ASSIGNMENTOF DEPOSIT ACCOUNT

Exhibit 10.6

ASSIGNMENT OF DEPOSIT ACCOUNT

References in the boxes above are for Lender’s use only and do not limit the applicability of this document to any particular loan or item.

Any item above containing “***” has been omitted due to text length limitations.

THIS ASSIGNMENT OF DEPOSIT ACCOUNT dated April 28, 2009, is made and executed between TOWER TECH SYSTEMS INC (“Grantor”) and GREAT WESTERN BANK (“Lender”).

ASSIGNMENT. For valuable consideration, Grantor assigns and grants to Lender a security interest in the Collateral, including without limitation the deposit accounts described below, to secure the Indebtedness and agrees that Lender shall have the rights stated in this Agreement with respect to the Collateral, in addition to all other rights which Lender may have by law.

COLLATERAL DESCRIPTION. The word “Collateral” means the following described deposit account (“Account”):

Savings Account Number 1347401 with Lender

together with (A) all interest, whether now accrued or hereafter accruing; (B) all additional deposits hereafter made to the Account; (C) any and all proceeds from the Account; and (D) all renewals, replacements and substitutions for any of the foregoing.

CROSS-COLLATERALIZATION. In addition to the Note, this Agreement secures all obligations, debts and liabilities, plus interest thereon, of Grantor to Lender, or any one or more of them, as well as all claims by Lender against Grantor or any one or more of them, whether now existing or hereafter arising, whether related or unrelated to the purpose of the Note, whether voluntary or otherwise, whether due or not due, direct or indirect, determined or undetermined, absolute or contingent, liquidated or unliquidated, whether Grantor may be liable individually or jointly with others, whether obligated as guarantor, surety, accommodation party or otherwise, and whether recovery upon such amounts may be or hereafter may become barred by any statute of limitations, and whether the obligation to repay such amounts may be or hereafter may become otherwise unenforceable.

RIGHT OF SETOFF. To the extent permitted by applicable law, Lender reserves a right of setoff in all Grantor’s accounts with Lender (whether checking, savings, or some other account). This includes all accounts Grantor holds jointly with someone else and all accounts Grantor may open in the future. However, this does not include any IRA or Keogh accounts, or any trust accounts for which setoff would be prohibited by law. Grantor authorizes Lender, to the extent permitted by applicable law, to charge or setoff all sums owing on the Indebtedness against any and all such accounts.

GRANTOR’S REPRESENTATIONS AND WARRANTIES WITH RESPECT TO THE COLLATERAL. With respect to the Collateral, Grantor represents and promises to Lender that:

Ownership. Grantor is the lawful owner of the Collateral free and clear of all loans, liens, encumbrances, and claims except as disclosed to and accepted by Lender in writing.

Right to Grant Security Interest. Grantor has the full right, power, and authority to enter into this Agreement and to assign the Collateral to Lender.

No Prior Assignment. Grantor has not previously granted a security interest in the Collateral to any other creditor.

No Further Transfer. Grantor shall not sell, assign, encumber, or otherwise dispose of any of Grantor’s rights in the Collateral except as provided in this Agreement.

No Defaults. There are no defaults relating to the Collateral, and there are no offsets or counterclaims to the same. Grantor will strictly and promptly do everything required of Grantor under the terms, conditions, promises, and agreements contained in or relating to the Collateral.

Proceeds. Any and all replacement or renewal certificates, instruments, or other benefits or proceeds related to the Collateral that are received by Grantor shall be held by Grantor in trust for Lender and immediately shall be delivered by Grantor to Lender to be held as part of the Collateral.

Validity; Binding Effect. This Agreement is binding upon Grantor and Grantor’s successors and assigns and is legally enforceable in accordance with its terms.

Financing Statements. Grantor authorizes Lender to file a UCC financing statement, or alternatively, a copy of this Agreement to perfect Lender’s security interest. At Lender’s request, Grantor additionally agrees to sign all other documents that are necessary to perfect, protect, and continue: Lender’s security interest in the Property. This includes making sure Lender is shown as the first and only security interest holder on the title covering the Property. Grantor will pay all filing fees, title transfer fees, and other fees and costs involved unless prohibited by law or unless Lender is required by law to pay such fees and costs. Grantor irrevocably appoints Lender to execute documents necessary to transfer title if there is a default. Lender may file a copy of this Agreement as a financing statement. If Grantor changes Grantor’s name or address, or the name or address of any person granting a security interest under this Agreement changes, Grantor will promptly notify the Lender of such change.

LENDER’S RIGHTS AND OBLIGATIONS WITH RESPECT TO THE COLLATERAL. While this Agreement is in effect, Lender may retain the rights to possession of the Collateral, together with any and all evidence of the Collateral, such as certificates or passbooks. This Agreement will remain in effect until (a) there no longer is any Indebtedness owing to Lender; (b) all other obligations secured by this Agreement have been fulfilled; and (c) Grantor, in writing, has requested from Lender a release of this Agreement.

LENDER’S EXPENDITURES. If any action or proceeding is commenced that would materially affect Lender’s interest in the Collateral or if Grantor fails to comply with any provision of this Agreement or any Related Documents, including but not limited to Grantor’s failure to discharge or pay when due any amounts Grantor is required to discharge or pay under this Agreement or any Related Documents, Lender on Grantor’s behalf may (but shall not be obligated to) take any action that Lender deems appropriate, including but not limited to discharging or paying all taxes, liens, security interests, encumbrances and other claims, at any time levied or placed on the Collateral and paying all costs for insuring, maintaining and preserving the Collateral. All such expenditures incurred or paid by Lender for such purposes will then bear interest at the rate charged under the Note from the date incurred or paid by Lender to the date of repayment by Grantor. All such expenses will become a part of the Indebtedness and, at Lender’s option, will (A) be payable on demand; (B) be added to the balance of the Note and be apportioned among and be payable with any installment payments to become due during either (1) the term of any applicable insurance policy; or (2) the remaining term of the Note; or (C) be treated as a balloon payment which will be due and payable at the Note’s maturity. The Agreement also will secure payment of these amounts. Such right shall be in addition to all other rights and remedies to which Lender may be entitled upon Default.

LIMITATIONS ON OBLIGATIONS OF LENDER. Lender shall use ordinary reasonable care in the physical preservation and custody of any certificate or passbook for the Collateral but shall have no other obligation to protect the Collateral or its value. In particular, but without limitation, Lender shall have no responsibility (A) for the collection or protection of any income on the Collateral; (B) for the preservation of rights against issuers of the Collateral or against third persons; (C) for ascertaining any maturities, conversions, exchanges, offers, tenders, or similar matters relating to the Collateral; nor (D) for informing the Grantor about any of the above, whether or not Lender has or is deemed to have knowledge of such matters.

DEFAULT. Each of the following shall constitute an Event of Default under this Agreement:

Payment Default. Grantor fails to make any payment when due under the Indebtedness.

Other Defaults. Grantor fails to comply with or to perform any other term, obligation, covenant or condition contained in this Agreement or in any of the Related Documents or to comply with or to perform any term, obligation, covenant or condition contained in any other agreement between Lender and Grantor.

False Statements. Any warranty, representation or statement made or furnished to Lender by Grantor or on Grantor’s behalf under this Agreement or the Related Documents is false or misleading in any material respect, either now or at the time made or furnished or becomes false or misleading at any time thereafter.

Defective Collateralization. This Agreement or any of the Related Documents ceases to be in full force and effect (including failure of any collateral document to create a valid and perfected security interest or lien) at any time and for any reason.

Insolvency. The dissolution or termination of Grantor’s existence as a going business, the insolvency of Grantor, the appointment of a receiver for any part of Grantor’s property, any assignment for the benefit of creditors, any type of creditor workout, or the commencement of any proceeding under any bankruptcy or insolvency laws by or against Grantor.

Creditor or Forfeiture Proceedings. Commencement of foreclosure or forfeiture proceedings, whether by judicial proceeding, self-help, repossession or any other method, by any creditor of Grantor or by any governmental agency against any collateral securing the Indebtedness. This includes a garnishment of any of Grantor’s accounts, including deposit accounts, with Lender. However, this Event of Default shall not apply if there is a good faith dispute by Grantor as to the validity or reasonableness of the claim which is the basis of the creditor or forfeiture proceeding

ASSIGNMENT OF DEPOSIT ACCOUNT

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and if Grantor gives Lender written notice of the creditor or forfeiture proceeding and deposits with Lender monies or a surety bond for the creditor or forfeiture proceeding, in an amount determined by Lender, in its sole discretion, as being an adequate reserve or bond for the dispute.

Events Affecting Guarantor. Any of the preceding events occurs with respect to any Guarantor of any of the Indebtedness or Guarantor dies or becomes incompetent or revokes or disputes the validity of, or liability under, any Guaranty of the Indebtedness.

Adverse Change. A material adverse change occurs in Grantor’s financial condition, or Lender believes the prospect of payment or performance of the Indebtedness is impaired.

Cure Provisions. If any default, other than a default in payment is curable and if Grantor has not been given a notice of a breach of the same provision of this Agreement within the preceding twelve (12) months, it may be cured if Grantor, after receiving written notice from Lender demanding cure of such default: (1) cures the default within fifteen (15) days; or (2) if the cure requires more than fifteen (15) days, immediately initiates steps which Lender deems in Lender’s sole discretion to be sufficient to cure the default and thereafter continues and completes all reasonable and necessary steps sufficient to produce compliance as soon as reasonably practical.

RIGHTS AND REMEDIES ON DEFAULT. Upon the occurrence of an Event of Default, or at any time thereafter, Lender may exercise any one or more of the following rights and remedies, in addition to any rights or remedies that may be available at law, in equity, or otherwise:

Accelerate Indebtedness. Lender may declare all Indebtedness of Grantor to Lender immediately due and payable, without notice of any kind to Grantor.

Application of Account Proceeds. Lender may take directly all funds in the Account and apply them to the Indebtedness. If the Account is subject to an early withdrawal penalty, that penalty shall be deducted from the Account before its application to the Indebtedness, whether the Account is with Lender or some other institution. Any excess funds remaining after application of the Account proceeds to the Indebtedness will be paid to Grantor as the interests of Grantor may appear. Grantor agrees, to the extent permitted by law, to pay any deficiency after application of the proceeds of the Account to the Indebtedness. Lender also shall have all the rights of a secured party under the South Dakota Uniform Commercial Code, even if the Account is not otherwise subject to such Code concerning security interests, and the parties to this Agreement agree that the provisions of the Code giving rights to a secured party shall nonetheless be a part of this Agreement.

Transfer Title. Lender may effect transfer of title upon sale of all or part of the Collateral. For this purpose, Grantor irrevocably appoints Lender as Grantor’s attorney-in-fact to execute endorsements, assignments and instruments in the name of Grantor and each of them (if more than one) as shall be necessary or reasonable.

Other Rights and Remedies. Lender shall have and may exercise any or all of the rights and remedies of a secured creditor under the provisions of the South Dakota Uniform Commercial Code, at law, in equity, or otherwise.

Deficiency Judgment. If permitted by applicable law, Lender may obtain a judgment for any deficiency remaining in the Indebtedness due to Lender after application of all amounts received from the exercise of the rights provided in this section.

Election of Remedies. Except as may be prohibited by applicable law, all of Lender’s rights and remedies, whether evidenced by this Agreement or by any other writing, shall be cumulative and may be exercised singularly or concurrently. Election by Lender to pursue any remedy shall not exclude pursuit of any other remedy, and an election to make expenditures or to take action to perform an obligation of Grantor under this Agreement, after Grantor’s failure to perform, shall not affect Lender’s right to declare a default and exercise its remedies.

Cumulative Remedies. All of Lender’s rights and remedies, whether evidenced by this Agreement or by any other writing, shall be cumulative and may be exercised singularly or concurrently. Election by Lender to pursue any remedy shall not exclude pursuit of any other remedy, and an election to make expenditures or to take action to perform an obligation of Grantor under this Agreement, after Grantor’s failure to perform, shall not affect Lender’s right to declare a default and to exercise its remedies.

MISCELLANEOUS PROVISIONS. The following miscellaneous provisions are a part of this Agreement:

Amendments. This Agreement, together with any Related Documents, constitutes the entire understanding and agreement of the parties as to the matters set forth in this Agreement. No alteration of or amendment to this Agreement shall be effective unless given in writing and signed by the party or parties sought to be charged or bound by the alteration or amendment.

Attorneys’ Fees; Expenses. Grantor agrees to pay upon demand all of Lender’s costs and expenses, including Lender’s attorneys’ fees and Lender’s legal expenses, incurred in connection with the enforcement of this Agreement. Lender may hire or pay someone else to help enforce this Agreement, and Grantor shall pay the costs and expenses of such enforcement. Costs and expenses include Lender’s attorneys’ fees and legal expenses whether or not there is a lawsuit, including attorneys’ fees and legal expenses for bankruptcy proceedings (including efforts to modify or vacate any automatic stay or injunction), appeals, and any anticipated post-judgment collection services. Grantor also shall pay all court costs and such additional fees as may be directed by the court.

Caption Headings. Caption headings in this Agreement are for convenience purposes only and are not to be used to interpret or define the provisions of this Agreement.

Governing Law. This Agreement will be governed by federal law applicable to Lender and, to the extent not preempted by federal law, the laws of the State of South Dakota without regard to its conflicts of law provisions. This Agreement has been accepted by Lender in the State of South Dakota.

Choice of Venue. If there is a lawsuit, Grantor agrees upon Lender’s request to submit to the jurisdiction of the courts of Minnehaha County, State of South Dakota.

No Waiver by Lender. Lender shall not be deemed to have waived any rights under this Agreement unless such waiver is given in writing and signed by Lender. No delay or omission on the part of Lender in exercising any right shall operate as a waiver of such right or any other right. A waiver by Lender of a provision of this Agreement shall not prejudice or constitute a waiver of Lender’s right otherwise to demand strict compliance with that provision or any other provision of this Agreement. No prior waiver by Lender, nor any course of dealing between Lender and Grantor, shall constitute a waiver of any of Lender’s rights or of any of Grantor’s obligations as to any future transactions. Whenever the consent of Lender is required under this Agreement, the granting of such consent by Lender in any instance shall not constitute continuing consent to subsequent instances where such consent is required and in all cases such consent may be granted or withheld in the sole discretion of Lender.

Notices. Any notice required to be given under this Agreement shall be given in writing, and shall be effective when actually delivered, when actually received by telefacsimile (unless otherwise required by law), when deposited with a nationally recognized overnight courier, or, if mailed, when deposited in the United States mail, as first class, certified or registered mail postage prepaid, directed to the addresses shown near the beginning of this Agreement. Any party may change its address for notices under this Agreement by giving formal written notice to the other parties, specifying that the purpose of the notice is to change the party’s address. For notice purposes, Grantor agrees to keep Lender informed at all times of Grantor’s current address. Unless otherwise provided or required by law, if there is more than one Grantor, any notice given by Lender to any Grantor is deemed to be notice given to all Grantors.

Power of Attorney. Grantor hereby appoints Lender as its true and lawful attorney-in-fact, irrevocably, with full power of substitution to do the following: (1) to demand, collect, receive, receipt for, sue and recover all sums of money or other property which may now or hereafter become due, owing or payable from the Collateral; (2) to execute, sign and endorse any and all claims, instruments, receipts, checks, drafts or warrants issued in payment for the Collateral; (3) to settle or compromise any and all claims arising under the Collateral, and in the place and stead of Grantor, to execute and deliver its release and settlement for the claim; and (4) to file any claim or claims or to take any action or institute or take part in any proceedings, either in its own name or in the name of Grantor, or otherwise, which in the discretion of Lender may seem to be necessary or advisable. This power is given as security for the Indebtedness, and the authority hereby conferred is and shall be irrevocable and shall remain in full force and effect until renounced by Lender.

Severability. If a court of competent jurisdiction finds any provision of this Agreement to be illegal, invalid, or unenforceable as to any circumstance, that finding shall not make the offending provision illegal, invalid, or unenforceable as to any other circumstance. If feasible, the offending provision shall be considered modified so that it becomes legal, valid and enforceable. If the offending provision cannot be so modified, it shall be considered deleted from this Agreement. Unless otherwise required by law, the illegality, invalidity, or unenforceability of any provision of this Agreement shall not affect the legality, validity or enforceability of any other provision of this Agreement.

Successors and Assigns. Subject to any limitations stated in this Agreement on transfer of Grantor’s interest, this Agreement shall be binding upon and inure to the benefit of the parties, their successors and assigns. If ownership of the Collateral becomes vested in a person other than Grantor, Lender, without notice to Grantor, may deal with Grantor’s successors with reference to this Agreement and the Indebtedness by way of forbearance or extension without releasing Grantor from the obligations of this Agreement or liability under the Indebtedness.

Survival of Representations and Warranties. All representations, warranties, and agreements made by Grantor in this Agreement shall survive the execution and delivery of this Agreement, shall be continuing in nature, and shall remain in full force and effect until such time as Grantor’s Indebtedness shall be paid in full.

Time is of the Essence. Time is of the essence in the performance of this Agreement.

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ASSIGNMENT OF DEPOSIT ACCOUNT

(Continued)

DEFINITIONS. The following capitalized words and terms shall have the following meanings when used in this Agreement. Unless specifically stated to the contrary, all references to dollar amounts shall mean amounts in lawful money of the United States of America. Words and terms used in the singular shall include the plural, and the plural shall include the singular, as the context may require. Words and terms not otherwise defined in this Agreement shall have the meanings attributed to such terms in the Uniform Commercial Code:

Account. The word “Account” means the deposit accounts described in the “Collateral Description” section.

Agreement. The word “Agreement” means this Assignment of Deposit Account, as this Assignment of Deposit Account may be amended or modified from time to time, together with all exhibits and schedules attached to this Assignment of Deposit Account from time to time.

Borrower. The word “Borrower” means TOWER TECH SYSTEMS INC and includes all co-signers and co-makers signing the Note and all their successors and assigns.

Collateral. The word “Collateral” means all of Grantor’s right, title and interest in and to all the Collateral as described in the Collateral Description section of this Agreement.

Default. The word “Default” means the Default set forth in this Agreement in the section titled “Default”.

Event of Default. The words “Event of Default” mean any of the events of default set forth in this Agreement in the default section of this Agreement.

Grantor. The word “Grantor” means TOWER TECH SYSTEMS INC.

Guarantor. The word “Guarantor” means any guarantor, surety, or accommodation party of any or all of the Indebtedness.

Guaranty. The word “Guaranty” means the guaranty from Guarantor to Lender, including without limitation a guaranty of all or part of the Note.

Indebtedness. The word “Indebtedness” means the indebtedness evidenced by the Note or Related Documents, including all principal and interest together with all other indebtedness and costs and expenses for which Grantor is responsible under this Agreement or under any of the Related Documents. Specifically, without limitation, Indebtedness includes all amounts that may be indirectly secured by the Cross-Collateralization provision of this Agreement.

Lender. The word “Lender” means GREAT WESTERN BANK, its successors and assigns.

Note. The word “Note” means the Note executed by TOWER TECH SYSTEMS INC in the principal amount of $10,000,000.00 dated April 28, 2009, together with all renewals of, extensions of, modifications of, refinancings of, consolidations of, and substitutions for the note or credit agreement.

Property. The word “Property” means all of Grantor’s right, title and interest in and to all the Property as described in the “Collateral Description” section of this Agreement.

Related Documents. The words “Related Documents” mean all promissory notes, credit agreements, loan agreements, environmental agreements, guaranties, security agreements, mortgages, deeds of trust, security deeds, collateral mortgages, and all other instruments, agreements and documents, whether now or hereafter existing, executed in connection with the Indebtedness.

GRANTOR HAS READ AND UNDERSTOOD ALL THE PROVISIONS OF THIS ASSIGNMENT OF DEPOSIT ACCOUNT AND AGREES TO ITS TERMS. THIS AGREEMENT IS DATED APRIL 28, 2009.

LASER PRO Lending, Vet, 5,43,00,003 Copr, Harlend Financial Solutions, Inc. 1997, 2009. All Rights Reserved, -SD o:\officers\apps\CFI\LPL\E90.FC TR-14464 PR-34

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