When we’re thinking about SIGINT, excessive power and bandwidth are not conducive to a low-profile survival radio strategy!
It’s often quite difficult to connect all the dots on the blog and channel. Hopefully this post can help! One side of it is avoiding detection when we’re thinking about signals intelligence (SIGINT). Every time a PTT is pushed, a timer begins. It’s only a matter of time before someone figures out who we are, where we are, and what we’re doing. In everyday life, this is no big deal. When SHTF, we should have a better understanding of physics. Although it isn’t explicitly said on the channel, reducing my electromagnetic footprint, is a big part of the program. Let me explain.
Many of us start out in the preparedness Community proclaiming our intention to buy a radio like the Yaesu FT-857, which is an extremely fine radio. In fact I’ve owned one of them in addition to an FT-897. Both are/were fine rigs! When operators get those radios out in the field, we often do so without thinking about the amount of output power we’re using. Generally that’s 100 Watts. This often happens because we’re still mixing up amateur radio for DX versus amateur radio for preparedness. The seasoned operators understand the concept of using only enough power to make the contact, but we’ll come back to this shortly.
Other operators start off with V/UHF radios for “squad” level voice communications. Many of the latest V/UHF models have more than 5 watts output for greater range. In a way that higher output power is pure marketing, but we’ll come back to that in another post. Like our Yaesu FT-857 manpack brethren, there is this mistaken believe that the radio has one setting for output power. Usually that is the “high” setting, regardless of the antenna connected to the radio or distance to the receiving station. The fear is, we must use as much power as available, to get the signal through. This is not wrong, but physics can offer some alternatives.
Here’s the thing. Voice Communications on FM, DMR, DSTAR, SSB even packet and APRS are extremely wide! Wide bandwidth voice or data modes require much more power to be effective than a narrow mode like JS8. The wider the bandwidth, the more power it takes to get that signal out into the world! The narrower the signals bandwidth, the further that signal will go, on the same amount of output power. Because of that narrow bandwidth, we can reduce our output power, without losing much effectiveness. At the end of the day, survival radio is all about “Reliable & Effective Communications”.
You often see me talking about radio efficiency on the channel. This is often connected to the “how we power our radios” discussion. It’s also related to the amount of power we need to get our signals out. Wide bandwidth signals like voice modes, require an awful lot of battery power to push those signals out into the world. Think about it like the difference in shooting a shotgun slug versus 5.56 NATO or even a .22 out a couple of hundred yards or meters. Think about the energy it takes to get that slug down range versus the smaller round. They’ll definitely both make it down range, but one will make it down range with much greater efficiency (less energy) than the other. The shotgun shell is like our wide bandwidth voice modes and the 5.56 is like JS8. Another good analogy is spot light versus the flood light. A spot light can reach farther, but effectively focuses on a single point. A flood light spreads its light over a wide area but doesn’t go very far. Does this make sense?
OK, so what does all this have to do with SIGINT? Lets look at the next image.
Each of the narrow squiggly lines in the above image is a signal. Powerful signals are easy to see, as they are much brighter in the waterfall. From midway in the waterfall to the right side of the waterfall, there are strong signals. These signals are easy to spot, for the SIGINT operator trying to detect or listen in on your communications. Now look at the waterfall again. This time midway in the waterfall and to the left. There are still signals present in the waterfall, but they are using much less power. Some of them are even using less bandwidth than others. There are also some which are almost impossible to see with your naked eye, but they are there! Those difficult to see signals often get passed over by a human, as they are indistinguishable from background noise with the naked eye. If we use lower power, it will be more difficult to see our signal. Using lower power also makes it more difficult for a human to hear our signals while receiving. Combine that with narrow bandwidth data modes, we are effectively hiding in the noise. Civilian SIGINT operators rarely have the level of sophisticated communications gear, to dig a -23db signal out of the noise. Add in a high noise floor, and that station becomes quite blind electromagnetically speaking.
You see, because of the operator fatigue envolved with scanning the waterfall for our signals manually, civilian SIGINT operators are focusing on strong, wide signals. Signals which are easy to see or hear in the waterfall. Government, Military and NGOs most certainly automate the signal detection process. For them it is better to fly low and avoid the radar. Even so, from the moment our signal is detected, there is a chain of command and logistics process initiated, before any action on our signal will take place. How much time is our best guess.
I understand this is an advanced survival radio topic and more abstract than most. Apologies for that, but it is what it is.
- Understand the electromagnetic footprint of your chosen mode.
- Use as little power as possible to reduce that footprint.
- Make up for using lower power by using narrow bandwidth data when possible.
- Take advantage of the increased operating time and greater efficiency of narrow bandwidth comms.
- Take advantage of the increased security of low power, narrow bandwidth comms.
- Understand how low power and narrow bandwidth can also reduce your comms loadout.
- Incorporate modes like JS8Call, VarAC 500hz, VaraHF 500hz, into your communications plan.
- Utilize NVIS to further mask your RF footprint from civilian eavesdroppers.