[TenTec] 5 mV = -67 dBm

[James Duffer]

Hi Ken,

We used the term dBC when aligning up mod levels of microwave equipment, 
since the equipment was Collins, I just assumed the C was for Collins Hi!.  
Just as you say, the documents and recordings were in dBC and the test 
equipment was standard HP.  This was many years ago, and the term may not be 
used.  This was on RML-1, and RML-4 FAA microwave link.

Jim


>From: Ken Brown <ken.d.brown at verizon.net>
>Reply-To: tentec at contesting.com
>To: tentec at contesting.com
>Subject: Re: [TenTec] 5 mV = -67 dBm
>Date: Sat, 26 Jul 2003 11:52:19 -1000
>
>There is a standard used in telephony and analog multiplexing wherin the 
>value of an audio level in dB(with a suffix I cannot remember) is expressed 
>as it would be read on an AC RMS voltmeter with a scale calibrated in dBm 
>at 600 ohms, regardless of the actual impedance. In other words an AC RMS 
>voltmeter which has a scale that is calibrated in decibles relative to 1 
>milliwatt at 600 ohms is used. A reading is taken and the level is called 
>dB(something). The impedance of the source or load may be thousands of ohms 
>or only a few ohms. So the dB(something) value is really not equal to dBm, 
>except in the special case where the impedance happens to be 600 ohms. 
>Nevertheless this way of specifiing a level is often used. I wish I could 
>remember what letter they follow dB with.
>
>Ken N6KB
>
>
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