OM POWER OM3500 HF Instruction Manual
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OM POWER OM3500 HF Instruction Manual

Shortwave power amplifier
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Instruction Manual
OM3500 HF
SHORTWAVE POWER AMPLIFIER
OM POWER, s. r. o.
930 30 Bác 126
SLOVAKIA

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Summary of Contents for OM POWER OM3500 HF

  • Page 1 Instruction Manual OM3500 HF SHORTWAVE POWER AMPLIFIER OM POWER, s. r. o. 930 30 Bác 126 SLOVAKIA...

  • Page 2: Important Safety Instructions

    • The amplifier contains high voltage circuits. Never turn the amplifier on without the upper lid in place. • The OM3500 HF amplifier is not to be used in a wet or humid environment nor to be exposed to rainfall.
  • Page 3 General description of the OM 3500 HF Amplifier The linear amplifier OM 3500 HF is designed for all short wave amateur bands from 1.8 till 29 MHz (including WARC – bands ) and all modes . It is equipped with a ceramic tetrode GU78b.
  • Page 4 General Description of OM3500 HF POWER AMPLIFIER HF PART In this amplifier a tetrode GU 78b is used in a grounded-cathode circuit (input into control grid). This amplifier achieves excellent linearity by the voltage stabilization of the control grid bias and the screen voltage. The power input is given to the control grid, using a broadband power transformer with an input impedance of 50 Ohms.

  • Page 5: Power Supply

    POWER SUPPLY Power supply of the amplifier is effected by two 2kVA toroidal transformers. A soft start is realized with the help of relays and resistors. The high anode voltage consists of 8 times 430V and 2A. Each of them has its own rectifier and filter.

  • Page 6: Main Supply

    During transmitting the middle pin is connected to the ground. The relays of the OM3500 HF have to be switched earlier than HF is applied (cold switching). Modern transceivers have a time delay between PTT switching and power output.

  • Page 7: Reflected Power

    Bar graph – measure the anode voltage, anode currency or tuning of the amplifier TUNING The OM3500 HF amplifier is operated in class AB. Thus it’s possible to obtain a maximum output power at an excellent linearity. For this purpose the amplifier has to be tuned carefully.
  • Page 8 The grid-current is shown with 2 LED diodes. It’s normal if the green LED is flashing or may be shining a little bit during peak operation. If you overload the amplifier the output power increases the grid current at very small rates and the red GRID-MAX-LED is shining and the safety devices the PA to STBY.
  • Page 9 The tuning table available to you is made by using a dummy load! Each amplifier will have other values depending on used frequency and antenna! Make your own list for your own antennas! Use tuning position (see later)! 2. Reduce the power output of your transceiver to the 0. 3.

  • Page 10: Indication Of Fault Conditions

    Should a fault condition appear during the tuning or operation of the amplifier the safety circuits of OM3500 HF will react. The amplifier will be turned to STBY mode. After approx. 1 sec the control circuits will switch the amplifier back to OPR. If the fault will repeat 3 times after each other the control circuits will turn the amplifier to STBY.

  • Page 11: Important Warning

    IMPORTANT WARNING • The OM3500HF amplifier is not to be used in a wet or humid environment nor to be exposed to rainfall. • The amplifier must be installed in such a way that free flow of hot air from the tube is allowed.

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