[arm-allstar] Tx A Level Setting

[David McGough]

Hi Chris,

Since the TX level only affects you local transmitted audio, you can
safely set this level "by ear" to a comfortable level. 

If you want to get more technical and set the level precisely, a deviation
meter is tool you need--functionality typically included in service
monitors. Since most hams only occasionally have a need for setting
deviation levels, it's hard to justify purchasing expensive test
equipment.

In this age of very inexpensive SDR radios, another technique can use to
-very- accurately set FM deviation. This method is called the Bessel null
technique, and while being rather technical to setup, it will yield
perfect results with a little practice...This method only requires a $10
USB SDR (see: https://www.ebay.com/sch/i.html?_nkw=RTL+SDR ) and a PC
computer running windows.  This video will show you how to proceed:

https://www.youtube.com/watch?v=lWcFqsh7ZvQ&t=4s

BTW, I've got this exact software setup, several RTL-SDR radios and an 
AirSPY radio. I use this setup to calibrate deviation meters and it works 
very well.


73, David KB4FXC



On Mon, 11 Dec 2017, "Chris Souleles via arm-allstar" wrote:

> What is the best way to determine correct setting for Tx A Level?  Now that I have added a voltage divider on the audio line between the FT7900 and the DMK URi it has put it within the SW adjustment range, but I don't know how to determine the best setting.  
The Rx side is working well with Rx Level at 500, pre-emphasis on, Rx boost on and voice peaks just at 5Khz.
The node is FT7900, DMK URi, RPI3.  
Thanks,  Chris - W6CS - 73
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