高频电子美股招股说明书(2026-07-28版)

SUBJECT TO COMPLETION, DATED JULY 28, 2026 PROSPECTUS SUPPLEMENT(TO PROSPECTUS DATED JULY 21, 2026) $100,000,000 Shares of Common Stock FREQUENCY ELECTRONICS, INC. This is an offering of $100,000,000 of shares of our common stock, par value $1.00 per share (“common stock”). We areoffering $62,500,000 of shares of common stock in this offering, and Edenbrook Value Fund, LP and Edenbrook Long Only ValueFund, LP, affiliates of Jonathan Brolin, a member of our board of directors, are offering a total of $37,500,000 of shares of commonstock held by them in this offering as selling stockholders. See “Selling Stockholders” beginning on page S-9 for additionalinformation regarding the selling stockholders. We will not receive any proceeds from the sale of the shares of common stock beingoffered by the selling stockholders. Our common stock trades on The Nasdaq Global Market (“Nasdaq”) under the symbol “FEIM.” On July 27, 2026, the lastreported sale price of our common stock on Nasdaq was $70.64 per share. Investing in our common stock involves risks that are described in the “Risk Factors” section beginning on page S-5 ofthis prospectus supplement and page 5 of the accompanying prospectus as well as in “Item 1A—Risk Factors” in our mostrecent report on Form 10-K that is incorporated by reference in this prospectus supplement. Public offering price (1)Assumes no exercise of the underwriters’ option to purchase additional shares of common stock.(2)See “Underwriting” for a description of the compensation payable to the underwriters. We have granted the underwriters a 30-day option to purchase up to $15,000,000 of additional shares of common stock from usat the public offering price, less underwriting discounts and commissions, and on the same terms and conditions as set forth above. Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved ofthese securities or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Anyrepresentation to the contrary is a criminal offense. The common stock is expected to be delivered to purchasers on or about, 2026. Craig-Hallum Morgan Stanley The date of this prospectus supplement is , 2026. TABLE OF CONTENTS Prospectus Supplement ABOUT THIS PROSPECTUS SUPPLEMENTSUMMARYTHE OFFERINGFORWARD-LOOKING STATEMENTSRISK FACTORSUSE OF PROCEEDSCAPITALIZATIONSELLING STOCKHOLDERSMATERIAL U.S. FEDERAL INCOME TAX CONSIDERATIONS FOR NON-U.S. HOLDERSUNDERWRITINGLEGAL MATTERSEXPERTSINCORPORATION OF CERTAIN DOCUMENTS BY REFERENCEWHERE YOU CAN FIND MORE INFORMATION Base Prospectus ABOUT THIS PROSPECTUS SUPPLEMENT This document is in two parts. The first part is this prospectus supplement, which describes the specific terms of this offeringand also adds to and updates information contained in the accompanying prospectus and the documents incorporated by reference intothis prospectus supplement and the accompanying prospectus. The second part, the accompanying prospectus, including thedocuments incorporated by reference therein, provides more general information, some of which may not apply to this offering.Generally, when we refer to this prospectus, we are referring to both parts of this document combined. Any statement made in this prospectus supplement, the accompanying prospectus or in a document incorporated or deemed tobe incorporated by reference into this prospectus supplement or the accompanying prospectus will be deemed to be modified orsuperseded for purposes of this prospectus supplement to the extent that a statement contained in this prospectus supplement, theaccompanying prospectus or any other subsequently filed document that is also incorporated by reference herein or therein modifies orsupersedes that statement. Any statement so modified or superseded will not be deemed, except as so modified or superseded, toconstitute a part of this prospectus supplement. Before buying any shares of common stock offered by us or the selling stockholders,you should read both this prospectus supplement and the accompanying prospectus together with the additional information describedbelow under the heading “Incorporation of Certain Documents by Reference.” We have filed or incorporated by reference exhibits to the registration statement of which this prospectus supplement forms apart. This prospectus supplement contains summaries of certain provisions contained in some of the exhibits to our registrationstatement, but reference is made to the actual documents for complete information. All of the summaries are qualified in their entiretyby the full text of these documents. You may obtain copies of these documents at no cost by writing to or telephoning us at the addressand telephone number given under the heading “Where You Can Find More Information.” We further note that the representations, warranties and covenants made by us in any agreement that is filed as an exhibit toany document t