- #1
mcalves
- 10
- 0
Hello all, this is a formula that calculates DDM (depth of modulation) at certain outputs of the ILS's Glideslope. I posted this question some time ago but I think I left out some important details. Any help is really appreciated.
This is basic info on the ILS
http://en.wikipedia.org/wiki/Instrument_Landing_System
db = 20log(E1/E2)
E1 is the input voltage before attenuation
E2 is the output voltage after attenuation
E1 and db seems like is always given. E2 is what needs to be solved.
My course book rearranges the formula to this: E2 = E1log-1(db/20)
-that makes NO sense to me. Log to negative power - or the reciprical?
this is one of the examples they have:
db = -3
E1 = .155
E2 = .155log-1(-3/20) = 0.109
more examples:
2.5log-1(-3/20) = 1.77
1.0log-1(-3/20) = 0.707
.494log-1(-3/20) = 0.342
Is there another way to rearrange the formula that makes sense?
Thank you.
This is basic info on the ILS
http://en.wikipedia.org/wiki/Instrument_Landing_System
db = 20log(E1/E2)
E1 is the input voltage before attenuation
E2 is the output voltage after attenuation
E1 and db seems like is always given. E2 is what needs to be solved.
My course book rearranges the formula to this: E2 = E1log-1(db/20)
-that makes NO sense to me. Log to negative power - or the reciprical?
this is one of the examples they have:
db = -3
E1 = .155
E2 = .155log-1(-3/20) = 0.109
more examples:
2.5log-1(-3/20) = 1.77
1.0log-1(-3/20) = 0.707
.494log-1(-3/20) = 0.342
Is there another way to rearrange the formula that makes sense?
Thank you.