UHF CDM1250 Signal Meter Mapped out

[drspinbag]

Here are my findings when going through the Motorola CDM1250 UHF version with my HP8924C Service Monitor. With the squelch opened up all the way, the threshold to where I can perceive the most minute evidence of a 1 kilohertz tone, is at -133 dBm, or a little more than an S-2. My squelch is set to open up at -129 dBm, or S-3. This is where I can actually hear someone talking somewhat, but not understand them. When I tested for SINAD, I got the same results, but describing it is easier to understand to those who are unfamiliar with SINAD testing.

The S-meter has an antenna symbol, and 5 bars. As the received signal increases, this symbol goes from flashing, then solid, then starts adding bars. Here's what they measure up to:


Flashing antenna symbol: -122 dBm (S-4)

Solid Antenna Symbol: -121 dBm (S-4) Still closer to an S-4 than S-5

Solid Antenna Symbol +1 Bar: -116 dBm (S-5)

Solid Antenna Symbol +2 Bars: -110 dBm (S-6)

Solid Antenna Symbol +3 Bars: -106 dBm (S-7)

Solid Antenna Symbol +4 Bars: -100 dBm (S-8)

Solid Antenna Symbol +5 Bars: -95 dBm (S-9) Just under an S-9

Anything more this meter will not change, like 10 over 9 and such.


Here is a good explanation of S Points(Units), and how they relate to dBm:

http://www.giangrandi.ch/electronics/radio/smeter.shtml

I just thought someone here might find this useful!