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I'm planning to use an Arduino ADC to sample radio signals from a DirecTV dish before passing them on to my computer. Before I can do that, I'd have to find coaxial connectors that can allow my Arduino (which has analog-in pins) to read this data. (I'm quite aware that the signal itself would require a square-law detector to be read.)

I have a strong suspicion that I wouldn't need a coaxial connector at all; I've contemplated just stripping the coaxial cable altogether. Does the central conductor just carry the voltage of the signal, and would it be okay for regular use if I stripped it?

Thanks in advance!

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In theory you should try to match impedances when connecting signals like that. But it sounds like you're trying to listen to a high-frequency radio signal with a low-frequency ADC? What ultimately is this for? – pjc50 Jul 13 '12 at 8:53
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The center connector should carry signal and the outer connector is ground. Don't forget that it too needs to be connected to Arduino's ground. – AndrejaKo Jul 13 '12 at 9:17
@pjc50 This is for a radio telescope design; afaik (correct me if I'm wrong), I don't need > 1 GSPS in order to make observations of astronomical sources. On the other hand, if I make sure the cable's impedance is right, I can just connect the end of the coax cable? – Chuxiao Cao Jul 13 '12 at 23:17

1 Answer

up vote 7 down vote

I don't know DirecTV, but since you're talking about a dish I presume it outputs RF signals, which go to your radio receiver to be demodulated to audio. You can't sample that with Arduino's ATmega 328 ADC: its bandwidth is only 38.5 kHz typical, which is suitable for sampling audio, but not RF.
Overmore, the output level will be much too low for the ADC.

If you would want to cut off the connector from the cable, and connect that to your PCB, use a terminating resistor that matches the cable's characteristic impedance, typically 50 Ω or 75 Ω.

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Hey, thanks for the response! I understand the issues with aliasing in high frequency signals; however, since the signals I'm looking for with my system are within the range of my Arduino's relatively slow sampling time, it should not be an issue. I am not looking to analyze RF signals per se, just measure the voltage a couple hundred times a second. – Chuxiao Cao Jul 13 '12 at 23:12

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