TNC-PI and Motorola Maxtrac Issues

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W3AWF

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I recently hooked my TNC-PI up to a Motorola Maxtrac and I am having some issues with it. It worked flawlessly for about a day until I noticed that it was transmitting way too much. Upon investigation it will transmit a beacon or retransmit a packet and then stay keyed up with no audio until the radio shuts itself down via the time out timer. As soon as I realized it I immediately reset the PI thinking that it could possibly be a software bug that just needed reset with no luck. After reviewing the code I am completely out of ideas as this is the first time I have interfaced a Maxtrac with a TNC and figured somebody here could point me in the right direction as to what the problem is.
 

krokus

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I recently hooked my TNC-PI up to a Motorola Maxtrac and I am having some issues with it. It worked flawlessly for about a day until I noticed that it was transmitting way too much. Upon investigation it will transmit a beacon or retransmit a packet and then stay keyed up with no audio until the radio shuts itself down via the time out timer. As soon as I realized it I immediately reset the PI thinking that it could possibly be a software bug that just needed reset with no luck. After reviewing the code I am completely out of ideas as this is the first time I have interfaced a Maxtrac with a TNC and figured somebody here could point me in the right direction as to what the problem is.
Is the Pi keeping the radio keyed, or is the radio keeping itself keyed?

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AK9R

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Might be worth asking John Hansen, the developer of the TNC Pi, how much current the TNC Pi's PTT circuit can handle. It's possible that the TNC Pi is closing the circuit but can't open it reliably.
 

jparks29

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I had the same issue with a Maxtrac on APRS as well, with an OpenTracker. Never figured it out, but I figure with how old they are, it was probably a maxtrac issue. At first I thought it might be RFI feeding back through the RJ mic connector, but ruled that out.
 

cmdrwill

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The Major problem: Maxtrac radios programmed below 146 mHz have the transmitter running wide open without any power control, that will cause all kinds of problems. Like locking the PTT line.

Yes there is a fix.
 

jparks29

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The Major problem: Maxtrac radios programmed below 146 mHz have the transmitter running wide open without any power control, that will cause all kinds of problems. Like locking the PTT line.

Yes there is a fix.
That would probably explain the time it blew a 15A fuse.... hahahaha
 
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