<PAGE>

                                                                   Exhibit 10.21

February 15, 2001

Mr. Martin Singer
3927 Snowbird Lane
Northbrook, IL 60062


Dear Marty,

The Board of Directors of PCTEL, Inc. is pleased to offer you the position of
Non-Executive Chairman of the Board, effective February 16, 2001, in addition to
retaining your current Director status.  In this extended capacity, you will be
asked to provide, in addition to normal Director responsibilities and time
commitments, a full two (2) days per week on PCTEL business, either at Corporate
Headquarters or in the field.  In addition to the above time frame, any
additional time needed to support PCTEL will require Board approval for
additional compensation.

As Chairman, your primary responsibility will be three fold; namely (1) provide
effective Board Governance (e.g. planning Board work activities consistent with
business strategy and circumstances; calling, arranging and conducting Board
meetings; organizing Board responsibilities/committees to address tasks at hand;
distributing information needed by Directors to perform their duties;
anticipating Board succession needs). (2) support and counsel the CEO and
executive staff in areas such as Research/Development, mergers and acquisitions
and strategic planning; and (3) perform such other tasks as may be necessary.

The above-added responsibility will carry the same term of office that your
current Director's position has, which is until the Annual Shareholders Meeting
2002.

As to compensation for the Chairmanship, in addition to your current Director
retainer and committee meeting fees, you will receive an additional annual
retainer of $100,000.  This sum will be paid monthly.  Further, PCTEL will
reimburse you for the annual cost of a family medical benefit plan and
disability insurance for up to 5 years (separate agreement for this plan to
follow); an annual car allowance in the amount of $12,000 paid on a monthly
basis and an expense budget to cover related expenses that position may incur.
<PAGE>

Marty Singer
February 15, 2001
Page Two

We will recommend to the Board of Directors that at the next Board Meeting, you
will be given a stock option entitling you to purchase 100,000 shares of Common
Stock of PCTEL at the then current fair market value.  Such options will vest
over a two year period (50% after the first year and the remaining 50% at the
end of the second year).

Details of the stock option plan are contained in the Stock Option Agreement.
Copies of these documents will be provided to you after Board approval.

On behalf of the Board of Directors and the Executive Management team and
employees of PCTEL, may I offer congratulations on your acceptance of this new
assignment and thank you for your ongoing commitment and support to the Company.
Should you have any questions, please do not hesitate to contact me or Tom
Capizzi, V.P. Human Resources & Administration at PCTEL, Inc. (408) 956-2171.


Sincerely,                              Acknowledged and Agreed to,


      /s/ Richard A. Alberding                /s/ Martin A. Singer
------------------------------------    --------------------------------
Richard A Alberding                              Marty A. Singer
Chairman of the Compensation Committee
Board of Directors, PCTEL, Inc.                     2/15/2001
                                        --------------------------------
                                                      Date

              2/16/2001                             2/16/2001
------------------------------------    --------------------------------
                Date                                Start Date



cc: T. Capizzi