Yaesu: Yaesu FT-8900R

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gvodvarka

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Nov 10, 2009
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Ontario, Ca.
Trying to find the best discriminator audio point to get raw audio for decoding DMR. The data out jack does not provide the right point or level. Anybody ideas? Thanks, Gary
 

gvodvarka

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Joined
Nov 10, 2009
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71
Location
Ontario, Ca.
I have the service manual. There are two discriminator chips. Does anyone know the best way to be able to connect to all bands. Gary
 

N1KK

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Jun 17, 2010
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discriminator output

I can see this is an old message but thought I would respond.

I have a FT-8900R and plan to look into tapping the discriminator output.
I have tride using the 9600 baud data port on the back with limited luck.

Looking at the schematic I can see they used 2 IC's for the discriminator.
Side LEFT and SIDE right of the radio. Both sides can receive different freqs at the same
time. The choice would be determined by what side will be the freq you want to listen
to or use. I just got this radio and from what limited reading of the manual and playing
I noticed the 800MHz band is only available on the LEFT side. Saying that I plan to explore
IFA Q1024 which is one of the 2 TA31136FN discriminator ICs. I looked this chip
up and pin 9 appears to be the unfiltered ouput. The output connects to a 1K resistor.
the other side of the resistor goes to a .001uF cap and then to Test Point TP1020.
The .001uF goes to ground and I think it might effect the audio so going straight to pin 9
of the chip might be better. The test point might be easier access but I don't know
the effect of the .001uF cap going to ground which is prior to the test point.

My use will be for DSDplus decoding APCO 25 on 800MHz.

Ken
 

N1KK

Member
Joined
Jun 17, 2010
Messages
54
discriminator output

I did the discriminator mod on the FT-8900R and found no difference in performace
using DSDplus. The data port set to 9600 worked from what I could tell as well
as tapped right at pin 9 of the discriminator IC. I was using DSDplus on 800MHz.

Ken
 
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