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Grundig Satellit 650: unstable FM reception

Ernst Erb Martin Renz Vincent de Franco Miguel Bravo-Cos Mark Hippenstiel Alessandro De Poi Heribert Jung Bernhard Nagel Eilert Menke Dietmar Rudolph † 6.1.22 
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Forum » In General » Grundig Satellit 650: unstable FM reception
Antonio Moreno
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23.Jan.18 19:32

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My receiver (Grundig Satellit Professional 650 version) has a long period unstable sensitivity/frequency stability on FM reception, apparently not depending on working elapsed time, nor ambient temperature changes.

I have checked the +30 v. supply (for tuning varicaps FM section), and is stable. Also most of internal dc power unit levels.

For strong RF signals, the volume received and tuning indicator may slowly vary accordingly over time (say 1/2 an hour) from level 3 to level 6-7 or so, and back, without any apparent reason nor changing any tunning control.

I have observed that some small detuning (several KHz) during low sensitivity periods may improve a little bit reception (and signal strength level), changing over time from below to above center tuning freq., or viceversa, but with received sound quality impaired.

I have also checked Local Osc Test points dc levels at both ends of FM band, and both are according to this model Grundig specs. (Thanks for the alignment info provided in RMorg!!).

Visual inspection of printed boards (in particular the RF-IFs ones) does not provide any additional clue.

Some times the reception is perfect for long time periods! (not so often).

LW, MW and SW are working completely OK (in fact the FM Front-end and IF sections are totally independient).

Does anyone have any orientation or possible solutions for this behaviour?. Thanks.

Bernhard Nagel
Bernhard Nagel
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24.Jan.18 09:39

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Dear Antonio Moreno,

two identical posts in the same forum and language flag are not necessary. Here we close and delete later on. See the original posting here.

Furthermore, specific questions shall always be started from the regarding model. The remaining post will be moved accordingly.

Bernhard Nagel

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