7639
« on: January 11, 2019, 2053 UTC »
Yes, the noise problem is complex and is the sum of several sources. I am not an expert, however, I am saying that the noise irritates me especially in the receiver of SDR RTL. Forgive me that I will repeat what I have read and have checked practically so far, maybe it will help someone improve their reception.
- antennas are more or less skimming depending on the type (for example Beverege vs vertical) and execution (type and matching of the power line). Use maching baloons and ferrite rings on connecting cables. Use band antennas and for broadband antennas matching the antenna box. The unmatched antenna may have more than 1 kohm of resistance in the band, so it will be hissing and not providing station signals. Even a simple LC filter will improve it.
- good grounding. Ground for the antenna system should be separated from the power supply system.
- classic linear power supplies are less noise than impulse ones used to power computers. Where possible, use shielding and grounding, unnoice filters, ferrite rings, inductors and blocking capacitors.
- making a computer (including a sound card) can affect the level of noise. My previous HP laptop with its power supply had high noise at -125dB. I gathered parts to build a linear power supply, thankfully my son got a Dell laptop and this one has noise at -141dB. Switching to work from the internal battery practically does not reduce the level of noise.
- the computer has a lot of oscillators producing garbage, but I did not meet those who buried in his motherboard. I did not have the chance to compare a Mac computer to a Windows PC. At the same time, I have the impression that the software that supports the computer / receiver can have different noise levels. My Icom is less harshly controlled by TalkPCR than controlled by PCRAnyWhere program.
The signal processed by the sound card has more noise than the receiver's audio amplifier or active loudspeaker. It is possible that the external USB sound card will have less noise than integrated in the computer.
- use HF band filters before entering the receiver. Using an ATT greatly improves the ratio of noise to signal. Check if it is better to set the HF gain manually or by AGC. Use possibly narrow IF filters. On the audio side in a difficult situation, readability can be improved by the Equalizer.
Write boldly about your improvements !!!
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