PPSTN Failsafe

[mohjo]

Saturday night @ midnight P.A. EMS Prov. Dispatch went down for approx. 10min. while techs were working on the radio system. They went over to the "Emergency Ch." while the system was down. I assume this would be the PPSTN failsafe frequency for EMS. I tried scanning the 137mhz-140mhz range but unfortunatly I didn't find anything. Was I doing this right? Is this an actual frequency off the system? Is it in the VHF range? Did anyone else try finding it? Lots of questions I know but this is veryn interesting.

 

[bush_man]

Back up

Provincial Ambulance used to use 158.760mhz, so it's possible you didn't scan high enough if they still have those VHF radios in the ambulances as backup? Just a thought...

 

[harryshute]

Good suggestion to try 158.760 as the conventional failsoft frequency for EMS as that makes sense. Even fits in well with the Alberta system VHF failsoft if they decide to go with it which would then be compatible. I too would have been searching the 137 to 140 range but we can't forget about those VHF ones that are already in use. Is 156.855 used as a Provincial fire common in Saskatchewan?.

 

[mohjo]

I'll give it a try. Unfortunatly it might be a while before the system goes down again. By posting this, I'm hoping to bring some attention to it, and get a few people looking accross the province. Ya know?

 

[harryshute]

I would also add 156.855 as a possible Fire failsoft. There are quite a few departments in Saskatchewan licensed on this as well. Sometimes thet will braodcast in advance when they take down a system. That would give you a chance to set up.

 

[Jay911]

I thought failsoft had to be one of the frequencies of the trunk, Harry? I would think that would mean that it would have to be in the 136-139 range for PPSTN.

158.76 and 156.855 are indeed province-wide allocations (trivia: these are for EMS (158.76) in all of BC, AB, and SK, and fire (156.855) in AB and SK) but when the controller falls over the site is supposed to go into open transmit on one of its repeaters - so I thought.

 

[harryshute]

Hi Jay if you go with the norm usually it would be one of the trunk frequencies. It may be more so with a Motorola failsafe system. The two VHF Provincial channels I suggested were to try in case the regular range doesn't turn up anything. With newer radios with wider bandwidth this is entirely possible. It could explain why no failsoft frequencies have been reported for PPSTN. When these two are heard you might assume they intend to be on the provincial channels rather than out of range.

The Sheriff 800 Mhz system in Alberta does not use a trunked repeater simplex when the unit goes out of range just the selected conventional frequency for the user. This system is set up more like a Motorola P25 system than an EDACS. The Sheriff uses talk groups divisable by 16 unlike Saskatchewan which uses the Harris one digit groups. I don't think this indicates one way or another which talk group numbering will be used for the Alberta system once it is set up.

 

[mohjo]

As I listened to the PPSTN yesterday, the tech's started working on the repeater site in my area. After work started, my scanner stopped trunk tracking the PPSTN. Funny thing is I was still hearing transmissions. Everytime RCMP would key in, it would always show the same frequency. It wouldn't change like it would if the system was trunking. Same for EMS. Everytime they would key in, it would always show the same frequency. All I can say is this must have been failsafe mode. The system must take a tg and assign it to one frequency. I hope I'm explaining this well enough so people understand. The other funny thing was, everytime the transmission was done my scanner wouldn't continue to scan. It would just stay locked onto that frequency/tg and would stay lit up like there was a continuous transmission. I would have to hit scan everytime. Very annoying.
Does this sound like failsafe to anyone else???

 

[harryshute]

The way you describe it, which is very well, I would say that's exactly what you heard. Could you still receive the data channel when this was being done? Were RCMP and EMS on Simplex mode or did it sound like the frequencies were still acting in repeater mode while this work was going on?

Were the frequencies you noted in failsoft the same as the usual frequencies for the repeater site in question?

In any event a great monitoring event which helps sort out this system.

 

[mohjo]

Thanx. The frequencies being used were the usual Voice Ch. Frequencies that the PPSTN uses in this area. In fact, the frequency that EMS was using was the frequency the data ch. would normally be on. Weird or what? It wasn't simplex either. Defenatly repeater.

 

[harryshute]

mohjo thanks for the quick reply and good information. You're report answers a lot of questions. It appears we may not need to be looking for a bunch of unknown frequencies for failsoft mode. It appears it simply uses the available channels at the site. It will be interesting to see if others report EMS using the channel usually used for data. Also the fact they are in repeater mode pretty well confirms this system is using the conventional type of failsoft rather than the weird system they are trying in Alberta.

 

[mikewazowski]

On a Motorola system, Failsoft uses the trunked repeaters as conventional channels. The repeaters stayed keyed up and a beep is heard about every 10 seconds. I assume other systems would behave in a similar manner.

Generally each talkgroup is assigned a Failsoft frequency. Several talkgroups could share the same frequency.

It's possible that during a controller failure, similar groups will dial over to an emergency channel which will put them all on the same trunked repeater.

As far as I can tell, you can assign any frequency pair as long as it falls within the bandplan of the system.

However, it would make more sense to use the trunked repeaters since they should still be on the air.

There might also be a problem once the system comes back online with signalling the radio that the system has returned to normal use.

I assume that once the constant carrier of the repeater drops, the radio goes looking for the control channel or something in the outbound packets signal the radio to go back.

 

[mohjo]

MikeOxlong, funny you say that. Just after the CC came back online, Fire called control saying they were having problems with some of there radio's. They said some of the radio's were saying something like "searching for CC" or something like that. I didn't quit hear the entire convesation.

 

[beeperboy]

It sounds like the techs had all of the channels disabled except the control channel. Depending on how the system is programmed, the CC can be set to revert to traffic if needed. So all radios listen to the CC, when somebody requests a talk path, the CC tells everyone to trunk to the CC, and it turns into a voice channel for the duration of the call. Then it reverts back to CC data once they are done. If you try to talk on another TG while the CC is being a voice channel, then you get either a busy, or more likely a loss of CC message, as there isn't one broadcasting. At least that's how the Motorola and MPT1327 systems that I maintained worked. It makes for a very slow, yet sort of usable trunked system while it's being worked on, or all other voice channels have failed. I don't think it is a failsoft sort of mode you heard, as the operators probably wouldn't be able to access it. Dunno, I need to brush up on P25 trunking protocol.

BB

 

[mohjo]

I don't know. RCMP stayed on the same voice channel everytime they keyed in. It was only EMS that stayed on the cc everytime they keyed in. Not to sure what kind of equipement they are using for the PPSTN. Maybe someone else could answer that.

 

[harryshute]

It is basically a Harris P25 system and the "CC Scan" is pretty typical when in failsoft. Harris seems not to use the beeping Motorola uses when in this mode. I still wonder what channel is used when is radio goes outside of any repeater reception.

 

[mohjo]

The other day I was listening to fire in my area. The radio's weren't quit hitting the tower sometimes so fire said they would be switching to F5 and dispatch would not be able to hear them. That was the end. I couldn't hear fire anymore.
Then today I just stumble apon this site. Go to page E1. It gives all the frequencies that are used for forest fires. .
http://www.environment.gov.sk.ca/Default.aspx?DN=82fc35db-6d35-4ee8-a979-979fad233fb3
Am I correct in assuming that all the fire departments in Sask. have these frequencies in there radio's incase they are out of range of the PPSTN rapeater? I don't want to submit this till I know these frequencies are actually in use. Any guesses???

 

[RBerezowski]

The other day I was listening to fire in my area. The radio's weren't quit hitting the tower sometimes so fire said they would be switching to F5 and dispatch would not be able to hear them. That was the end. I couldn't hear fire anymore.
Then today I just stumble apon this site. Go to page E1. It gives all the frequencies that are used for forest fires. .
http://www.environment.gov.sk.ca/Default.aspx?DN=82fc35db-6d35-4ee8-a979-979fad233fb3
Am I correct in assuming that all the fire departments in Sask. have these frequencies in there radio's incase they are out of range of the PPSTN rapeater? I don't want to submit this till I know these frequencies are actually in use. Any guesses???

No, all fire departments in Sask. won't have these frequencies. Only the departments and agencies actually involved in fighting forest fires would have access to these frequencies. The other departments in the province have other simplex frequencies in their radios that they can use when out of range of the PPSTN. The actual simplex frequencies used would depend on which department it was.

Rob
Regina, Sask.

 

[mohjo]

ah I see. Doing a tafl search did alert me to some of the frequencies being used by fire departments that use a simplex frequency. I just thought maybe there would be a list of simplex frequencies set aside in the province incase they were out of the range of the repeater, but it looks like each department would be in charge of there own simplex frequency. I did sumit what I found under the Natural Resouces database as thats what all those frequencies were registered under. It just hasen't made it on to the database yet. Thanks for the help.