2.4GHz or 5 GHz ?

JohnSwift10

I have a raspberry pi in my greenhouse controlling the watering and temperature which has a USB wifi adapter so that I have a choice of 2.4 GHz or 5 GHz.

My router is a Virgin Media Hub 5.

Using wavemon the signal strengths are

5 GHz    57%, -70 dBm, ch 108, 5540 MHz 4 sta,  2% chan, Radio Measure, Spectrum Mgmt                   

2.4 GHz 49%, -76 dBm, ch   1, 2412 MHz 7 sta, 24% chan, Radio Measure                        

Which one is the better signal ?        

Newcad

That depends what you mean by "better".

The 2 4 ghz has the higher power level:

https://en.m.wikipedia.org/wiki/DBm

matelodave

Newcad said:

That depends what you mean by "better".

The 2 4 ghz has the higher power level:

https://en.m.wikipedia.org/wiki/DBm

no it doesn't -76dbm is a lot lower than -70dbm ( in fact its around a quarter of the power)

a difference of 3db is roughly half or double the power so -73 dbm is half the power of -70dbm, -76dm is therefore half the power of -73dbm and -80 dbm is one tenth of the power of -70dbm (the scale is logarithmic, not linear)

However that said 2.4ghz tends to travel further and penetrate buildings better than 5ghz and unless you need the higher speed of 5ghz I'd be inclined to use 2.4ghz but in the end, just try it out 

cerebus

2..4ghz is better at penetrating solid objects than 5ghz but the signal also depends how far the pi is from your router

I would be taking your laptop into the greenhouse and checking each signal and picking the one that gives you the best signal without dropouts 

Heedtheadvice

I would agree with M and C above.

There are several variables that you probably cannot take into account in your measurements given.

One thing that is very significant is interference transmissions from other adjacent WiFi devices especially when you have such low signal levels. If you take your laptop into the greenhouse ( as suggested ) it could  e well worth running a signal analysis app such S WiFi Analyser. This will enable you to see ifvghere are any other signals on the same WiFi channels you have in use to then allow you to pick one with the better effective signal to noise ratio ( here another signal can be considered as noise). Select the channel with the best reception level compared to the other signals. This is usually done by the router - as measured at it's location but that might not be optimum at the greenhouse which might otherwise struggle a bit at those given power levels.

As monitoring the greenouse is likely to be slow, the 2.4GHz range is fine and might be best chosen if the rest of your property reception requires faster signals and is optimum on 5GHz and you can then select different optimum channels for the two different locations.

Having said that it is really just guidance and 'suck it and see' still applies!