mini l tuner for portable use
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Mini L-Tuner by DK2TY Designed for portable use with a 21m wire. SWR < 1.5 from 10–
60m. Power up to 100W CW for antennas with high impedance. Note: You must use a
small 3m counterpoise, or 3m coaxial cable and than a choke.
Wire Lengths:
• 6.4m wire: 10–20m bands
• 13.5m wire: 10–40m bands
• 21m wire: 10–60m bands
Materials Required:
• 12-pole rotary switch
• Polyvaricon (2x270pF in series)
• BNC socket
• Built-in banana socket
• Amidon T 106-2 core (No Chinese clones; they have poor Q-factor!)
• Housing/Enclosure
• Enamelled copper wire (max 1mm)
Construction:
• Wind 27 turns, tapped at: 2, 4, 6, 8, 10, 12, 14, 17, 20, 23, 26, and 27.
• Solder the 12-First, create a short circuit at the 12-pole switch; this short circuit is
the connection for the 27th turn.
• Pay close attention to the winding direction on the core.
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That’s a link on your Android smartphone.
We can’t access it.
73 Manfred DB3KE
Thank you, I know. I tried to upload a PDF file from my Android Smartphone. But i had no succes. I send you the PDF to your darc email. If you know how to uplod a PDF to the reflector with the mobile please let me know.
73, Edwin
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As far as I remember, the reflector cannot act as a file storage area; you need to put it on your own web storage and post a link to the file there if you want to make a your file available to the readers.
73 Ed.
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I wouldn’t want to load the capacitor with 100 W… 
73 Armin
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The recommended wire lengths are very high-impedance on most bands, being more or less half a wavelength long.
Because high impedance also means high voltage, the maximum voltage (along with the maximum current) is also a factor when determining the maximum usable power with the variable capacitor.
These miniature variable capacitors are typically rated for a maximum DC voltage of 100 V and are operated at power levels of max. 5–10 watts.
Rough calculation: With an antenna impedance of 2000 ohms, the voltages at 10/15/20/100 watts are approximately 141/174/200/448 volts.
Therefore, a review of the specified values is strongly recommended.
Note: These RMS voltage values can be used for comparing DC voltage values. However, in AC applications like the present case, the peak voltage is relevant: V(peak)=V(RMS)×1.414
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At 10 watts and 2000 ohms, the peak voltage is 200 volts. 632 volts at 100 watts.
73, Peter - HB9PJT
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Try it, I testet with 100W
It works with the mobile. I opened the PDF an copied the text.
With a very thin 21 m wire 0.25 mm2 I need 10uH on 40m. That means 4000 Ohm on the feeding point.
But it works!!
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Be careful with your comments—you haven’t tested it.
73 Edwin
Mini L/C Tuner (based on DK4TY’s design).
100W using a miniature film variable capacitor? That can’t possibly work - that was my initial thought. So, I decided to build one and put it to the test!
The verdict: Successfully tested at 100W, running FT8 on the 10-meter band.
The setup consisted of a 6.20m wire antenna mounted on a fiberglass mast, the mini-tuner, 2 meters of RG58 coax cable and a common-mode choke.
However - and this is key: Naturally, you must *not* tune the unit at the full 100W power level, rather, you should only apply the 100W load once the tuner has already been tuned.
Also tuned on 14 MHz, no problems with 100W! So I think for portable use and a maximun of 50W output power should not cause any problems.
DF5TR Bert
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