As more of us use selective level meters to receive the longwave band,
I have put up this list that enables to convert from dBm to Voltage in
mV or uV and to S-units, to get an idea about the signal strengths measured
with various receivers. For conversion of dBu to dBµV/m for my receiving
setup, have a look here.
|
dBu*
( R= 75 Ohm, 0 dbu= 0.775 V) |
|
S-units
(S9=100 uV, R=50 Ohm) |
|
- 7 dBm | - 17 dBu | 99.88 mV | S9+60 | |
|
- 23 dBu |
|
|
|
- 17 dBm | - 27 dBu | 31.58 mV | S9+50 | |
|
- 33 dBu |
|
|
|
- 27 dBm | - 37 dBu | 9.99 mV | S9+40 | |
|
-43 dBu |
|
|
|
- 37 dBm | -47 dBu | 3.16 mV | S9+30 | |
|
-53 dBu |
|
|
|
- 47 dBm | -57 dBu | 1.00 mV | S9+20 | |
|
- 63 dBu |
|
|
|
- 57 dBm | - 67 dBu | 315.85 uV | S9+10 | |
|
- 73 dBu |
|
|
|
-67 dBm | - 77 dBu | 100 uV | S9 | |
|
- 83 dBu |
|
S8 |
|
|
- 89 dBu |
|
S7 |
|
|
- 95 dBu |
|
S6 |
|
|
- 101 dBu |
|
S5 |
|
|
- 107 dBu |
|
S4 |
|
|
- 113 dBu |
|
S3 |
|
|
- 119 dBu |
|
S2 |
|
|
- 125 dBu |
|
S1 |
|
|
- 131 dBu |
|
S0 |
|
- 127 dBm | - 137 dBu | 0.10 uV | S0 |
Some further explanations:
Decibel (dB): Equal to one-tenth
of a bel (After Alexander Graham Bell) The preferred
method and term for representing the ratio of different audio or rf
levels. It is a mathematical
shorthand that uses logarithms (a shortcut using the powers of 10 to
represent the actual number)
to reduce the size of the number. For example, instead of saying the
dynamic range is 32,000 to 1,
we say it is 90 dB [the answer in dB equals 20 log x/y, where x and
y are the different signal
levels]. Being a ratio, decibels have no units. Everything is relative.
Since it is relative, then it
must be relative to some 0 dB reference point. To distinguish between
reference points a suffix
letter is added as follows:
0 dBu A voltage reference point
equal to 0.775 Vrms. This reference originally was labelled dBv (lower-case)
but was too often confused with dBV (upper-case), so it was changed to
dBu (for unterminated).
0 dBm A power reference point equal
to 1 milliwatt. To convert into an equivalent voltage level, the impedance
must be specified. For example, 0 dBm into 600 ohms gives an equivalent
voltage level of 0.775 V, or 0 dBu (see above); however, 0 dBm into 50
ohms, for instance, yields an equivalent voltage of 0.224 V.