Capacitors... good antennas?

DragonMaster · 22nd September 2006, 08:01 PM

Could capacitors be great antennas?

I have the impression that it is the case. I get a better signal by hooking up a non-polarized electrolytic cap than a bare wire on my tuner's antenna input. (And putting both makes an even stronger signal)

All that makes me wonder if audio equipment PSUs could be picking up RFI through the caps...

CBS240 · 23rd September 2006, 02:46 AM

Could it be the coil component of the electrolytic that is acting as the antenna?

Enzo · 23rd September 2006, 03:06 AM

The antenna connection to your receiver is a super high gain circuit of high impedance, so the microvolts of signal can be amplified. The power supply caps are generally grounded, and they are in very low impedance circuits, and circuits without gain. Even if the inductance of the cap raises the impedance at RF, the wiring and other stuff ought to be better antennae than the caps.

The size and shape of the part might act as a slightly better antenna at the frequencies you are using than the piece of wire, or it could be the wire is actually coupling to something else nearby which dampens its reception.

I don't think that the powr supply caps are the source of your RFI. The experiment would be to attach your antenna cap to the power supply just as you did to the antenna terminal and see if there is a noise difference. DOn't forget to keep the covers on the amp for the test.

22nd September 2006, 08:01 PM	#1
DragonMaster diyAudio Member Join Date: Dec 2003 Location: Montreal	Capacitors... good antennas? Could capacitors be great antennas? I have the impression that it is the case. I get a better signal by hooking up a non-polarized electrolytic cap than a bare wire on my tuner's antenna input. (And putting both makes an even stronger signal) All that makes me wonder if audio equipment PSUs could be picking up RFI through the caps... __________________ Antoine http://dmsaudio.ca/

23rd September 2006, 02:46 AM	#2
CBS240 diyAudio Member Join Date: Aug 2005 Location: K-town	Could it be the coil component of the electrolytic that is acting as the antenna? __________________ All the trouble I've ever been in started out as fun......

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23rd September 2006, 03:06 AM	#3
Enzo diyAudio Member Join Date: Sep 2004 Location: Lansing, Michigan	The antenna connection to your receiver is a super high gain circuit of high impedance, so the microvolts of signal can be amplified. The power supply caps are generally grounded, and they are in very low impedance circuits, and circuits without gain. Even if the inductance of the cap raises the impedance at RF, the wiring and other stuff ought to be better antennae than the caps. The size and shape of the part might act as a slightly better antenna at the frequencies you are using than the piece of wire, or it could be the wire is actually coupling to something else nearby which dampens its reception. I don't think that the powr supply caps are the source of your RFI. The experiment would be to attach your antenna cap to the power supply just as you did to the antenna terminal and see if there is a noise difference. DOn't forget to keep the covers on the amp for the test.