From cbfsb!att!linac!pacific.mps.ohio-state.edu!zaphod.mps.ohio-state.edu!mips!darwin.sura.net!mlb.semi.harris.com!heimdall.mlb.semi.harris.com!rliles Thu Apr 23 10:46:17 EDT 1992
Article: 17894 of rec.radio.amateur.misc
Path: cbfsb!att!linac!pacific.mps.ohio-state.edu!zaphod.mps.ohio-state.edu!mips!darwin.sura.net!mlb.semi.harris.com!heimdall.mlb.semi.harris.com!rliles
From: rliles@heimdall.mlb.semi.harris.com (Ray Liles)
Newsgroups: rec.radio.amateur.misc
Subject: PK-232 RF Ground Loop Modification
Keywords: PK-232 PK232 mod rf
Message-ID: <1992Apr23.050638.4987@mlb.semi.harris.com>
Date: 23 Apr 92 05:06:38 GMT
Sender: news@mlb.semi.harris.com
Organization: Harris Semiconductor, Melbourne FL
Lines: 63
Nntp-Posting-Host: heimdall.mlb.semi.harris.com


The following modification was developed to eliminate a RF ground loop
occurring  between my Kenwood TS-440 and AEA PK-232 TNC.  Whether or not this
mod will apply to your application, will depend on equipment type and
operational configuration.

In my station, I run all my equipment off the same power supply, to enable UPS 
capability by means of a lead-acid battery floating across the supply.  In
using the TS-440 and PK-232, I experienced RF ground looping, whenever I
transmitted and left the PK-232 audio cable connected to the ASFK input on the
TS-440.  While trying several *recommended* mods, this is what I developed,
which has worked quite well.

Parts required: 1 - 1N4001 diode (or equilavent 1N4004, etc)

Remove the mother board from the PK-232 housing and turn upside down.  

Position the board with the rear side close to you and the front of the board
with LEDs facing away. 

Cut a 1/8" section of the ground trace near the power connector.

Place the diode with cathode (banded end) at the connector and the anode end on
the other side of the cut trace.

NOTE:   DO NOT perform this for the entire ground system!  Leave the ground
        trace on the side of the mother board alone.

                                       < LEDS >
                        o  o  o  o  o            o  o  o  o  o
                ---------------------------------------------------
                |                       FRONT                     |
                |                                                 |
                |                                                 |
                |                                                 |
  |--------|    |                                                 |
  | bottom |    |                                                 |
  |  view  |    |                                              | ||
  |--------|    |                            ground trace ->   | ||
                |                                              | ||
                |                                              | ||
                |   ground trace --:         diode             | ||
                |                  |      :--[__|]--:          | ||
                |                  V      |         |          | ||
                |   ______________________|_______  |_   ______/ ||
                |   ______________________________  __[X]_______/ |
                ---------------------------------------------------
                                                   ^   ^
                               cut trace section --:   :-- power connector






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  \  \  \                                         |  Harris Semiconductor     
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    \ |\  \                                       |  P.O. Box 883             
      |      WA4VME                               |  Melbourne, Florida 32902 
      |      Ray H. Liles                         |  407-729-4640 (Office)    
      |      rliles@heimdall.mlb.semi.harris.com  |  407-729-4029 (FAX)       
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