W0DBW- Disambiguation on Repeater Tone Encoded Squelch and How PL Can Benefit SWIARC

The SWIARC repeater on 146.820 shares the same frequency and offset as a repeater in Des Moines Iowa. Some repeater users east of Council Bluffs are plagued by interference coming from the Des Moines repeater. It has been suggested that SWIARC add a PL Tone to the repeater to eliminate the interference experienced by these remote users further east of Council Bluffs.

Debate on the negative impact of the presence of PL on the repeater is driven to some degree by a misunderstanding of PL Tone. An explanation of PL, more correctly known as Continuous Tone Coded Squelch System or CTCSS is not covered here. What this memo accomplishes is a suggestion that could best serve users on both sides of the debate.

If it is possible it should be considered that a PL Tone be added not to the input, but to the output of the repeater. Individuals without a tone board or CTCSS capable transceiver will still be able to use the repeater. If there is no tone requirement to get into the repeater, no individual will be denied access. The presence of PL on the output (when the repeater transmits) creates the “option” for users to utilize PL as a way to squelch out interference coming from the Des Moines repeater or other stations transmitting on 146.820.

If you are a station with a transceiver not capable of CTCSS squelch, then you will not be negatively impacted by the suggested configuration of the repeater. Your radio will simply receive the transmission from the repeater as usual, and you will be blissfully unaware of the presence of the PL tone.

If you are a station with a transceiver capable of CTCSS squelch, then you will be able to use it and isolate the SWIARC repeater from other transmissions that are not using the same tone. The Des Moines repeater seems to transmit without the presence of a PL tone. Your transceiver using tone squelch will block out the Des Moines repeater. Your radio squelch will only open for the SWIARC repeater having the matching PL tone. Your station will not key up both repeaters due to the fact that the Des Moines repeater requires a PL tone to get in. Because the Des Moines repeater has the PL requirement, it is simply not necessary to implement a PL requirement on the SWIARC repeater.

It is not being suggested that a tone be added to the repeater input. I am of the opinion that a tone should not be added to the repeater input since that would deny certain users access to the repeater. It also complicates transceiver configuration for novice users and those traveling though the area. Adding a PL tone to the output denies no user access to the repeater, and provides an optional way for users to further reduce interference.

Hopefully reading this short memo helps to alleviate some of the confusion surrounding the issue. One final note, it has been suggested that the Vertex repeater does not have the ability to transmit with PL tone encoding. It should be established if it is possible to enable, upgrade, or implement the feature and if such implementation is practical. If it is not possible or cost prohibitive, then the entire debate is merely academic.

-w0dbw