Base-step-offset

[brucewarming]

Ok, I want to learn for myself on how to figure this out, but even looking around at the other postings, I'm lost.
I see where postings say base+ch+step size, off set or something like that. I have imported the latest W.V. Interoperabilty into win 96 and loaded to the scanner, theres TWO (2) custom tables which I also loaded and have bank and ch's set to MO, also the listed talk groups.The local tower N. Mountain (Berkeley Co.) has a active control channel-
460.1625 CC
460.2375
460.3625
460.6375
So if someone is willing to help me learn this. Using this freq group Base freq is? And how do I come by that freq? then the step would be? Again how do I get that number? And then the offset?
For the time being would it be good to have a seperate bank just for the N. Mountain site? I do know the whole system is under construction and I would like to keep up with it to completion. Thanks

 

[johnyvico]

there are some system that have mutli base and off set . if u make the doantoin to this site like i did for $5 , you import win96 to this site . and it will fix all that for u . but if u want to do it manully . first go the the right page on here that has your city . and the freqs . it should have a box with the base offset then size , if there is none this its normal . your pro 96 wich i have is atoto set to 406.00 for freq 380 offset and 12.5 step . it only need to changed if it says so in the freqs . if u need more help leave me a message on here

 

[brucewarming]

I'am a member and have did the down load from the data base and installed it to the scanner (PRO 96)with win 96.
I was asking on how these numbers are come by. The math to it. Base, Step, Offset. Thanks

 

[basstuba]

please check your pm.there maybe info that might can help

 

[SCPD]

I'am a member and have did the down load from the data base and installed it to the scanner (PRO 96)with win 96. I was asking on how these numbers are come by. The math to it. Base, Step, Offset. Thanks

Hi Bruce,

There's nothing magical here - maybe some algebra but not much else. You have a set of channels. Each channel has a number and a frequency. There happens to be a mathematical relationship between the two. For me, the easiest way is by example so here goes ...

Suppose channel "A" is known to the trunked system as 400 and has a frequency of 406.9 Mhz.

If this is the lowest numbered channel on the system you could use this as your base and offset. You need at least two frequencies to make a guess as to the step value.

Basic formula is ...

Frequency = Base + (channel # - offset) * step.

So for channel "A" above ...

Frequency = 406.9 mhz + (400 - 400) * step ... since 400 - 400 equals zero and zero times anything is zero, we get 406.9 MHz for channel A.

This only works for the first channel. To complete the formula for use with other channels - we need a step size.

Let's add a second channel to this ... channel "B" is at 407.9 MHz and is known on the trunked system as channel 440. The distance between channel A and channel B in Mhz is 1.0 MHz. The distance between A and B in "steps" is 440 - 400 = 40 units. The step size times this distance should equal the difference in Mhz between the two channels.

Some algebra ...

Step * (440 - 400) = (407.9 - 406.9)

Step * 40 = 1.0 Mhz

Step = 1.0 Mhz / 40

... so ... Step = 0.025 Mhz (ie. 25 khz).

So using a base of 406.9 Mhz, an offset of 400 and a step size of 25 khz would work for channels A and B. If we're lucky, additional channels will also fit this formua.

The messy part is when you get some channels that don't fit. Separate them from the ones that do fit and try to find a new base / offset / step size that works for them.

You may end up with one, two, or more sets of base / offset / step size when you're done.

-rick

 

[brucewarming]

ok, thank you, I will monkey with that for awhile and see how I do! I'll let you know.

 

[brucewarming]

win96 help

I had been having problems with getting the (win 96) help file open, so I was missing alot of reference there. I got it open after posting last, that also gives me some more information to work with.