CTCSS on Simoco Radios after Dec 31st 2009

[Rob_Brookes]

As far as we are currently aware, CTCSS, sub-audible tone muting, is to be a mandatory requirement on the UKSAR team working channels after December 31st 2009. The primary reason for this is that an ever increasing number of teams and regions are now using Simoco radios for GPS tracking and it's inevitable that we will all be hearing the data being sent by the portables and bases radios of other teams. This just increases the already high level of spurious noise on the channels and so I did some work to try and find a way of at least reducing this level. In fact after a modification to the programming software very kindly made for us by TMC Radio in Australia, we are actually now able to use CTCSS to mute out the GPS data noise completely. This method is also applicable to any make of radio that is capable of handling CTCSS tones. It has been tested with a number of makes including Icom, Tait and Motorola and all no longer hear any GPS data noise once CTCSS has been programmed.

Because of the way in which Simoco radios work, the data sent as GPS position reports is still heard by the radios themselves even if it's no longer passed to the loudspeaker. Hence all GPS tracking functions are carried out normally but the data itself can no longer be heard.

I must warn you though, after 4 years of audible data for GPS tracking, it's very weird to watch it all now happen in complete silence!

CTCSS.pdf