Remote Base Configurations
A local issue prompted some thinking..
IRLP is nice as it can add put some activity on a local repeater, especially when connected to a reflector. This may help draw some of the local hams out of the wood-work and get them on the system. The reflectors advise for obvious reasons that users should disconnect your node if a local conversation becomes extended. They feel short local greetings are okay while connected, but do not want you to tie up the reflector with a 10 minute local QSO. This make perfect sense, what a waste of bandwidth and annoyance to remote people to hear a bunch of area-specific chatter.
However this is sort of catch 22. You want local folks on your system, as that's why you probably added IRLP in the first place (the enticement). But they can't chit-chat locally... What if not everyone on your repeater knows about IRLP or that your connected to something (as it can appear pretty seamless sometimes, or when there is little remote activity). Or perhaps only a handful (members) know the IRLP codes?
So now that you brought some locals out of the wood work, they start to talk locally... What to so about this? It would seem the best way is to have a (local) virtual channel that does not get sent over IRLP and a remote channel.
This is simple enough to do with external Com-Spec boards. Basically you set up a community repeater. So if users use say tone 100.0 Hz they are talking local, but if they use 107.2 Hz it also gets linked over IRLP. To accomplish this you'd tie the Com-Spec decoder logic output to the IRLP COR. Now if someone needs to slip a quick local comment in, or make a QST, they can do it by running 100.0 Hz, as normally everyone would run 107.2 Hz.
You could rig up a (timed) monitor only function. Where a DTMF command can
temporarily disconnect/switch the IRLP COR so that you can interject a local QST/comment.
But it could still keep the IRLP audio coming across.
Another option is to use an Scom 7K programmed with a custom version of the WA1ZYX remote base programming available at http://www.ccdx.org/zedyx/scom/7k/rembase.htm
The programming allows us to have three modes: off, monitor and transcieve. The off mode is obvious, the monitor mode is used when listening to a reflector/conference bridge (like for the shuttle flights), and transcieve mode is normal IRLP mode.
The 7K is set up with dual PL decoders so that 100hz is local repeat only and the club tone is fully featured. This is easily done with the IF statement that was introduced with firmware
version 2.04. Basically you diode OR the decoders to the PL input, and the club tone decoder also feeds one of the digital inputs. The IF statement is set up so that
IF (digital input is active)
(set command list to full range)
(enable TX2 PTT)
(set command list to partial range)
(disable TX2 PTT)
The partial command list that is active when the 100hz decoder is active includes PL / Carrier Squelch mode select, PL Paging, 911 patch and not much else. Switch to the club tone and you
can do anything. If you are in the middle of an IRLP connection you can switch to 100hz and interject a comment and know that it won't go over the IRLP connection. Most club members have two adjacent memory slots in their radios, one with the club tone, a second one with 100hz.
An earlier implementation (before the 2.04 firmware came out) used the RX2 and RX3 ports of the 7K with the audio connections and the CORs tied together and the two PL decoders connected to the different PL decode inputs.
Sub Audible Paging
In a similar fashion you could temporarily send out a separate PL/DCS tone briefly for a silent voice page. Much like how two-tone paging would open someone's receiver. When a control-op or user lets say doesn't want to be bothered with all the local chatter, the could switch to a channel in their radio with a separate paging receive tone (there could be many if you addressed the encoder DIPS). A user wishing to page someone would enter a DTMF page tone, which would interject the separate or secondary subaudable tone for a few seconds (555/PIC) so that you can make a voice page.
Some use the term "PL Paging". Keying a 757* on the input switches the 100hz system transmitter PL encoder on, then when the user unkeys it is turned back off again. This allows someone to key 757* then say "Paging (callsign)" then unkeying. (757 was chosen because it translated to PLP on the telephone dial... i.e. easy to remember.)
Just some thoughts for anyone building a system.