Sometimes it's worth paying extra

We've all been there, weighing the cost of a branded item in the supermarket and wondering whether the cheaper own-brand equivalent is as good. Sometimes feeling agrieved when the packaging suggests the two were made and packaged in the same factory, with just a different label or wrapper slapped on at some point along the production line. I'm looking at you, bourbon biscuits. I'm looking at you, own-brand pain relief. Squash. Mouthwash. Loo roll. There are almost as many ways for us to be screwed over by brands as there are products on the shelves.

Sometimes, though, it's worth paying extra for the brand - an appreciable difference in quality for the extra cost. Jaffa Cakes, for one. Yorkshire Tea, for another. And, as it turns out, radar bike lights.

Full disclosure. I had the opportunity to try the Sigtuna radar rear light pictured for free, in exchange for a fair review on a well-known e-commerce platform. And for free, I shouldn't complain. But the gist of my 3-star review was this:

As a light, it works well. It has an excellent seatpost mount, a variety of light intensities and patterns, and is very visible. I feel seen! I can also report that the "standby" works, whereby the light goes off if you're stationary for 10 seconds or more. I'm not a big fan of this - I like to be visible when I'm standing at a junction - but your mileage may vary. Anyway, as a light this works very well. But what about as a radar device? Well, don't mistake this for a Garmin alternative - it doesn't talk to your cycle computer, and instead relies on a "cheep cheep" audio alert for an oncoming vehicle. That does work, and is clearly audible, but it claims to detect vehicles up to 70m behind you, and that's where the problem lies. A Garmin claims more than double that, but 70m would still be useful. However, in my tests commuting to work, the detection was more like 10m at best, and often less. If you haven't already heard or sensed a car behind you at less than 10m, you maybe shouldn't be cycling on public roads, but if you're relying on this to give you 70m warning, well, you're going to be disappointed. A real shame.

But here's the rub. This Sigtuna radar light currently retails at £30. The latest, greatest Garmin, the RCT715, is £300. Ten times as much! But it actually works, and is widely acknowledged to be class-leading. Whereas the Sigtuna is just a nice light that beeps when you already knows there's a car behind you. So just a light, then, basically. And there are other good rear lights available for less than 30 quid.

I asked an AI LLM (Google's Gemini) why the Sigtuna's radar performance was so poor, and if there was anything I could do to improve it. This was the (annoyingly excellent and comprehensive) response:

The short answer is that cheap budget-friendly radar lights (like the £30 Sigtuna) often suffer from severe hardware limitations, including low-grade radar transmitter-receiver modules, weak signal processing, poor antenna tuning, and a lack of proper firmware filtering.

While name-brand units (like the Garmin Varia or Coospo TR70) use high-spec components and sophisticated Doppler-shift algorithms to filter out environmental noise and pick up vehicles from a safe distance, ultra-budget units often cut corners to hit a low price point. As a result, they struggle to separate real vehicle signatures from background noise beyond a few meters, reducing their effective range to almost nothing.

Unfortunately, there is very little you can do to physically improve the radar's range or detection capability, as it is bottlenecked by its internal hardware. However, a few positioning and troubleshooting steps can ensure you aren't accidentally making it worse:

• Check the Mount Angle: Ensure the light is mounted completely vertically and straight. If the unit is angled too far downward toward the road or tilted toward one side, the radar beam will project into the tarmac or off to the shoulder rather than scanning the straight path of oncoming traffic behind you.
• Clear Obstructions: Make sure there are no saddlebags, loose straps, or mud flaps hanging directly behind or below the unit that could block or distort the radar waves.
• Accept It as a "Light Only": Treat the device purely as a well-mounted, highly visible rear light with a bonus audio cue for cars that are already right on top of you. Relying on it for early hazard warning isn't safe, so sticking to traditional situational awareness (and regular glances if safe to do so) remains your best bet.

Ultimately, because reliable vehicle tracking requires precision radio-frequency hardware and advanced processing, this is a case where the old adage holds true: you generally get what you pay for.

At least my "real" intelligence came to the same conclusion - just accept it as a "light only".

TLDR: If - and if it's a massive if - the Sigtuna worked as claimed, and detected vehicles 70m away, or even something close to that, it would be a great bargain and easy to recommend. As it is, it seems that radar rear lights must join Jaffa Cakes and Yorkshire Tea as products worth paying extra for. ★★★☆☆

BUY: Sigtuna radar rear light, currently £29.99 from Amazon

Full disclosure: I received this item for free in exchange for an honest review.