As we review our results, please note that in our comments today and in the accompanying slides, we reference a certain non-GAAP measures, specifically in accordance with our 52/53 week calendar.
Revenue was $750.7 million, an increase of 1.8%.
Organic revenue excluding $5.7 million of storm restoration services in the quarter declined 6.2%.
As we deployed 1 gigabit wireline networks, wireless/wireline converged networks and wireless networks, this quarter reflected an increase in demand from one of our top five customers.
Adjusted gross margins were 14.3% of revenue, reflecting the continued impacts of the complexity of a large customer program.
Adjusted general and administrative expenses were 8.5%, and all of these factors produced adjusted EBITDA of $45.7 million or 6.1% of revenue, an adjusted diluted loss per share of $0.07, compared to a loss of $0.23 in the year ago quarter.
Liquidity was strong as cash and availability under our credit facility was $570.5 million.
Finally, during the quarter, we repurchased 1.32 million shares of our common stock for $100 million, representing just over 4.15% of common stock outstanding.
Even after the substantial repurchase, notional net debt only increased by $14.6 million during the quarter.
In sum, over the last four quarters, we have reduced notional net debt by over $275 million, increased availability under our credit facility by a similar amount and meaningfully reduced shares outstanding.
As our most recent share repurchase authorization has been exhausted, our Board has newly authorized $150 million in share repurchases.
These wireline networks are generally designed to provision 1 gigabit network speeds to individual consumers and businesses, either directly or wirelessly using 5G technologies.
We are providing program management, planning, engineering and design, aerial, underground and wireless construction, and fulfillment services for 1 gigabit deployments.
During the quarter, we experienced increased demand from one of our top five customers, organic revenue decreased 6.2%.
Our top five customers combined produced 69.4% of revenue, decreasing 15.5% organically, while all other customers increased 25.3% organically.
Comcast was our largest customer at 18.8% of total revenue or $140.9 million.
Comcast grew 28.8% organically.
Revenue from AT&T was $126.2 million or 16.8% of revenue.
Verizon was our third largest customer at 15.7% of revenue or $117.8 million.
Lumen was our fourth largest customer at $100.5 million or 13.4% of revenue.
And finally revenue from Windstream was $36 million or 4.8% of revenue.
Of note, fiber construction revenue from electrical utilities was $44.1 million in the quarter or 5.9% of total revenue.
This activity increased organically 125% year-over-year.
In fact, over the last several years, we have meaningfully increased the long-term value of our maintenance and operations business, a trend which we believe will parallel our deployment of 1 gigabit wireline direct and wireless/wireline converged networks as those deployments dramatically increase the amount of outside plant network that must be extended and maintained.
Backlog at the end of the fourth quarter was $6.81 billion versus $5.412 billion at the end of the October 2020 quarter, increasing approximately $1.4 billion.
Of this backlog, approximately $2.787 billion is expected to be completed in the next 12 months.
Headcount increased during the quarter to 14,276.
Contract revenues for Q4 were $750.7 million and organic revenue declined 6.2%.
Q4 '21 included an additional week of operations due to the company's 52/53 week fiscal year.
Adjusted EBITDA was $45.7 million or 6.1% of revenue compared to $44.5 million or 6% of revenue in Q4 '20.
Non-GAAP adjusted gross margins were at 14.3% in Q4 and increased 10 basis points from Q4 '20.
Gross margins were within our range of expectations for the quarter, but approximately 80 basis points below the midpoint of our expectations.
This variance reflected approximately 100 basis points of pressure from a large customer program offset in part by approximately 20 basis points of improved performance for several other customers.
G&A expense increased 25 basis points, reflecting higher performance-based compensation offset in part by lower administrative costs, compared to Q4 '20.
The Q4 '21 non-GAAP effective income tax rate was 30%, including incremental tax benefits related to recent tax filings.
For planning purposes for fiscal 2022, we estimate the non-GAAP effective income tax rate will be approximately 27%.
Non-GAAP adjusted net loss was $0.07 per share in Q4 '21, compared to a net loss of $0.23 per share in Q4 '20.
During Q4, we repurchased 1,324,381 shares of our common stock at an average price per share of $75.51 in the open market for $100 million.
Our Board of Directors has approved a new authorization of $150 million for share repurchases through August 2022.
Over the past four quarters, we have reduced notional net debt by $276.4 million.
We ended the quarter with $11.8 million of cash and equivalents, $105 million of revolver borrowings, $421.9 million of term loans and $58.3 million principal amount of convertible notes outstanding.
As of Q4, our liquidity was strong at $570.5 million, cash flows from operations were robust at $102.4 million, bringing our year-to-date operating cash flow to $381.8 million from strong conversion of earnings to cash and prudent working capital management.
The combined DSOs of accounts receivable and net contract assets was at 136 days, reflecting the impact of a large customer program.
Capital expenditures were $20.4 million during Q4 net of disposal proceeds, and gross capex was $21.9 million.
Looking ahead to fiscal year 2022, we expect net capex to range from $150 million to $160 million.
Telephone companies are deploying fiber-to-the-home to enable 1 gigabit high speed connections, increasingly, rural electric utilities are doing the same.

Summary:
Adjusted general and administrative expenses were 8.5%, and all of these factors produced adjusted EBITDA of $45.7 million or 6.1% of revenue, an adjusted diluted loss per share of $0.07, compared to a loss of $0.23 in the year ago quarter.
Non-GAAP adjusted net loss was $0.07 per share in Q4 '21, compared to a net loss of $0.23 per share in Q4 '20.