[App_rpt] app_rpt setup and requirements.

Steve Rodgers hwstar at rodgers.sdcoxmail.com
Mon Oct 9 01:09:31 EDT 2006


See below for the answers.

On Sunday 08 October 2006 19:11, Eric Fort wrote:
> Hopefully those on the list can answer a few questions about getting
> app_rpt setup and what is really required.
> 1.  why is the arib needed and what exactly does it do?

The main task of the ARIB is to separate the audio from the signaling. 
FXS connections carry audio (AC) and signalling (DC) on the same twisted pair.
The signalling and the audio need to be separated when interfacing to a radio.

> 2.  Why do I need 2 fxs ports for full duplex operation?  my phone is full
> duplex when plugged into the same port why can't the audio for the radio
> be?  

> Come to think of it I can buy a little phone with a headset jack for 
> next to nothing and have seperate tx (mike) and rx (speaker) audio.  this
> just takes a 2 to 4 wire hybrid common to most phones.  why do I need the
> arib at all?
> 3.  Why do I need the arib at all?

For full-duplex repeater operation 2 FXS ports are an absolute requirement. To 
see why, keep reading.  If you are not running a repeater, onty one FXS port 
is needed, and a two wire connection can be used.

We prefer to set up repeaters instead of half-duplex configurations like 
Echolink or IRLP. We feel the full duplex repeater configuration gives us 
more control as we can issue commands while the transmitter is still 
transmitting, and we don't have to wait for a transmitter to unkey before 
starting a new transmission.

Why the two FXS port requirement for full duplex audio? For full duplex audio 
(simultaneous receive and transmit) as used with repeaters, no receive audio 
can be allowed to couple into the transmit audio, without going through  
audio processing (muting, mixing, etc) first. The hybrid transformers used in 
phones don't have to be perfect full duplex devices. What I mean by perfect 
full duplex device, is that no receive audio is discernable in the transmit 
audio. Phones are not perfect full duplex devices, in fact, some receive 
audio is purposely introduced in the transmit audio to generate a sidetone.  
Even the hybrid transformer  is still not going to do an acceptable job of 
rejecting the receive audio on the transmit port, hence the need for a 4-wire 
connection back to Asterisk using 2FXS ports.

> 4.  is the rbi-1 really needed?  what function does it serve?  I've seen
> mention of using an ft-897 directly without it.  How is this done?  why hf
> only for the 897 when the 897 covers hf, 6m, 2m, and 440?

The RBI-1 is only required it you want to change the frequency of your radio 
remotely, and you have the Kenwood mobile radios which are compatible with 

> 5.  what about interfacing other radios used for repeaters such as micor,
> maxtrack, etc.

We do it all the time. My repeaters are all Motorola Mitrek, or GE Custom MVP.
Other guys use Maxtracs, and Desktracs or other synthesized commerial land 
mobile radios.

> Thanks,
> Eric - kg6kqt

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