Ok, sorry about that.
For VHF and UHF systems you have a base frequency and a spacing (5.0, 6.25, 12.5kHz, etc). Any system in these bands has a table which is programmed in both fixed and mobile equipment to provide the values to calculate operating freqencies.
To perform the calculation you need to at least know one frequency and a hex id which the system uses to represent that freq. First thing....you take the hex id and convert it to decimal (via Windows calculater). You then multiple the spacing in the MHz range (i.e., 12.5 is 0.0125) and multiply it by the now channel decimal id. You then subtract the frequency from the value returned. Whatever value you are given will be used to apply against the other hex/decimal ids to derive a frequency. Here's an example:
What we know: $189 = 406.1625
$189 converted to decimal is 393
(393*0.0125) - 406.1625 = 401.25 (401.25 is the common value)
Take a hex id we don't know the freq for and apply the above plugging in what we do know...
$1FB = 507
(507*0.0125) + 401.25 = 407.5875
Therefore $1FB = 407.5875
Simply put, every increment from $17C is the spacing increment of the frequency. If your combo is 406 (Base = $17C) and 12.5, then $17D is 406.0125, $17E is 406.0250, $17F is 406.0375, and so on.
Now, there is a catch. The technique I referred to above, and the style LLNL uses, is one that uses only one base freq and spacing. With these types of systems you can have up three different ranges which means you can have three different base freqs with their own independent spacing. With a system which only uses one range you can have available to use up to 380 frequencies. If you want or need another frequency range you must have each range equal, together, 380. So one range could be 180 and another 200 frequencies. You have to have a combination of base freq and spacing to fulfill the ranges without breaking the rules.
The first range (or base freq) will always start with a hex id of $17C. Anytime you ever see $17C used and can figure it out you have your base freq for the first (and possibly only range). Any hex id below $17C is used as mobile transmit and isn't important enough to calculate. It's only needed to pair up with the mobile receive within Trunker so that radio ids can be associated with their group call.
So in theory you could do 406MHz to 407.5000 with a 25kHz spacing and have another range of 410 to 411 with a spacing of 12.5kHz. One of the rules is that any range cannot start or end within another. Soif we used 406 to 408, a second range could not have a base freq of 407. It would have to be higher than 408.
I've written more on this subject and have it available at my website. In addition is a spreadsheet to help figure these systems out. It requires a bit of knowledge on these systems beforehand but it allows you to calculate just about anything needed. The URL is
http://tricari.home.attbi.com/download.html.
Btw, Travis AFB is an example of a system which uses two ranges. You can do a search within the forums to read more about it.
-Wayne
