Field day Brouwersdam

Today we (Chris, John, Adri and I) went to Zeeland to check the QRM level near the Ouddorp lighthouse (it was ok), and I wanted to check the performance of a 80m vertical delta loop. Included are some images.


The 80 meter delta loop consists of 80m of wire, and a 1:4 current balun. It has two functions, it does the common mode rejection from a symmetric antenna to an asymmetric transmission line, and it transforms the 200 Ohm impedance to the 50 Ohm. The measured SWR was around 1.7 at the resonance frequency of 3650 kHz. Still confused? This is what we made:


The 1:4 Guanella balun (invented by Gustav Guanella, 1909-1982) was discussed earlier in this blog: link Why this design? I never found an opportunity to test a delta loop in the field,  I didn’t have a good antenna for 80 meter, and I never tested my Guanella Balun. A significant advantage is also that the Delta loop only requires one mast rather than two (or even three) required for the dipole.

The radiation pattern of this design is interesting when you put it in NEC, it appears as if all power is radiated upwards and it has a little bit of directivity, so this is an antenna for NVIS (near vertical incidence skywave) activities. During NVIS you stay under the critical frequency which was about 4 MHz during the event.

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Azimuth pattern, the antenna has 7 dB gain apparently, but it changes by frequency (it sweeps over the full 80 meter band here)
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Charge intensity
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Elevation pattern, NEC suggests that most of the power is going upwards

Here is the log of the QSOs we made, all locally (of course because of the time of day and the frequency):

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For DX contacts on 80m you need to be there around sunrise and sun-set.

Last update: 20-April-2018


Never throw away a metal box

I used this one for a FM stop band filter.


After you’ve finished your tea, save the metal box for an electronics experiment, or just to store something.

Last update: 24-Mar-2018

Is there any propagation? Yes of course there is on 40 meter.

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40m, 500mW WSPR TX mode, last 12 hours relative to Mar 9, 2018 10:26

Propagation mechanism

From this WSPR graph you can see that 40m radio waves propagate well over the ocean, that the F layers are likely reflectors at 250 km altitude and that the skip distance is around 500km. Here is the explanation in more detail.

The first WSPR fact is that you are only heard either within approximately 30 km via the ground-wave (over the surface direct line of sight) or at distances greater than 500km. Between 30 and 500 km you usually get no reports whereas there should be some listeners. I rarely get reports from for instance the university of Twente where there is a
permanently running WSPR receiver. Instead, the first signal reports seem more to arrive from southern Germany and the center of France, roughly at 500 to 800 km from Rotterdam. The mechanism that likely explains this is a reflection of the radio wave against an ionospheric layer at a height of probably around 250km, but this depends of course on the critical angle. An ionosonde can tell you what the height of the reflecting layer is, my guess is that it is around 250km, so this is a F2 layer. All of what you see in the WSPR plot is observed during the night time the D and E region descrease in intensity (number of free electrons). Within the EU we see single, double or maybe triple hop reflections, but nothing seems to go any further than that.

But now the long paths over the north Atlantic, these paths can only be explained by more than 3 hops, there should be tens of hops to explain a path across the Atlantic ocean. The first surface reflection towards the west seen from Rotterdam will be over a water surface, the north Atlantic in particular. There are no reports from the UK, my explanation is that it is too close to the transmitter. Over the ocean the propagation is much better, water (and ice) are very good reflectors, and the signal goes on until you hit the east coast of the united states and also Costa Rica in central America. The WSPR signal survives maybe one or two hops over the continental US, and then it dissipates because land is a worse reflecting surface than water or ice. This is the general tendency of HF radio propagation, on 20 and 40m it is very difficult to get any reports from the central US, Texas, Oklahoma and Kansas and northward. Most of my QSOs are with the
Eastern states because of the mechanism described before, land is not a good reflector, water is better.

Some logbooks like allow you to plot the states that you have worked in the USA, this summarizes the contact mostly on 20 and 40m over the last several months (1000 QSOs back actually, on average I do some 8 per day). It also shows that the eastern states are confirmed, and this is in agreement with the WSPR propagation plot, propagation over land is less effective than over sea water or ice.

IMG_1842 _cleaned

Last update: 10-3-2018 9:15

DelfiC3 cubesat recording

The DelfiC3 project is described here and the purpose of this experiment was to see whether a 3 element Yagi for 2 meter is sufficient to catch the signal. With the airspy, and the yagi shown below and sdrshap we found an SNR of approximately 10dB. You need to stay a few meter away from the notebook that records the data to avoid radio frequency interference.

This is the 3 element yagi discussed further down this blog

This was the passage on 27-feb-2018 at 9:40 at the campus of the TU Delft. The elevation was approximately 30 degrees, and the ground track was eastwards. Mind that the satellite transmit power is no more than approximately 2 Watt and that the distance to the transmitter is some 2000 km.

PE4WJ added: the TX power is 10dB under the total power consumption, which is 2.4W. So 2.4 Watt minus 10dB = 0.24 Watt, or 23.8 dBm.

Last update: 5-Mar-2018




The Antarctic WSPR station on Neumayer station heard my 500 mW signal on 40m. I was in WSPR transmit mode.


What matters in radio propagation is power spectral density, the bandwidth is really small, (6 Hz) and the power is roughly that what you put in a flashlight. More about station Neumayer can be found here.

Last update: 7-Feb-2018

40m band

Screenshot of what I did last night on 40m with up to 16 receive frequencies in the waterfall. Good to have the software mute when I use the FT991A to transmit on a nearby wire antenna, the airspy hf+ is on a separate active antenna. My only wish is CAT control to this rig via MK2.

Last update: 4-Feb-2018