One UK share I own has jumped by 27% in value so far this year. Yes, this year. Not the past 12 months, but rather the past 12 days!

As a long-term investor, such a share price jump grabs my attention but my focus is on the picture over a more extended time period.

Over the past five years, this stock – although it still sells for pennies today(13 January) – has jumped 799%.

Exciting moment for a key industry

The stock in question is radio frequency-based component maker Filtronic (LSE: FTC).

I have bought the share on several occasions over the past few months. Why? I feel excited about its prospects – even after that stunning price rise.

Here is what I wrote about the medium-sized company in November: “One of the things I like about this is that I see a number of possible drivers for substantial growth in its business (and hopefully therefore its valuation too) next year and beyond.”

That seems to be borne out already less than a fortnight into the New Year. Filtronic told the market in the middle of last month that it expected to outperform market expectations at the full-year level.

Then today, the company issued another trading update less than a month after the most recent one, saying that it “now expects to deliver stronger results for the full year than the recently upgraded market expectations”.

With SpaceX as a key customer right now, my interpretation is that either the SpaceX relationship is delivering handsomely or – perhaps in addition – that client’s reputation is helping attract new customers for the specialist engineering firm.

Here’s why I think it could still be a bargain

Still, despite those positive updates, does this share deserve to have jumped as much as it has?

My feeling is that, in fact, it ought to have jumped even more – and hopefully will later on in 2025.

SpaceX’s ambitious plans for expanding its satellite Internet provision capability could be a sales bonanza for Filtronic as it has been helping supply components for the space company.

Meanwhile, with expansion of its activities on both sides of the pond in recent months, I think Filtronic is now well-positioned to ramp up sales and production. That could be good for revenues and especially profits if the business can exploit economies of scale.

Meanwhile, I think its expertise gives it pricing power, something that could help improve its long-term profitability.

So, while a price-to-earnings (P/E) ratio of 69 would ordinarily make me fall out of my chair, in this case I think the potential for earnings growth means the prospective P/E ratio could be much lower.

There are risks here – with a lot riding on a single customer, if for any reason SpaceX’s plans change, that could be bad news for the Filtronic share price.

But I am hopeful of a bumper year for the UK tech firm and think its shares are still a potential bargain. That is why I have been buying more for my portfolio.