MDSR LIF for the Panasonic RF4800, RF4900, DR49, etc
Contents
1. MDSR LIF for the Panasonic RF4800 RF4900 DR49 etc By Luke Snow KJ6ENWE LukeSnow Gmail com This extraction point should work for the RF4800 and RF4900 models This installation puts the LIF board inside of the receiver drawing signal and power from the radio The output signal is routed to the back panel No irreversible changes to the body of the rig were made and only a few solder joints were needed Please note that the output signal strength at the point listed below loads down the transistor lt does not seem to detune as readjusting nearby variable inductors doesn t improve gain This didn t seem to be a problem however as this radio has ample RF gain adjustability See below IF Loading 1 Input Signal Connection Figures 1 3 a Connect IF to signal to collector of Q32 or in RF4800 schematic TR32 b Connect the shield to the ground side of neighboring C255 the side nearest to the back of the receiver 2 Power Connection Figures 1 2 a Connect 12 volt power from the radio to the LIF board This is near CP16 See the photos and use a volt meter to confirm location polarity of the power connection 3 Output Signal Connection Figures 4 5 a The version used for this installation was the RF4900LBS This version of the RF4900 had a jack in the back for connecting to a record cassette player This interface had screws and therefore after a bit of soldering could be bagged and taped away no need to remove it Sheet m2. etal was cut to size with screw holes drilled out Screws were put through the holes and a 3 5mm audio jack was put in place Refer to the photos IF Loading Without being connected to the LIF the voltage output at the above extraction point was about 40mVpp for a strong local station When connected to the LIF the voltage output dropped to about half 20mVpp To remedy this an op amp circuit would probably be the circuit of choice Use a non inverting op amp with a gain of 0 5 or even less am still experimenting with the best gain to use and this intermediate buffer circuit is not yet shown in the figures below Service Manual http www freeinfostuff com RF4800 RF 4800Service pdf Regio i F k ae hi CoA Figure 1 Top view Figure 2 Side view Figure 3 Extraction point close up Figure 4 Output port modified for 3 5mm mono audio jack Figure 5 Inside case view of 3 5mm jack Stock components bagged and taped radio can be returned to stock configuration
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