Signal Widget [Solved]

Emoncms
#1

## Signal Widget configuration ?

Have tried setting up SIgnal Widget, but without luck.
There is no signal on the icon, but may it add some settings to this widget before it will work?

Below I show the value of RSSI as a Feed Value, and Signal Widget next to it.?

#2

You have a negative value as the feed which is how dB is measured but the widget requires a positive value ie 66

–
Mark

#3

Thanks Mark
A virtual feed that add 100 to the value solve the problem, and now the signal widget works perfectly

1 Like
#4

RSSI is typically a ngative number. But dB, as used in this context, is a number
referenced to 1 milliwatt (0 dBm) i.e. it represents a ratio, and as such, can be either negative or positive.

While a negative number in the widget might seem odd, it would actually be correct.

That’s not to say the number can’t be positive, as the likelihood of a received signal being that strong is very low unless the transmitter and receiver are physicaly located very close to each other.

#5

That would not give you the correct value

ie -66+100=34, -52+100=48

Multiply the value by -1 to achieve the correct reading

#6

But it would give a reading that moved in the correct direction, a bigger negative number is a poorer signal, a smaller negative, or bigger positive, signal is a better signal. To amplify (in decibel terms) you add a constant. So doing as Sune did amplified the signal, which I think is the correct approach.

1 Like
#7

@Bielefeldt
You might actually need a constant bigger than 100, because I think I’ve seen logs with an RSSI - of what I suspect is actually noise pickup - below -100dB. The RFM69CW data sheet has the range going from 0 down to -115 dBm.

1 Like
#8

Hi Robert

It looks more realistic with 115 than with the factor 100.

Thank you for your input.

OEM_Dashboard.JPG1147Ă—1185 129 KB

#9

Typically you can not get dBm to 0. Generally, -30 is the maximum but considered over powered. It’s like screaming in one’s ear. 100% signal is considered around -50 dBm. If stronger than -45 you should be reducing power output. But in reality, anything -66 and stronger is considered “100%” signal strength as there should not be any, or very little data loss. -67 to -70 is considered good signal strength, -71 to -80, not so great. Anything weaker than -80 is poor.