Tag Archives: HF

DIY: HF/VHF Portable Mini Tuner de ON6MU




By Guy, de ON6MU

Schematic fig1

QRP mini tuner matcher

RE-AT2HF6/P Parts list

  • alu box of 70mm X 40mm X 33mm

  • 2 female PL 259 chassis

  • C1 = variable capacitor of at least 300pF or better 500 pF

  • S1 = 10 or more position rotary switch

  • L1 = 0,7mm insulated copper wire, 6 turns par connection closely together, 9mm outside diameter (8mm inside)
    taps every 6 turns and the last two sections (L1′ and L1”) 4 turns spaced at 1mm and 3turns spaced by 2 mm.
    The first two sections has a ferrite core inside.
    Could be that lower frequencies needs higher inductance, experiment with by adding a core in the last few sections (see fig2)

  • I added two bolts on the alu-box chassis to – if needed – connect the tuner to ground or for using a counterpoise.

  • R1: 1.5k carbon 1/4w (non-inductive resistor); optional to allow drain of possible static build-up on the antenna (or use a 10mH inductor)

  • R2: 2 x 470 carbon 1/2w parallel (non-inductive resistor); optional to have some little protection during switching when using a carier, as the switch could open the the connection for a fraction of a second during switching.

The coil

  • Wind 6 turns x – 2 connections on your switch (in this project a 10-position rotary switch is used, being 8 times 6 = 48 + 4 + 3 = 55 turns) over a 7mm screwdriver (or simular obkject hi) and make a tap every connection. Solder each tap.

  • Solder each tap to each connection of your switch and stretch L1′ (being 4 turns) at 1mm spacing and L1”(being only 3 turns) at 2 mm spacing. You can replace L1” by 3 turns of silver wire to allow better Q on higher frequencies (VHF).

  • Minituner insides…

Fig.2

  • Alex VE7DXW changed 5 of the lower 6 wdg air coils with 1 wdg, 2wdg, 4wdg, 4wdg, 6wdg ferrite core coils, which gives higher L values
    Thanks Alex!

Specifications

  • manual operation

  • frequency range (depending on the coil min & max inductance):
    160m…6m
    (Up to 150Mc if: L1” is silver(plated) wire, High Q switch, minimum capacitance of C is small enough and close connections are used in respect to 50 Ohms impedance)

  • 10 Watt +-

  • direct feed through

  • small and compact design ideal for low power QRP transceivers, like the Yaesu FT-817, or of course for receivers…

  • connection for counterpoise/ground

Notes:
If you elect to use an antenna tuner, it is extremely important that you understand exactly how to use tuners and what they can and cannot do. A few watts of RF can easily become lost in an incorrectly adjusted antenna matching device. The whole idea of a QRP station is to keep things simple and economical, so I cannot overemphasize the priority of a clean, efficient connection of the amplifier output to a resonant antenna.

 

Homemade aluminum box


73″

Source: users.belgacom.net/hamradio/