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Radio set to a tone for tx & rx receives no-tone transmissions on same channel



Hey all,

I've slowly been building out a communications system for my family, a mixture of FRS/GMRS handhelds and GMRS mobile units.  My goal was to program a channel into each labeled "Family" (well not on the FRS units, but you get the idea), all set to the same CTCSS code.  The hardest part of this (I thought) was digging up the CTCSS frequencies for the units that only use a "code" for CTCSS, but I eventually got it all figured out.  So now, my mobiles and handhelds all have a common channel which should filter out any outsiders' transmissions.

So I started testing...

And I almost immediately discovered that my Radioddity DB-20G, on which the channel is confirmed to have a CTCSS tone set (i.e. the "CTCSS/DCS Encode" and "CTCSS/DCS Decode" fields for the channel are both not empty and set to the correct frequency), the channel happily receives transmissions on that channel which have no CTCSS tone set at all...

Anyone have any thoughts as to how this could be happening?

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I do not have a DB20-G, but I think I know the answer anyways so I downloaded and installed the Radioddity CPS, which is very similar to the software for a number of other Chinese radios.

If you are using the software, hit the ">>" under "More" for the channel you are trying to configure and it will bring up a dialog with all the parameters.  Right under the "CTCSS/DCS Decode" and "CTCSS/DCS Encode" boxes, you'll see one called "Squelch Mode".  Set it to "CTCSS/DCS".

If you are programming by hand, look for the corresponding menu item and change it from "Carrier" to "CTCSS/DCS".

Please let us know if that fixes the issue.  If you've already done that, then I would say the firmware has a bug, since it's opening squelch for any signal (carrier) rather than only for one with that Decode tone.

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