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Cold water LNB cooling test


One of the visitors to my site asked me if it would not have a positive effect on the reception of weak LNB cooling signals in the current hot days. The idea is interesting, so I decided to try it.

Although I do not have any precise laboratory measuring equipment, I decided to perform the experiment in improvised home conditions. It does not aim to obtain exact absolute numbers. I am only interested in finding out whether the cooling of the LNB will observably affect its activity. And also have some fun.

The procedure is simple. I stretched a garden hose to the LNB, from which I will water the LNB with cold water. Since I do not have the ability to measure the temperature inside the LNB, I will record the signal strength of the selected packet depending on the time. If the LNB is watered long enough, it can be assumed that its internal temperature will decrease. And I'll notice any fluctuation in signal strength.

Fig. 1 - Garden hose stretched to the LNB

I am aware that the signal strength may be changed by other influences in the given time interval. However, if the signal strength changes significantly, it will be possible to verify the correct interpretation of the measured values by repeating the attempt.

Default situation
 Air temperature  30 ° C in the shade, 45 ° C in the sun
 Water temperature  12°C
 LNB  Invacom SNF-031 with a plastic cover directly exposed to the sun's rays
 Receiver  VU+ Duo2, OpenPLI

When selecting a transponder for testing, it turned out that today the conditions for such an experiment are not suitable. All previously weak signals had 0 dB. The weakest signal from the transponders that could be received was 8 dB. Which is quite a lot. It can be assumed that a small effect on such a signal will be difficult to observe. Unfortunately, nothing weaker was available.

Control data before the start of the experiment
 Date  11/8/2020
 Time  15:02 CEST
 Transponder   Astra 2G, 10994 H 22000 5/6
 Signal  8,2 dB
 Azimuth  14661 pulses
 Elevation  21541 pulses

This was followed by lowering the dish to the service position, ie to the minimum adjustable elevation, so that the LNB was as low as possible from the ground. I installed the garden hose and returned the dish to its previous position.

Fig. 2 - Hose location detail

New control measurement
 Date  11/8/2020
 Time  15:33 CEST
 Transponder   Astra 2G, 10994 H 22000 5/6
 Signal  8,1 dB
 Azimuth  14656 pulses
 Elevation  21591 pulses

Then I turned on a stream of water on the LNB and started recording the signal strength at 1 minute intervals. From 15:40 to 16:10 I performed a total of 31 measurements. I originally wanted to draw a graph from them, but it turned out that it didn't make sense. The signal strength value was kept constant at 8.1 dB throughout.

Fig. 3 - LNB water cooling

Although the signal fluctuated from 7.9 to 8.4 dB at irregular intervals, it was probably caused by a light breeze, which could sway slightly over such a large area of the dish.

I do not know if there are conclusive conclusions from this experiment. It is argued that cooling the LNB with water at 12 ° C for 30 minutes has no visible effect on the signal strength of the received transponder. You could say the other way around. The increased temperature load in these summer months does not have a significant negative effect on the LNB's activities. However, it is necessary to take into account the fact that I do not know how the temperature inside the LNB has changed. Even if the effect of cooling is not more pronounced with a weak signal.

So the experiment did not bring any real measures to improve the signal. Nevertheless, it was an interesting idea that fascinated me and its implementation was fun. Maybe I will repeat it again under other conditions after better theoretical preparation.

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