60 window (below the Slonim Loran line on 137781.25 Hz). Then I attempted to send a 4-character EbNaut transmission on 137.510 KHz, which was successfully decoded with some margin.

Now if that's not QRP... anyway fascinating, considering that the small ferrite antenna might be carried in a handbag, buried in the ground or taken to a cave.

Best 73,
Markus (DF6NM)

137kHz

This winter, I went on 137kHz WSPR RX for the first time at this QTH. I used my earth-electrode antenna in the ground. Really, I ought to try TXing from this QTH. One possibility is my TX transverter on my website (see schematic). I used this at the old QTH before my 2013 stroke with best DX 250km.

See https://sites.google.com/site/g3xbmqrp3/mflf/137khz_tvrtr

472kHz

For the last few nights I have given this band a miss. I seem to spot the same stations again and again. Someone pointed me towards 2m FT8 and that is where I have been looking lately. There is no doubt I shall return to 136kHz and 472kHz, but I think I need to sort out a better antenna on these bands!

136kHz RX

As 10m and 6m were quiet, I have QSYed to 136kHz RX on WSPR and OPERA.

136kHz WSPR RX and OPERA RX

At about 1920z I QSYed to 136kHz RX from 50.280MHz (6m) MSK144 RX.  As yet, no spots.

136kHz last night

There is no doubt that I have to improve my RX system on LF and MF.

Last night I spotted the same few stations on 136kHz WSPR and OPERA, giving reports way down on others spotting the same stations.

Next season I shall definitely have to try a mini-whip E-field probe which, although tiny, work really well on 136kHz and 472kHz RX as long as they are positioned to minimise noise pick-up. Usually this means as far away as possible from houses and in the clear. I know I can do better.

Up to now, I have just been using my earth-electrode "antenna" in the ground. It works, but is directional and probably 10-20dB down on an optimised E-field probe.

Now on 136kHz RX

For about 45 minutes now I have been on 136kHz WSPR RX and 136kHz OPERA RX. G4FTC (123km) has just started to be spotted on WSPR. I have to check OPERA on a different machine.

UPDATE 2222z: I am about to switch everything off. Best DX on 136kHz WSPR was G8HUH (250km). No new stations spotted this evening.

UPDATE 2247z: Now QRT.

136kHz RX yesterday evening

Yesterday evening I was on 136kHz RX again. On WSPR RX  2E0ILY, G4FTC and G8HUH (250km) were spotted. On OPERA RX the only station spotted was G3XDV (61km).

Return to 136kHz RX

About an hour ago, I QSYed to 136kHz RX. Both WSPR and OPERA are being monitored. As yet, no spots on WSPR. I need to look on a different PC to check OPERA.

UPDATE 1936z: So far G4FTC (123km) spotted on WSPR and G3XDV (61km) spotted on OPERA.

136kHz RX last evening

As is my norm, I QSYed from 6m (sometimes 10m) to LF (sometimes MF). The shack PC was on battery power to keep the SMPSU noise to a minimum. I did not stay on overnight instead I was monitoring OPERA and WSPR RX during the evening hours. Best DX spotted on WSPR was 2E0ILY (209km) and G3XDV (61km) on OPERA.

QSYed to LF RX

Rather early, I have QSYed to 136kHz WSPR RX and 136kHz OPERA RX. I hope I catch some stations this evening.

UPDATE 2055z:  G3XIZ, 2E0ILY and G4FTC spotted on 136kHz WSPR and G3XDV spotted on 136kHz OPERA. All these are using the earth-electrode "antenna" in the ground as the RX antenna.

630m and 2190m RX

Last night I did not go on LF or MF as my shack PC was playing up. I intend to go on 136kHz WSPR RX and 136kHz OPERA RX tonight. I  need my shack PC on battery power otherwise noise is chronic.

630m last night

In the end I just remained on until the shack PC's battery went flat. This was just after 0300z. The batteries last a long time! 

On WSPR G3XIZ, G8HUH and 2E0ILY were copied and G3XDV copied on OPERA. If I am honest, I was disappointed.

LF RX

At the moment I am monitoring 136kHz WSPR RX and OPERA RX. As yet, nothing copied.

UPDATE 2006z: G3XIZ copied on 136kHz WSPR.

LF disappointment

Yesterday evening and overnight I was on 136kHz WSPR RX with a preamp in circuit. Only 2 stations were spotted - G3XIZ (46km) and G8HUH (250km) and, if I am honest, the preamp made little difference, whereas I was hoping for much more.

With G3XIZ there may have been a slight improvement but with G8HUH he was no better. I am not quite sure what this is telling me. I think it means external noise is the limiting factor at this QTH. Unless I take further steps to reduce the external noise I am unlikely to spot many more stations. There was one station on OPERA (G3XDV?) who was quite strong, but I did not have any OPERA software running. I shall try again tonight. If possible, I'll run both WSPR and OPERA software at the same time.

136kHz WSPR RX

Thanks to the great kindness of an individual who shall remain nameless, I am looking on 136kHz WSPR with better sensitivity. This amateur did not want me to pay, but gave it in the true spirit of amateur radio. There are some very kind people out there. In my experience, the true spirit of our hobby is alive and well - thank you.

At some point in the future I hope I can be as generous to someone as many people have been to me in recent years. A great many people have shown me kindness and I am so grateful for their help in so many ways.

Results of 630m WSPR RX experiment with earth-electrode "antenna" in ground.

A couple of Gs came on. G3XIZ (46km) was 2-3dB better S/N on the earth-electrodes than on the compromise vertical. He is end-on to the "loop" in the ground. G6AVK was not copied at all. He is orthogonal to the "loop" in the ground. I was quite surprised not to spot him at all though.

Conclusions? The earth-electrode "antenna" in the ground is quite effective at 136kHz, but more directional.