[App_rpt-users] DMK URI questions

Sat Nov 2 17:36:45 UTC 2013

Typically, when using non-descriminator audio you will not use app_rpt de-emphasis because the audio coming out of your radio is already de-emphasized. 

On the transmit side you want generally want to use the radio’s mic input which needs no app_rpt pre-emphasis. The exception to that is if you want app_rpt to generate transmit CTCSS. In that case you feed the modulator and pre-emphasize with app_rpt. 

Flat audio means no filters are applied. Flat systems generally take discriminator audio and feed it to the modulator. The audio itself is not what you might think of as flat as the highs are emphasized out of the repeater and passed through the system. The audio is pre/de-emphasized by the user’s radio and the repeater system never filters it. 

App_rpt is not a flat audio system. App_rpt is a line (mic/speaker) audio system. That way it interfaces to easily to telephones, sound files, generated tones and etc. The audio needs to be pre/de-ephhasized either by the radio or with app_rpt itself just before it goes to the radio. 
--
Tim
:wq

On Nov 2, 2013, at 9:53 AM, Doug Crompton <doug at crompton.com> wrote:

> OK the two differing opinion responses explain the difference.
> 
> If I decide to start with simple USB and CTSS decoding in my transceiver fed to the URI cos pin would I use flat audio or dempahsized audio from the transceiver?  In the case of the Alinco either the 1200 baud or 9600 baud audio data port outputs?  And what input to the Alinco for TX (1200 or 9600)?  
> 
> This is confusing because I am not sure if a setting of simple USB also means you send demphasized audio to the interface or do you always send "flat" audio to the interface. And the same question for audio from the interface to the TX.
> 
> I am assuming the term "flat" means before any pre/demphasis. 
> 
> 73 Doug
> WA3DSP
> http://www.crompton.com/hamradio
> 
> 
> Subject: Re: [App_rpt-users] DMK URI questions
> From: tim.sawyer at mac.com
> Date: Sat, 2 Nov 2013 08:56:01 -0700
> CC: app_rpt-users at ohnosec.org
> To: doug at crompton.com
> 
> The DMK URI works with either SimpleUSB or USBradio (DSP). 
> 
> - Both USBradio and SimpleUSB can do CTCSS high pass filtering and de-emphasis.
> - SimpleUSB cannot do noise squelch, CTCSS squelch or pre-emphasis.
> - SimpleUSB requires less CPU.
> 
> You may not desire or be able to use USBradio:
> - If you have a low speed (less than 800 Mhz) CPU
> - If you can’t get discriminator audio out of your radio
> - If your radio does not produce enough high frequency discriminator audio
> - If you find the squelch action of your radio better than that of USBradio
> 
> Personally I prefer SimpleUSB over USBradio. I use with commercial Motorola repeaters on congested hill tops. The squelch and CTCSS decode are miles better than USBradio in my opinion.
> 
> Tim
> :wq
> 
> On Nov 2, 2013, at 7:41 AM, Doug Crompton <doug at crompton.com> wrote:
> 
> 
> OK Perhaps I am not using the right Allstar terminology here.  My understanding is that simple USB works similar to IRLP in that you use pre/dempahsized audio and COS and there is no further processing. CTSS tones, squelch, etc. are not decoded by the SW but rather by the incoming DC level of COS.
> 
> On the other hand in what I call DSP the CTSS, etc. are decoded by the software. As a for instance the GM300 example on the DMK site uses no COS just audio in, out, and PTT. When using this mode you use flat audio from the RX or audio that has not been demphasized. 
> 
> DSP is digital signal processing.  That is what the SW does to look at the incoming signal to decode things like CTSS, DTMF, squelch noise etc.  I am assuming that simple USB just uses the COS signal to detect carrier. My question was why would one prefer one method over the other or does one work better than the other. 
> 
> 73 Doug
> WA3DSP
> http://www.crompton.com/hamradio
> 
> 
> From: kj6ko at innercite.com
> To: doug at crompton.com
> Subject: Re: [App_rpt-users] DMK URI questions
> Date: Sat, 2 Nov 2013 00:13:15 -0700
> 
> Doesn't matter.  It's a preference thing.  By the time audio gets to the internet, it is all digitized and de-emphasized.  What comes out the other end depends on what you want.  If you are going to feed a modulator directly, you need pre-emphasized audio, and I don't think the URI will do that.  It will de-emphasize DISC audio on RX.  You should just use MIC audio into the radio and de-emphasized audio into the URI to keep it simple.  I would ALWAYS use "CTCSS Valid" signal out of the radio (if avail) and feed the signal to the COS port of the URI.
>  
> COS and CTCSS are meant to be used together, like in a repeater, but it doesn't have to be
>  
> MIC DC and MIC AC??  you will have to read the radio manual on that one.
>  
> PS:  DSP does NOT mean FLAT Audio.  It means "Digital Signal Processing" and really has nothing to do with audio shape.
>  
> I guess I'm not sure what you mean by "DSP vs Simple USB"??  Is there a device called a "DSP?" 
>  
> I'm guessing you should keep it simple and use the "Simple USB" because that is what it is...simple!  Not much involved, Audio in, audio out, PTT Out and COR/CTCSS in.(Either or).  For a CTCSS detect, you need to find something that will give a GND or +5VDC when an active PL Tone is received.  I think the DMK device can do this for you if you don't have one on your radio, in which case you will HAVE to use discriminator audio for RX.  The DMK will de-emphasize it before it goes out over the network. 
> ----- Original Message -----
> From: Doug Crompton
> To: app_rpt-users at ohnosec.org
> Sent: Friday, November 01, 2013 10:53 PM
> Subject: [App_rpt-users] DMK URI questions
> 
> About a week ago I asked about DMK URI connections to an Alinco radio and I got several responses. I do have a few more questions regarding that. 
> 
> The Alinco has both flat and pre/de-emphasized audio available on its data connector as 1200 baud and 9600 baud connections.
> 
> I assume I would use the 1200 baud connections along with COS and PTT for a simple USB interface and the 9600 baud connections along with just the PTT for a DSP interface?
> 
> Do I use the  (Alinco 9600 baud) audio to the TX also? Does the DSP pre-emphasize audio or is the processing just on the receive side?
> 
> Why would I want to use one over the other (DSP vs simple USB)? Which is preferred and/or works better? I am thinking there might be some differing opinions here!
> 
> The DMK URI has both mic_DC and mic_AC inputs. Does this refer to frequency response or just that one has DC blocking?
> 
> If you are using flat response (DSP) would the audio in (from the receiver) connections at the URI end matter?
> 
> The DMK URI has both COS and CTSS inputs. Why would you use one over the other? When using DSP I assume neither is needed?
> 
> All of the questions above assume I am using the Acid release on a faster processor.
> 
> 73 Doug
> WA3DSP
> http://www.crompton.com/hamradio
> 
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