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!
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.
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.
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.
As many SOTA-enthusiasts, I’m continuously trying to improve weight, size and performance of my equipment. Over the last two to three years, the following configuration has crystallized for my SOTA activations:
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.
Once again it was time to dictate a diet to the equipment. Last year, on my hikes around the Rappenseehütte, I had „only“ 2.5 kg of equipment with me, considerably less than on the Hammerspitze, where I carried 5 kg. But 2.5 kg additional weight is still too much on long hikes.
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!
The impedance of an End Fed Half Wave (EFHW) dipole lies in a range of approx. 2k Ohm to 4k Ohm. In order to achieve a reasonable matching at 50 Ohm, a transformer can be used.
As a starting point I simply copied the design of a broadband transfomer, using a ferrite toroid FT 140-43 from Amidon with a turns ratio of 3:24. The transmission ratio, which is the square of the turns ratio (1:8), is 1:64. This means an impedance of 3200 Ohms will be transformed to 50 Ohms. The above mentioned range of 2k to 4k will fall in a range of approx. 30 to 60 Ohms which results in a slight (but acceptable) mismatch.
There are several manuals available, e.g. here or here.
Edit 2021-11-03: There is a discussion on the SOTA-Reflector which indicates, that the cross-over winding technique causes additional loss. Apparently it is more efficient to make all windings as close as possible.
While operating on DM/BW-852 I encountered an issue with the Keyer/Mic- encoder of my KX3. A detailed description can be found here: Link
Elecraft support confirmed the encoder being the root cause :
„We […] do know that extreme temperature changes, more typically found with the KX2 and KX3, may cause shorter life spans for them. The most common failure mode we see with the encoders is that the viscous damping material used in the shafts will leak out onto the encoder itself, which in turn, causes them to fail or skip as the encoder is turned.„
A delta loop antenna is not particularly suitable for SOTA. It requires much more space than a vertical and the set-up is more complex.
Nevertheless I’d like to show this design here because sometimes space (and weight) don’t matter and a low take off angle is welcome.
If you are looking for a delta loop for the 40 metre band, try this Link.
A possible application could be the VK/ZL/JA <> EU S2S event or the Trans- Atlantic S2S QSO party.
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.