I would agree with
@Nigel123 and
@foxhole , you've found the correct sort of product, it's just that you're probably scraping the bottom of the barrel as far as performance and reliability of service goes.
It's tempting think that all the products are the same and you're just paying for a brand and marketing, but as lots of group tests show, there's a big difference in performance between products.
Some of this is because of design: Cheaper products tend to be limited in speed e.g. N300 vs AC750, AC1200, AC1900, AC2600 and on and on. Then there's the type of wireless signal that a device works with: 2.4GHz has better potential range, but suffers far more drop-outs due to interference from other wireless devices in the crowded 2.4GHz band compared to the more robust 5GHz wireless band. Many of the N300 extenders only work on 2.4GHz, even the well known brand names. These things are easy to weed out though by looking at the spec sheets. What's harder to determine is the real-world performance.
Two products with close or even near-identical specifications can give rather different performance results when measured up close, and at distance, and on the different wireless GHz bands if supported. To add to this, there may be features in the product that help to boost performance beyond what a basic extender can achieve.
I am just about to install a Netgear EX6120 for a customer. The device is an AC1200 extender (300Mbps + 900Mbps) and works on 2.4GHz and 5GHz. It has some clever tech too. It can operate the two GHz speeds independently so that 2.4GHz doesn't slow down the 5GHz connections, or I can choose to tie those two pipelines together for better reliability or speed. This is a £35 extender, but by no means top of the range. It's possible to spend over £100 on the higher-end models. TP-Link, D-Link, Belkin, Edimax, Linksys and others have similar products and go equally high-end too.
Netgear was my choice because I know the performance and they're relatively easy to configure if the customer has to do it themselves at some point. This particular model is specified well enough to take full advantage of the features of the ISP-supplied wireless router without going OTT. Sometimes you get exactly what you pay for, and it this case, I think this extender is worth the extra over something sold in a supermarket. Each to their own though.
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