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Showing posts from May 17, 2019

AnyTone AT588 Receive self oscillation

I am using this AnyTone 144MHz 10/25/50W FM mobile device last years for local  144MHz traffic.
A lot of power from a very small VHF mobile rig 
Though it will get very hot in longer chats at the 25 or 50W level
The RX-standby power is  0.25A
But sometimes it happens that sudden the squelch seem to open and a loud noise comes out.
The RX signal level showed 5 bars even with disconnected  antenna.
The signal happens to be generated internal.
The noise/signal disappears when just touching the power cord or AnyThing(...) external at the device
Ghostly ...
Found internal a beautiful well build device with gold plated PCB.
I have no service document or diagram. Hard to believe that this professional build device would suffer from a self oscillating pre-amp stage, but i can't draw an other conclusion.
I could not see any malfunctioning parts.  A wide-band design no tuning parts.
Suspect is the first RX FET to have a constant parasitic self-oscillation.
Hard to detect with my RF detect…