[OZAPRS] Using Maxon Radios for RX

Chris Hill chris.hill at crhtelnet.com.au
Tue Jun 20 21:35:55 EST 2006

Hi Craig,

Try reducing the transmit deviation of the source radio.

I think you'll find that the Maxon receivers are fitted with IF filters
"12.5kHz channel spacing", which means an acceptance bandwidth of approx
8kHz...   not good for the 10kHz to 16kHz occupied bandwidth of the
2m APRS packet signal!

You can see the 455kHz IF filter is an "LT455FW", at 

I'm guessing a bit here (really hard to tell based on the blurry photos,
lack of spec sheets etc) that you at least need to replace the 455kHz IF
with a "D" model (I'm guessing "D" is right for 16kHz b/w).   A likely
seems to be:

I don't know what they've done for filtering at the first IF...

Hope this helps,


-----Original Message-----
From: ozaprs-bounces at aprs.net.au [mailto:ozaprs-bounces at aprs.net.au] On
Behalf Of Craig Turner
Sent: Tuesday, 20 June 2006 6:45 PM
To: vk3jfk at amsat.org; VK / ZL APRS Users
Subject: [OZAPRS] Using Maxon Radios for RX


With all these maxon radios being bought, is anyone using them for RX as 
well as TX? I am trying to set up a TNC-X with the X-Track option in my 
car. At the moment its set up in my lounge room, with an antenna located 
outside on the roof. I'm in an area that gets good coverage from 
VK1RGI-1 on Mt Ginni in the ACT.

Anyway, my TX seems to work fine.

I have the input GND connected to Pin 4 on the Maxon, and the TNC-X rx 
line connected to Pin 2 (which is labelled in the maxon service manual  
as 'Muted Demodulation Output) I have tried also pin 9, which is 
labelled (Data out low level filtered output), which doesn't seem to 
work either.

I have limited sucess by using a HT and a TT about 10 feet away from the 
antenna, and it works, but not much further than that.

Anyone got any advice?

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