MRMap Development Team 10/01/2009
One where I’ve so far failed miserably is putting a single selcall tone onto the end of the transmis-
sion made by the rebroadcast radios so as to act as an indication that you are still within range of
base. This is sometimes called a ‘Comfort Tone’. I couldn’t get a tone at all from either of the
rebro radios using ‘PTT Data Ext’. It would seem from trying all the others that only the actual
microphone PTT button can initiate the sending of the ‘PTT Off’ selcall tone.
As a way around this I tried adding the tone to the end of the base transmission as it’s passed
straight through the rebro and, sure enough, if the microphone PTT was pressed then a tone was
sent. However under these circumstances you would already know that you were still within range
of base as you would then hear them speak. What’s needed is a tone at the end of the otherwise
silent, automatic group poll sent out by MRMap. This I couldn’t achieve but I’ll keep on trying until
I’m sure it can or can’t be done. I did get some odd delay effects under certain circumstances but
not an actual tone so it may be some setting I have wrong (again!) Unfortunately, doing it this
way adds yet more time to the operation cycle of the rebro and there is already a short but notice-
able period after a handset transmits, when it can’t open the rebro receiver for a second or two. I
also need to look at this. If anyone wants to help with the selcall tone testing, please feel free!
Still left To Do:-
Just whether it will work with a duplex wide area repeater really. The rest is just tidying up
and refining the timing values. As so far described it will work and will probably be suitable for
those who just want to mute out the FFSK data noise. As and if I refine any of the config values,
I’ll update this document on the blog page and on the documents download page of the MRMap
website.
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