trying to get an electret mic to work with a radio looking for a carbon style - Page 3 - Electronic Circuits Projects Diagrams Free

jfarrow · 2nd August 2009, 06:05 PM

To bring you up to speed:

Bypassed the mystery capacitor/resisitor network with a new shielded line to the NAT.

Used a resistor (1.4K ohms) with capacitor in parallel to drop bias voltage to about 4v when xmiting.

I can hear several noises in the Mic audio line, 90% is the alternator.

If you pull the mic line in to the NAT, noise ceases.

If you shut of the alternator in flight, noise ceases.

If you press PPT, noise ceases (this, I imagine, is because by pressing PPT you connect the mic directly to the radio, bypassing the NAT and so eliminating for that moment the ground loop).

EVERYTHING is grounded! NAT to NAT case, all shields, radio to radio case, shields at radio end plus I think the headset shields also. This relay idea seems to be a reliable, simple solution.

jfarrow · 2nd August 2009, 11:02 PM

The circuit with the relay is a success. No more noise.

Mike - how do you that idea - thinking outside the box!

One last question re the music in - how do you wire a stereo socket for a mono input? Connect left and right together? Do a need to put a 1k resistor in series in each before connecting?

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Similar
Title	Starter	Forum	Replies	Latest
High quality CARBON pots for audio	xmat	Datasheet/Parts Requests	11	19th March 2008 08:43 PM
zero carbon emissions...	philba	Alternative Energy	16	30th June 2007 02:48 PM
Carbon monoxide Detector Help	pouchito	General Electronics Chat	54	23rd November 2006 09:32 AM
FM radio channel memory - how does it work	vwchico	General Electronics Chat	12	23rd September 2005 10:29 PM
Carbon resistors power	sbayeta	General Electronics Chat	15	2nd August 2003 12:41 AM

2nd August 2009, 06:05 PM	#31
jfarrow	To bring you up to speed: Bypassed the mystery capacitor/resisitor network with a new shielded line to the NAT. Used a resistor (1.4K ohms) with capacitor in parallel to drop bias voltage to about 4v when xmiting. I can hear several noises in the Mic audio line, 90% is the alternator. If you pull the mic line in to the NAT, noise ceases. If you shut of the alternator in flight, noise ceases. If you press PPT, noise ceases (this, I imagine, is because by pressing PPT you connect the mic directly to the radio, bypassing the NAT and so eliminating for that moment the ground loop). EVERYTHING is grounded! NAT to NAT case, all shields, radio to radio case, shields at radio end plus I think the headset shields also. This relay idea seems to be a reliable, simple solution.

2nd August 2009, 11:02 PM	#32
jfarrow	The circuit with the relay is a success. No more noise. Mike - how do you that idea - thinking outside the box! One last question re the music in - how do you wire a stereo socket for a mono input? Connect left and right together? Do a need to put a 1k resistor in series in each before connecting?