Sunspots - Monday July 30th 2018

Solar flux is 68 today and the sunspot number 0 .  A= 5 and K=1.

137kHz E-field probe on the car mag-mount

Many years ago, I tried looking for my tiny 137kHz beacon with a small E-field probe mag-mounted on the car. After seeing the signal quite well on the far side of Cambridge at about 24km, I stopped the test. As you can see, the EFP used readily available parts and was very simple.

At some point I should rebuild this and try from the QTH we moved to almost 5 years ago, maybe using the earth-electrode "antenna" on TX. I have felt too unwell since my stroke.

See https://sites.google.com/site/g3xbmqrp3/antennas/137efp

HAARP 80m WSPR test

A reminder that WI2XFX, in Alaska, will be on the air tonight on 3.5926 USB dial (2300z for about 30 minutes) with a huge ERP on WSPR using the HAARP antennas. See the ARRL site for more details. I may try looking for it using my earth electrode "antenna" in the ground.

10m FT8

For a change today I am on 10m FT8. Although an earlier CQ got no response I have already spotted an Italian.

UPDATE 0858z: Quite a bit of Es already today on 10m FT8 as the map shows.

UPDATE 1514z: 263 different stations spotted on 10m FT8 RX today including the USA and Canada-  and we are approaching sunspot minimum. I shall probably remain on until about 1900z tonight when I need the rig for another band (2m FM net) and then the HAARP 80m WSPR test.

UPDATE 1710z: So far 342 different stations on 10m FT8 today in 5 continents. With FT8 who needs sunspots!

Now QRT

On both 6m and 10m I have now gone QRT and disconnected everything. I noticed a CT calling "CQ NA" , although I am not sure if he was copying stations from "across the pond" on 6m FT8.

Tomorrow I may try 10m FT8, although I want to see if I can see the 80m WSPR test from the HAARP station in Alaska in the late evening UK time.

Sunspots - Sunday July 29th 2018

Solar flux is 68 today and the SSN still zero. A= 5 and K=1.

6m FT8 RX

Well, I am glad I stayed on 6m FT8 RX last night! In the end 19 USA, Canadian and Caribbean stations  were spotted from Puerto Rico to Nova Scotia. This was just on my V2000 vertical omni fed with CB coax. No doubt better equipped stations will have spotted or worked far more.

This morning I am on 6m FT8 RX. So far, just EU and North Africa spotted.

UPDATE 1018z: So far 42 different stations in 17 countries spotted on 6m FT8 RX this morning.

UPDATE 1552z: 152 different stations spotted so far today on 6m FT8 RX.

UPDATE 1906z:  Currently 217 different stations spotted in just the last day on 6m FT8 RX. 59 different DXCC countries spotted on 6m FT8 RX since Friday lunchtime. Not bad for a simple RX antenna (V2000 omni vertical) fed with CB coax.

Simple pleasures - NOT amateur radio

This was my granddaughter at the Norfolk seaside last week. If it's hot, simple pleasures please.

10m WSPR TX (500mW)

As is usual, I am on 10m WSPR TX again. Best DX spot so far this morning is SQ3XZ (1113km). This is clearly Es.

UPDATE 1550z: 62 spots today by 7 different stations on 10m WSPR so far today.

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)