Filtronic has just given itself room to grow fourfold. The Sedgefield RF specialist's new 44,000 sq ft manufacturing plant, opened in February and paid for entirely from its own operating cash flow, is sized to support more than £200m of annual revenue. Last year's turnover was £55.5m.

Filtronic makes the high-frequency amplifiers and transceivers that let SpaceX's Starlink ground stations exchange data with the satellite constellation overhead at multi-gigabit speeds.

Building a factory sized for four times current revenue is a direct statement about how much bigger that relationship, and the wider defence and space business behind it, is expected to get.

Filtronic makes solid state power amplifiers and transceivers in the E-band, the very high frequency range needed to move large volumes of data reliably between the ground and low Earth orbit satellites.

It is a specialist, technically demanding niche. High frequencies mean more bandwidth but also more signal loss and heat, and Filtronic's engineering, built up over decades, is what lets it package and combine high-power gallium nitride devices into the amplifiers that newer satellite networks need.

High-power gallium nitride generates serious heat at these frequencies, and managing that heat while combining several GaN chips into one high-power output is the specific problem Filtronic has spent decades solving.

It is a narrow niche with only a handful of specialist manufacturers worldwide, which is a large part of why SpaceX has been willing to back a single UK supplier rather than spread the work around.

The company has been in County Durham since 2014, when it moved its manufacturing and R&D operations to NETPark, the science park run by Business Durham on behalf of Durham County Council. It moved its registered office there from Yorkshire in 2022.

Filtronic's roots go back further: it was founded at Leeds University in 1977 and grew into one of the largest spin-outs to come out of a UK university, before its more recent RF and mmWave-focused incarnation built its business around defence, telecoms infrastructure and space customers.

SpaceX is now its largest customer by some distance. The relationship began in 2024 and has escalated through a series of contracts, culminating in a £47.3m ($62.5m) order announced in August 2025, the largest single contract in Filtronic's history.

That order covers a new generation of gallium nitride E-band amplifiers for the Starlink network, a step up in output power and thermal performance from Filtronic's earlier products. SpaceX also holds warrants over Filtronic shares, exercisable at prices from 33p to 92.8p and vesting as orders are delivered, which on full exercise could take its stake to around 15%.

The structure ties SpaceX's own financial interest to Filtronic remaining ahead on the technology, an unusual structure for a customer-supplier relationship, closer to investor terms than a standard purchase agreement.

The company has been deliberately building beyond SpaceX. It supplies Leonardo on the Tempest fighter programme and BAE Systems Maritime Services on naval radar. It also does defence work for QinetiQ and the Defence Science and Technology Laboratory, alongside contracts with the European Space Agency, Viasat and Airbus on satellite and direct-to-device programmes.

Peter Stocken, the company's business development lead for defence and space in the Middle East, Africa and Asia-Pacific, has pointed to the AUKUS programme, and specifically its Pillar 2 work on electronic warfare and radar, as the next target the new Sedgefield capacity makes achievable. Filtronic's RF components already sit inside systems supplied to BAE Systems Maritime Services, one of the central industrial players in AUKUS.

SpaceX itself went public in June 2026, pricing its Nasdaq listing at $135 a share and valuing the company at around $1.77 trillion, one of the largest stock market flotations on record.

A County Durham manufacturer sitting inside the supply chain of a listing that size is, in itself, a marker of how far this piece of Sedgefield engineering now reaches.

The FY2026 results, published on 4 August, show a company investing ahead of its next stage of growth. Revenue was £55.5m, similar to the £56.3m recorded the previous year, when revenue had more than doubled from £25.4m.

Adjusted EBITDA fell to £11.3m from £17.0m, and operating profit dropped 70% to £4.0m, as the company added headcount and spent on engineering and manufacturing capacity, the price of the scale it is now building towards.

Chief executive Nat Edington described FY2026 as "a year of continued investment, customer diversification and operational scaling", pointing to organic sales growth and adjusted EBITDA that came in slightly ahead of the company's own expectations.

Alongside that investment, the business remains debt-free, funded the new facility entirely from its own operating cash flow, ended the year with net cash of £11.3m, and enters the new financial year with an order book covering around 90% of expected FY2027 revenue.

Trading is expected to be weighted to the second half as manufacturing shifts from older gallium arsenide to gallium nitride production, and shares fell more than 8% on the results day.

NETPark doesn't get the attention Newcastle's Quayside or Team Valley get in most accounts of the North East economy, but the site already carries more than one piece of this story.

Alongside Filtronic, it hosts the Compound Semiconductor Applications Catapult and a North East Satellite Applications Centre of Excellence, both run by Business Durham. Filtronic's own facility is the sharpest example on site of a genuinely hard-to-replicate piece of UK manufacturing capability, a supplier important enough to SpaceX that the relationship includes an equity stake, built into the contract back in 2024.

Whether that shared infrastructure turns into a lasting cluster, or Filtronic remains a single company's supply chain with useful neighbours, is the next thing worth watching.