HAFB UHF Trunking.
From Mike Smith N7YUO
I am employed at Hill AFB. In June, I travel to Hill AFB Range, aka 'Eagle Range', etc.
Here is the official Air Force statement about the trunking system: (In Part)
Description
Hill AFB has acquired a new state of the art trunking system that provides handheld, mobile and base station radio users radio coverage to over 30 thousand square miles including Hill AFB, the Utah Test and Training Range (UTTR, North and South) and Salt Lake City. This system also includes dispatcher centers consisting of Security Police, Fire Department, Hill Consolidated Command Post, Aircraft Directorate, Disaster Preparedness, Base Operations, UTTR Range Control, and soon 388th MOCC.
Operation
A trunked system uses repeater channels to create a communications path. Hill AFB’s system is a four site system having 25 repeater channels, 10 on HAFB, 5 at Grassy Mountain at Oasis, 5 at Cedar Mountain by Dugway Proving Ground, and 5 at Salt Lake City at the Federal Building.
OK, now that we have heard the official version, we need to understand these things:
1. The bandplan listed in RR (in my expert opinion) is not correct.
Base 406.5, Spacing 408, offset 12.5 ( Offsets are 380-759, not 12.5! )
2. Last time I checked, RR was missing one frequency
3. The lowest actual frequency is 406.5625, 19d hex, 413 dec.
4. The highest actual frequency is 410.3625, 2cd hex, 717 dec
5. The lowest possible freq (in dec) is 380. (Courtesy of RR member fmon Frank)
6. The highest possible freq (in dec is 759. (from fmon)
When you program your custom trunking table,
the low must be 413 or lower
the high must be 717 or higher
These are the correct frequencies that I have verified.
6227c1 HAFB Golf Course
DESCR=Type II NetWkd 116.3 Hz
v406.5625,19d,021,ffff,0 (Not listed in RR database)
v406.9625,1bd,041,ffff,0
v407.3625,1dd,061,ffff,0
v407.7625,1fd,081,ffff,0
v408.1625,21d,0a1,ffff,0
v408.5625,23d,0c1,ffff,0
av408.9625,25d,0e1,ffff,0
av409.3625,27d,101,ffff,0
v409.7625,29d,121,ffff,0
dv410.1625,2bd,141,ffff,0
6227c2 South Range Cedar Mtn
DESCR=Type II NetWkd 116.3 Hz
dv406.7625,1ad,031,ffff,0
v407.1625,1cd,051,ffff,0
v407.5625,1ed,071,ffff,0
v407.9625,20d,091,ffff,0
v408.3625,22d,0b1,ffff,0
6227c3 North Range Grassy Mtn
DESCR=Type II NetWkd 116.3 Hz
v408.7625,24d,0d1,ffff,0
av409.1625,26d,0f1,ffff,0
av409.5625,28d,111,ffff,0
av409.9625,2ad,131,ffff,0
dv410.3625,2cd,151,ffff,0
6227c4 SL Federal Building
DESCR=Type II NetWkd 116.3 Hz
v406.7625,1ad,031,ffff,0
v407.1625,1cd,051,ffff,0
av407.5625,1ed,071,ffff,0
av407.9625,20d,091,ffff,0
dv408.3625,22d,0b1,ffff,0
Base, Offset, and Step: How they work.
There is an article by freq of nature about Base Offset & Step. I need to get with him and help write
a new article with correct information (when I get time) Until then, I will try to present the info here.
Examples of incorrect info: "Channel number 17C hex (=380 decimal) is the base frequency"
"Channels are numbered sequentially upwards and the step between each channel in kHz is the offset."
Base Offset & Step are parts of an algebraic formula used to calculate the frequency in Motorola VHF/UHF.
Take any two frequencies and their dec numbers:
407.9625 = 20d = 525. (This freq has 525 'steps' of 12.5 kHz)
408.3625 = 22d = 557. (This freq has 557 'steps' of 12.5 kHz)
To determine the Base and Offset, I first subtract to determine an "Offset Frequency" (My terminology)
407.9625 - (525 x .0125 MHz) = 401.400. (If the step is correct, both offset freqs will be the same)
408.3625 - (557 x .0125 MHz) = 401.400. (If the step is not correct, both offset freqs will be different)
Now don't get confused !! It is simpler to calculate using MHz: 12.5 kHz = .0125 MHz.
Now to determine Base, take the Offset Frequency and add, using the lowest possible Offset which is 380:
401.400 + (380 steps of 12.5 kHz): 401.4 + (380 x .0125 MHz) = 406.15.
So, now we have:
Base: 406.15, Offset: 380, Step: 12.5 kHz. Low freq: 413 or less (I use 380) High freq: 717 or greater.
And, for further confirmation, here is an old message from K7UHP when this TSYS first went digital:
Mon Sep 12, 2005 8:54 am RE: HAFB and PRO2096 Fixed
I programmed it using the software and it now works.
I had to use the multi table and selected
the low channel at 413, the high channel at 717,
Base of 406.1500, Offset 380 and Step 12.5 and it now works fine.
All Motorola VHF/UHF trunked frequencies are identified by a Hex/Dec number.
This is simply the number of Steps upward from an "Offset Frequency"
The Offset is simply the number of Steps downward from a Base frequency.
Base - (Offset x Step in MHz) = Offset Frequency.
Offset Frequency + (Dec x Step in MHz) = Operating Frequency
