mpdonala said:
I actully put the scanner in scan with trunker running and when the line lit up on unitrunker I worte down the freq that it showed. I verified it several time when that situation occured and everything was the same each time so I added the freq like you told me thanks I'll give it a try. So are you saying it is the same base step and offset for both sets??? Thanks Mark Could you give a break down on your equation I am trying to figure it out. Thanks
Wow ... very impressive.
Oh crud.
That means this is likely a multi-table system. You will need two or three table entries for each system. It also looks like the tables will be different for each site. Sorry Mark, you picked a hard example. Let's deal with one site for now ... there one where CC == 407.7625 mhz.
There's a big jump in frequency from channel 200 to 208. Delete channel 210 from this site. It belongs on the other site.
Keep the other base/offset mentioned above. The LCN Low will be 380 and the LCN hi will be 519. Suppose the second table will start at 520. Here's why: let's use channel 208 as the start of the second table. 208 hex is 512+8=520 decimal. The frequency at this channel happens to be 410.4625. We'll use that as the base. Need a guess for the step size. The next channel after 208 (520 decimal) is 20D (512+13 = 525 decimal) at 410.7250 mhz.
The distance in megahertz between these two channels is 410.725 - 410.4625 = 0.2525 mhz which is the same as 252.5 hz. The distance in channel #s between these two channels is 525 - 520 = 5. That would suggest a step size of 252.5 / 5 = 50.5 khz - which is a very unlikely step size. We're looking for something like 12.5 or 25 khz. We'll set aside this channel for now and look further down.
The formula for a bandplan table entry ... takes the channel # from the control channel to calculate a frequency.
The formula is Freq = Base + (channel # - offset) * step.
There's more info on the Wiki (I'm too lazy to type out more).
I'm guessing channel 525 is suspect (perhaps not the correct frequency). Looking further down though ... look at channels 29A and 29B. Those are right next to each other and with a difference of 12.5 khz. That suggests a rational step size for at least these two channels.
Look at channels 2A0 and 2A8. These have a channel distance of 8 and a frequency distance of 0.1 mhz. Divide 0.1 mhz by 8 gives you 0.0125 mhz - or 12.5 khz. Another good sign.
We know they have the same step but are channels 29A, 29B, 2A0 and 2A8 in the same table (have the same base/offset)? Plug in some numbers to see if it works. Use channel 29A as your base and offset.
Base = 412.2875
Offset = 666 (aka 29A in hexadecimal)
Step = 12.5 khz
Plug channel 29B into the above formula ...
Freq = 412.2875 + (667 - 666) * 0.0125 = 412.2875 + 0.0125 = 412.3000 mhz.
Does that match 29B ?
Plug channel 2A0 into the formula ...
Freq = 412.2875 + (672 - 666) * 0.0125 = 412.2875 + 6* 0.0125 = 412.3625 mhz.
Does that match 2A0 ?
You may want to play around with using 280 or 265 as the base / offset. It may include all of the above channels plus lowered number channels. This isn't definitive but should put you closer (give or take a channel).
-rick