Replacing one of the KX3’s encoders

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.

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.

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Delta Loop for the 20m band

A delta loop antenna is not particularly suitable for SOTA. It requires much more space than a vertical and the set-up is more complicated.
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. One possible scenario could be the VK/ZL/JA <> EU S2S event.

loop1
Delta Loop on HB0/Li-004, Augstenberg, 2359m a.s.l. during our DX-pedition to the Principality of Liechtenstein in September 2013. DL4AAE worked many JA’s on 20m with 100 Watts output power.  Note: the horizontal wire has been attached to the pole in order to avoid sagging.

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EFHW- Dipole with Traps

While searching for an alternative to my Linked- Dipole I tripped over the posting of Pedro, CT1DBS, illustrating an end-fed half-wave (EFHW)- Dipole with Traps. Here is the Link to his article. With this design changing bands can be done in no time thaks to the traps. Lowering or modifying the antenna is no longer necessary.

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SOTA Equipment – updated

This is what my equipment looks like after I started a programme to reduce the weight (s. the 2 kg Challenge). I’m going to use it on long hikes and trips to high summits where weight comes into play.

sota-light

From left to right: EFHW- Dipole with traps (40m, 30m, 20 m), 10m Nylon rope (red), tent peg, antenna bag, Unun 1:64, 1m RG58, bag for MTR 3B and Palm Pico Paddle, earplugs,  1250mAh LiPo battery 2S, power cable with fuse, 3 velcro straps, lashing belt, tape, writing board with log sheets, pencil, spare fuse, headlight, 3 x 10m guy rope with tent pegs, support plate 8mm (for guy wires), army knife,  6m fiberglass telescopic pole (57cm long).

The equipment as shown in the picture weighs 2067 grams. However, it is possible to leave the guy ropes out and attach the GRF pole to the summit cross using the lashing belt. Additionally, if a 1000mAh LiPo will be used instead of the 1250mAh LiPo, the total weight of my equipment is slightly above 1700 grams. This is 3 kg less than what I’m usually carrying around and definitely a big improvement.

Endgespeister Dipol/ End Fed Half Wave- Dipole

Please scroll down for the English version!

IMG_9413
Endgespeister Halbwellendipol: Realisierung mittels T- Stück.

Die Idee stammt aus der CQ-DL 06/2014. Dort wurde ein Artikel mit dem Titel „Endgespeiste λ/2 Koaxantenne“ veröffentlicht.
Beschrieben wird ein endgespeister Halbwellendipol, dessen Fußpunkt- Impedanz mittels Viertelwellentrafo in die Nähe von 50Ω gebracht wird.

Die Antenne ist einfach in der Herstellung und leicht im Freien aufzubauen, da sie – vertikal betrieben – nur einen Aufhängepunkt benötigt. Nachteil dieser Antennenform: Es handelt sich um eine Monoband- Antenne.

Eine gute Erklärung zur Wirkungsweise des Viertelwellen- Transformators findet man im Praxisbuch Antennenbau von Max Rüegger, HB9ACC, Kapitel 7.1.3.

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SOTA Equipment

Used for trips to the local summits.

From left to right: Folding stool, 2200mAh LiPo battery in a ’safe bag‘, throw bag (250g), 30m Nylon rope (3mm) , 2 x 10m Nylon rope (3mm) with tent pegs, KX3 with Palm Pico Paddle (on the KX3-Go-Box), 40m- and 30m- wire-dipole (w/o BALUN), 20m end-fed dipole, plywood board (serves as table), headlight, tape, writing board with log sheet, pencil, KX3 power cable with Power Pole plug, headphones, angle adapter BNC – UHF, Army knife, RG223 (20m), velcro straps, 3 x 10m guy rope with tent pegs, 10m fiberglass telescopic pole (67cm long), support plate 22mm (black, for guy wires), support plate 8mm with pulley block (blue, for antenna), 2 lashing belts.

SOTA_equipment

As the trips are usually not tiring I don’t optimize the weight of the equipment more than necessary. I prefer a minimum of comfort (folding stool and plywood board) and the choice between several antennas and options to set them up: In a tree with throw bag and rope or on the fiberglass pole which can either be attached to a fence post or secured with guy- ropes.
The monoband antennas have been replaced with a linked dipole in the meantime. However, a further optimized antenna (End Fed Half Wave Dipole with Traps) is already under construction.

KX3 Go Box

Having played with the KX3 for a couple of weeks I wanted to try it outdoor. But Hiking comprises some risk for the rig: rain and snow, shock and vibration and scratches from other things in the rucksack. The first attempt with bubble wrap worked but was not to my full satisfaction. A box was needed!

I searched the web for availalbe solutions (which are quite a few) and found Tom’s great Go Box:  http://www.oe2atn.at/tom/gobox/ – the most professional one I found.

However, I had something different in mind: The box should look understated in order not to attract thieves on a long hike or a stay on a camping site. By accident I tripped over an empty first aid box. Slightly too big for the KX3 but apart from that very nice.

[edit]: From time to time, while turning the dial, I noticed that VFO A seems to get stuck at a certain position. The frequency reading in the display „jumps“ back several 10 Hertz then moves on again and „jumps“ back. This can happen several times. Suddenly the failure disappears and the VFO works as intended.
This video from KC9W describes exactly my situation: https://www.youtube.com/watch?v=COPj2skxWys

One explanation was that the old version of encoder has been used inside my KX3. But taking a close look revealed that it is already the new version. (Link to ELECRAFT’s KX3 VFO Encoder FAQ)
Other possible explanations for this weird behaviour include excessive mechanical stress to the encoder.

When opening the Go Box, I found that the VFO A knob has left a mark in the foam in the lid. Possibly, under such pressure, the foam is no longer able to absorb external shock. Instead, pressure applied to the lid will be transferred directly to the VFO A knob and the encoder.
As a counter measure I removed the foam from the lid (as can be seen in the picture below). Now there is some space between lid and VFO A knob even if the lid is closed. Instead, I put a large piece of foam on top of the bezel. If the lid is closed the foam will be compressed and keeps the KX3 in its place. But it no longer applies any pressure to the VFO A knob. If this temporary solutions works, I’ll have to think about something more professional…

go-box