Short Wave blackout

Yesterday we experienced that the short wave suddenly became quiet. Today we can rad the following on SpaceWeather:

"MAJOR X-CLASS SOLAR FLARE (UPDATED): On Sept. 6th at 1202 UT, sunspot AR2673 unleashed a major X9.3-class solar flare--the strongest solar flare in more than a decade. X-rays and UV radiation from the blast ionized the top of Earth's atmosphere, causing a strong shortwave radio blackout over Europe, Africa and the Atlantic Ocean".

Interestingly we (I and a few fellow ham operators) had the blackout earlier, at around 09 UT, 11 local time. already an hour later at 12 local time (10 UT), the ionosphere and hence the short wave  were regaining the capability to forward our transmissions.

Here you can see a map on how the short wave around the world was impacted.

It still remains however, why we noticed this before it was supposed to happen?

I love my SARK 110 - A simple magnetic loop experiment.

I love my SARK 110! 

This afternoon I made a very quick experiment with a magnetic loop. I took what I had: A full size loop that I have been using for 6 m, made of a 3 mm insulated copper wire stretched over a thin wooden cross. The circumference is therefore about 6 m. In series with the loop I put a vacuum capacitor, 20 – 1000 pF (7500V). It is a real beast! Heavy! I guess more than 2 kg. That is the reason that it could not be mounded in or closer to the loop.  In this experiment I simply put it on a table close by. Therefore about an extra meter was added to the circumference. On the same extra line I put a 61 mm diameter toroid number 43 material. The loop was made to have one (full) turn on the toroid, the “transceiver side” had from the beginning two turns, as an example that I have read in the literature. Note that putting the capacitor close to the feeding point like this is possible, but maybe unorthodox. This was also tried in the same paper as above. Anyway when connecting the SARK 110 antenna analyser I found that feeding impedance at this point was lower than expected, so I added another 2 turns on the “transceiver side” of the toroid, making it 4 full turns in total. In the previously mentioned paper the antenna side only passed through the toroid, not making a full turn, hence that 2 turns on the “transceiver side” is approximately similar to my 4. Here are two pictures of the experiment.

The third picture shows the SWR and IZI on 40 m, when tuned for about 7100 KHz. This loop is rather large and it was tuned to 40 m when minimizing the capacitance, close to 20 pF. It was not possible to tune to higher frequencies that about 7400 KHz.

IZI just below 50 ohm, and VSWR below 1.5, not bad!

When increasing the capacitance it is possible to tune to 80 m as well as 160 m. The last picture shows when tuned to about 1950 KHz.  Notice that SWR has increased and that IZI is rather low. My guess is that this depends on the fact that more turns on secondary as well as primary (keeping the same relationship) side on the coupling (toroid) transformer are needed for this low frequency. 

I am aware of the fact that this loop probably is rather useless for transmission as the relatively thin copper wire will contribute to large losses, as the radiation resistance is expected to be in the order of 0.08 ohm on 40 m, 0,008 ohm on 80 m and 0.01 milliOhm on 160 m. This difference was noted when listening on 40 and 80 m. The received signals were in most cases but not all, one S-unit better on my broadband dipole on 40 m, but about 3 – 4 S-units better on the dipole on 80 m. I will check 160 m tonight. Maybe even try to listen on the MW band for interesting broadcasting stations.

Next step is copper tubing and a slightly smaller loop as my goal is a loop for mainly 20 to 40 m bands. But that experiment will be performed after arriving in EA5 in October.

Ohh how wonderful it is to use the SARK 110 in such experiments, no guessing anymore – or at least fewer guesses.

The reason for this experiment was to learn some lessons.

Lessons learned: 

1. It is possible to have the feeding point and capacitor very close to each other and low on the antenna. This makes it much more easier for me, and I will be able to mount the capacitor at the lowest part of the antenna and thus be able to tune manually. It is also practical to have the feeding point at the low end. The basic instinct is to have the current maximum as high as possible, but this kind of antenna has a current maximum "all over", more or less.
2. Feeding with a toroid transformer seems plausible. This also makes a final construction simpler.
3. The SARK 110, is working very efficient when doing the adjustments. I will not need at remotely controlled capacitor motor, in order to do the fine tuning. I can do this manually using the SARK 110.
4. As expected the wire loop is to "lossy". I will look for 1/2" copper pipes. There are some plastic insulated 12 mm pipes available in coils of 5 m (e.g. here), prisol-tubes. 5 m seems to be coiled in about 4 coils. Will it be possible to "uncoil" those 5 m to one?That would be just perfect. But are those "soft" and possible to unwind to just one turn? I will have to ask my "plumber friends", SM6MNS and local cottage neighbour Tommy. 5 m circumference would be almost prefect for at magnetic loop for 40 -- 15 m.