My projects

RF - Software and Tools

For 160mtrs contest operation a multitude of receive and transmit antennaes needed to be controlled and selected. Some of the antenaes will be powered by a seperate poweramplifier. For ease of operation a remote control was needed for quick selection of one of the receive antennaes.

Driving more than one poweramplifier can be done by using a simple passive power splitter arrangement. Drawback of this approach is that you do not have fine grain control on the driving power for each power amplifier. In most cases you need different driving power because the poweramplifiers are not equal. One PA might be a tetrode tube amplifier, needing only 20W of input power to get full output level and the other might be a triode of bipolar PA needing substantial more driving power. One way to overcome this is to use different sets of attenuators (a.o. fixed resistive attenuators, different lengths of coax cable, etc). End result is a time consuming and not satisfactory and optimal operation.

This active splitter design preclude all those drawbacks !. A description is given for a 4 port 144MHz design, but also a 2 port and a 3 port 432 MHz design have been constructed.

 Driving more than one poweramplifier can be done by using a simple passive power splitter arrangement. Drawback of this approach is that you do not have fine grain control on the driving power for each power amplifier. In most cases you need different driving power because the poweramplifiers are not equal. One PA might be a tetrode tube amplifier, needing only 20W of input power to get full output level and the other might be a triode of bipolar PA needing substantial more driving power. One way to overcome this is to use different sets of attenuators (a.o. fixed resistive attenuators, different lengths of coax cable, etc). End result is a time consuming and not satisfactory/optimal operation.

This active splitter design preclude all those drawbacks !. A description is given for a 3 port 432MHz design, but also 2-and a 4 port  144MHz designs have been constructed.

During (contest) operation we used for the 70cm band some pre-amplifiers based on the design of oz1pif (OZ1PIF, 2009). As an active element this design uses a Agilent ATF-54143 Low Noise Enhancement Mode Pseudomorphic HEMT. Pre-amplifiers were mounted near the antenna and switched by means of some RF coaxrelais. Although performance is very good a number of HEMT's where destroyed during transceive operation. After ruling out any mall configuration in receive-transmit sequencing the only cause of destruction could be the RF power at the input due to the finite isolation of the coaxrelais. This paper investigates the permissible RF power level at the input of the pre-amplifier and as such provides some metrics to the required isolation level.

Athena now compatible with n1mmlogger+ 

Athena is the goddess of wisdom, peace, warfare, strategy, handicrafts and reason, shrewd companion of heroes and the goddess of heroic endeavour

The goddess Athena was a superb strategist and many of the Greek myths recount tales of her help given to various gods, goddesses, and heroes as they went into battle or faced seemingly impossible tests. Although she was widely known in one of her roles as "Athena Goddess of War", it was as a mediator and a planner that she excelled. She always worked to prevent war, but once war had been joined the goddess Athena fought efficiently for her side.

In this constellation Athena will be used as a graphical interface to display N1mmLogger compatible real time contests statistics including goal data. Athena can help you with the best strategy and do welll in e.g. the CQ "Worldwide War"contest....

During the design and construction of my 160 mtrs power amplifier the need arose to have a well defined 50 Ohm load. This article describes the construction of such a 50 Ohm load capable of sinking 4 kW with 100% duty cycle for very long period of time. Constructed is water-cooled load consisting of 18 times 250 Watt high power flange mount resistors. 

 

Filament inrush protection is required for most tubes. Upon applying AC (or DC) power to the cold filament this inrush current is limitted by the source resistance and cold filament resistance. In case of AC operation this source resistance is mostly the secundairy transformer resistance in series with, if applicable a series resistor (serie resistor to set the filament voltage for correct filament voltage under steady state operation). Cold filament resistance will be a fraction of the "hot" filament resistance as calculated from the datasheet (filament voltage divided by filament current).

For EME and contest operation the need arose to get on the 70cm band power levels around 1 KW. Design and construction should be such that no major de-tuning exists over a contest timeframe and more or less unattended operation is possible. These design criteria where possible by using a GS23B tetrode tube in a cavity design.

Goal was to have for contest operation a stable and virtual no tune amplifier capable of delivering 1KW of output power. This goal has during 2003 been accomplished, based on the design of DL4MEA. This design is using a Russian GS35B tube. At some points this design has been altered and those will be described below in more detail.

  • Measurement of the kathode and grid current
  • Anode lecher lines changed to single tubes and seperate (doorknob) anode capacitors
  • Added is a novel controlcircuit for fault monitoring and TX-RX sequence
    • Cathode current
    • Grid current
    • Anode supply voltage
    • Heater supply votage
    • Blower air temperature
    • Blower air flow

 

To align a power amplifiers for optimum CW (pulse) operation this pulse controller was developed. Also it can be used when a dummyload with non adequate powerhandling is availabe (average powerhandling requirement is reduced by a factor of 2 to 3). It will control the exciter (transceiver), obtain a forward power voltage sample and output this voltage for measurement with a DC voltmeter. Input is a footswitch for continues pulse operation or a paddle/pushbutton for single shot measurement. Pulse parameters (duration, sample delay time and duty cycle) are controlled by an single chip microcontroller.

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