Exhibit 10.29

THE SECURITIES  EVIDENCED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED UNDER THE
SECURITIES ACT OF 1933, AS AMENDED (THE "ACT"),  OR APPLICABLE STATE LAW, AND NO
INTEREST  THEREIN  MAY BE  SOLD,  DISTRIBUTED,  ASSIGNED,  OFFERED,  PLEDGED  OR
OTHERWISE  TRANSFERRED UNLESS (A) THERE IS AN EFFECTIVE  REGISTRATION  STATEMENT
UNDER THE ACT AND APPLICABLE STATE SECURITIES LAWS COVERING ANY SUCH TRANSACTION
INVOLVING SAID SECURITIES,  (B) THE COMPANY RECEIVES AN OPINION OF LEGAL COUNSEL
FOR THE HOLDER OF THESE SECURITIES SATISFACTORY TO THE COMPANY STATING THAT SUCH
TRANSACTION IS EXEMPT FROM REGISTRATION OR (C) THE COMPANY  OTHERWISE  SATISFIES
ITSELF THAT SUCH TRANSACTION IS EXEMPT FROM REGISTRATION.

July 12, 2004                                                         $________

                              TERABEAM CORPORATION

                           CONVERTIBLE PROMISSORY NOTE

      Terabeam Corporation,  a Washington corporation (the "Company"), for value
received,  promises to pay to  ___________  (the  "Holder") the principal sum of
$_________, subject to adjustment from time to time in accordance with Section 2
of this Note and Article VII of the Merger  Agreement (the "Principal  Amount").
Capitalized terms not defined herein shall have the meanings given such terms in
that certain Agreement and Plan of Merger and Reorganization  among the Company,
Harmonix  Corporation and the stockholders of Harmonix  Corporation (the "Merger
Agreement").

      The  following  is a  statement  of the  rights  of  the  Holder  and  the
conditions to which this Note is subject, to which the Holder, by the acceptance
of this Note, agrees:

1.    Principal and Interest; Payment; Prepayment

      (a) Principal and Interest.  Interest shall accrue on the unpaid Principal
Amount at a rate of 6.75% per annum, simple interest ("Interest"), measured from
the date set forth  above.  Interest  only shall be due and payable on the fifth
day of the first month of each  quarter  during the term of this Note.  Interest
will be computed on the basis of a 360-day  year of twelve  30-day  months.  The
outstanding  Principal  Amount and any accrued and unpaid  Interest shall become
due and  payable on July 12, 2005 (the  "Maturity  Date").  Notwithstanding  the
foregoing,  the entire unpaid  Principal  Amount,  together with all accrued and
unpaid Interest thereon,  shall become  immediately due and payable in the event
of any Event of Default (as defined below).

      (b)  Payment.  All  payments  shall be made in lawful  money of the United
States of  America  at such  place as the  Holder  hereof  may from time to time
designate in writing to the

CONVERTIBLE PROMISSORY NOTE                                TERABEAM CORPORATION.

<PAGE>

Company.  Payment shall be credited  first to the accrued  interest then due and
payable and the remainder applied to principal.

      (c) Prepayment. The Company may at any time prepay in whole or in part the
Principal Amount and any accrued and unpaid Interest thereon.

2.    Purchase Note Subject to Merger Agreement; Offset

      This Note is a "Purchase Note" under the Merger Agreement and is expressly
subject to Article VII thereof.  As  contemplated in the Merger  Agreement,  the
Principal  Amount  and  Interest  is subject to  adjustment.  For  informational
purposes  only,  the  Company  may amend  Schedule A hereto from time to time to
reflect the Principal Amount after any such adjustment.

3.    Conversion

      At any time after the date  hereof,  and  subject  to  Article  VII of the
Merger Agreement, Holder shall have the right, at its sole discretion, to notify
the Company in writing of its desire to convert the outstanding Principal Amount
and any accrued and unpaid Interest into fully paid and nonassessable  shares of
common stock of YDI  Wireless,  Inc.  ("YDI"),  the Company's  corporate  parent
("Common  Stock")  at a  conversion  price  of  $27.27  per  share  (subject  to
adjustment  for stock splits,  stock  dividends,  recapitalizations  and similar
events), effective as of the date of such notice. The number of shares of Common
Stock to be issued upon such conversion shall be equal to the quotient  obtained
by dividing (x) the  then-outstanding  Principal Amount (subject to any reserved
amounts  permitted  pursuant  to Article  VII of the Merger  Agreement)  and any
accrued and unpaid  Interest  by (y) $27.27  (subject  to  adjustment  for stock
splits, stock dividends, recapitalizations and similar events).

4.    Issuance of the Stock Upon Conversion; Fractional Shares

      As soon as practicable after conversion of this Note, the Company,  at its
expense,  will cause to be issued in the name of and delivered to the Holder,  a
certificate  or  certificates  for the  number of fully  paid and  nonassessable
shares  of  Common  Stock to  which  the  Holder  shall be  entitled  upon  such
conversion,  which certificates shall include legends restricting transfer under
the federal and state securities laws. No fractional  shares will be issued upon
conversion of this Note. If, upon conversion of this Note, a fraction of a share
results,  the  Company  will  pay  the  cash  value  of that  fractional  share,
calculated based on the per share value determined pursuant to Section 3 hereof.

5.    Holder's Representations

      The Holder represents and warrants that:


CONVERTIBLE PROMISSORY NOTE                                 TERABEAM CORPORATION
                                      -2-
<PAGE>

            (a) it is familiar  with each of YDI and the Company,  the nature of
its business  and its  financial  prospects,  and the Holder has the capacity to
protect its own interests, and

            (b)  it is  acquiring  the  Note  and  the  securities  that  may be
purchased upon  conversion for investment for its own account,  not as a nominee
or  agent,  and not  with a view to,  or for  resale  in  connection  with,  any
distribution.  It  understands  that  the Note  and the  securities  that may be
purchased upon conversion have not been, and will not be,  registered  under the
Securities Act of 1933, as amended,  by reason of a specific  exemption from the
registration  provisions  of such Act, the  availability  of which depends upon,
among  other  things,  the bona fide  nature of the  investment  intent  and the
accuracy of the Holder's representations.

6.    Company Representations and Warranties

      The Company represents and warrants that:

            (a) It is a corporation  duly  organized and validly  existing under
the laws of the State of  Washington.  The Company has all  requisite  corporate
power and  authority  to carry on its business as  presently  conducted,  and to
carry out the  transactions  contemplated  in this  Note.  The  Company  is duly
qualified to transact business and is in good standing as a foreign  corporation
in each  jurisdiction  in which the  failure  to be so  qualified  would  have a
material  adverse  effect  on  the  Company's  financial  condition,   business,
operations or property.

            (b) The execution,  delivery and  performance by the Company of this
Note has been duly  authorized  by all  requisite  action of the Company and its
directors  and  shareholders.  This Note has been duly executed and delivered by
the Company,  and this Note  constitutes  a valid and binding  obligation of the
Company, enforceable against the Company in accordance with its terms.

            (c)  No   consent,   approval,   order  or   authorization   of,  or
registration,  qualification,  designation,  declaration  or  filing  with,  any
federal,  state, local or provincial  governmental  authority on the part of the
Company is required in  connection  with the  consummation  of the  transactions
contemplated by this Note, except for filings pursuant to the federal securities
laws and to applicable state Blue Sky laws.

7.    Transfer of Note; Restrictions on Transfer

      This Note may be transferred  only in compliance with  applicable  federal
and state  securities  laws and only upon  surrender  of the  original  Note for
registration  of transfer,  duly  endorsed,  or  accompanied  by a duly executed
written  instrument of transfer in form satisfactory to the Company.  A new Note
for like principal  amount and interest will be issued to, and registered in the
name of, the transferee. Interest and principal are payable


CONVERTIBLE PROMISSORY NOTE                                 TERABEAM CORPORATION
                                      -3-
<PAGE>

only to the  registered  holder of the Note. The Holder agrees to provide a Form
W-9 to the Company upon request.

8.    Events of Default

      If any of the events specified in this Section 8 shall occur (an "Event of
Default"),  the  Holder  may,  so long as such  condition  exists,  declare  the
outstanding Principal Amount and accrued but unpaid Interest immediately due and
payable, by notice in writing to the Company:

            (a) The  institution by the Company of proceedings to be adjudicated
as bankrupt or  insolvent,  the filing by the Company of a petition or answer or
consent seeking  reorganization or release under the federal  Bankruptcy Act, or
any other  applicable  federal  or state law,  the  appointment  of a  receiver,
liquidator  or  trustee  for  the  purpose  of  taking   possession  of  all  or
substantially  all of the Company's assets, an assignment by the Company for the
benefit  of  creditors,  or the  taking of  corporate  action by the  Company in
furtherance of any such action;

            (b) If, within 90 days after the  commencement  of an action against
the Company  (and  service of process on the  Company)  seeking any  bankruptcy,
insolvency, reorganization, liquidation, dissolution or similar relief under any
present or future  statute,  law or regulation,  such action shall not have been
resolved  in  favor of the  Company  or all  orders  or  proceedings  thereunder
affecting the operations or the business of the Company  stayed,  or if the stay
of any such order or proceeding  shall thereafter be set aside, or if, within 90
days after the appointment without the consent or acquiescence of the Company of
any trustee,  receiver or liquidator of the Company,  such appointment shall not
have been vacated; or

            (c) Failure to pay the  Principal  Amount and Interest  when due, if
such failure is not cured within ten (10) days after the Holder's  delivery of a
notice of such failure.

9.    Miscellaneous

      9.1   Remedies

      The  Company  and  all   endorsers  of  this  Note  hereby  waive  notice,
presentment, protest and notice of dishonor.

      9.2   Attorneys' Fees

      The  Company  and all  endorsers  of this Note  agree to pay the  Holder's
reasonable  expenses and costs in collecting and enforcing this Note,  including
reasonable attorneys' fees.


CONVERTIBLE PROMISSORY NOTE                                 TERABEAM CORPORATION
                                      -4-
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      9.3   Holder as Owner

      The  Company  may deem and treat the  holder of record of this Note as the
absolute owner for all purposes regardless of any notice to the contrary.

      9.4   No Shareholder Rights

      This Note shall not entitle  the Holder to any voting  rights or any other
rights as a shareholder  of YDI or the Company or to any other rights except the
rights  stated  herein;  and no  dividend  shall be payable  or shall  accrue in
respect of this Note or the  securities  into  which  this Note is  convertible,
until this Note is converted.

      9.5   Shareholders, Officers and Directors Not Liable

      In no event  shall any  shareholder,  officer  or  director  of YDI or the
Company be liable for any amounts due or payable pursuant to this Note.

      9.6   Notices

      Unless  otherwise  provided,  any notice under this Note shall be given in
writing and shall be deemed  effectively given (a) upon personal delivery to the
party to be notified, (b) upon confirmation of receipt by fax by the party to be
notified, (c) one business day after deposit with a reputable overnight courier,
prepaid for  overnight  delivery and  addressed  as set forth below,  or at such
other address as such party may designate by ten days' advance written notice to
the other party given in the foregoing manner.

      If to the Holder:

                    To the address or number last furnished in writing to the
                    Company by the Holder

      If to the Company:

                    Terabeam Corporation
                    20 Industrial Drive East
                    South Deerfield, MA  01373
                    Fax: (413) 665-0089
                    Attn: General Counsel

      9.7   Amendments and Waivers

      Any term of this Note may be amended and the observance of any term may be
waived (either generally or in a particular instance and either retroactively or
prospectively)  only with the  written  consent of the  Company  and the Holder;
provided,  however,  that the  Company may amend  Schedule A hereto  without the
Holder's  consent to reflect any


CONVERTIBLE PROMISSORY NOTE                                 TERABEAM CORPORATION
                                      -5-
<PAGE>

adjustments  to the  Principal  Amount  as  provided  in  Section  2 above.  Any
amendment or waiver shall be binding on each future Holder and the Company.

      9.8   Governing Law; Jurisdiction; Venue

      This Note shall be governed by and  construed  under the laws of the state
of Washington  without  regard to  principles  of conflict of laws.  The parties
irrevocably  consent  to the  jurisdiction  and venue of the  state and  federal
courts located in King County, Washington in connection with any action relating
to this Note.

      9.9   Successors and Assigns

      The terms and conditions of this Note shall inure to the benefit of and be
binding on the respective successors and assigns of the parties.

      9.10  Severability

      If one or more provisions of this Note are held to be unenforceable  under
applicable law, such provision shall be excluded from this Note, and the balance
of this Note shall be  interpreted  as if such  provision  were so excluded  and
shall be enforceable in accordance with its terms.

      ORAL AGREEMENTS OR ORAL  COMMITMENTS TO LOAN MONEY,  EXTEND CREDIT,  OR TO
FORBEAR FROM ENFORCING  REPAYMENT OF A DEBT ARE NOT ENFORCEABLE UNDER WASHINGTON
LAW.

                                           TERABEAM CORPORATION


                                           By:  ________________________________
                                           Name:________________________________
                                           Its: ________________________________


AGREED AND ACCEPTED:


__________________ ("HOLDER")


By:  ________________________________
Name:________________________________
Its: ________________________________


CONVERTIBLE PROMISSORY NOTE                                 TERABEAM CORPORATION
                                      -6-
<PAGE>

                                   SCHEDULE A

                   Schedule of Adjustments to Principal Amount


CONVERTIBLE PROMISSORY NOTE                                TERABEAM CORPORATION.