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Did you use the sleeve of the mic input as the GND reference, or did you make the<br>(often smokey) mistake of even connecting to the sleeve of the headphone output,<br>which, if the chip didnt blow up from being shorted is at VCC/2??<br><br>JIM<br><br><div><div id="SkyDrivePlaceholder"></div><hr id="stopSpelling">Date: Wed, 22 Feb 2012 21:15:15 -0800<br>From: n6gkj.cm98@yahoo.com<br>To: app_rpt-users@ohnosec.org<br>Subject: [App_rpt-users] Noisy Sound FOBS<br><br><table border="0" cellpadding="0" cellspacing="0"><tbody><tr><td style="font: inherit;" valign="top">Hey guys,<br><br>I just got in some really cheap CM108 type sound FOB's from China, they work, I use the DSP for COR and CTCSS with the DB25 pins for ptt. However, I am hearing some really noisy sound when I access this node. I setup a DMK URI on the same node, no noise. <br><br>Has anyone encountered this before?<br><br>Is it the cheap sound FOB's or is there something else I need to do.<br><br>I have my audio voitage divider feeding the RX Input, I have that fed by a 10uf cap. No DC bias on the chip. I am feeding the FOB with a VHF Maxtrac 300 discriminator audio, JU551 in position A. plenty of audio, PL detect and COR is very reliable. I use this as a RX only node. A very simple hardware configuration.<br><br>Any ideas?<br><br>Ron Simpson,<br>
N6GKJ Amateur Radio<br>
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