[arm-allstar] FT7900 Node

David McGough kb4fxc at inttek.net
Sun Dec 10 20:46:34 EST 2017 

Hi Chris,

A five-foot cable may give you trouble in some situations, but, if you've 
got no RF getting into the audio or ground-loop buzzing, etc., it'll 
probably work for now.

The ground connections seem okay, based on your description.  Does the RX 
audio from the radio go straight to the URI pin 21?  If so, I'm pondering 
why the RX level would have changed??

Anyhow, if it's stable, working, the audio levels are in-range and sound
clear, follow the age-old adage: If it ain't broke, don't fix it!

73, David KB4FXC


On Sun, 10 Dec 2017, Chris Souleles wrote:

> Ground measures good using a DMM.  I've connected the shield of the cable which is attached to the chassis of the FT7900 to URi pin 19, and the ground wire from the data port of the FT7900 to pin 20 of the URI.  
> Maybe I should disconnect the shield and just use the ground wire from the data port of the FT7900, although I'm not sure why this would make a difference.  
> The cable from the FT7900 data port to the URi is 5 feet long.
> The node is functioning.  I'm just trying to get the settings closer to the default if possible.  
> Thanks,  Chris - W6CS - 73      From: David McGough <kb4fxc at inttek.net>
>  To: Chris Souleles via arm-allstar <arm-allstar at hamvoip.org> 
> Cc: Chris Souleles <csouleles at prodigy.net>; Doug Crompton <wa3dsp at gmail.com>
>  Sent: Sunday, December 10, 2017 3:18 PM
>  Subject: Re: [arm-allstar] FT7900 Node
>   
> 
> Hi Chris,
> 
> Adding resistors to make a voltage divider on the transmit audio side
> shouldn't change anything about the receiver audio---the RX level should
> remain constant????  It the RX level does change, make sure to check the
> quality of the ground path between the URI and the radio.
> 
> For the transmit audio side, try something like (hopefully my ASCII art 
> will make it across e-mail!):
> 
> <pre>
> 
>         100K
> URI>----/\/\/\-+--------------->RADIO TX AUDIO
>               |  4.7K
>               +--/\/\/\--+
>                           |
> GND>----------------------+---->RADIO GND
> 
> </pre>
> 
> 
> 73, David KB4FXC
> 
> 
> 
> On Sun, 10 Dec 2017, "Chris Souleles via arm-allstar" wrote:
> 
> > Doug - Installed a voltage divider on the line from the radio output to the URi.  10K resistor from the radio, 4.7K resistor to ground, center to the URi.  Started with two 10K which allowed increasing the Tx A Level a small amount.
> 10K/4.7K only allowed me to get the Tx A Level to 40 (instead of 20), but now the Rx Level is 900 (instead of 550) with Rx boost on.   Seems like the audio quality is a little better this way.  
> It may be with the FT7900, one or the other of the SW adjustments will be close to the limit.  
> Chris, W6CS - 73
> 
>       From: Doug Crompton via arm-allstar <arm-allstar at hamvoip.org>
>  To: ARM Allstar <arm-allstar at hamvoip.org> 
> Cc: Doug Crompton <wa3dsp at gmail.com>
>  Sent: Sunday, December 10, 2017 11:55 AM
>  Subject: Re: [arm-allstar] FT7900 Node
>   
> Chris,
> 
>   The TX levels are not adjustable beyond the level control in
> simpleusb-tune-menu. The best thing to do is to use a resistive voltage
> divider on the TX audio line from the radio to the DMK. Try two 10K
> resistors in series, one end grounded the other end to the radio and the
> center to the DMK. You can of course experiment with values. It is not
> necessary to get the numbers centered at 500 but having it to close to the
> low end could mean you are over driving the input to the DMK.
> 
> It is not unusual for one side to be pre/de-emphasized and the other not.
> Certainly your RX side seems to be working. If the DTMF is working fine
> then you probably have it right. On the other (TX) side you can hear the
> difference as that is what you are hearing on your transceiver from your
> node radio. So go into the menu and change it while someone is talking and
> you should hear a distinct difference. If it sounds mushy and lack of highs
> then you probably need to set pre-emphasis on.
> 
> 
> *73 Doug*
> 
> *WA3DSP*
> 
> *http://www.crompton.com/hamradio <http://www.crompton.com/hamradio>*
> 
> 
> On Sun, Dec 10, 2017 at 2:04 PM, "Chris Souleles via arm-allstar" <
> arm-allstar at hamvoip.org> wrote:
> 
> > I tried to fix the formatting in the email..... hope this comes through
> > better.
> >
> >      From: Chris Souleles via arm-allstar <arm-allstar at hamvoip.org>
> >  To: ARM Allstar <arm-allstar at hamvoip.org>
> > Cc: Chris Souleles <csouleles at prodigy.net>
> >  Sent: Sunday, December 10, 2017 10:58 AM
> >  Subject: [arm-allstar] FT7900 Node
> >
> > I've just installed a Yaesu FT-7900 in a node with an RPI3 and DMK URi
> > running latest version of HAMVOIP. I have it basically working and I'm
> > trying to optimize the audio.  I have a couple questions.  (node
> > connections and simple usb at bottom of this email)
> >
> > The Tx A level has to be set down to 20 for things to work.  Any higher
> > and I start to get audio distortion and some audio cut out.  Is there
> > something I should change in the interface to get this closer to the
> > default value or is running at 20 ok as long as it works?  I'm running the
> > FT-7900 in the low power mode.  (I'm not exactly sure what Tx A Level
> > setting does)
> >
> > I have to run pre-emphasis on and de-emphasis off for it to work.  If I
> > turn de-emphasis on then some of the DTMF tones don't work (mostly 3 and
> > 6).  If I turn pre-emphasis off then I get some audio cut out,  Is it
> > normal to have one on and the other off?
> >
> > When I look at Rx Voice Level it hits the 5 KHZ on peaks when I talk
> > sideways to the mic.
> >
> > I'm interfacing to the data port on the FT-7900 as follows.  Straight
> > wires, no resistors.FT7900 PTT pin 3            - URi pin 1
> > FT7900 COS pin 6            - URi pin 8FT7900 Audio in pin 1      - URi
> > pin 22FT79009 Audio out pin 5  - URi pin 21FT7900 GND  pin 2          -
> > URI pin 20FT7900 shield                    - URI pin 20
> >
> > Simple USBCard is                        0Name
> > is                    USBRx Level                    550Rx no
> > delay                0Rx  audio delay          10Tx A
> > level                    20Tx B level                    0Pre-
> > emphasis            yesDe-emphasis              noPL filter
> >          yesRx boost                    yesPTT
> > active            activelowPTT status            unkeyedCTCSS
> >      ignoredCOS                    CM108/CM119 active highCOS test
> >      unkeyedCOS composite  unkeyed
> >
> > _______________________________________________
> >
> > arm-allstar mailing list
> > arm-allstar at hamvoip.org
> > http://lists.hamvoip.org/cgi-bin/mailman/listinfo/arm-allstar
> >
> > Visit the BBB and RPi2/3 web page - http://hamvoip.org
> >
> >
> > _______________________________________________
> >
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> >
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> 
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> 
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> 
> 
>   
> _______________________________________________
> 
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> 
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> 
> 
> 
>

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