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Automatic Antenna Coupler Model 253


  • Adjustable reactive network used for matching the unbalanced 50 ohm output impedance of transmitters and transceivers to a variety of balanced and unbalanced loads.
  • Automatically tunes from 1.8 to 30 MHz.
  • Capacitor and Inductor up/down switches for manual adjustment.
  • Provision for selecting one of four antennas or for bypassing the matching network.
  • Built-in memory stores settings for each of the four antenna positions on each of seven band settings, giving a total of 28 memory combinations.
  • Includes dual range power and SWR meter.


Mods & Tips


  • Circuit Type: Reversible "L" network.
  • RF Power Rating: 2 KW maximum.
  • Frequency Range: 1.8 to 30 MHz.
  • Input Impedance: 50 ohms, nominal.
  • DC Power Input: 12 - 14 Volts, 2 amps maximum.
  • Tuning Accuracy: 1.5:1 VSWR maximum after tuning; 2.5:1 VSWR maximum during tuning.
  • Automatic Tuning Time: 5 seconds typical, 30 seconds maximum (from home position).
  • Manual Tuning: Full range manual tuning available via front panel up/down switches
  • Memory Tuning: Tuner automatically returns to settings last used for each antenna switch position. Separate settings are stored for each band if remote band connector is used. Retuning (auto or manual) updates memory.
  • Tune Power: 50 watts minimum, 150 watts maximum. Radiated power at least 6 dB below input during tuning.
  • Antenna Switch: 4 position. Position 4 configurable for coax, single wire, or balanced line fee. Internal balun standard.
  • Output Matching Range: At least 10:1 VSWR, any phase angle, 1.8 to 30 MHz. 1300 ohms maximum parallel equivalent resistance at 1500 watts output (2 KV peak, >26:1 VSWR). 5000 ohms maximum parallel equivalent resistance across balanced line at 1500 watts output (4 KV peak).
  • Minimum Full Power Longwire Length: Single wire feed: 180/F (MHz) feet at 1500 watts output.
  • Over Voltage: "ARCING" indicator illuminates when RF voltage exceeds 2 KV. Tuner is reset to bypass mode if ARCING or OVER indication remains on for more than 1 second. Hot switching protection provided by internal relay interlock system.
  • Size: HWD 5.5" x 14" x 10.5", overall (138 x 356 x 267 mm).
  • Weight: 9 lbs 9 oz., (4.34 Kg).

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