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Problems with reception

Whoopee wrote:

I am Kenny from Germany and I'm using your RDS Spy Software but i have problems. I try to explain it in English…

I'm already in my "Test-Phase" with your Software and i'm using a Sangean ATS 909 to fetch the RDS-signal from it. I connect it with a 3,5mm stereo-cable into the MIC-Input
of my Laptop (Lenovo R60).
Data and Ground are connected and it works, BUT only with strong stations. If i receive a weak station and then connect the cable into the mic-input the station is not more receivable/ I can't
hear this station anymore, because of murmuring (like "sch…….") but if i disconnect the cable the station is there again. The murmuring is getting much louder if i connect the cable to the mic-input.

What can it be? Any ideas? I'm using a 4,7k resistor and 10µF in Data-cable. I think the problem comes from the ground. If i connect the ground the murmuring is getting louder.Without ground, it's all OK.

Greetings from the Baltic Sea

Kenny

admin wrote:

This problem is caused by the same phenomena that is known for years – computers produce radio interference. This is especially notable if both of these conditions are met:

1) A radio receiver with built-in or simple telescopic antenna is used
2) This receiver is connected via a conductive cable to the PC.

It this case the PC becomes a part of the antenna! In other words the antenna includes the interference source. Very ineligible.

What can you do? Eliminate at least one of the two conditions above.

1) Use external (outdoor) antenna connected via shielded coaxial cable (signal to signal, shielding to ground). This is hard to realise on some receivers.
2) Make the cable non-conductive for rf signal.
The fastest way is to make a few coils on the cable about 80 cm far from the receiver. This will probably not improve the situation as expected so another steps are:
use ferrite beads on the cable or
use optocouplers (advanced users) or
separate all wires by 1 uH inductors or
try to connect the cable ground through a resistor (in this case no more than 270R).

As each case is specific, there's no universal advice that will always apply. Most times one must combine more methods. When I had similar problem in past, I did following with the cable:
made about 8 coils on the cable (wound on paper tube), connected all wires (incl. ground) through 1 uH inductors, clipped a ferrite bead on each end of the cable. The result was great, no interference at all! Total cable length was about 5 meters.