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Thread: How To Tell The Difference: Null Modem Or Straight Cable Determination

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    Scammer hater PBP Moderator Rank No Warranty's Avatar
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    How To Tell The Difference: Null Modem Or Straight Cable Determination

    The #1 loading problem is communication between PC and IRD. This is usually a serial and null modem cable problem.

    Null Modem cables look like straight serial cables and the only way you can tell the difference by looking is most Null Modem cables are marked with "NM" or "Null Modem".
    Some dealers are shipping Pansats with straight modem cables and NOT Null Modem.
    If your cable is not marked, the only way you can tell them apart is with a multimeter or continuity tester. With a straight thru serial cable, pin 2 should lead to pin 2 and pin 3 should lead to pin 3.

    A null modem cable pin 2 should lead to pin 3 and pin 3 should lead to pin 2.

    If straight thru then all pins should point to the same number on the other end.

    Your local rat shack has the replacement adapter for under $10.00 , Part # 26-0264 ~ female DB9 to male DB9 ~ pins 5 straight & 2 & 3 crossed ..

    Want to know what cable you need to flash that shiny,new receiver ? There are two types of cables used, and both look the same on the outside, but are wired differently internally. They are the straight DB9 RS232 female to female cable, and the Null 9 pin RS232 female to female cable. The straight DB9 cable has all pins connected the same at both ends(pin 1-1, 2-2,3-3,etc.). The Null cable(also known as a Null-Modem) has pins 2 and 3 crossed(pin 2-3, 3-2). You can use a straight DB9 cable to program receivers requiring a Null cable, by purchasing an inexpensive Null adapter to attach to one end of the straight DB9 cable. This allows one cable to be used for any receiver.

    Hope this helps.

  2. #2

    Re: How To Tell The Difference: Null Modem Or Straight Cable Determination

    Quote Originally Posted by No Warranty View Post
    The #1 loading problem is communication between PC and IRD. This is usually a serial and null modem cable problem.

    Null Modem cables look like straight serial cables and the only way you can tell the difference by looking is most Null Modem cables are marked with "NM" or "Null Modem".
    Some dealers are shipping Pansats with straight modem cables and NOT Null Modem.
    If your cable is not marked, the only way you can tell them apart is with a multimeter or continuity tester. With a straight thru serial cable, pin 2 should lead to pin 2 and pin 3 should lead to pin 3.

    A null modem cable pin 2 should lead to pin 3 and pin 3 should lead to pin 2.

    If straight thru then all pins should point to the same number on the other end.

    Your local rat shack has the replacement adapter for under $10.00 , Part # 26-0264 ~ female DB9 to male DB9 ~ pins 5 straight & 2 & 3 crossed ..

    Want to know what cable you need to flash that shiny,new receiver ? There are two types of cables used, and both look the same on the outside, but are wired differently internally. They are the straight DB9 RS232 female to female cable, and the Null 9 pin RS232 female to female cable. The straight DB9 cable has all pins connected the same at both ends(pin 1-1, 2-2,3-3,etc.). The Null cable(also known as a Null-Modem) has pins 2 and 3 crossed(pin 2-3, 3-2). You can use a straight DB9 cable to program receivers requiring a Null cable, by purchasing an inexpensive Null adapter to attach to one end of the straight DB9 cable. This allows one cable to be used for any receiver.

    Hope this helps.
    Most of the Null Modem Cables are Not labeled these days with NM

    And Radio Shack Employees for the most part have no idea about the difference between the 2.

    Here are the diagrams for how they are wired.
    Attached Thumbnails Attached Thumbnails How To Tell The Difference: Null Modem Or Straight Cable Determination-rs232-straight-cable-png   How To Tell The Difference: Null Modem Or Straight Cable Determination-rs232-null-modem-cable-diagram-jpg  
    Last edited by SETWIRE; February 15th, 2012 at 03:04 PM.

  3. #3

    Re: How To Tell The Difference: Null Modem Or Straight Cable Determination

    Quote Originally Posted by SETWIRE View Post
    Most of the Null Modem Cables are Not labeled these days with NM

    And Radio Shack Employees for the most part have no idea about the difference between the 2.

    Here are the diagrams for how they are wired.
    To add...and that's true like my buddy "SETWIRE" said most null modem cables are not labeled these days with NM but you can look at the color of the cables, if it's dark gray or very dark gray in color most likely you have null modem cable. Straight modem cables at most are light gray or very light gray in color.
    And like "No Warranty" said if you have straight modem cable and in need of null modem cable you can get part number 26-0264 from Radio 'Rat" shack under the $10 but still if you don't have serial port in your PC desktop/laptop, you’ll need a USB adapter to work with the straight or null modem cable. I use BELKIN FSU409 (it’s old) but you may find a newer adapter model.

    Hope this post will be at great help to you.
    Last edited by askendria; March 31st, 2012 at 04:30 AM.

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