Document:

<PAGE>

                                                                     Exhibit 4.9

THIS NOTE HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED
(THE "SECURITIES ACT"), OR ANY STATE SECURITIES LAW AND MAY NOT BE SOLD,
TRANSFERRED OR OTHERWISE DISPOSED OF UNLESS REGISTERED UNDER THE SECURITIES ACT
AND UNDER APPLICABLE STATE SECURITIES LAWS OR SPEEDCOM WIRELESS CORPORATION
SHALL HAVE RECEIVED AN OPINION OF ITS COUNSEL THAT REGISTRATION OF SUCH
SECURITIES UNDER THE SECURITIES ACT AND UNDER THE PROVISIONS OF APPLICABLE STATE
SECURITIES LAWS IS NOT REQUIRED.

                         SPEEDCOM WIRELESS CORPORATION

                                PROMISSORY NOTE
                                ---------------

U.S. $250,000                                                 New York, New York
                                                                   June 11, 2001

          FOR VALUE RECEIVED, the undersigned, Speedcom Wireless Corporation, a
Delaware corporation (the "Company"), hereby promises to pay to the order of SDS
                           -------
Merchant Fund, L.P. or any future permitted holder of this promissory note (the
"Payee"), at the principal office of the Payee set forth herein, or at such
 -----
other place as the holder may designate in writing to the Company, the principal
sum of up to TWO HUNDRED FIFTY THOUSAND DOLLARS (U.S. $250,000), or such other
amount as may be outstanding hereunder, together with all accrued but unpaid
interest, in such coin or currency of the United States of America as at the
time shall be legal tender for the payment of public and private debts and in
immediately available funds, as provided in this promissory note (the "Note").
                                                                       ----
Concurrently with the issuance of this Note, the Company is issuing separate
notes (the "Other Notes") to separate investors pursuant to the Purchase
            -----------
Agreement (as defined in Section 3(d) hereof).

          1.   Principal and Interest Payments.
               -------------------------------

               (a)  The Company shall repay in full the entire principal balance
then outstanding under this Note on the first to occur (the "Maturity Date") of:
                                                             -------------
(i) April 17, 2002; or (ii) the acceleration of the obligations as contemplated
by this Note. The Company may prepay all or any part of this Note, together with
the Other Notes, in whole or in part at any time, without penalty or premium, as
set forth in Section 5(d) hereof.

               (b)  Interest on the outstanding principal balance of this Note
shall accrue at a rate of ten percent (10%) per annum. Interest on the
outstanding principal balance of the Note shall be computed on the basis of the
actual number of days elapsed and a year of three hundred and sixty (360) days
and shall be payable by the Company (i) on a quarterly basis, commencing on
September 11, 2001 and on each three-month anniversary thereafter, continuing
<PAGE>

throughout the term of this Note, and (ii) in full on the Maturity Date.
Furthermore, upon the occurrence of an Event of Default, then to the extent
permitted by law, the Company will pay interest to the Payee, payable on demand,
on the outstanding principal balance of the Note from the date of the Event of
Default until payment in full at the rate of fourteen percent (14%) per annum.

               (c)  At the Maturity Date, the outstanding principal amount of
this Note plus all accrued and unpaid interest herein shall be due and payable
in cash or, at the option of the Payee, converted into equity securities which
may be issued in connection with a possible private placement by the Company of
its equity securities to certain institutional investors completed at or prior
to the Maturity Date (the "Proposed Financing"). Upon the conversion of this
                           ------------------
Note, the outstanding principal amount of this Note, together with accrued
interest hereon, shall be deemed to be the consideration for the Payee's
interest in the new equity securities on the Maturity Date.

               (d)  The Company shall use its best efforts to prepare and file
with the Securities and Exchange Commission as soon as possible following the
closing of the Proposed Financing, but in any event no later than sixty (60)
days from the date hereof (the "Filing Date"), a registration statement covering
                                -----------
shares of the Company's common stock underlying the equity securities (the
"Registration Statement"). If the Registration Statement is not filed on or
 ----------------------
prior to the Filing Date, the Company shall pay as liquidated damages for such
failure and not as a penalty to the Payee an amount equal to two percent (2%) of
the purchase price paid by the Payee for this Note for each thirty (30) day
period in which the registration statement is not filed on or prior to the
Filing Date (the "Periodic Amount"). The parties agree that the Periodic Amount
                  ---------------
represents a reasonable estimate on the part of the parties, as of the date of
this Note, of the amount of damages that may be incurred by the Payee if the
Registration Statement is not filed on or prior to the Filing Date.

          2.   Payment on Non-Business Days.  Whenever any payment to be made
               ----------------------------
shall be due on a Saturday, Sunday or a public holiday under the laws of the
State of New York, such payment may be due on the next succeeding business day
and such next succeeding day shall be included in the calculation of the amount
of accrued interest payable on such date.

          3.   Events of Default.  The occurrence of any of the following events
               -----------------
shall be an "Event of Default" under this Note:
             ----------------

               (a)  the Company shall fail to make the payment of any amount of
any principal outstanding for a period of three (3) business days after the date
such payment shall become due and payable hereunder; or

               (b)  the Company shall fail to make any payment of interest for a
period of three (3) business days after the date such interest shall become due
and payable hereunder; or

                                       2
<PAGE>

               (c)  the Proposed Financing shall fail to have been consummated
by April 17, 2002; or

               (d)  the Company shall fail to make the payment of any fees
and/or liquidated damages under this Note or the Note and Warrant Purchase
Agreement by and among the Company, the Payee, and the other purchasers party
thereto, dated as of the date hereof (the "Purchase Agreement") which failure is
                                           ------------------
not remedied within five (5) business days after the occurrence thereof; or

               (e)  the Company shall default in the performance or observance
of any covenant, condition or agreement contained in any of the Transaction
Documents (as defined in the Purchase Agreement, the "Transaction Documents")
                                                      ---------------------
(or the Company makes an announcement, statement or threat that it does not
intend to honor its obligations under any of the Transaction Documents) and such
default is not fully cured within five (5) business days (other than with
respect to an announcement, statement or threat) after the occurrence thereof in
the case of failure within the Company's control or thirty (30) business days in
the case of a default due to circumstances outside of the Company's control,
after the earlier of (x) the date on which any executive officer of the Company
shall have obtained actual knowledge of such failure (or such announcement,
statement or threat) and (y) the date on which written notice thereof has been
given to the Company by the Payee which is not covered by any other provisions
of this Section 3(e); or

               (f)  any representation, warranty or certification made by the
Company herein or in any of the other Transaction Documents or in any
certificate or financial statement shall prove to have been false or incorrect
or breached in a material respect on the date as of which made; or

               (g)  the Company or any of its Subsidiaries (as defined the
Purchase Agreement, the "Subsidiaries") shall (i) default in any payment of any
                         ------------
amount or amounts of principal of or interest on any Indebtedness (as defined in
the Purchase Agreement, the "Indebtedness") (other than the Indebtedness
                             ------------
hereunder) the aggregate principal amount of which Indebtedness of all such
persons is in excess of $100,000, whether such Indebtedness now exists or shall
hereinafter be created, and such default entitles the holder thereof to declare
such indebtedness to be due and payable, and such indebtedness has not been
discharged in full or such acceleration has not been stayed, rescinded or
annulled within ten (10) business days of such acceleration, or (ii) default in
the observance or performance of any other agreement or condition relating to
any Indebtedness or contained in any instrument or agreement evidencing,
securing or relating thereto, or any other event shall occur or condition exist,
the effect of which default or other event or condition is to cause, or to
permit the holder or holders or beneficiary or beneficiaries of such
Indebtedness to cause with the giving of notice if required, such Indebtedness
to become due prior to its stated maturity; or

               (h)  A judgment or order for the payment of money shall be
rendered against the Company or any Subsidiary in excess of $100,000 in the
aggregate (net of any

                                       3
<PAGE>

applicable insurance coverage) for all such judgments or orders against all such
persons (treating any deductibles, self insurance or retention as not so
covered) that shall not be discharged, and all such judgments and orders remain
outstanding, and there shall be any period of thirty (30) consecutive days
following entry of the judgment or order in excess of $100,000 or the judgment
or order which causes the aggregate amount described above to exceed $100,000
during which a stay of enforcement of such judgment or order, by reason of a
pending appeal or otherwise, shall not be in effect; or

               (i)  an "Event of Default" has occurred and is continuing under
any Other Notes issued to any other holders pursuant to the Purchase Agreement;
or

               (j)  the Company shall (i) apply for or consent to the
appointment of, or the taking of possession by, a receiver, custodian, trustee
or liquidator of itself or of all or a substantial part of its property or
assets, (ii) admit in writing its inability to pay its debts as such debts
become due, (iii) make a general assignment for the benefit of its creditors,
(iv) commence a voluntary case under the Bankruptcy Code or under the comparable
laws of any jurisdiction (foreign or domestic), (v) file a petition seeking to
take advantage of any bankruptcy, insolvency, moratorium, reorganization or
other similar law affecting the enforcement of creditors' rights generally, (vi)
acquiesce in writing to any petition filed against it in an involuntary case
under the Bankruptcy Code or under the comparable laws of any jurisdiction
(foreign or domestic), or (vii) take any action under the laws of any
jurisdiction (foreign or domestic) analogous to any of the foregoing; or

               (k)  a proceeding or case shall be commenced in respect of the
Company or any of its Subsidiaries without its application or consent, in any
court of competent jurisdiction, seeking (i) the liquidation, reorganization,
moratorium, dissolution, winding up, or composition or readjustment of its
debts, (ii) the appointment of a trustee, receiver, custodian, liquidator or the
like of it or of all or any substantial part of its assets or (iii) similar
relief in respect of it under any law providing for the relief of debtors, and
such proceeding or case described in clause (i), (ii) or (iii) shall continue
undismissed, or unstayed and in effect, for a period of thirty (30) consecutive
days or any order for relief shall be entered in an involuntary case under the
Bankruptcy Code or under the comparable laws of any jurisdiction (foreign or
domestic) against the Company or any of its Subsidiaries or action under the
laws of any jurisdiction (foreign or domestic) analogous to any of the foregoing
shall be taken with respect to the Company or any of its Subsidiaries and shall
continue undismissed, or unstayed and in effect for a period of thirty (30)
consecutive days.

          4.   Remedies Upon An Event of Default.  If an Event of Default shall
               ---------------------------------
have occurred and shall be continuing, the Payee of this Note may at any time at
its option, (a) declare the entire unpaid principal balance of this Note,
together with all interest accrued hereon, due and payable, and thereupon, the
same shall be accelerated and so due and payable, without presentment, demand,
protest, or notice, all of which are hereby expressly unconditionally and
irrevocably waived by the Company; provided, however, that upon the occurrence
                                   --------  -------
of an Event of Default described in (i) Sections 3(j) and (k), the outstanding
principal balance and accrued

                                       4
<PAGE>

interest hereunder shall be automatically due and payable, and (ii) Sections
3(a) through (i), the Payee may demand the prepayment of this Note pursuant to
Section 5 hereof; or (b) exercise or otherwise enforce any one or more of the
Payee's rights, powers, privileges, remedies and interests under this Note or
any of the other Transaction Documents or applicable law. No course of delay on
the part of the Payee shall operate as a waiver thereof or otherwise prejudice
the right of the Payee. No remedy conferred hereby shall be exclusive of any
other remedy referred to herein or now or hereafter available at law, in equity,
by statute or otherwise.

          5.   Prepayment Options.
               ------------------

               (a)  Prepayment.  Notwithstanding anything to the contrary
                    ----------
contained herein, the Payee shall have the right, at such Payee's option, to
require the Company to prepay all or a portion of the sum of the outstanding
principal amount and any interest accrued and outstanding under this Note (the
"Prepayment Price"), provided, that such prepayment is requested upon the
 ----------------    --------
occurrence of a Major Transaction (as defined in Section 5(e) below) or a
Triggering Event (as defined in Section 5(e) below). Nothing in this Section
5(a) shall limit the Payee's rights under Section 4 hereof. The Company shall
immediately notify the holders of the Other Notes if the Payee has requested
prepayment pursuant to this Section 5.

               (b)  Mechanics of Prepayment at Option of Payee.  At least thirty
                    ------------------------------------------
(30) days prior to the occurrence of a Major Transaction and within one (1) day
after the occurrence of a Major Transaction or a Triggering Event, the Company
shall deliver written notice thereof via facsimile and overnight courier
("Notice of a Prepayment Event") to the Payee and the holders of the Other
  ----------------------------
Notes. At any time on or after the earlier of the Payee's receipt of a Notice of
a Prepayment Event and the Payee becoming aware of a Major Transaction or a
Triggering Event, the Payee may require the Company to prepay all or a portion
of the outstanding principal amount and any interest accrued and outstanding
under this Note by delivering written notice thereof via facsimile and overnight
courier ("Notice of Prepayment at Option of Payee") to the Company, which Notice
          ---------------------------------------
of Prepayment at Option of Payee shall indicate the amount of principal and
interest accrued and outstanding under this Note that the Payee is electing to
have prepaid, the sum of which shall be the Prepayment Price.

               (c)  Payment of Prepayment Price.  Upon the Company's receipt of
                    ---------------------------
a Notice of Prepayment at Option of Payee from the Payee, the Company shall
immediately notify the Payee by facsimile of the Company's receipt of a Notice
of Prepayment at Option of Payee and the Payee which has sent such a notice
shall, in the case of a Major Transaction, deliver to the Company this Note
which Payee has elected to have prepaid on or before the consummation or closing
of such Major Transaction and, in the case of a Triggering Event, promptly
submit to the Company this Note which Payee has elected to have prepaid. The
Company shall pay the Prepayment Price to Payee, in the case of a Major
Transaction, at or prior to the closing of the Major Transaction, and, in the
case of a Triggering Event, within five (5) business days after the Company's
receipt of a Notice of Prepayment at Option of Payee; provided that this Note
                                                      --------
shall have been so delivered to the Company. If the Company shall fail to prepay
all of the Prepayment Price (other than pursuant to a dispute as to the
arithmetic calculation of the

                                       5
<PAGE>

Prepayment Price), in addition to any remedy the Payee may have under this Note
and the Purchase Agreement, the Prepayment Price payable in respect of such
unprepaid Notes shall bear interest at the rate of two percent (2.0%) per each
period of thirty (30) consecutive days, pro rated for any period of less than
thirty (30) days until paid in full. Until the Company pays such unpaid
Prepayment Price in full to the Payee, the Payee shall have the option (the
"Void Optional Prepayment Option") to, in lieu of prepayment, require the
 -------------------------------
Company to promptly return to the Payee this Note that was submitted for
prepayment by Payee under this Section 5(c) and for which the Prepayment Price
has not been paid, by sending written notice thereof to the Company via
facsimile (the "Void Optional Prepayment Notice"). Upon the Company's receipt of
                -------------------------------
such Void Optional Prepayment Notice(s) and prior to payment of the full
Prepayment Price to Payee, (i) the Notice(s) of Prepayment at Option of Payee
shall be null and void with respect to this Note submitted for prepayment and
for which the Prepayment Price has not been paid and (ii) the Company shall
immediately return this Note submitted to the Company by the Payee for
prepayment under this Section 5(c) and for which the Prepayment Price has not
been paid. A Payee's delivery of a Void Optional Prepayment Notice and exercise
of its rights following such notice shall not affect the Company's obligations
to make any payments which have accrued prior to the date of such notice.

               (d)  Company's Prepayment Option.  The Company may prepay, at the
                    ---------------------------
option of its Board of Directors, all or any portion of the outstanding
principal amount of this Note and the accrued and unpaid interest thereon upon
five (5) business days prior written notice to the Payee (the "Company
                                                               -------
Prepayment Notice") at a cash price equal to sum of the outstanding principal
-----------------
amount and any interest accrued and outstanding (the "Company Prepayment
                                                      ------------------
Price"). The Company may not deliver a Company Prepayment Notice to the Payee
-----
unless the Company has clear and good funds for a minimum of the amount it
intends to prepay in a bank account controlled by the Company. The Company
Prepayment Notice shall state the date of prepayment (the "Company Prepayment
                                                           ------------------
Date"), the Company Prepayment Price, the amount of the Note of such Payee to be
----
prepaid, the amount of accrued and unpaid interest through the Company
Prepayment Date and shall call upon the Payee to surrender to the Company on the
Company Prepayment Date at the place designated in the Company Prepayment Notice
such Payee's Note. The Company Prepayment Date shall be no more than five (5)
trading days after the date on which the Payee is notified of the Company's
intent to prepay the Note (the "Company Prepayment Notice Date"). If the Company
                                ------------------------------
fails to pay the Company Prepayment Price by the sixth (6/th/) trading day
following the Company Prepayment Notice Date, the prepayment will be declared
null and void and the Company shall lose its right to deliver a Company
Prepayment Notice to the Payee in the future. On or after the Company Prepayment
Date, the Payee shall surrender the Notes called for prepayment to the Company
at the place designated in the Company Prepayment Notice and shall thereupon be
entitled to receive payment of the Company Prepayment Price.

               (e)  For purposes of this Note, (1) "Major Transaction" means the
                                                    -----------------
consummation of any of the following transactions: (i) the consolidation, merger
or other business combination of the Company with or into a person or entity
(other than (A) pursuant to a migratory merger effected solely for the purpose
of changing the jurisdiction of incorporation

                                       6
<PAGE>

of the Company, or (B) a consolidation, merger or other business combination in
which holders of the Company's or any of its Subsidiaries voting power
immediately prior to the transaction continue after the transaction to hold,
directly or indirectly, the voting power of the surviving entity or entities
necessary to elect a majority of the members of the board of directors (or their
equivalent if other than a corporation) of such entity or entities); (ii) the
sale or transfer of all or substantially all of the Company's or any of its
Subsidiaries' assets; or (iii) the consummation of a purchase, tender or
exchange offer made to the holders of more than 30% of the outstanding shares of
the Company's common stock; provided, however, that during the six months
                            --------  -------
following the date of issuance of this Note a Strategic Merger shall not be
deemed a Major Transaction, (2) "Strategic Merger" means a merger with another
                                 ----------------
entity in the same industry as the Company, in which the Company is the
surviving entity and its Common Stock remains publicly traded subsequent to the
merger and an investment of at least $7,000,000 has been made in the Company's
Common Stock or convertible preferred stock; and (3) "Triggering Event" means
                                                      ----------------
(i) any representation or warranty made by the Company in the Purchase Agreement
or any of the Transaction Documents shall prove to have been false or incorrect
in a material respect at the time when made; or (ii) the Company has breached a
material covenant or other term or condition of the Purchase Agreement or any
related agreement delivered therewith; or (iv) the Company has entered into a
Subsequent Financing (as defined in Section 3.10 of the Purchase Agreement).

          6.   Other Notes.  This Note is one of the Notes referred to in the
               -----------
Purchase Agreement. Any and all payments or prepayments of this Note by the
Company shall be made on a pro rata basis with the Other Notes. The Company
shall promptly notify the holder of this Note of any notices sent or received,
or any actions taken with respect to the Other Notes.

          7.   Replacement.  Upon receipt of a duly executed, notarized and
               -----------
unsecured written statement from the Payee with respect to the loss, theft or
destruction of this Note (or any replacement hereof), and without requiring an
indemnity bond or other security, or, in the case of a mutilation of this Note,
upon surrender and cancellation of such Note, the Company shall issue a new
Note, of like tenor and amount, in lieu of such lost, stolen, destroyed or
mutilated Note.

          8.   Parties in Interest, Transferability.  This Note shall be binding
               ------------------------------------
upon the Company and its successors and assigns and the terms hereof shall inure
to the benefit of the Payee and its successors and permitted assigns. This Note
may be transferred or sold, subject to the provisions of Section 17 of this
Note, or pledged, hypothecated or otherwise granted as security by the Payee.

          9.   Amendments.  This Note may not be modified or amended in any
               ----------
manner except in writing executed by the Company and the Payee.

          10.  Notices.  Any notice, demand, request, waiver or other
               -------
communication required or permitted to be given hereunder shall be in writing
and shall be effective (a) upon hand delivery by telecopy or facsimile at the
address or number designated below (if delivered on a business day during normal
business hours where such notice is to be received), or the first

                                       7
<PAGE>

business day following such delivery (if delivered other than on a business day
during normal business hours where such notice is to be received) or (b) on the
second business day following the date of mailing by express courier service,
fully prepaid, addressed to such address, or upon actual receipt of such
mailing, whichever shall first occur. The Company will give written notice to
the Payee at least thirty (30) days prior to the date on which the Company
closes its books or takes a record (x) with respect to any dividend or
distribution upon the common stock of the Company, (y) with respect to any pro
rata subscription offer to holders of common stock of the Company or (z) for
determining rights to vote with respect to a Major Transaction or a Triggering
Event, dissolution, liquidation or winding-up and in no event shall such notice
be provided to such holder prior to such information being made known to the
public. The Company will also give written notice to the Payee at least twenty
(20) days prior to the date on which dissolution, liquidation or winding-up will
take place and in no event shall such notice be provided to the Payee prior to
such information being made known to the public.

     Address of the Payee:    SDS Merchant Fund, L.P.
                              c/o SDS Capital Partners
                              One Sound Shore Drive
                              Greenwich, CT 06830
                              Attention: Steve Derby
                              Telecopier: (203) 629-0345

     Address of the Company:  Speedcom Wireless Corporation
                              1748 Independence Boulevard, D-4
                              Sarasota, Florida 34243
                              Attention:  Jay Wright, Chief Financial Officer
                              Telecopier: (941) 358-6208

          11.  Governing Law. This Note shall be governed by and construed in
               -------------
accordance with the internal laws of the State of New York, without giving
effect to the choice of law provisions. This Note shall not be interpreted or
construed with any presumption against the party causing this Note to be
drafted.

          12.  Headings.  Article and section headings in this Note are included
               --------
herein for purposes of convenience of reference only and shall not constitute a
part of this Note for any other purpose.

          13.  Remedies, Characterizations, Other Obligations, Breaches and
               ------------------------------------------------------------
Injunctive Relief.  The remedies provided in this Note shall be cumulative and
-----------------
in addition to all other remedies available under this Note, at law or in equity
(including, without limitation, a decree of specific performance and/or other
injunctive relief), no remedy contained herein shall be deemed a waiver of
compliance with the provisions giving rise to such remedy and nothing herein
shall limit a Payee's right to pursue actual damages for any failure by the
Company to comply with the terms of this Note. Amounts set forth or provided for
herein with respect to payments and the like (and the computation thereof) shall
be the amounts to be received by the Payee and shall not,

                                       8
<PAGE>

except as expressly provided herein, be subject to any other obligation of the
Company (or the performance thereof). The Company acknowledges that a breach by
it of its obligations hereunder will cause irreparable and material harm to the
Payee and that the remedy at law for any such breach may be inadequate.
Therefore the Company agrees that, in the event of any such breach or threatened
breach, the Payee shall be entitled, in addition to all other available rights
and remedies, at law or in equity, to seek and obtain such equitable relief,
including but not limited to an injunction restraining any such breach or
threatened breach, without the necessity of showing economic loss and without
any bond or other security being required.

          14.  Failure or Indulgence Not Waiver.  No failure or delay on the
               --------------------------------
part of the Payee in the exercise of any power, right or privilege hereunder
shall operate as a waiver thereof, nor shall any single or partial exercise of
any such power, right or privilege preclude other or further exercise thereof or
of any other right, power or privilege.

          15.  Enforcement Expenses.  The Company agrees to pay all costs and
               --------------------
expenses of enforcement of this Note, including, without limitation, reasonable
attorneys' fees and expenses.

          16.  Binding Effect.  The obligations of the Company and the Payee set
               --------------
forth herein shall be binding upon the successors and assigns of each such
party, whether or not such successors or assigns are permitted by the terms
hereof.

          17.  Compliance with Securities Laws.  The Payee of this Note
               -------------------------------
acknowledges that this Note is being acquired solely for the Payee's own account
and not as a nominee for any other party, and for investment, and that the Payee
shall not offer, sell or otherwise dispose of this Note other than in compliance
with the laws of the United States of America and as guided by the rules of the
Securities and Exchange Commission. This Note and any Note issued in
substitution or replacement therefore shall be stamped or imprinted with a
legend in substantially the following form:

          "THIS NOTE HAS NOT BEEN REGISTERED UNDER THE SECURITIES
          ACT OF 1933, AS AMENDED (THE "SECURITIES ACT"), OR ANY
          STATE SECURITIES LAW AND MAY NOT BE SOLD, TRANSFERRED OR
          OTHERWISE DISPOSED OF UNLESS REGISTERED UNDER THE
          SECURITIES ACT AND UNDER APPLICABLE STATE SECURITIES LAWS
          OR SPEEDCOM WIRELESS CORPORATION SHALL HAVE RECEIVED AN
          OPINION OF ITS COUNSEL THAT REGISTRATION OF SUCH
          SECURITIES UNDER THE SECURITIES ACT AND UNDER THE
          PROVISIONS OF APPLICABLE STATE SECURITIES LAWS IS NOT
          REQUIRED."

          18.  Severability.  The provisions of this Note are severable, and if
               ------------
any provision shall be held invalid or unenforceable in whole or in part in any
jurisdiction, then such

                                       9
<PAGE>

invalidity or unenforceability shall not in any manner affect such provision in
any other jurisdiction or any other provision of this Note in any jurisdiction.

          19.  Consent to Jurisdiction.  Each of the Company and the Payee (i)
               -----------------------
hereby irrevocably submits to the jurisdiction of the United States District
Court sitting in the Southern District of New York and the courts of the State
of New York located in New York county for the purposes of any suit, action or
proceeding arising out of or relating to this Note and (ii) hereby waives, and
agrees not to assert in any such suit, action or proceeding, any claim that it
is not personally subject to the jurisdiction of such court, that the suit,
action or proceeding is brought in an inconvenient forum or that the venue of
the suit, action or proceeding is improper. Each of the Company and the Payee
consents to process being served in any such suit, action or proceeding by
mailing a copy thereof to such party at the address in effect for notices to it
under the Purchase Agreement and agrees that such service shall constitute good
and sufficient service of process and notice thereof. Nothing in this Section 19
shall affect or limit any right to serve process in any other manner permitted
by law.

          20.  Company Waivers.  Except as otherwise specifically provided
               ---------------
herein, the Company and all others that may become liable for all or any part of
the obligations evidenced by this Note, hereby waive presentment, demand, notice
of nonpayment, protest and all other demands and notices in connection with the
delivery, acceptance, performance and enforcement of this Note, and do hereby
consent to any number of renewals of extensions of the time or payment hereof
and agree that any such renewals or extensions may be made without notice to any
such persons and without affecting their liability herein and do further consent
to the release of any person liable hereon, all without affecting the liability
of the other persons, firms or Company liable for the payment of this Note, AND
DO HEREBY WAIVE TRIAL BY JURY.

               (a)  No delay or omission on the part of the Payee in exercising
its rights under this Note, or course of conduct relating hereto, shall operate
as a waiver of such rights or any other right of the Payee, nor shall any waiver
by the Payee of any such right or rights on any one occasion be deemed a waiver
of the same right or rights on any future occasion.

               (b)  THE COMPANY ACKNOWLEDGES THAT THE TRANSACTION OF WHICH THIS
NOTE IS A PART IS A COMMERCIAL TRANSACTION, AND TO THE EXTENT ALLOWED BY
APPLICABLE LAW, HEREBY WAIVES ITS RIGHT TO NOTICE AND HEARING WITH RESPECT TO
ANY PREJUDGMENT REMEDY WHICH THE PAYEE OR ITS SUCCESSORS OR ASSIGNS MAY DESIRE
TO USE.

                 [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]

                                       10
<PAGE>

          IN WITNESS WHEREOF, the Company has executed and delivered this Note
as of the date first written above.

                                             SPEEDCOM WIRELESS CORPORATION

                                             By:________________________________
                                                Name:
                                                Title:

                                       11<PAGE>

                                                                    Exhibit 4.10

THIS NOTE HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED
(THE "SECURITIES ACT"), OR ANY STATE SECURITIES LAW AND MAY NOT BE SOLD,
TRANSFERRED OR OTHERWISE DISPOSED OF UNLESS REGISTERED UNDER THE SECURITIES ACT
AND UNDER APPLICABLE STATE SECURITIES LAWS OR SPEEDCOM WIRELESS CORPORATION
SHALL HAVE RECEIVED AN OPINION OF ITS COUNSEL THAT REGISTRATION OF SUCH
SECURITIES UNDER THE SECURITIES ACT AND UNDER THE PROVISIONS OF APPLICABLE STATE
SECURITIES LAWS IS NOT REQUIRED.

                         SPEEDCOM WIRELESS CORPORATION

                                PROMISSORY NOTE
                                ---------------

U.S. $750,000                                                 New York, New York
                                                                   June 11, 2001

          FOR VALUE RECEIVED, the undersigned, Speedcom Wireless Corporation, a
Delaware corporation (the "Company"), hereby promises to pay to the order of
                           -------
Oscar Private Equity Investments, L.P. or any future permitted holder of this
promissory note (the "Payee"), at the principal office of the Payee set forth
                      -----
herein, or at such other place as the holder may designate in writing to the
Company, the principal sum of up to SEVEN HUNDRED FIFTY THOUSAND DOLLARS (U.S.
$750,000), or such other amount as may be outstanding hereunder, together with
all accrued but unpaid interest, in such coin or currency of the United States
of America as at the time shall be legal tender for the payment of public and
private debts and in immediately available funds, as provided in this promissory
note (the "Note").  Concurrently with the issuance of this Note, the Company is
           ----
issuing separate notes (the "Other Notes") to separate investors pursuant to the
                             -----------
Purchase Agreement (as defined in Section 3(d) hereof).

          1.   Principal and Interest Payments.
               -------------------------------

               (a)  The Company shall repay in full the entire principal balance
then outstanding under this Note on the first to occur (the "Maturity Date") of:
                                                             -------------
(i) April 17, 2002; or (ii) the acceleration of the obligations as contemplated
by this Note. The Company may prepay all or any part of this Note, together with
the Other Notes, in whole or in part at any time, without penalty or premium, as
set forth in Section 5(d) hereof.

               (b)  Interest on the outstanding principal balance of this Note
shall accrue at a rate of ten percent (10%) per annum. Interest on the
outstanding principal balance of the Note shall be computed on the basis of the
actual number of days elapsed and a year of three hundred and sixty (360) days
and shall be payable by the Company (i) on a quarterly basis,
<PAGE>

commencing on September 11, 2001 and on each three-month anniversary thereafter,
continuing throughout the term of this Note, and (ii) in full on the Maturity
Date. Furthermore, upon the occurrence of an Event of Default, then to the
extent permitted by law, the Company will pay interest to the Payee, payable on
demand, on the outstanding principal balance of the Note from the date of the
Event of Default until payment in full at the rate of fourteen percent (14%) per
annum.

               (c)  At the Maturity Date, the outstanding principal amount of
this Note plus all accrued and unpaid interest herein shall be due and payable
in cash or, at the option of the Payee, converted into equity securities which
may be issued in connection with a possible private placement by the Company of
its equity securities to certain institutional investors completed at or prior
to the Maturity Date (the "Proposed Financing"). Upon the conversion of this
                           ------------------
Note, the outstanding principal amount of this Note, together with accrued
interest hereon, shall be deemed to be the consideration for the Payee's
interest in the new equity securities on the Maturity Date.

               (d)  The Company shall use its best efforts to prepare and file
with the Securities and Exchange Commission as soon as possible following the
closing of the Proposed Financing, but in any event no later than sixty (60)
days from the date hereof (the "Filing Date"), a registration statement covering
                                -----------
shares of the Company's common stock underlying the equity securities (the
"Registration Statement"). If the Registration Statement is not filed on or
 ----------------------
prior to the Filing Date, the Company shall pay as liquidated damages for such
failure and not as a penalty to the Payee an amount equal to two percent (2%) of
the purchase price paid by the Payee for this Note for each thirty (30) day
period in which the registration statement is not filed on or prior to the
Filing Date (the "Periodic Amount"). The parties agree that the Periodic Amount
                  ---------------
represents a reasonable estimate on the part of the parties, as of the date of
this Note, of the amount of damages that may be incurred by the Payee if the
Registration Statement is not filed on or prior to the Filing Date.

          2.   Payment on Non-Business Days.  Whenever any payment to be made
               ----------------------------
shall be due on a Saturday, Sunday or a public holiday under the laws of the
State of New York, such payment may be due on the next succeeding business day
and such next succeeding day shall be included in the calculation of the amount
of accrued interest payable on such date.

          3.   Events of Default.  The occurrence of any of the following events
               -----------------
shall be an "Event of Default" under this Note:
             ----------------

               (a)  the Company shall fail to make the payment of any amount of
any principal outstanding for a period of three (3) business days after the date
such payment shall become due and payable hereunder; or

               (b)  the Company shall fail to make any payment of interest for a
period of three (3) business days after the date such interest shall become due
and payable hereunder; or

                                       2
<PAGE>

               (c)  the Proposed Financing shall fail to have been consummated
by April 17, 2002; or

               (d)  the Company shall fail to make the payment of any fees
and/or liquidated damages under this Note or the Note and Warrant Purchase
Agreement by and among the Company, the Payee, and the other purchasers party
thereto, dated as of the date hereof (the "Purchase Agreement") which failure is
                                           ------------------
not remedied within five (5) business days after the occurrence thereof; or

               (e)  the Company shall default in the performance or observance
of any covenant, condition or agreement contained in any of the Transaction
Documents (as defined in the Purchase Agreement, the "Transaction Documents")
                                                      ---------------------
(or the Company makes an announcement, statement or threat that it does not
intend to honor its obligations under any of the Transaction Documents) and such
default is not fully cured within five (5) business days (other than with
respect to an announcement, statement or threat) after the occurrence thereof in
the case of failure within the Company's control or thirty (30) business days in
the case of a default due to circumstances outside of the Company's control,
after the earlier of (x) the date on which any executive officer of the Company
shall have obtained actual knowledge of such failure (or such announcement,
statement or threat) and (y) the date on which written notice thereof has been
given to the Company by the Payee which is not covered by any other provisions
of this Section 3(e); or

               (f)  any representation, warranty or certification made by the
Company herein or in any of the other Transaction Documents or in any
certificate or financial statement shall prove to have been false or incorrect
or breached in a material respect on the date as of which made; or

               (g)  the Company or any of its Subsidiaries (as defined the
Purchase Agreement, the "Subsidiaries") shall (i) default in any payment of any
                         ------------
amount or amounts of principal of or interest on any Indebtedness (as defined in
the Purchase Agreement, the "Indebtedness") (other than the Indebtedness
                             ------------
hereunder) the aggregate principal amount of which Indebtedness of all such
persons is in excess of $100,000, whether such Indebtedness now exists or shall
hereinafter be created, and such default entitles the holder thereof to declare
such indebtedness to be due and payable, and such indebtedness has not been
discharged in full or such acceleration has not been stayed, rescinded or
annulled within ten (10) business days of such acceleration, or (ii) default in
the observance or performance of any other agreement or condition relating to
any Indebtedness or contained in any instrument or agreement evidencing,
securing or relating thereto, or any other event shall occur or condition exist,
the effect of which default or other event or condition is to cause, or to
permit the holder or holders or beneficiary or beneficiaries of such
Indebtedness to cause with the giving of notice if required, such Indebtedness
to become due prior to its stated maturity; or

               (h)  A judgment or order for the payment of money shall be
rendered against the Company or any Subsidiary in excess of $100,000 in the
aggregate (net of any

                                       3
<PAGE>

applicable insurance coverage) for all such judgments or orders against all such
persons (treating any deductibles, self insurance or retention as not so
covered) that shall not be discharged, and all such judgments and orders remain
outstanding, and there shall be any period of thirty (30) consecutive days
following entry of the judgment or order in excess of $100,000 or the judgment
or order which causes the aggregate amount described above to exceed $100,000
during which a stay of enforcement of such judgment or order, by reason of a
pending appeal or otherwise, shall not be in effect; or

               (i)  an "Event of Default" has occurred and is continuing under
any Other Notes issued to any other holders pursuant to the Purchase Agreement;
or

               (j)  the Company shall (i) apply for or consent to the
appointment of, or the taking of possession by, a receiver, custodian, trustee
or liquidator of itself or of all or a substantial part of its property or
assets, (ii) admit in writing its inability to pay its debts as such debts
become due, (iii) make a general assignment for the benefit of its creditors,
(iv) commence a voluntary case under the Bankruptcy Code or under the comparable
laws of any jurisdiction (foreign or domestic), (v) file a petition seeking to
take advantage of any bankruptcy, insolvency, moratorium, reorganization or
other similar law affecting the enforcement of creditors' rights generally, (vi)
acquiesce in writing to any petition filed against it in an involuntary case
under the Bankruptcy Code or under the comparable laws of any jurisdiction
(foreign or domestic), or (vii) take any action under the laws of any
jurisdiction (foreign or domestic) analogous to any of the foregoing; or

               (k)  a proceeding or case shall be commenced in respect of the
Company or any of its Subsidiaries without its application or consent, in any
court of competent jurisdiction, seeking (i) the liquidation, reorganization,
moratorium, dissolution, winding up, or composition or readjustment of its
debts, (ii) the appointment of a trustee, receiver, custodian, liquidator or the
like of it or of all or any substantial part of its assets or (iii) similar
relief in respect of it under any law providing for the relief of debtors, and
such proceeding or case described in clause (i), (ii) or (iii) shall continue
undismissed, or unstayed and in effect, for a period of thirty (30) consecutive
days or any order for relief shall be entered in an involuntary case under the
Bankruptcy Code or under the comparable laws of any jurisdiction (foreign or
domestic) against the Company or any of its Subsidiaries or action under the
laws of any jurisdiction (foreign or domestic) analogous to any of the foregoing
shall be taken with respect to the Company or any of its Subsidiaries and shall
continue undismissed, or unstayed and in effect for a period of thirty (30)
consecutive days.

          4.   Remedies Upon An Event of Default.  If an Event of Default shall
               ---------------------------------
have occurred and shall be continuing, the Payee of this Note may at any time at
its option, (a) declare the entire unpaid principal balance of this Note,
together with all interest accrued hereon, due and payable, and thereupon, the
same shall be accelerated and so due and payable, without presentment, demand,
protest, or notice, all of which are hereby expressly unconditionally and
irrevocably waived by the Company; provided, however, that upon the occurrence
                                   --------  -------
of an Event of Default described in (i) Sections 3(j) and (k), the outstanding
principal balance and accrued

                                       4
<PAGE>

interest hereunder shall be automatically due and payable, and (ii) Sections
3(a) through (i), the Payee may demand the prepayment of this Note pursuant to
Section 5 hereof; or (b) exercise or otherwise enforce any one or more of the
Payee's rights, powers, privileges, remedies and interests under this Note or
any of the other Transaction Documents or applicable law. No course of delay on
the part of the Payee shall operate as a waiver thereof or otherwise prejudice
the right of the Payee. No remedy conferred hereby shall be exclusive of any
other remedy referred to herein or now or hereafter available at law, in equity,
by statute or otherwise.

          5.   Prepayment Options.
               ------------------

               (a)  Prepayment.  Notwithstanding anything to the contrary
                    ----------
contained herein, the Payee shall have the right, at such Payee's option, to
require the Company to prepay all or a portion of the sum of the outstanding
principal amount and any interest accrued and outstanding under this Note (the
"Prepayment Price"), provided, that such prepayment is requested upon the
 ----------------    --------
occurrence of a Major Transaction (as defined in Section 5(e) below) or a
Triggering Event (as defined in Section 5(e) below). Nothing in this Section
5(a) shall limit the Payee's rights under Section 4 hereof. The Company shall
immediately notify the holders of the Other Notes if the Payee has requested
prepayment pursuant to this Section 5.

               (b)  Mechanics of Prepayment at Option of Payee.  At least thirty
                    ------------------------------------------
(30) days prior to the occurrence of a Major Transaction and within one (1) day
after the occurrence of a Major Transaction or a Triggering Event, the Company
shall deliver written notice thereof via facsimile and overnight courier
("Notice of a Prepayment Event") to the Payee and the holders of the Other
  ------------------------------
Notes. At any time on or after the earlier of the Payee's receipt of a Notice of
a Prepayment Event and the Payee becoming aware of a Major Transaction or a
Triggering Event, the Payee may require the Company to prepay all or a portion
of the outstanding principal amount and any interest accrued and outstanding
under this Note by delivering written notice thereof via facsimile and overnight
courier ("Notice of Prepayment at Option of Payee") to the Company, which Notice
          ---------------------------------------
of Prepayment at Option of Payee shall indicate the amount of principal and
interest accrued and outstanding under this Note that the Payee is electing to
have prepaid, the sum of which shall be the Prepayment Price.

               (c)  Payment of Prepayment Price.  Upon the Company's receipt of
                    ---------------------------
a Notice of Prepayment at Option of Payee from the Payee, the Company shall
immediately notify the Payee by facsimile of the Company's receipt of a Notice
of Prepayment at Option of Payee and the Payee which has sent such a notice
shall, in the case of a Major Transaction, deliver to the Company this Note
which Payee has elected to have prepaid on or before the consummation or closing
of such Major Transaction and, in the case of a Triggering Event, promptly
submit to the Company this Note which Payee has elected to have prepaid. The
Company shall pay the Prepayment Price to Payee, in the case of a Major
Transaction, at or prior to the closing of the Major Transaction, and, in the
case of a Triggering Event, within five (5) business days after the Company's
receipt of a Notice of Prepayment at Option of Payee; provided that this Note
                                                      --------
shall have been so delivered to the Company. If the Company shall fail to prepay
all of the Prepayment Price (other than pursuant to a dispute as to the
arithmetic calculation of the

                                       5
<PAGE>

Prepayment Price), in addition to any remedy the Payee may have under this Note
and the Purchase Agreement, the Prepayment Price payable in respect of such
unprepaid Notes shall bear interest at the rate of two percent (2.0%) per each
period of thirty (30) consecutive days, pro rated for any period of less than
thirty (30) days until paid in full. Until the Company pays such unpaid
Prepayment Price in full to the Payee, the Payee shall have the option (the
"Void Optional Prepayment Option") to, in lieu of prepayment, require the
 -------------------------------
Company to promptly return to the Payee this Note that was submitted for
prepayment by Payee under this Section 5(c) and for which the Prepayment Price
has not been paid, by sending written notice thereof to the Company via
facsimile (the "Void Optional Prepayment Notice"). Upon the Company's receipt of
                -------------------------------
such Void Optional Prepayment Notice(s) and prior to payment of the full
Prepayment Price to Payee, (i) the Notice(s) of Prepayment at Option of Payee
shall be null and void with respect to this Note submitted for prepayment and
for which the Prepayment Price has not been paid and (ii) the Company shall
immediately return this Note submitted to the Company by the Payee for
prepayment under this Section 5(c) and for which the Prepayment Price has not
been paid. A Payee's delivery of a Void Optional Prepayment Notice and exercise
of its rights following such notice shall not affect the Company's obligations
to make any payments which have accrued prior to the date of such notice.

               (d)  Company's Prepayment Option.  The Company may prepay, at the
                    ---------------------------
option of its Board of Directors, all or any portion of the outstanding
principal amount of this Note and the accrued and unpaid interest thereon upon
five (5) business days prior written notice to the Payee (the "Company
                                                               -------
Prepayment Notice") at a cash price equal to sum of the outstanding principal
-----------------
amount and any interest accrued and outstanding (the "Company Prepayment
                                                      ------------------
Price"). The Company may not deliver a Company Prepayment Notice to the Payee
-----
unless the Company has clear and good funds for a minimum of the amount it
intends to prepay in a bank account controlled by the Company. The Company
Prepayment Notice shall state the date of prepayment (the "Company Prepayment
                                                           ------------------
Date"), the Company Prepayment Price, the amount of the Note of such Payee to be
----
prepaid, the amount of accrued and unpaid interest through the Company
Prepayment Date and shall call upon the Payee to surrender to the Company on the
Company Prepayment Date at the place designated in the Company Prepayment Notice
such Payee's Note. The Company Prepayment Date shall be no more than five (5)
trading days after the date on which the Payee is notified of the Company's
intent to prepay the Note (the "Company Prepayment Notice Date"). If the Company
                                ------------------------------
fails to pay the Company Prepayment Price by the sixth (6/th/) trading day
following the Company Prepayment Notice Date, the prepayment will be declared
null and void and the Company shall lose its right to deliver a Company
Prepayment Notice to the Payee in the future. On or after the Company Prepayment
Date, the Payee shall surrender the Notes called for prepayment to the Company
at the place designated in the Company Prepayment Notice and shall thereupon be
entitled to receive payment of the Company Prepayment Price.

               (e)  For purposes of this Note, (1) "Major Transaction" means the
                                                    -----------------
consummation of any of the following transactions: (i) the consolidation, merger
or other business combination of the Company with or into a person or entity
(other than (A) pursuant to a migratory merger effected solely for the purpose
of changing the jurisdiction of incorporation

                                       6
<PAGE>

of the Company, or (B) a consolidation, merger or other business combination in
which holders of the Company's or any of its Subsidiaries voting power
immediately prior to the transaction continue after the transaction to hold,
directly or indirectly, the voting power of the surviving entity or entities
necessary to elect a majority of the members of the board of directors (or their
equivalent if other than a corporation) of such entity or entities); (ii) the
sale or transfer of all or substantially all of the Company's or any of its
Subsidiaries' assets; or (iii) the consummation of a purchase, tender or
exchange offer made to the holders of more than 30% of the outstanding shares of
the Company's common stock; provided, however, that during the six months
                            --------  -------
following the date of issuance of this Note a Strategic Merger shall not be
deemed a Major Transaction, (2) "Strategic Merger" means a merger with another
                                 ----------------
entity in the same industry as the Company, in which the Company is the
surviving entity and its Common Stock remains publicly traded subsequent to the
merger and an investment of at least $7,000,000 has been made in the Company's
Common Stock or convertible preferred stock; and (3) "Triggering Event" means
                                                      ----------------
(i) any representation or warranty made by the Company in the Purchase Agreement
or any of the Transaction Documents shall prove to have been false or incorrect
in a material respect at the time when made; or (ii) the Company has breached a
material covenant or other term or condition of the Purchase Agreement or any
related agreement delivered therewith; or (iv) the Company has entered into a
Subsequent Financing (as defined in Section 3.10 of the Purchase Agreement).

          6.   Other Notes.  This Note is one of the Notes referred to in the
               -----------
Purchase Agreement. Any and all payments or prepayments of this Note by the
Company shall be made on a pro rata basis with the Other Notes. The Company
shall promptly notify the holder of this Note of any notices sent or received,
or any actions taken with respect to the Other Notes.

          7.   Replacement.  Upon receipt of a duly executed, notarized and
               -----------
unsecured written statement from the Payee with respect to the loss, theft or
destruction of this Note (or any replacement hereof), and without requiring an
indemnity bond or other security, or, in the case of a mutilation of this Note,
upon surrender and cancellation of such Note, the Company shall issue a new
Note, of like tenor and amount, in lieu of such lost, stolen, destroyed or
mutilated Note.

          8.   Parties in Interest, Transferability.  This Note shall be binding
               ------------------------------------
upon the Company and its successors and assigns and the terms hereof shall inure
to the benefit of the Payee and its successors and permitted assigns. This Note
may be transferred or sold, subject to the provisions of Section 17 of this
Note, or pledged, hypothecated or otherwise granted as security by the Payee.

          9.   Amendments.  This Note may not be modified or amended in any
               ----------
manner except in writing executed by the Company and the Payee.

          10.  Notices.  Any notice, demand, request, waiver or other
               -------
communication required or permitted to be given hereunder shall be in writing
and shall be effective (a) upon hand delivery by telecopy or facsimile at the
address or number designated below (if delivered on a business day during normal
business hours where such notice is to be received), or the first

                                       7
<PAGE>

business day following such delivery (if delivered other than on a business day
during normal business hours where such notice is to be received) or (b) on the
second business day following the date of mailing by express courier service,
fully prepaid, addressed to such address, or upon actual receipt of such
mailing, whichever shall first occur. The Company will give written notice to
the Payee at least thirty (30) days prior to the date on which the Company
closes its books or takes a record (x) with respect to any dividend or
distribution upon the common stock of the Company, (y) with respect to any pro
rata subscription offer to holders of common stock of the Company or (z) for
determining rights to vote with respect to a Major Transaction or a Triggering
Event, dissolution, liquidation or winding-up and in no event shall such notice
be provided to such holder prior to such information being made known to the
public. The Company will also give written notice to the Payee at least twenty
(20) days prior to the date on which dissolution, liquidation or winding-up will
take place and in no event shall such notice be provided to the Payee prior to
such information being made known to the public.

     Address of the Payee:    Oscar Private Equity Investments, L.P.
                              666 Fifth Avenue, 34th Floor
                              New York, NY 10103
                              Attention: Brett Messing
                              Telecopier: (212) 484-1030

     Address of the Company:  Speedcom Wireless Corporation
                              1748 Independence Boulevard, D-4
                              Sarasota, Florida 34243
                              Attention: Jay Wright, Chief Financial Officer
                              Telecopier: (941) 358-6208

          11.  Governing Law.  This Note shall be governed by and construed in
               -------------
accordance with the internal laws of the State of New York, without giving
effect to the choice of law provisions. This Note shall not be interpreted or
construed with any presumption against the party causing this Note to be
drafted.

          12.  Headings.  Article and section headings in this Note are included
               --------
herein for purposes of convenience of reference only and shall not constitute a
part of this Note for any other purpose.

          13.  Remedies, Characterizations, Other Obligations, Breaches and
               ------------------------------------------------------------
Injunctive Relief. The remedies provided in this Note shall be cumulative and in
-----------------
addition to all other remedies available under this Note, at law or in equity
(including, without limitation, a decree of specific performance and/or other
injunctive relief), no remedy contained herein shall be deemed a waiver of
compliance with the provisions giving rise to such remedy and nothing herein
shall limit a Payee's right to pursue actual damages for any failure by the
Company to comply with the terms of this Note. Amounts set forth or provided for
herein with respect to payments and the like (and the computation thereof) shall
be the amounts to be received by the Payee and shall not, except as expressly
provided herein, be subject to any other obligation of the Company (or the

                                       8
<PAGE>

performance thereof). The Company acknowledges that a breach by it of its
obligations hereunder will cause irreparable and material harm to the Payee and
that the remedy at law for any such breach may be inadequate. Therefore the
Company agrees that, in the event of any such breach or threatened breach, the
Payee shall be entitled, in addition to all other available rights and remedies,
at law or in equity, to seek and obtain such equitable relief, including but not
limited to an injunction restraining any such breach or threatened breach,
without the necessity of showing economic loss and without any bond or other
security being required.

          14.  Failure or Indulgence Not Waiver.  No failure or delay on the
               --------------------------------
part of the Payee in the exercise of any power, right or privilege hereunder
shall operate as a waiver thereof, nor shall any single or partial exercise of
any such power, right or privilege preclude other or further exercise thereof or
of any other right, power or privilege.

          15.  Enforcement Expenses.  The Company agrees to pay all costs and
               --------------------
expenses of enforcement of this Note, including, without limitation, reasonable
attorneys' fees and expenses.

          16.  Binding Effect.  The obligations of the Company and the Payee set
               --------------
forth herein shall be binding upon the successors and assigns of each such
party, whether or not such successors or assigns are permitted by the terms
hereof.

          17.  Compliance with Securities Laws.  The Payee of this Note
               -------------------------------
acknowledges that this Note is being acquired solely for the Payee's own account
and not as a nominee for any other party, and for investment, and that the Payee
shall not offer, sell or otherwise dispose of this Note other than in compliance
with the laws of the United States of America and as guided by the rules of the
Securities and Exchange Commission. This Note and any Note issued in
substitution or replacement therefore shall be stamped or imprinted with a
legend in substantially the following form:

          "THIS NOTE HAS NOT BEEN REGISTERED UNDER THE SECURITIES
          ACT OF 1933, AS AMENDED (THE "SECURITIES ACT"), OR ANY
          STATE SECURITIES LAW AND MAY NOT BE SOLD, TRANSFERRED OR
          OTHERWISE DISPOSED OF UNLESS REGISTERED UNDER THE
          SECURITIES ACT AND UNDER APPLICABLE STATE SECURITIES LAWS
          OR SPEEDCOM WIRELESS CORPORATION SHALL HAVE RECEIVED AN
          OPINION OF ITS COUNSEL THAT REGISTRATION OF SUCH
          SECURITIES UNDER THE SECURITIES ACT AND UNDER THE
          PROVISIONS OF APPLICABLE STATE SECURITIES LAWS IS NOT
          REQUIRED."

          18.  Severability.  The provisions of this Note are severable, and if
               ------------
any provision shall be held invalid or unenforceable in whole or in part in any
jurisdiction, then such invalidity or unenforceability shall not in any manner
affect such provision in any other jurisdiction or any other provision of this
Note in any jurisdiction.

                                       9
<PAGE>

          19.  Consent to Jurisdiction.  Each of the Company and the Payee (i)
               -----------------------
hereby irrevocably submits to the jurisdiction of the United States District
Court sitting in the Southern District of New York and the courts of the State
of New York located in New York county for the purposes of any suit, action or
proceeding arising out of or relating to this Note and (ii) hereby waives, and
agrees not to assert in any such suit, action or proceeding, any claim that it
is not personally subject to the jurisdiction of such court, that the suit,
action or proceeding is brought in an inconvenient forum or that the venue of
the suit, action or proceeding is improper. Each of the Company and the Payee
consents to process being served in any such suit, action or proceeding by
mailing a copy thereof to such party at the address in effect for notices to it
under the Purchase Agreement and agrees that such service shall constitute good
and sufficient service of process and notice thereof. Nothing in this Section 19
shall affect or limit any right to serve process in any other manner permitted
by law.

          20.  Company Waivers.  Except as otherwise specifically provided
               ---------------
herein, the Company and all others that may become liable for all or any part of
the obligations evidenced by this Note, hereby waive presentment, demand, notice
of nonpayment, protest and all other demands and notices in connection with the
delivery, acceptance, performance and enforcement of this Note, and do hereby
consent to any number of renewals of extensions of the time or payment hereof
and agree that any such renewals or extensions may be made without notice to any
such persons and without affecting their liability herein and do further consent
to the release of any person liable hereon, all without affecting the liability
of the other persons, firms or Company liable for the payment of this Note, AND
DO HEREBY WAIVE TRIAL BY JURY.

               (a)  No delay or omission on the part of the Payee in exercising
its rights under this Note, or course of conduct relating hereto, shall operate
as a waiver of such rights or any other right of the Payee, nor shall any waiver
by the Payee of any such right or rights on any one occasion be deemed a waiver
of the same right or rights on any future occasion.

               (b)  THE COMPANY ACKNOWLEDGES THAT THE TRANSACTION OF WHICH THIS
NOTE IS A PART IS A COMMERCIAL TRANSACTION, AND TO THE EXTENT ALLOWED BY
APPLICABLE LAW, HEREBY WAIVES ITS RIGHT TO NOTICE AND HEARING WITH RESPECT TO
ANY PREJUDGMENT REMEDY WHICH THE PAYEE OR ITS SUCCESSORS OR ASSIGNS MAY DESIRE
TO USE.

                 [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]

                                       10
<PAGE>

          IN WITNESS WHEREOF, the Company has executed and delivered this Note
as of the date first written above.

                                        SPEEDCOM WIRELESS CORPORATION

                                        By:______________________________
                                           Name:
                                           Title:

                                       11

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