#1 2015-01-17 16:20:56

Stanley
Member
From: Kuala Lumpur, Malaysia
Registered: 2014-12-01
Posts: 65
Website

MicroAPRS modem no decode packets with some radios / TNC combo

I'm getting some feedback that some radio with data ports could not decode whatever packets that was sent by MicroAPRS modem ?

In my circuit, I just use the LINE LEVEL out ( max output ) to the handy mic ( tried both Wouxun UVD1P and TYT F8 ) ..

For receiving handy, they can still adjust the volume level to fine tune the acceptable sound level ( not too soft, not over distorted sound ) but for dual band radio with data ports, this is not possible... and the decoding failed..


Is everyone else faces this issue too ??


As on my side, I never had this issue but faces no packet decode this for the following setup :-

Yaesu FT8900 with data port to 51TNC ..


Stanley
9W2SVT/ N5SVT
http://9W2SVT.blogspot.com

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#2 2015-01-18 17:56:21

markqvist
Administrator
Registered: 2014-12-01
Posts: 112

Re: MicroAPRS modem no decode packets with some radios / TNC combo

Hi Stanley!
You should most probably NOT use LINE LEVEL output to the handy!!! This is WAY too much voltage, since these radios expect MIC level, at around 15 to 25 milllivolts! The line level output will be around 1500 millivolts! This will cause a lot of distortions and generally wreak havoc with decode wink

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#3 2015-01-21 04:19:38

Stanley
Member
From: Kuala Lumpur, Malaysia
Registered: 2014-12-01
Posts: 65
Website

Re: MicroAPRS modem no decode packets with some radios / TNC combo

Yes... thanks for the advise...

I learn this the hard way about the mic level vs line out level ...


Luckily, there are extra space on the PCB copper traces for me to add the 1K and 100K before the audio out ... I managed to dropped the signal down to 50mV to 100mV range and the packets was still decoded at the receiving end...

I scope the audio out and they seems to be within the range after the 100K and 1K voltage divider...

16328581301_827e7b5cd6_n.jpg by stanley_seow, on Flickr


Stanley
9W2SVT/ N5SVT
http://9W2SVT.blogspot.com

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#4 2015-01-21 08:23:04

markqvist
Administrator
Registered: 2014-12-01
Posts: 112

Re: MicroAPRS modem no decode packets with some radios / TNC combo

That looks good smile I'm glad you were able to add it directly on your PCBs! That was lucky big_smile

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