by William Eric McFadden

The KX3 Mini Travel Kit is a small but complete low-power, CW-only, HF station in a rugged and weather-resistant LowePro Nova 1 camera bag. The KX3 Mini Travel Kit is designed for transport by bicycle or foot.

The KX3 Mini Travel Kit is currently under development. Photos may not represent the current state of the station. This page will change as various ideas are tested and accepted or rejected.

Quick Jump:  

The Rig
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Elecraft KX3 The heart of the KX3 Mini Travel Kit is an Elecraft KX3 low-power, transceiver equipped with the KXAT3 Internal Automatic Antenna Tuner, KXFL3 Dual-Passband Roofing Filter, Side KX Endplates and Cover (link), and Cooler KX Lite heat-sink (link).

The trail-friendly KX3's all-band (160-6m) coverage, all-mode (CW/SSB/AM/FM/data) capability, competition-grade receiver, truly generous feature-mix, small size, low weight, and battery-friendly design make the KX3 an extraordinary field-radio.

Portable Power
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The KX3 can operate over a voltage range of 8vdc to 15vdc. I do not keep battery cells installed in my KX3 so I must power my KX3 with an external power source.

Talentcell 12v LiPO battery Currently, I carry a Talentcell 12v 3000mAh lithium ion battery pack (link) in the KX3 Mini Travel Kit. While this small, lightweight, and inexpensive LiPO battery is called by its manufacturer a "12 volt battery", the battery, which is made up of three 3.7v LiPO cells connected in series, is actually an 11.1v battery. However, 11 volts is more than enough to keep the KX3 happy and the battery should have sufficient capacity to power the KX3 for several hours in the field. As a bonus, the Talentcell battery also includes a USB port which can be used to power or charge a smartphone or tablet, if needed, even while the battery is powering the KX3.

I would like to be able to charge my Talentcell 12v battery while afield without using an inverter and the supplied AC charger but a lack of information about the battery and its BMS make it unclear how one can safely do this. Answers by Talentcell to questions posed by others in the Talentcell Amazon store are nebulous at best. One answer indicated occasional charging with a motorcycle charging system is safe while another answer indicated charging with an automobile charging system isn't safe. One answer indicates a maximum input voltage at the 12v port of 25v is safe yet a reply to a direct email I sent said 12.6v and 2A are the maximums. One answer indicated that charging the battery with solar while simultaneously powering a radio is safe so long as the solar panel output is between 15v and 18v. Talentcell does make an automotive charger: (info: 1 | 2). The Talentcell website says their 21W solar panel is direct plug-in compatible with their 12v batteries but also says the solar panel contains an "intelligent chip" so it's unclear whether the battery's BMS alone is sufficient to prevent battery damage if maximums are exceeded.

Initial tests indicate it might be safe to trickle-charge the Talentcell 12v battery while the battery is powering my KX3 using my 5-watt PowerFilm FM15-300N Foldable Solar Charger and no solar charge controller. The open-circuit voltage generated by the panel is within the required range and the 300mA maximum current the panel can supply is well under the 2A maximum. With the solar panel and battery connected together with the battery's supplied Y-cable, the output on the third leg of the cable measures just over 12.5v with the battery nearly fully charged, so it appears the battery would act to prevent the KX3 from seeing the full solar panel output voltage of 18v. It's unclear what would happen if the battery's internal BMS detects an over-charge condition. Would it disconnect the battery from the 12v input/output port and, thus, let the KX3 see the full solar panal output voltage of 18v? More testing is needed.

Update: It turns out that the Talentcell internal BMS does disconnect the 12v input/output port when an overcharge condition is reached. This means if I'm floating the solar panel across the battery while I'm also powering the a radio with the battery, the radio might suddenly see a voltage greater than 18v. The good news is the LiPO battery didn't burst into flames or otherwise fail, so I can charge the Talentcell with solar while afield so long as I'm careful to never have the KX3 attached when full-charge is likely to be reached.

Update: Prompted by a blog-post by K4SWL (link), I measured the discharge characteristics and determined the true Ah-rating of my 3000mAh Talentcell battery. I configured my KX3 to transmit in beacon-mode, at five-second intervals, the message "CQ POTA de WD8RIF K", at power-output of 5w, into a dummy load while I measured battery-voltage and Ah-delivered with a "Model 150 High Precision Watt Meter and Power Analyzer". I stopped the test when battery-voltage dropped to 9vdc during transmit.

Time (UTC) V (RCV) V (XMT) Amps (XMT) XMIT PWR Ah Battery LEDs
1248 12.45 11.8 1.42 5 0.6 (not recorded)
1347 11.35 10.85 1.36 4 0.885 (not recorded)
1416 10.98 10.46 1.31 4 1.165 (not recorded)
1445 10.72 10.25 1.31 4 1.273 3
1457 10.66 10.2 1.31 4 1.577 3
1528 10.48 10 1.31 3.5 1.577 3
1545 10.34 9.87 1.25 3.5 1.737 3
1604 9.94 9.04 1.91 5 1.918 2

It's interesting to note that as voltage-under-transmit drops the KX3's transmit power drops slightly until the voltage-under-transmit drops to about 9v, at which point the KX3 compensates by increasing current-draw and transmitter output jumps back to 5w.

Based on the numbers, I consider the Talentcell 12v 3000mAh lithium ion battery pack to actually provide 2Ah to the KX3 when the KX3 is configured to transmit at 5w.

Note to Self: W1PID is using a PowerFilm LightSaver and a Baofeng USB to 10V Smart Charger to power an MTR-4B transceiver (link). The LightSaver (link) solar panel charges an internal 3200mAh battery and outputs 5vdc to a USB port. The Baofeng USB to 10V Smart Charger (link) converts 5vdc from a USB port to 10vdc. The KX3 can operate with a supply voltage as low as 8.5vdc so such a scheme might work with the KX3. While both the LightSaver and the Baofeng are limited to 500mA output, W1PID says his scheme works with the MTR-4B because at reduced voltage the MTR-4B produces lower output power and draws less current. It is unclear at this point if the KX3 would behave similarly.

Portable Antennas
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antenna & sundries The KX3 Mini Travel Kit includes a proven 28½' end-fed wire and three 17' counterpoise wires. This is the same antenna I've used successfully with my KX3 for hundreds of National Parks on the Air (NPOTA) and Parks on the Air (POTA) activations. I feed this antenna, without feedline, through a 4:1 impedance transformer or, sometimes, a BNC-to-dual-banana adapter. The KXAT3 autotuner in the KX3 can easily find a match for this antenna on all the bands of interest.

To hang the 28½' wire in a tree, I carry a 100-yard spool of dental floss and a couple of large fishing weights. When I don't want to fuss with throwing a line through trees, I use an inexpensive Goture Red Fox 7.2m carbon-fiber telescoping fishing pole that I strap to my bicycle or to an existing post and deploy the 28½' wire either as a sloper or as an inverted-vee. (I have removed the top three sections from the Red Fox because they're really too whippy to support a wire.) The Red Fox does not fit in the LowePro Nova 1 bag; it need to be carried separately.

The CW Key
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Whiterook MK-33 The KX3 has a perfectly adequate built-in memory keyer so I don't need to carry an external memory keyer with the KX3 Mini Travel Kit.

To key the KX3, I use a very lightweight Whiterook MK-33 single-lever paddle (photo | link).

The Whiterook MK-33 has become my paddle of choice for field operations and I have one in each of my various field-kits.

Miscellaneous
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The KX3 has a built-in speaker but I prefer to copy CW through stereo headphones. I carry a pair of iHip-brand ($5 at Big Lots) shoestring-lead earbuds in the KX3 Mini Travel Kit which sound good and might be rugged enough to last more than a few outings.

The Carrying Case
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The carrying case is a repurposed LowePro Nova 1 camera bag.

I had purchased my first Nova 1 to carry an SLR camera. After I no longer needed the Nova 1 to carry a camera, I used it for my K1 Travel Kit.

When I discovered that my KX3 fits well inside the Nova 1, with room left for the battery, key, antenna, and other sundries, I scoured eBay to buy a like-new Nova 1 for my KX3 Mini Travel Kit. This well-padded and rugged bag accommodates the KX3 transceiver, the battery, the key, earbuds, antenna, unun or balun, cables, and other items. While not fully waterproof, the bag should provide sufficient protection for the KX3 while in transport from all but the heaviest rain.

Human-Powered Transport
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I built the KX3 Mini Travel Kit to encourage me to engage in human-powered-transport field operations, in particular, for the annual Adventure Radio Society Flight of the Bumblebees event.

Biking

KX3 Mini Travel Kit on the bicycle When I originally used a LowePro Nova 1 as a camera bag, I had built an easy-to-mount, easy-to-remove, rear-rack-fixture for my bicycle to allow me to safely carry the camera bag. This same fixture now allows me to safely carry the KX3 Mini Travel Kit on the bicycle. A pannier hanging on the other side of the bicycle is used to carry a clipboard with copy-paper and logsheets, a towel to sit on, bug-spray, etc. The Goture Red Fox pole straps nicely to my bicycle's top bar.

I've carried the KX3 Mini Travel Kit on the bicycle to perform POTA activations of Lake Hope State Park (K-1968) and Zaleski State Forest (K-5455) via the Moonville Rail Trail on June 6, 2022 and on June 10, 2022; to participate in the 2021 Flight of the Bumblebees / POTA activation of Strouds Run State Park (K-1994) on July 31, 2022; and to participate in Bike Your Park Day while performing POTA activations of Lake Hope State Park (K-1968), Zaleski State Forest (K-5455), and Turkey Ridge (K-9509) via the Moonville Rail Trail on September 24, 2022.

Hiking

The removable shoulder strap on the LowePro Nova 1 allows easy transport of the KX3 Mini Travel Kit while traveling by foot. A backpack can be used to carry additional items such as a clipboard with paper and logsheets, the Red Fox pole and stake, and a towel to sit on.