[evlatests] [Fwd: Noise Diode Output Variation]

[Rick Perley]

    Bob has provided us the following information.  Keeping temperatures 
stable to a few degrees should suffice -- remember that the noise diodes 
physical temperature will not change as fast as air temperature. 

-------- Original Message --------
Subject: 	Noise Diode Output Variation
Date: 	Wed, 03 Feb 2010 11:59:21 -0700
From: 	Bob Hayward <rhayward at aoc.nrao.edu>
Organization: 	NRAO
To: 	Perley, Rick (NRAO-AOC) <rperley at aoc.nrao.edu>



Rick,

According to the manufacturer's data sheets, our noise diodes will 
typically have an output power variation of 0.01 dB per degree Celsius. 
This corresponds to a 0.23%/C.

So for those noise diodes exposed to the ambient temperature in the 
Vertex Cabin (like Ka & Q), a +/-5C temperature fluctuation would result 
in a +/-2.3% variation in the Tcal value.

I guess the worry is how big a temperature swing there is in the Vertex 
Cabin and how fast it actually varies...

-Bob