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Echolink and the Kenwood TM-V71A

Discussion in 'Echolink/IRLP Tech Board' started by KG5WLK, Dec 19, 2017.

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  1. KB0MNM

    KB0MNM Ham Member QRZ Page

    KA9JLM- Signal ground is pin 5 and should be wired straight through for any de-9 to de-9 that conforms to RS-232. So when you look at the DB-25, you find that signal ground is pin 7. Now would you like to address "Protective Ground" and "Shield"?
  2. KA9JLM

    KA9JLM Ham Member QRZ Page

    Not sure why you are talking about a DB-25.

    A DB-9 is what is being used. No need to complicate things.

    A lesson on the difference in DTE and DCE would be more beneficial.

  3. KB0MNM

    KB0MNM Ham Member QRZ Page

    I agree. In earlier days of computing, the terms DTE and DCE stood for Data Terminal Equipment and Data Communications Equipment. That seems cryptic to most newer folks, because they do not realize that many of the older terminals have been replaced with Personal Computers ( ie. Laptop, Tablet, etc. ) which often have built-in modems and/or wireless links and/or Ethernet(tm) ports and/or USB ports. The standard wiring for a DB-25 equipped problem which required a null modem ( Type VII ) per GC Electronics P/N 43-041 was pin 1 to pin 1 ( Protective Ground, the mistake that I started to describe in the second iteration of pin 5 ). Modern telecomm trainers recommend that pin 1 to 1 and the overall shield *not* be connected end-to-end, but rather the shield and protective ground be connected only at ONE END of the cable, due to problems that may exist between equipment bonding circuits. The remainder for a 'typical' ( and there were a few other wiring plans for DB-25 to DB-25 ) null modem: Pin 2 to Pin3, Pin 3 to Pin 2, pins 4 & 5 to pin 8, pin 8 to pins 4 & 5, Pin 7 to 7 ( this is the signal ground, not protective ground ), pin 20 to pins 22 and 26, pins 22 and 6 to pin 20. One variation had pins 6 & 8 to pin 20, pin 20 to pins 6 & 8. So why is it important to know all this? Because when you use a De-9 connection that needs the 'gender' ( male or female ) fixed, it means that someone has already tried to imply something about the equipment being connected. The fact that the standard De-9 female to male for PC to controlled equipment does not fit does not mean the job cannot be done. It just means that it is up to you to read your radio manual.{{{ The description of standard DTE (PC) RS-232 is pin 1, Data Carrier Detect Input from other device; Pin 2 Receive Data Input from other device ( thus it must be connected to the radio Transmit ), Pin 3 Transmit Data Output to the other device ( thus it must be connected to the radio Receive ), pin 4 Data Terminal Ready Output to the other device ( this usually matches Data Set Ready ), pin 5 signal ground ( for De-9 to De-9 and true RS-232, this is the most essential Signal ground- and should be connected to pin 5 at the radio ), pin 6 Data Set Ready Input from the other device (this usually matches Data Terminal Ready), Pin 7 Request to send Output to the other device (usually matches Clear to Send), Pin 8 Clear to send input from the other device ( Usually matches Request to send ), Pin 9 Ring indicator matches Pin 9 Ring Indicator. Ref. Pocket PCRef Glover/Young page 44, 7th Edition ISBN 1-885071-13-2}}}. Protective Ground is also referred to as frame ground, not to be confused with signal ground. Signal Ground is the one that you will need. Frame ground and protective ground are not available on the De-9 interface specified. If you do not need a null-modem, you will need a 'straight-through' gender mender. There may be another tech out there who has experienced the same cabling issue as your TM-V71a with a TM-D700a. 73
    KA9JLM likes this.
  4. KG5WLK

    KG5WLK Ham Member QRZ Page

    Thanks everyone for the replies and great info. I am up and running!

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