[arm-allstar] FT7900 Node

Sun Dec 10 18:18:07 EST 2017

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.Â  10K resistor from the radio, 4.7K resistor to ground, center to the URi.Â  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.Â  Â Seems like the audio quality is a little better this way.Â Â 
It may be with the FT7900, one or the other of the SW adjustments will be close to the limit.Â Â 
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,

Â  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.
>
>Â  Â  Â  From: Chris Souleles via arm-allstar <arm-allstar at hamvoip.org>
>Â  To: ARM Allstar <arm-allstar at hamvoip.org>
> Cc: Chris Souleles <csouleles at prodigy.net>
>Â  Sent: Sunday, December 10, 2017 10:58 AM
>Â  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.Â  I have a couple questions.Â  (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.Â  Any higher
> and I start to get audio distortion and some audio cut out.Â  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?Â  I'm running the
> FT-7900 in the low power mode.Â  (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.Â  If I
> turn de-emphasis on then some of the DTMF tones don't work (mostly 3 and
> 6).Â  If I turn pre-emphasis off then I get some audio cut out,Â  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.Â  Straight
> wires, no resistors.FT7900 PTT pin 3Â  Â  Â  Â  Â  Â  - URi pin 1
> FT7900 COS pin 6Â  Â  Â  Â  Â  Â  - URi pin 8FT7900 Audio in pin 1Â  Â  Â  - URi
> pin 22FT79009 Audio out pin 5Â  - URi pin 21FT7900 GNDÂ  pin 2Â  Â  Â  Â  Â  -
> URI pin 20FT7900 shieldÂ  Â  Â  Â  Â  Â  Â  Â  Â  Â  - URI pin 20
>
> Simple USBCard isÂ  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  0Name
> isÂ  Â  Â  Â  Â  Â  Â  Â  Â  Â  USBRx LevelÂ  Â  Â  Â  Â  Â  Â  Â  Â  Â  550Rx no
> delayÂ  Â  Â  Â  Â  Â  Â  Â  0RxÂ  audio delayÂ  Â  Â  Â  Â  10Tx A
> levelÂ  Â  Â  Â  Â  Â  Â  Â  Â  Â  20Tx B levelÂ  Â  Â  Â  Â  Â  Â  Â  Â  Â  0Pre-
> emphasisÂ  Â  Â  Â  Â  Â  yesDe-emphasisÂ  Â  Â  Â  Â  Â  Â  noPL filter
>Â  Â  Â  Â  Â  yesRx boostÂ  Â  Â  Â  Â  Â  Â  Â  Â  Â  yesPTT
> activeÂ  Â  Â  Â  Â  Â  activelowPTT statusÂ  Â  Â  Â  Â  Â  unkeyedCTCSS
>Â  Â  Â  ignoredCOSÂ  Â  Â  Â  Â  Â  Â  Â  Â  Â  CM108/CM119 active highCOS test
>Â  Â  Â  unkeyedCOS compositeÂ  unkeyed
>
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