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.„
While operating on DM/BW-852 I encountered an issue with the Keyer/Mic- encoder of my KX3. For about a minute it wasn’t possible to change the keyer speed. Luckily the speed was set to a reasonable value (20 wpm). Then, maybe by touching the knob differently, it worked again.
A couple days ago, when preparing the activation, I had the same issue while trying to reduce the KX3’s output power. I pushed the button (the display showed 10 W) and turned the knob. The reading went down to 9.8 and stayed there regardless of any further turning. I switched to „keyer speed“ by pushing the knob (which actually worked) and tried to change the keyer speed to no avail. Then I switched back to output power and turned the knob again: the encoder did not work. Even after switching the KX3 off an on, it remained in this state.
Next I opened the KX3, took out the CP- board and did some resistance measurements at the back side of [Z4]. Now the encoder seemed to be working again. After assembling the KX3 everything worked smoothly.
It looks like the encoder has an issue. But before I replace it (or even all four of them) I asked the experts at ELECRAFT for a confirmation. The reply arrived within a few hors (!)
„Hi Roman, Thanks for the contact. To your questions on the KX3 encoders, we have received reports of some encoders losing some of the damping fluid that is embedded into the shaft and sleeve. These are sealed but can leak. When this happens, some of the fluid will get into the optical encoders and cause the symptoms you are seeing. Generally, we recommend all 4 be replaced at the same time to save having to do them individually. We do this with the K3 and K3S encoders in much the same way. The KX3 encoder is Elecraft part #E640018 at $2.08 each.“
The encoders are already ordered and will be replaced as time permits. Thanks ELECRAFT for the fast support!
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.
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.
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.
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.
On the trip to DL/AL-093 my rucksack was pretty heavy. Carrying all the things for an overnight stay in the alpine hut plus food & water plus radio & antennae added up to a total weight of more than 13 kg.
Back home I put everything from the KX3 to the pencil on the scales. The result was alarming: my SOTA- gear was weighing about 4700 grams! This is acceptable for trips to the low mountains but is definitely too much for higher summits and long hikes.
The top three contributors were:
Fiberglass pole (10m)
KX3 in Go- Box
Multiband Dipole with coax
A search for alternatives unfolded:
A lightweight 6m fiberglass pole is available but has a slight drawback: The usable height is only about 5 metres.
The MTR3B would significantly reduce the weight of a KX3 while only slightly reducing the operating comfort. It is possible to work on three bands. My signal would drop about 1 S- unit due to 6dB lower output power. This seems acceptable considering the reports I usually get.
An End Fed Half Wave Dipole (possibly with traps) appears to be a good alternative to the Multiband Dipole. Only a short piece of coax is required instead of 10 metres and – if mounted as inverted L – it has a lower footprint. A big bonus on a summit with restricted space. If built with traps, changing bands can be done in no time.
With these three measures the total weight of my SOTA- gear can be reduced by about 2.5kg without losing much performance.
The fiberglass- pole is already available and will replace the 10m Mast in the future.
A MTR3B Kit has been purchased. Assembly report is available here.
Antenna design hints for a Three Band EFHW Dipole can be found here.
Nachdem ich einige SOTA- Referenzen mit Monoband- Antennen aktiviert hatte, entstand der Wunsch nach einer Mehrbandantenne, denn der Bandwechsel war eine zeitraubende Angelegenheit. Die Antenne sollte mindestens die Bänder 40m, 30m und 20m abdecken, optional 15m. Der Umbau sollte nicht länger als drei Minuten dauern.
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.
Für den noch zu bauenden Mehrband- Dipol sollte eine Mantelwellensperre entworfen werden. Es gibt einen sehr guten Beitrag im Antennenbuch von HB9ACC. Leider ist das pdf im Moment nicht online verfügbar. Das ‚Transmission Line Transformers Handbook‚ von W2FMI in englischer Sprache ist ebenfalls sehr empfehlenswert.