[aprssig] Mic-E Repeater

[Stephen H. Smith]

aprssig.kd5uzz at spamgourmet.com wrote:

>Has anyone here built a mic-e enabled voice repeater? I'm unable to
>find any information with Google. My understanding is that you
>basically fool the repeater controller into thinking the user has
>stopped transmitting whenever a TNC detects a packet (simple OR gate
>with Rcvr COR and TNC decode signal?). Any suggestions on what TNC I
>should use? I'm guessing the easiest thing would be to have a TNC that
>lights an LED while it decodes a packet. Will I need an audio delay
>circuit in the controller? Thanks!
>  
>
A search for "Mic-E Repeater" on Google netted this page in about 2 seconds:
      http://wes.johnston.net/aprs/aprs5a.htm      

Basically any TNC with a DCD indicator can be used to briefly mute the 
repeat audio during packet bursts. The trick is that you must use true 
software DCD so that the DCD doesn't false trigger on voice peaks, 
touch-tone bursts, etc.   (Watch how frequently, the simple hardware 
energy-detect DCD on a TNC-2, MFJ, etc falses on voice peaks, squelch 
crashes, etc.)  False DCDs muting the repeat audio will keep punching 
holes and "hiccups" into voice transmissions.

The majority of Mic-E systems are built using KPC3s because they can be 
set for true software DCD (i.e. run open squelch), unlike most others.   
Normally the RX side of the KPC3 is wired across the repeater receiver 
audio while the TX side is connected to a transceiver on 144.39.  The CD 
OUTPUT pin of the KPC3 is used to mute repeat audio during the packet.   
In turn, the squelch line of the 144.39 receiver is connected to the 
EXTERNAL CD INPUT of the KPC3 in order to prevent the TNC from keying up 
on 144.39 until the channel is clear. 

This is all assuming you want to prevent packet bursts from being 
retransmitted by the repeater.  If you are willing to let packets pass 
through the repeater,  a receiver tuned to the repeater output, a 
transceiver on 144.39 and a TNC  can be setup anywhere within 
full-quieting range of the repeater to do the same thing. 

[ I am currently doing this here in southern California.  I am 
monitoring the 146.700 Sunset Ridge repeater with a dedicated 
crystal-controlled receiver (the RX from a commercial VHF repeater 
actually) from about 20 miles away. Any packets repeated by this sytem 
are decoded here at my house, retransmitted on 144.39 and also gated to 
the Internet. ]


Stephen H. Smith             wa8lmf (at) aol.com
                                                    
Home Page:                   http://wa8lmf.com

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