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15066Re: Reviving my OT2M - Sensitivity and noise issues

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  • awaschka@bellsouth.net
    Dec 30, 2012
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      A correction to my previous post. When fully connected, the Tm-221 does NOT stop receiving. And the intermittent warbly squeal is coming from the 221 speaker, not the 350. It is very quiet, and seems to be synchronized with the blinking green light (GPS received?) on the OT2M. I still suspect some kind of a gorund loop. Looking on the OT2M schematic in the vicinity of the RS-232 port, I see all 4 data lines but I can not find a ground. Are the digital and analog grounds isolated in the OT2M?



      --- In tracker2@yahoogroups.com, "awaschka@..." <awaschka@...> wrote:
      > I traded trucks a year ago and am just now getting around to re-installing my setup, which is as follows:
      > Garmin Nuvi 350, powered from separate switching regulator, connected with ARgent data cable to:
      > OT2M V1.0
      > Connected to Kenwood TM-221, Tx through mike connector, Rx through external speaker jack
      > I would prefer not to use the speaker jack, but found (in my previous installation), that I was not getting good decode performance using the mike connector Rx audio which is only about 0.1 Vpp into 10K, per Kenwood manual. I am using the Eq jumper. I found the note about the wrong value of C2, and I suspect that my unit is wrong, but since I'm using the Eq jumper, that would not seem to matter.
      > Question: What level is required to drive the receive input of the Ot2m?
      > When I connect up the mike connector with everything else hooked up, the radio stops receiving, I hear a high-pitched squeal (I think from the 350 speaker). When I disconnect either the mike connector, the port A connector to the Garmin or the FMI cable on the GArmin itself, everything goes back to normal. I suspect a ground loop of some kind as this setup was working in my other truck, but at the moment its got me baffled.
      > Question: Any ideas on what might be going on here?
      > Thanks,
      > Al
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