Trying to Figure out Base and offset numbers

[joegen62]

Hello again,
I work at Ford Motor Co. and the RR Data base shows the band plan as Motorola Type II, My BC245XLT requires a base Freq. and Offset but RR does not show one. I tried plugging in the primary frequencies with the default base and offset but it will not track the control channel. I have tried experimenting withsome base freq. but nothing comes up.
Any ideas as to where I can find or figure out what these figure would be.
Thanks

 

[crayon]

joegen62,

Type II moto systems usually do not need the base/offset settings keyed into a scanner.

I have not ever ran a 245xlt, but it has been around long enough that I am sure there are plenty of websites with information showing how to correctly program the radio.

Good luck!

 

[DaveH]

VHF and UHF Moto systems have three base/offset/step sets ("ranges"),
although not all are "used" in every system. Looking at the Ford system, it
very likely uses two ranges. Figuring them out requires some software and
radio setup to monitor the control channel and decode the channel numbers
being sent to the radios. Otherwise it is by experimentation and could take
quite a bit of time.

Unfortunately, I think the BC245 can only handle one set of base/offset/
step. It was a very early trunking radio and they probably thought at the time
that this was good enough. So if you set up one set, you'll get only partial
tracking, of the one range you can set up at one time.

You could try the following to see if you get partial tracking:

base = 451.0000
offset = 380
step = 0.0125 (12.5kHz)

(I believe the 245 reverses the meaning of offset and step; be careful)

If that doesn't work, try changing the step to 0.025 (25kHz); and you
could change the base frequency to: 451.0125, 451.0125, or 451.0375.
The first base could not be higher than 451.0375, the lowest frequency
used in that range.

The second base might be 460.0000, but the offset must be known and
much harder to find by trial/error. That's where the software comes in. Look
for someone in your are to run Trunker or Treport software on the system.
Once there's some raw data, we could go from there.

Dave

 

[crayon]

Type II moto systems usually do not need the base/offset settings keyed into a scanner.

Strike that.

800/900 MHz Type II moto systems usually do not need the base/offset settings keyed into a scanner.

 

[joegen62]

I will strike that last one...LOL

The funny thing is I can pick up the voice channels when i'm not trunking and when I try to change the base around a bit it tries to track but no go.
I do have a BCD396T which will allow me to put up to three band plans for the base and offset. There is a write up I came across on RR the details some pretty nasty things you have to go through involving some HEX conversions and formulas to get the base and offset Take a look at this and see if any of this makes sense. In the mean time I am up to the challenge and will continue working on it.
Thanks for the help.
PS... My new BCD396T is pretty cool stuff once you figure out things.

http://www.freqofnature.com/information0001.html

 

[DaveH]

Converting hex to decimal or the other way is not a big deal...the Windows
calculator will do it easily. The example shows how to "calculate" the base for
one range of a system. This is "sort of" easy because the offset is always 380.
Trial and error will work up to a point. The Ford system uses two, possibly
three ranges. With this there are too many unknowns. What is needed is the
channel numbers mapped to frequencies.

Give someone 10 minutes during a busy thime using Trunker/Treport and
the system could be figured out. In fact, if someone can get just the channel
numbers, without correlating to frequencies, it could still be figured out. If
Windsor was within 1 or 2 hours drive, I'd schedule a drive-by in my spare
time to take a run; but it's a good 8-10 hours at legal speeds. Better that
someone closer could take a run at this.

Trunker, Treport etc. require a tap off the discriminator of some suitable
receiver, plus a data slicer, plus the software running on a PC. This sounds
like a lot, but I've been using the same setup since 1998 and was not that
difficult to achive. Some newer software works through the PC soundcard
(T4Win and possibly the new "Unitrunker") but still requires a disc. tap.

Another alternative, if someone has inside info on how the radios are
programmed (start/stop frequencies for each range and step), that would
help (I'm not suggesting anything unorthodox).

The BC396 should be able to handle this system, once the parameters
are calculated

Dave

 

[joegen62]

Well, I must say it sounds like a lot but I am amazed in whats involved. I ahave been scanning for some time now but up until about 4 years or so, I was mostly scanning conventional stuff and the odd trunking system. With alot more companies and institutions going digital and others like LTR and EDACS it come time to upgrade to a digital scanner.

I also am having to learn a bit more about the process of trunking in order to keep up with the times. So I will have to ask if tapping into a disc. is a big job and what are the risks. Now, I do have extensive electronic experiance but that is mostly limited to fixing TV's and projects. Not much into communications thouigh but you know what , I am willing to learn something new. So i will do some homework on this and will let you know how it goes.

Thanks a bunch for the information.