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Exhibit 10.1.20 Second Extension Amendment to the iDEN Infrastructure 5 Year Supply Agreement SECOND EXTENSION AMENDMENT
TO THE
IDEN INFRASTRUCTURE 5 YEAR SUPPLY AGREEMENT This Second Extension Amendment to the iDEN Infrastructure 5 Year Supply Agreement (Amendment) is
entered into this 14th day of December, 2004 (Effective Date) between MOTOROLA, INC.,
a Delaware corporation, by and through its Global Telecom Solutions Sector, with offices at 1421 W.
Shure Drive, Arlington Heights, Illinois 60004 (Motorola), and, NEXTEL COMMUNICATIONS, INC., a
Delaware corporation, with offices at 2001 Edmund Halley Drive, Reston, VA 20191 (Nextel); WHEREAS, Motorola and Nextel previously entered into (i) the iDEN Infrastructure 5 Year Supply
Agreement effective as of the 1st day of January, 1999; and (ii) the Term Sheet for Subscriber
Units and Services dated as of the 31st day of December 2003; WHEREAS, Motorola and Nextel previously entered into the Extension Amendment dated March 16, 2004,
and effective as of January 1, 2004, which extended the term of the agreements described in (i) and
(ii) of the foregoing recital through the earlier of December 31, 2004 or execution of a new
agreement (the iDEN Infrastructure 5 Year Supply Agreement, as amended by the Extension Amendment
shall be referred to herein as the Existing Agreement; the Term Sheet for Subscriber Units, as
extended by the Extension Amendment shall be referred to herein as the Handset Term Sheet); WHEREAS, Motorola and Nextel previously entered into the 6:1 Interconnect Resolution Agreement
dated as of the 30th day of September, 2004, which amended the terms of the Funding Model (attached
as Exhibit A to the Extension Amendment); and WHEREAS, Motorola and Nextel wish to further extend the term of the Existing Agreement through
December 31, 2007. WHEREAS, Motorola and Nextel intend that all terms, except as modified herein, of the Existing
Agreement (as amended by the Extension Amendment or other amendments) shall remain in full force
and effect. NOW, THEREFORE, in consideration of the promises and mutual obligations contained herein and for
other good and valuable consideration, the receipt and sufficiency of which are hereby mutually
acknowledged, Motorola and Nextel agree as follows: 1. General Except as set forth herein, all capitalized terms not defined herein shall have the meanings given
to them in the Existing Agreement or the Handset Term Sheet, as appropriate. 2. Modifications to Existing Agreement Motorola and Nextel hereby agree as follows (all references are to sections in the Existing
Agreement).  a)
    Section 28, Term, is hereby amended by substituting December 31, 2007 in place of the
date December 31, 2004.  b)
    The date December 31, 2004 which appears in Section 2(c) of the Extension Amendment
is hereby amended to read December 31, 2007.  c)
    Section 4 of the Extension Amendment, entitled Extension of the Handset Term Sheet,
shall remain unmodified, and shall not (nor shall the Handset Term Sheet referenced
therein) be deemed modified, extended or otherwise affected by any of the terms of this
Amendment. Motorola and Nextel Confidential Proprietary 1




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Second Extension Amendment to the iDEN Infrastructure 5 Year Supply Agreement 3. Entire Agreement This Amendment and its Exhibits and the Existing Agreement constitute the entire understanding
between the Parties concerning the subject matter hereof and supersede all prior discussions,
agreements and representations, whether oral or written and whether or not executed by Nextel and
Motorola. No modification, amendment or other change may be made to this Amendment unless reduced
to writing and executed by authorized representatives of both Parties. IN WITNESS WHEREOF, Motorola and Nextel have entered into this Amendment as of the Effective Date
first written above. MOTOROLA, INC. 
Global Telecom Solutions Sector
    
    
    
    NEXTEL COMMUNICATIONS, INC.By:
    
    /s/ Charles F. Wright
    
    
    
    By:
    
    /s/ Brian MeadowsName:
    
    Charles F. Wright
    
    
    
    Name:
    
    Brian MeadowsTitle:
    
    Senior Vice President
    
    
    
    Title:
    
    Senior Vice President
 Motorola and Nextel Confidential Proprietary 2