[TenTec] Orion freezes due to RFI??

[Henry Gardiner]

     Regarding RF pickup on the Jupiter via the speaker jack:
     My RX-350D is said to be the receiver section of the Jupiter.  My 
problem was the transmission of rf energy out of the receiver and into the 
very nearby antenna.  The antenna itself is simply a wire on the end of a 
piece of coax.  And no proper RF ground yet!  While I have this pickup 
problem, I know of one other ham who doesn't because he has a better 
antenna and ground system.
     So, for the sake of another solution, I present the following:
     I installed bypassing for the speaker jack.  0.1 uF disc capacitors to 
ground from each of the three pins on the jack.  Also a three-winding 
common-mode blocking transformer.  I used three lengths of 22 ga magnet 
wire twisted together at a convenient rate.  This was wound through the 
FT50-72 core 5 times. This was interposed in the circuit between the jack 
pins and the nearby pcb connectors, using the same polarity in each case.
     And, amazingly enough, the audio amp doesn't break into high frequency 
oscillation.

Henry Gardiner AC5LA


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