NOISE TEMPERATURE AND PHYSICAL TEMPERATURE OF LOW NOISE AMPLIFIERS.
(June 4 2013)
This page reports measurements performed in order to evaluate the data from the 2013 EME meeting in Orebro.

#### The DDK design.

The G4DDK amplifier owned by SM0ERR was run in front of a table fan at a room temperature of 27.7 C, within experimental accuracy the same room temperature that was present in Orebro. The room temperature was set by use of a fan heater arranged to not cause much air circulation around the measurement system. The temperature on the box was found to be 28.6 C at thermal equilibrium with Te=13.62K after 100 averages of 64 averages.

Then the table fan was switched off. After one hour the room temperature was 27 C and the temperature on the box was 34.2 C.

Finally the fan heater was switched off, the table fan was switched on and the doors were opened. After one more hour the room temperature was 26.4 C, the box temperature 27.3 C and Te was 13.45 K. Te as a function of the box temperature is shown in figure 1. The box temperature at thermal equilibrium is 1 degree above room temperature when the box is in the air flow of the table fan and 7.2 degrees above room temperature without the table fan. The corresponding corrections for Te are 0.13 K and 0.93 K respectively. Figure 1. Te of a G4DDK amplifier (SM0ERR) at different temperatures of the box.

A thermometer was attached to the gold plated side of a L LNA. As a first step Te and LNA physical temperature was measured at some different voltages.

7V T=36.0 Te=18.69K
10V T=40.1 Te=19.16K
13V T=43.5 Te=19.55K
15V T=49.2 Te=20.15K (a paper was folded over the LNA to degrade cooling slightly)

Then some thermal isolation was put on the thermometer and a table fan was started to direct room temperature air on the LNA. Again Te and LNA physical temperature was measured at some different voltages.

15V T=34.6 Te=18.37K
11V T=32.3 Te=18.13K
7V T=29.7 Te=17.76K

Finally the thermal isolation was removed from the thermometer head and some copper coolers were glued on the unit. The table fan was left running and the room temperature was 27.0 C.

7V T=28.3 Te=17.65K Figure 2 shows Te as a function of the physical temperature. Figure 1. Te of a L LNA amplifier at different physical temperatures.