5 to 28 MHz Random wire antenna – 12.8m (42 ft)

Some time ago I had a S2S-QSO with N1ZF. In the following e-mail contact we exchanged information and photos about the antennas used for this QSO.
This is when I became aware of the „Random Wire Antenna“ that Paul had successfully used. It consists of a 12.8 metre long wire as radiating element and an equally long ground radial. Matching is done with the KX3’s internal ATU. Since the ATU cannot match any impedance, it is important to choose a wire length that is not a multiple of half a wavelength. This way the „odd“ length of 12.8 meters emerges.

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4S- Li- Ion SOTA battery

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This battery consists of recycled Li-Ion cells type 18650.

Time and again, we have to deal with defective Li-Ion batteries in the repair café next door where I’m working in. Usually individual cells became defective or the battery management unit is broken. The (remaining) cells are sometimes still as good as new (i.e. close to their original capacity) – too good to throw away!

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10V reference voltage source

The work with lithium cells called for voltages to be measured with an accuracy of at least 50 mV, for instance to prevent overcharging of the cells.
Over the years, a number of multimeters have accumulated in my shack – with quite different quality. Now the question was: which meter should I trust? For some of the devices, not even information about their accuracy was available any more.

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Delta Loop for the 40 metre band

A delta loop antenna – especially for the 40 metre band – is not exactly suitable for SOTA. It is huge and requires a lot of space. Furthermore the set up is time-consuming.
Nevertheless I’d like to show this design here because:

  • During sunspot minimum 40 m still offers the opportunity to work a lot of DX.
  • The delta loop provides the required take off angle to work the DX.
  • Sometimes space (and time) don’t matter.
  • It’s fun building it 😉

A possible application could be intercontinental S2S events.

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Delta loop on HB0/Li-004, Augstenberg, 2359m a.s.l.

Here is the Link to the 20 metre version of the delta loop.
During our DX-pedition (Link) to the Principality of Liechtenstein in Sept. 2013. DL4AAE worked hundreds of JA’s on 20 metres with this antenna and 100 W output power.

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Balcony On The Air

Since the end of March I was more frequently QRV from our balcony. This was possible because we had unusual warm and dry weather. Also, I had more time due to the Corona crisis: As we all know, many events were cancelled and short-time work became effective.

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The “ operator’s workplace “ is located on the bench next to the terminal box of my 40 metre long wire (not in the picture, you only see the board on which it is mounted). A short piece of coaxial calbe connects the KX3 to the antenna. The built-in ATU provides the necessary matching. The KX3 is powered by a 17 Ah AGM battery (brown wooden box), which in turn is powered by a 10 watt solar cell with a PWM regulator.

Usually I am on the air from late afternoon, when the D-layer absorption decreases and the 60-metre band comes to life. When sporadic-E is present, I like to switch to the higher bands, which are now – in times of sunspot minimum – rather poorly used.

With a maximum output power of 10 watts and a long wire, no miracles are to be expected. But it works all across Europe and sometimes remarkable contacts can be made that will remain in your memory.
Moreover, it’s incredibly relaxing to be out in the open with the world’s greatest pastime.

QRP L- tuner for 5 MHz … 28 MHz

Recently I came across an article from Andrew, VK1AD, in which he describes a QRP L- tuner for 3.5 MHz to 52 MHz. It can be found here.
Andrew’s article is based on an essay by Peter, VK3YE, published in VK’s Amateur Radio magazine, Edition 5, May 2017.
I really wanted to try this easy to build L- tuner, because I thought it might perform even better than my EFHW- transformers (UnUns) and the EFHW- dipole I’m currently using for my SOTA activations.

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