The reasons why you might have issues

1-Strength

Pretty obvious, if the signal isn’t strong enough then you will have difficulty connecting, maintaining a connection and likely get a slow connection speed. But how do you know this is the issue? The WiFi signal has to handshake and select a matching protocol to connect and that takes a few seconds. So you can’t just wave your device around like a portable radio.

2-Channel overlap 

2.4 GHz will transmit further, has more usable channels and works on older devices. Many security cameras and smart home devices will only work here. Yes, it is slower, typically 56 Mbs, but only 4K TVs really need something faster (technically they will work at 27 Mbs if they’re the only device on it). Most reliable connectivity on this band, it has 14 channels imaginatively named 1-14. * UK specs only, other countries may differ. 

Check out https://en.wikipedia.org/wiki/List_of_WLAN_channels for the fine details for any country

5 Ghz  can allow for much faster speeds, at the expense of poor penetration through walls *some houses in UK use aluminium foil to keep heat in. This kills 5 GHz very effectively! So if you get almost no signal this may be why. Also some 5GHz channels 

https://www.tradestoreonline.co.uk/aluminium-products/how-to-use-aluminium-foil-as-a-wall-application/

Bandwidth

You can set 5 GHz channels to use 20, 40 or even 80 Mhz wide channels.

Channels

32-177 in the UK, though you will not find many routers that can access them all. Mine goes from 36-161, see DFS requirements below. In practice only a few seem to work in practice, so can be tedious to find unused ones. The bonus is that 5GHz channels do not overlap like 2.4 GHz ones.

DFS Requirements (Channels 52–144): Channels in the middle and upper bands require Dynamic Frequency Selection (DFS) in the UK to prevent interference with weather and military radar systems. If a router or access point detects radar signals on these channels, it must legally switch channels, which can cause temporary disconnects. Some hardware imports locked to US configurations may fail to enable these channels properly or restrict power levels when set to a UK region code.

Check out https://en.wikipedia.org/wiki/List_of_WLAN_channels for the fine details for any country

3-Ripples in a pond

Remember in the 1970s, you might be in a car or walking with your brand new transistor radio while listening to the brand new Radio 1? Then you pass a building or go under a bridge and the signal would fade?

AM Frequency and Wavelength Range

• Frequency Range: Commercial AM radio broadcasts operate on frequencies from 535 kHz to 1,700 kHz (medium wave band). [1]

• Lowest Frequency (540 kHz): Has the longest wavelength at about 555 meters (1,821 feet). [1]

• Highest Frequency (1,700 kHz): Has the shortest wavelength in the band at about 176 meters (579 feet). [1]

So as you walked or drove along direct reception signals would combine with signals reflected off walls, buildings, cars etc.

This created the ripples in a pond effect, where the main signal would either be reinforced or reduced by one or multiple reflected signals. This would create either distortion, or lack of signal strength or complete absence of reflection.

You could easily ‘solve’ the problem either by moving the aerial, or the radio a few metres away.

Wi-Fi Frequencies and Wavelengths

• 2.4 GHz Band: Has a longer physical wavelength (about 12 cm or 4.9 inches), allowing signals to travel farther and better penetrate solid objects like walls. [1, 2, 3, 4]

• 5 GHz and 6 GHz Bands: Have shorter wavelengths (about 6 cm for 5 GHz and 5 cm or less for higher bands), which provide faster data speeds but have more trouble passing through physical barriers. [1, 2, 3]

This means that in a domestic or office environment many ripples or standing waves are set up, causing many signal blackspots.

So moving either the router, or the receiving device a few cm in any direction may improve the signal stability and strength.

The solution

This is not a sponsored article, other apps and solutions are available. I purchased this product years ago and it has been very useful on Android and several house and ISP moves.

WiFI Analyser from olgor.com

https://play.google.com/store/apps/details?id=abdelrahman.wifianalyzerpro

This is regularly updated with new features and bands as they appear, it will only work on bands that can be received on your mobile phone.

It allowed me to -

1. See the channel usage on each available band (but not 6 GHz, as my phone cannot receive it)

2. Track signal strength over time and as I moved around my house and outside

3. See an overview of channels use and recommendation with AI feature

4. Devices on my network with names and IP Addresses

5. Details of each Network with signal strength , IP address, frequency, Security level and bandwidth

6. Menu of network tools, including speed test, router overview and more

My Issue

Over the last 2-3 days I have had an increasing intermittent loss of signal, each time for 2-5 minutes on all devices. I have lived at this address for around 5 years and had various ISPs, Virgin Media, 5G Broadband from Tesco(O2 at the time), Voxi (Vodafone) and tested others. 

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Most of my devices connect through WiFi, only one Media PC and the TV connect directly via ethernet  CAT 6 cable and they where fine.

Some screenshots of the WiFi Analyser APP and its screens

So it must be a WiFi issue, but what? Then I remembered the WiFi Analyser Anrdoid App, which I had uninstalled from my phone. So I installed it again and remembered I had paid for the Pro version as I had found it useful many times before in three house locations and at my partners house where we found aluminium foil in the walls. As soon as I looked at the channel usage it was obvious. 

Modern routers are supposed to be intelligent and pick unused channels. This has proved many times not to work, especially as new people move near you. Indeed new neighbours have recently moved into three houses a short distance away. So they were all clustered on channels 1, 6, 11. Even though my signal on 2.4 Ghz was stronger there were several not far below and definitely in my bandwidth. I still looked  to see if the signal was falling in strength and it was not significantly.  I moved my signal from auto on channel 6, to channel 8

I did manage to capture 2 other signals on 5 GHz though not screenshot them, they too were all on auto on channel 100, so I moved to channel 108.

The difference was apparent straight away and that is what pushed me to write this article. I have helped in WiFi diagnosis several times at work locations (with 70 employees) as well as at home(s)and used this or similar APPs to help understand the issues and diagnose the solution successfully where many people would complain to the ISP when it is not their fault.

Sidenote: I also wrote software to change the guest network names and passwords monthly across 12 sites automatically and email the admin staff on a Meraki WiFi system via the API, it was fun as it did a job that staff often overlooked.