In Part 3 I described how to generate a keyed CW signal using the ADALM PLUTO software-defined radio and SDR-Console software. This post focuses on the assembly of 2.4GHz uplink components.
Modification of the ‘Wifi’ Power AmplifierThe EDUP power amplifier is intended for boosting WiFi signals and includes both a power amplifier and receive preamplifier. When it detects RF of sufficient amplitude it quickly switches to transmit mode. The changeover has been found to cause distortion with SSB signals. Therefore it is common practice to disable the automatic changeover when using the amplifier in amateur radio applications, i.e. putting it into permanent transmit mode. The modification for this appears on several websites and was also published in the RadCom article I have mentioned in a previous post (G Read, 2019). I modified the amplifier by connecting a 100k resistor between TP2 And TP4 (see photo).
ConstructionThe transmit amplifier for the uplink comprises two SPF5189Z broadband amplifiers, a 2.4GHz bandpass filter and the modified power amplifier. 5V power for the broadband amplifiers is provided by a linear voltage regulator based on a 7805 (see below). I reused an old diecast metal box from a previous project to house the electronics. The box also provides additional heat-sinking for the power amp module. The 12V input to the 5V regulator is taken from the power amp PCB.
|5V linear regulator|
Further WorkThe next job is to improve the 2.4GHz uplink antenna. I have purchased an 80cm dish, which I intend to feed with a short yagi or a patch antenna.
ReferenceRead, Giles (2019). ‘The Easy-100 No-tune uplink converter for QO-100 (Es’hail-2) sat’, Radcom, June 2019, pages 28-31.
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