Very lightweight SOTA microphone

I have been looking for an alternative to the rather bulky and heavy Elecraft MH3 handheld microphone for quite some time. Since I mainly operate CW, the solution could be somewhat improvised.
Inspired by an article about a very light microphone in the SOTAreflector, I started the following mini-project:

A headset from my Baofeng UV-5R was available, lying around unused. The aim was to replace its weird dual plug with a simple 3.5 mm stereo plug and change the wiring so that it could be used with the KX3. The tiny speaker I would simply trim as I’m already using earbuds for my activations.



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.


4S- Li- Ion SOTA battery

2020-07-15 11.37.27

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!


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.

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.


Was macht die Angelrute auf dem Berg?

A large squid pole on a summit immediately attracts the attention of other people. Even if no sound can be heard (because I’m always using headphones). If the summit is crowded, you don’t have to wait long until the first person appears and starts asking questions.

Unfortunately people tend to show up right at the moment when the pile- up starts. Then, because I don’t want to stall the pile- up, I just hand them a SOTA- flyer and mumble a few friendly words. I’m sure I could have explained better if there was more time for a chat.


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.



Please scroll down for the English version!

Die hier gezeigten Powerbanks sind aufgrund ihres Gewichts für SOTA nur sehr eingeschränkt zu verwenden. Allenfalls zu einer „Drive-on Location“ würde man so ein Monstrum mitnehmen. Oder in den Campingurlaub, was tatsächlich die Motivation für den Bau der beiden Powerbanks war – man kann ja auch vom Campingplatz funken!