On my last Deployment to Iraq, I went to a crash course class on Spectrum Management for terrestrial frequency engineering. An important component missing from the class was how to determine the Emission Designator codes using FCC guidelines. Normally, this is not an issue in the military because all RF systems are well documented. The problem arose when new civilian models of equipment were introduced into southern Iraq for preparation of standing up the Consulate. Frequently, the owners of the equipment would not have the technical specifications of the equipment or a vendor point of contact. I would locate the information required by Internet searches or receive the information by going through the various levels of personnel at the vendor to reach the one that understood what I was looking for. There were always a couple pieces of equipment that, at the time, were difficult to find any information for.
The Emission Designator code is used in our database, Spectrum XXI, to identify the type of signal coming from a device, and how it will be affected by known signals already in the database. Spectrum XXI is the database that is connected with the FCC to de-conflict and request updates or new frequencies for systems. Without the Emission Designator the inputted request frequency has no size, it is just the center of a carrier that occupies zero space on the spectrum.
Step 1: Solution
I decided to self-study the FCC codes and known similar models of hardware to understand how to properly code the Emission Designator. At the time, I could only find information on the FCC website and a couple of forums that were not restricted by our government network. The senior personnel that trained me insisted that the owners of the equipment must bring in the technical data before issuing them a frequency. This was not a current option due to time constraints.
Step 2: Learning Phase - Getting Started
I started easy with one of our basic radios, a RT-1523. I knew how it functioned and its Emission Designator, 25K00F1E. Using the FCC website, I broke it down to sections.
25K - Carrier Bandwidth
00 - Unknown
F - First Symbol
1 - Second Symbol
E - Third Symbol
This looked off to me because of the unknown factor. I looked at a few other Emission Designators and realized that the 00 is part of the carrier.
25K00 - Carrier Bandwidth
F - First Symbol
1 - Second Symbol
E - Third Symbol
This makes much more sense. The carrier bandwidth code uses the two spaces behind the hertz level code to show that the carrier size is partially less than the given hertz level code.
Hertz Level Codes:
G – Gigahertz
M – Megahertz
K – Kilohertz
H – Hertz
An example would be 1M20. This would stand for a 1.2 Mb carrier. I have not seen the G or H codes used in my work so far, but they are understood values.
Step 3: Learning Phase - 1st Symbol
For the other three symbols, FCC does provide charts. The most commonly used symbols for the First Symbol for military equipment are:
N – Emission of an un-modulated carrier
J – Single-sideband, suppressed carrier
F – Frequency modulation
G – Phase modulation
The symbol N is used to setup a test frequency range for equipment in certain areas. This allows the operators to make hardware and programming changes without running the risk of causing interference with another system.
For our HF nets we use the J symbol. All of our current Military HF-ALE nets use this type of emission and it is based on Amplitude Modulation. AM naturally produces a two-sided carrier that uses more spectrum bandwidth. By removing one of the sides, that bandwidth is available again. The downside for this method is the cost and complexity of the hardware for the radio increases.
Symbol F is used for most of our point-to-point radio systems use. By adjusting the actual frequency being used, the carrier is modulated.
The next symbol, G, is most commonly used for data applications as it allows more modulation changes for higher bandwidth on the same size carrier as the others. Modulation is accomplished by shifting the oscillation of the wave by a set number of degrees. There are usually different levels of modulation settings available on hardware that uses Phase-shifting keying.
Step 4: Learning Phase - Second Symbol
The Second Symbol has to do with the information being modulated. Here are the most common military used symbols:
0 – No modulating signal
1 – A single channel containing quantized or digital information without the use of a modulated sub-carrier
3 – A single channel containing analog information
7 – Two or more channels containing quantized or digital information
The 0 (zero) Symbol is once again used for test carriers that just need a blank space of spectrum and power.
The 1 Symbol is used with several civilian radio systems that the Military uses for quick deployment.
Symbol 3 is used for most voice communication radios. Some of the radios can send data, but they do not use this symbol when doing so.
The Symbol 7 is used for our data communications.
Step 5: Learning Phase - Third Symbol
The last or Third Symbol is for the type of information being transmitted:
N – No information transmitted
D – Data transmission, telemetry, telecommand
E – Telephony
W – Combination of the above, including the others not listed within this sheet.
The D Symbol is almost always used for any data communication since most of our video and audio go through encoding before being broadcasted. The Symbol D is not used when items are not encoded.
Plain audio for voice is coded as the Symbol E.
When the above are all mixed together and not server-side encoded first, you must use the Symbol W.
Step 6: Working With Similar Civilian-off-the-shelf (COTS) Systems
Going back to my original issue, the radio that these personnel wanted to use was not a brand I could find any information on. So, I used a spectrum analyzer with the radio to see how large a carrier wave it would produce in its current setting. I found it to be just slightly larger than an 8Khz carrier. I went looking through the Internet for a hand held radio that had an 8K*0F1E Emission Designator. The most similar system to the off brand radio I found was the Motorola XTS 5000 Radio. The XTS 5000 does use 8K10F1E for one its settings. I researched what information I could find on this designator code and found it to be a baseline FCC approved Code.
Step 7: Final Product for the COTS
Finally, I then developed a small specification sheet on what I could tell about the radio. This would allow any future operators to have the information needed to work with a Spectrum Engineer in developing any additional frequency assignments. In the end, the personnel that come in to help setup the Consulate were able to use their systems legally in Iraq without issues.
Step 8: References
For Emission Designator info:
RT-1523: FM 6-02.72 dated JUN 2002
HF-ALE: FM 6-02.74 dated SEPT 2003
Motorola XTS 5000 Radio