Michael J. Ferrantino
Analyst · Sidoti & Co
Thank you, James. Good morning, and thank you to our shareholders for your interest in MtronPTI and attending our Q3 2023 earnings call. The completion of the third quarter also marks the completion of our first year as a public company. As a brief reminder, MtronPTI has been providing RF solutions to the marketplace since 1965. We are a global company with 3 manufacturing locations in the U.S. and India.
With consistent investment in research and development, we have a robust product pipeline averaging over 260 new product introductions a year. Our customer base is growing with over 300 active customers today. We continue to focus on our core markets of Defense and Aerospace, Avionics and Space, each of which continues to demonstrate significant tailwinds. Design wins in these markets tend to be very sticky, and program life cycles are long.
Let me now summarize for you where MtronPTI stands for the third quarter 2023. Compared to prior year, revenue for the 3 months ended September 30 increased 29.4% to $10.9 million, and revenue for the 9 months increased 31.2% to $30.4 million. The revenue increase for the quarter and year-to-date periods over the prior year numbers reflect strong Defense product shipments. Gross margins were 42.8% for the 3 months compared to 32.4% for the prior year, and 39.7% for the 9 months compared to 35.6% for the prior year; benefiting from the favorable product mix, along with increased product volumes.
Backlog was $50.3 million at September 30 compared to $46.2 million at the beginning of the year and $44.1 million at the end of the third quarter of 2022. Backlog increased during 2023, primarily due to an increase in Defense product orders. The company reported operating income of $4.4 million for the 9 months ended September 30 compared to operating income of $2 million for the prior year period. The increase reflects both higher revenue and higher margins impacted by favorable product mix as described earlier.
For the 9 months ended September 30, Engineering, Selling and Administrative costs increased $1.5 million over the prior year, primarily as a result of $1.2 million of administrative cost increases, including public company costs of $735,000, which represent the incremental direct costs of being a public company with no comparable amount being recorded within the prior year when results were presented on a stand-alone basis.
Our investment in Research and Development increased $125,000 to $1.6 million for the 9 months ended September 30 as compared to the prior year. Net income was $3.4 million for the 9 months ended September 30, 2023. Diluted net income per share for the 9 months ended September 30 was $1.25 compared to $0.60 for the prior year period. Our adjusted EBITDA was $5.3 million for the 9 months ended September 30 versus $2.9 million for the prior year period. Note that adjusted EBITDA was calculated on a stand-alone basis for the 9 months ended September 30, 2022, and does not include any adjustments for the potential impact from additional costs of being a publicly traded company.
Finally, as we conclude, I would like to thank all of the 300-plus members of our team who have diligently worked to execute our plans, contributing greatly to these results. With a strong backlog and a robust pipeline, we believe we are well positioned for the continued organic growth. We're working hard to drive efficiencies throughout the organization by leveraging our India operation, making key investments in talent and equipment to improve yields and reduce cycle times. We are also working hard to extend our legacy of acquisitions with a focus on companies for cargoes that provide synergistic products, increased technical capabilities and access to new and growing markets.
I will now open the floor to questions. Operator, please open the call to any questions.