[App_rpt-users] RTCM Parameter question

Tue Mar 19 19:28:39 UTC 2013

On SVN (the same place you find all of the app_rpt/Allstar stuff sources):

http://svn.ohnosec.org/viewvc/projects/allstar/voter/?root=svn

From: bill.hurlock at cpcomms.com
To: telesistant at hotmail.com; app_rpt-users at ohnosec.org
Subject: RE: [App_rpt-users] RTCM Parameter question
Date: Tue, 19 Mar 2013 18:42:19 +0000

Thanks. Where do I find the source kit at you mentioned?

Bill Hurlock

From: Jim Duuuude [mailto:telesistant at hotmail.com]

Sent: Tuesday, March 19, 2013 2:36 PM

To: Bill Hurlock; app_rpt mailing list

Subject: RE: [App_rpt-users] RTCM Parameter question

Unless you have a particularly quirky receiver, leave it at 0.

Quoting from the source kit (README-DSPBEW):
Baseband Examination Window

Typically, the discriminator of an FM communications receiver produces 
results containing audio spectrum from the "sub-audible" range 
(typically < 100 Hz) to well above frequencies able to be produced by 
modulating audio. These higher frequencies can be utilized to determine 
signal quality, since they can only contain noise (or no noise, if a 
sufficiently strong signal is present).

For receivers (such as the Motorola Quantar, etc) that do not provide 
sufficient spectral content at these "noise" frequencies (for various 
reasons), The "DSP/BEW (Digital Signal Processor / Baseband Examination 
Window)" feature of the RTCM firmware may be utilized. 

These receivers are perfectly capable of providing valid "noise" signal 
with no modulation on the input of the receiver, but with strong 
modulation (high frequency audio and high deviation), it severely 
interferes with proper analysis of signal strength.

This feature provides a means by which a "Window" of baseband (normal 
audio range) signal is examined by a DSP and a determination of whether 
or not sufficient audio is present to cause interference of proper 
signal strength is made. During the VERY brief periods of time when it 
is determined that sufficient audio is present to cause interference, 
the signal strength value is "held" (the last valid value previous to 
the time of interference) until such time that the interfering audio is 
no longer present.  

The DSP/BEW feature is selectable, and should not be used for a receiver 
that does not need it.

> From: 
bill.hurlock at cpcomms.com

> To: app_rpt-users at ohnosec.org

> Date: Tue, 19 Mar 2013 18:21:50 +0000

> Subject: [App_rpt-users] RTCM Parameter question

> 

> I can't seem to find any reference to what item 17 does in the RTCM setup menu. It says DSP/BEW and appears to have 2 choices 0 or 1.

> 

> Bill Hurlock

> CPCommunications

> 856-234-1661 Home Office

> 856-264-1010 Cell

> 914-345-9292 Ext.429

> www.cpcomms.com

> WA2TQI

>  

> Providing Solutions for Audio and Video Communications

> 

> 

> 

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