[OZAPRS] 12.5Khz radio

[Chris Hill]

Hi All,

A slight correction to the figures given before.

2.2kHz is (2.2-1.2)/1.2 = 0.83333 of an octave higher than 1.2kHz.

At a pre-emphasis slope of 6dB/octave, the 1.2kHz tone should be
transmitted
0.8333.Octave * 6dB/Octave = 5dB lower than the 2.2kHz tone.

-5dB = 10^(-5/20) = 0.56234 of the 2.2kHz tone's deviation

= 0.56234 * 3kHz deviation = 1.69 kHz deviation

(Not the 1.78kHz deviation I originally said).


73 Chris vk6kch



-----Original Message-----
From: ozaprs-bounces at marconi.ics.mq.edu.au
[mailto:ozaprs-bounces at marconi.ics.mq.edu.au]On Behalf Of Chris Hill
Sent: Thursday, 18 December 2003 3:36 PM
To: ozaprs at marconi.ics.mq.edu.au
Subject: RE: [OZAPRS] 12.5Khz radio


Hi Gavin,

You should be able to successfully interoperate this radio with _most_
other
amateur APRS users.

First, the easy bit; transmit.  If you run the two audio tones into the
modulator as per the normal voice path, they will undergo pre-emphasis
(6dB
per octave), so the 2.2kHz tone will transmitted with 5dB more deviation
than the 1.2kHz tone.  I recommend that you set the 2.2kHz tone to be
transmitted to air with 3.0kHz of deviation, meaning the 1.2kHz tone will
be
transmitted to air with 1.78kHz deviation.

[SNIP]


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