Overview

SOTAbeams Pico Tuner End-Fed Half-Wave Tuner Kit

SOTAbeams Pico Tuner Kit is the smallest 10 watt rated tuner designed for installation on the feedpoint of SOTAbeams or home brew end fed half wave antennas. It is a single band tuner kit that is configurable for operation on any single frequency band between 7 and 30 MHz (40M – 10M).

High quality components are used to provide low loss operation and clear online instructions make building the kit easy. A test resistor (dummy load) is included to allow you to configure the tuner before attaching your antenna. To provide the best performance floating antenna terminals using an Isolated Link Coupling arrangement are used. The Pico Tuner PC board includes strain relief attachment points for the antenna and, importantly, a counterpoise. A counterpoise with a length of 0.18 wavelengths is recommended. Configured to be fed with RG-174 coax the pc board also incorporates a strain relief for the coax itself.

The Pico Tuner is designed using a rugged 200V ceramic trimmer in parallel with a specially selected 200V high Q surface-mount RF capacitor to offer a 10 watt rating making it the ideal tuner for KX-3 users.

Pico Tuner – End-Fed Half-Wave Tuner Kit Specifications:
- Power rating – 10 Watts
- Bands – may be built to work on any single band, 7 – 30 MHz
- PC Board size – 18 x 57mm (0.7 x 2.25 in.)
- Weight – 3 grams (<0.15 oz.) approx.

Additional information for building your Pico Tuner:
If working with surface mount devices, specifically surface mount capacitors, is something you would be uncomfortable with you can use the resistor test holes to mount a leaded capacitor (not included).

If building your Pico Tuner for 10-12-15M you can leave out the 100pF capacitor and just use the trimmer. You will have to use more turns on the toroid to resonate it of course. As a start try 21 MHz – 22T, 24 MHz – 18T and 28 MHz – 16T. Values based on the trimmer set half way (approx. 25 pF).

If you replace the toroid with a T50-10 mix (not supplied) and just use the trimmer, the Pico Tuner should work on 6M. Try 9T on the toroid as a start.

While the Pico Tuner is designed as a single-band tuner, multi banding is possible. I did the math and 12M-10M, 15M-12M and 17M-15M look possible (trimmer in parallel with 100pF). If you don't install the SMD capacitor (or use a lower padding capacitor) other possibilities arise.

There is also a second set of SMD capacitor pads on the Pico Tuner which would allow experimenters to install additional padding capacitance to allow the use of bands lower than 7 MHz. Bear in mind that in such cases, the tuning range will be reduced.

Documentation

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