SUPPLEMENTAL INDENTURE

Exhibit 4.2(a)

SUPPLEMENTAL INDENTURE

Supplemental Indenture (this “Supplemental Indenture”), dated as of March 16, 2011, among TuTV LLC (the “Guaranteeing Subsidiary”), a subsidiary of Univision Communications Inc., a Delaware corporation (the “Issuer”), and Wilmington Trust FSB, as trustee (the “Trustee”).

W I T N E S S E T H

WHEREAS, the Issuer has heretofore executed and delivered to the Trustee a Senior Notes Indenture (the “Indenture”), dated as of November 23, 2010, providing for the issuance of $815,000,000 aggregate principal amount of 8 ¹⁄₂% Senior Notes due 2021 (the “Notes”);

WHEREAS, the Indenture provides that under certain circumstances the Guaranteeing Subsidiary shall execute and deliver to the Trustee a supplemental indenture pursuant to which the Guaranteeing Subsidiary shall unconditionally guarantee all of the Issuer’s Obligations under the Notes and the Indenture on the terms and conditions set forth herein and under the Indenture (the “Guarantee”); and

WHEREAS, pursuant to Section 9.01 of the Indenture, the Trustee is authorized to execute and deliver this Supplemental Indenture.

NOW THEREFORE, in consideration of the foregoing and for other good and valuable consideration, the receipt of which is hereby acknowledged, the parties mutually covenant and agree for the equal and ratable benefit of the Holders of the Notes as follows:

(1) Capitalized Terms. Capitalized terms used herein without definition shall have the meanings assigned to them in the Indenture.

(2) Agreement to Guarantee. The Guaranteeing Subsidiary accepts all obligations applicable to a Guarantor under the Indenture, including Article X of the Indenture (which is deemed incorporated in this Supplemental Indenture and applicable to this Guarantee) and, as applicable, Sections 5.01(b) and Section 5.02 of the Indenture. The Guaranteeing Subsidiary acknowledges that by executing this Supplemental Indenture, it will become a Guarantor under the Indenture and subject to all the terms and conditions applicable to Guarantors contained therein.

(3) Execution and Delivery. The Guaranteeing Subsidiary agrees that the Guarantee shall remain in full force and effect notwithstanding the absence of the endorsement of any notation of such Guarantee on the Notes.

(4) Releases. The Guarantee of the Guaranteeing Subsidiary shall be automatically and unconditionally released and discharged, and no further action by the Guaranteeing Subsidiary, the Issuer or the Trustee is required for the release of the Guaranteeing Subsidiary’s Guarantee, upon satisfaction of all of the conditions set forth in Section 10.06 of the Indenture.

(5) No Recourse Against Others. No past, present or future director, officer, employee, incorporator or stockholder of the Issuer or the Guaranteeing Subsidiary shall have any liability for any obligations of the Issuer or the Guarantors (including the Guaranteeing Subsidiary) under the Notes, any Guarantees, the Indenture or this Supplemental Indenture or for any claim based on, in respect of, or by reason of, such obligations or their creation. Each Holder by accepting Notes waives and releases all such liability. The waiver and release are part of the consideration for issuance of the Notes.

(6) Governing Law. THIS SUPPLEMENTAL INDENTURE WILL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK.

(7) Counterparts. The parties may sign any number of copies of this Supplemental Indenture. Each signed copy shall be an original, but all of them together represent the same agreement.

(8) Effect of Headings. The Section headings herein have been inserted for convenience of reference only, are not considered a part of this Supplemental Indenture and shall in no way modify or restrict any of the terms or provisions hereof.

(9) The Trustee. The Trustee shall not be responsible in any manner whatsoever for or in respect of the validity or sufficiency of this Supplemental Indenture or for or in respect of the recitals contained herein, all of which recitals are made solely by the Guaranteeing Subsidiary.

(10) Benefits Acknowledged. The Guaranteeing Subsidiary’s Guarantee is subject to the terms and conditions set forth in the Indenture. The Guaranteeing Subsidiary acknowledges that it will receive direct and indirect benefits from the financing arrangements contemplated by the Indenture and this Supplemental Indenture and that the guarantee and waivers made by it pursuant to this Guarantee are knowingly made in contemplation of such benefits.

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IN WITNESS WHEREOF, the parties hereto have caused this Supplemental Indenture to be duly executed, all as of the date first above written.

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