HF/6M Antenna Tuner Preselector and Antenna Switcher
RE-AT1HF6

By Guy, de ON6MU
revision 3

RE-AT1HF6 Schematic fig1

Parts list

• alu box of 200mm X 130mm X 70mm

• 3 female PL 259 chassis

• Analog Meter (as sensitive as possible and calibrate the scale with a good SWR meter)

• C1 = variable capacitor of +/- 2 x 500 pF (air spaced)(1kv). C1 isisolated from the ground!

• C2 = variable capacitor +/- 280pF (air spaced)

• S1 = 6 pos. switch

• S2 = mini toggle switch

• S3 = solid 380v/10A toggle switch

• P1 = 10k log variable resistor

• D1, D2 = 2 germanium diodes AA15,AA109 etc.

• R1, R2 = 50 Ohm (2 x 1/4watt 100 Ohm parallel)

• R3 = 4k7 1watt carbon

• C3,C4 = 4n7

• C5 = 22nF

• L1 = 1,5mm insulated copper wire, 27 turns close together, 19mm outside diameter (16mm inside)
  taps at 10, 9 and 8

• L2 = 1,5mm insulated copper wire, 5 turns with 1mm space, 19mm outside diameter (16mm inside)
  tap at turn 3

• L3 = 1 mm insulated copper wire, 4 turns no space, 9mm outside diameter (7mm inside)

• L4 = RG-58 coax wound around a 8 cm long carbon rode and fixed with tape

• L0 & L0' = 1,5 turns approx. 6 cm as long as the centre part L0" which is 1 mm separated.
  you also can use self-adhesive copper tape instead of wire or a toriod.

• L0" = 6 cm long copper wire (or copper line of 5 mm wide if you use a PCB)
  (L0, L0' and L0" makes out the SWR meter which is laid out as in the schematic fig1)

Specifications

• long wave, medium wave and shortwave preselector tuner lets you boost your favorite stations while rejecting images, intermod and other phantom signals on your shortwave receiver.

• frequency range: 2Mc...52Mc
  180m band depending on the mismatch of the antenna used and/or maximum inductance. Experimenting with the coils can be desirable.

• 150 Watt +-

• switchable between two antenna's

• shoke antenna output

• band-pass type (harmonic filter)

• pre-selector

• SWR meter (if needed, else you can simply leave it out HI)
  

Revision 2 notes:

• improved SWR bridge

• R3: to drain any possible static build-up on your antenna

Revision 3 notes:

• L3 added and last of L1 tap changed to allow tuning up to 52MHz!

• L1 changed (was at 9, 9, 9 and 4) for better bandspread and higher top frequency range
  L2 (was 1mm, 10 turns close together, 18mm outside diameter) removed in revision 3 (click on the link for revision 2).

• Choke antenna output added to prevent HF-currents on the transmission cables (to improve immunity when using badly tuned antenna's)
  Can be used on good antenna's too of course.
  

• Notes: remember that you can always experiment with inductance (L1, L2, L3) to best suit your specific needs.

Pictures

original prototype

revision 2

All revisions

This is how Herman PA3EHZ made the tuner:

click images to enlarge
Thanks Herman for the pics!

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. I cannot overemphasize the priority of a clean, efficient connection of the amplifier output to a resonant antenna.

Don't forget to check these out:
.ON6MU Homebrew projects
.Radioamateur related projects

.ON6MU Ham mods
.Modifications of transceivers


73"

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