Need help determining offset & base for 400Mhz Mot Trunk

[VicLewin]

Hi all, first post here so hope I got the right forum here.

I have a Pro-95 scanner. While playing around with the tune function, I found two Motorola control channels in the 400 range. I went to the Canadian TAFL site and looked up the numbers and found they are assigned to a local hotel here. I then found all the frequencies for the hotel and over the last few days have played around with it, in an attempt to trunk the system. Unfortunately, I have not been able to get it to trunk
properly. I know its because I don't have the offset and base
frequency issue worked out. I was able to save some IDs, but I
don't hear anything at all. I actually think there are 2 systems because the listings on the TAFL site indicate slightly different registrations for the frequencies. They are both the same hotel, but I am thinking one trunk system is for the actual hotel and the other is for the Casino.

Anyway, I tried using the manual to program the bank, but can see that it
isn't so simple. It appears you need to figure out the offset and
base and I have found a couple of webpages talking about how it
can be done, but mathematics wasn't my forte and I can't get a
handle on it. I also looked at one of the tutorial pages here at Radioreference, but again, I can't make heads or tails out of it.

I am wondering if I posted all the frequencies here, maybe 8 in total, would someone be able to make use of their gift of mathematical genius to work out the offset and base frequencies for me?

Any help would be most welcomed and greatly appreciated!

Many thanks, Vic

 

[fireant]

If its a motorola system you only need to program the control channel and you can listen to them unless the system switches control channels and you will need to program them all. Make sure you are in open mode on the bank so you can get the talkgroup Id's unless you have the ones you want to listen to saved and then you can put it on closed mode. Hope this helps!!!

fireant

 

[werinshades]

If its a motorola system you only need to program the control channel and you can listen to them unless the system switches control channels and you will need to program them all. Make sure you are in open mode on the bank so you can get the talkgroup Id's unless you have the ones you want to listen to saved and then you can put it on closed mode. Hope this helps!!!

fireant

Not true..only works in 800 & 900 Mhz. Motorola systems. He needs to get the base and off set frequencies. Get a calculator and subtract .0125 from the lowest frequency. If that doesn't work, add .0125 to the highest frequncy.

(Ex. 476.1125..Try Base Freq. 476.1000. ....or..476.9000.. Try Base Freq 476.9125. I had to play around for a week till I figured out a couple of mine as well..good luck

 

[loumaag]

Actually the easiest way is to run Trunker on the system and get two frequencies and the hex channels they are on. Unless it uses a multiple base system then that is enough to calculate the base/offset/spacing. If you don't have trunker (or access to anyone else who does have it running) go ahead and post the 8 freqs, please indicate what seems to be grouped with what and make sure you specify the CC frequency. People might be able to provide some educated guesses on what might work.

BTW, the base frequency is always lower than any voice frequency it is used for. So you cannot have a base frequency as 476.9125 and expect your radio to decode 476.9000 as a voice channel from it.

 

[VicLewin]

If its a motorola system you only need to program the control channel and you can listen to them unless the system switches control channels and you will need to program them all. Make sure you are in open mode on the bank so you can get the talkgroup Id's unless you have the ones you want to listen to saved and then you can put it on closed mode. Hope this helps!!!

fireant

Hi and thanks for your response. As someone else mentioned, it will only work in 800/900 with that method. What you suggested is exactly what I started doing and it wasn't working correctly.

Thanks for taking the time to offer your input, its much appreciated!

Vic

 

[VicLewin]

Get a calculator and subtract .0125 from the lowest frequency. If that doesn't work, add .0125 to the highest frequncy.

(Ex. 476.1125..Try Base Freq. 476.1000. ....or..476.9000.. Try Base Freq 476.9125. I had to play around for a week till I figured out a couple of mine as well..good luck

Sounds a lot easier then the 2 webpages I read, no doubt about that. I'll try and fool around with that later tonight.

Much thanks for that suggestion my friend!

Vic

 

[VicLewin]

Actually the easiest way is to run Trunker on the system and get two frequencies and the hex channels they are on. Unless it uses a multiple base system then that is enough to calculate the base/offset/spacing.

Unfortunately, I am on Mac and Trunker is no use to me. I did read about that program, but out of luck. Thanks for suggesting it though Lou.

If you don't have trunker (or access to anyone else who does have it running) go ahead and post the 8 freqs, please indicate what seems to be grouped with what and make sure you specify the CC frequency. People might be able to provide some educated guesses on what might work.

Ok, I responded to each of the 3 messages separately so I could thank each of you individually. I am going to compose a message with the frequencies in a bit along with some other caveats which might help you out. I will indicate the two CCs and also the way the TAFL lists the "owner" of the freqs so you will be able to see why I think its 2 separate systems.

I very much appreciate any help or guesses you, or any one else, might be able to provide. Its not that it is an absolute must listen, but its one of those situations where you really want to be able to figure it out!

Thanks again and I'll post the message with the freqs and extra info later tonight.

All the best everyone and hope you can assist me! Vic

 

[VicLewin]

Here are the freqs and info!!

Alright, here is the info on the frequencies that have 2 CCs in the 400mhz spectrum:

TX Freq RX Freq
422.462500 427.462500 HALIFAX,NS (SHERATON HOTEL) PARK PLACE ENTERTAINMENT 
422.562500 427.562500 HALIFAX,NS (SHERATON HOTEL) PARK PLACE ENTERTAINMENT
422.662500 427.662500 HALIFAX,NS (SHERATON HOTEL) PARK PLACE ENTERTAINMENT
424.887500 429.887500 HALIFAX,NS SHERATON HOTEL  CASINO NOVA SCOTIA HOTEL
ZZ424.987500 429.987500 HALIFAX,NS SHERATON HOTEL  CASINO NOVA SCOTIA HOTEL
427.462500 422.462500 HALIFAX,NS (SHERATON BASE) PARK PLACE ENTERTAINMENT
ZZ427.562500 422.562500 HALIFAX,NS (SHERATON BASE) PARK PLACE ENTERTAINMENT
427.662500 422.662500 HALIFAX NS (SHERATON BASE) PARK PLACE ENTERTAINMENT

I put a ZZ in front of the 2 freqs that are, at this moment, showing as the active CCs. So, to me, it looks like there are 2 systems. The hotel has 3 Freqs, 1 being a CC and the Casino has 2 Freqs, 1 being a CC. Is that what it looks like to you guys?

Here is some info that may be useful. Without being able to setup the offset and base, I just put the CC freqs in to two separate banks. One bank is the hotel, the other is the Casino. What happens is when it is scanning and locks on the CC, I see a TG ID on the Pro-95 display, but it would flash rapidly like it was very rapidly going from scanning to locking on the TG. I hear no transmissions, it just does what is described above. For example, it shows TG 00016, but wouldn't just stay on the VC.

NOW, a little more on the scanner display flashing, which after referring to the manual, is when I realized I needed more info than just the freqs. As mentioned, when I am scanning the banks it seems to stop like it has a transmission going, but the screen flickers, quite rapidly, like it isn't locking on or something. I decided to watch it closely and it showed a TG ID #. But what caught my eye was the frequency that was displayed. It was 406.00000. The other bank shows a different freq, its 406.xxxxx. I can't remember the rest offhand. Not sure those "flashing" freqs are important, but thought I would mention it.

Finally, here are the two links where I read about how to figure out offset and base when it is unknown:

http://home.att.net/~wwhitby/tt_ids.htm

About half way down page, look for: Determining Base and Offset Frequencies for the BC245xlt

And from this website, the following page:

http://www.radioreference.com/modules.php?name=Content&pa=showpage&pid=21

Unfortunately, I can't get a grip on any of it.

So, hope all the above is enough for someone to take on the challenge of figuring out how to get these systems to trunk properly for me!

Many many thanks and look forward to any help that is offered!

Best regards, Vic

 

[werinshades]

422.462500 427.462500 HALIFAX,NS (SHERATON HOTEL) PARK PLACE ENTERTAINMENT
422.562500 427.562500 HALIFAX,NS (SHERATON HOTEL) PARK PLACE ENTERTAINMENT
422.662500 427.662500 HALIFAX,NS (SHERATON HOTEL) PARK PLACE ENTERTAINMENT

Try Base Frequency : 427.4125


424.887500 429.887500 HALIFAX,NS SHERATON HOTEL CASINO NOVA SCOTIA HOTEL
ZZ424.987500 429.987500 HALIFAX,NS SHERATON HOTEL CASINO NOVA SCOTIA HOTEL

Try Base Frequency: 429.8725

That's the best I can come with the information provided. I only need the input frequency actually. It sounds to me like you need to determine the proper frequencies first...check back with us.

 

[EricCottrell]

Re: Here are the freqs and info!!

Alright, here is the info on the frequencies that have 2 CCs in the 400mhz spectrum:

TX Freq RX Freq
422.462500 427.462500 HALIFAX,NS (SHERATON HOTEL) PARK PLACE ENTERTAINMENT
422.562500 427.562500 HALIFAX,NS (SHERATON HOTEL) PARK PLACE ENTERTAINMENT
422.662500 427.662500 HALIFAX,NS (SHERATON HOTEL) PARK PLACE ENTERTAINMENT
424.887500 429.887500 HALIFAX,NS SHERATON HOTEL CASINO NOVA SCOTIA HOTEL
ZZ424.987500 429.987500 HALIFAX,NS SHERATON HOTEL CASINO NOVA SCOTIA HOTEL
427.462500 422.462500 HALIFAX,NS (SHERATON BASE) PARK PLACE ENTERTAINMENT
ZZ427.562500 422.562500 HALIFAX,NS (SHERATON BASE) PARK PLACE ENTERTAINMENT
427.662500 422.662500 HALIFAX NS (SHERATON BASE) PARK PLACE ENTERTAINMENT

The last three frequencies are for a base unit to talk through the repeaters licensed on the first three frequencies. Normally you do not have business band repeaters "inverted" so I suspect the 427.5625 is a spur or image of another frequency due to the receiver being near a very strong signal. The transmitter on 424.9875 may have a spur on 427.5625.

Most UHF systems keep it simple and will chose either the lowest frequency used or one that is "easy to enter" like 422.000 or 422.400. I would try using a step of 12.5 KHz and base frequencies of 422.4625, 422.4500, 422.400, 422.000 and 420.000 MHz. Some systems get alittle fancy and use 25.0 KHz steps since the frequency spacing is a multiple of 25 KHz. I would try base frequencies of 422.4625 and 422.4375 with 25 KHz steps.

73 Eric

 

[DaveH]

The channels appear to be on a 25kHz grid. The standard offset channel number
of 380 is a fairly safe bet. The number of channels and spread suggest it is a
single-range system.

Unless this is an inverted system i.e. outputs higher that inputs (which I doubt,
but you can confirm), the base frequency very likely is between 421.0125 and
422.4625. This IS a Motorola system, correct?

Reason for the ~ 421MHz lower limit is that typically in Canada frequencies
in the 420-421MHz range are are paired with 409-410MHz (-11MHz
spacing).

The problem is the base frequency. There are 59 possibilities in the above
range. If you are going to try them exhaustively, start at the low end. I don't
think the lowest voice channel is likely, because if the system ever expands
and adds a voice channel below 422.4625, the system range has to be changed
in every radio (poor planning).

Instead of some exhaustive trail/error search, give me 5 minutes or less with
Trunker (or Treport or DEMO88 or T4Win) and I could tell you with >95%
certainty how to set this system up. If you can't run it, why not find someone
in the Halifax area who can.

Dave

 

[mciupa]

This IS a Motorola system, correct?
Dave

If it isn't, is it possibly an LTR regular system?
Does the Pro -95 do LTR trunking?

 

[fireant]

No the pro 95 does not do LTR wish it did though!!!

fireant