HF/6M Antenna Tuner Preselector
and Antenna Switcher

By Guy, de ON6MU
revision 3

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

• 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

• 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).

• Shoke 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.
  

Pictures

original prototype

revision 2

All revisions

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

.ON6MU Ham mods
.Modifications of transceivers


73"

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