07 February 2022


Last ditch radio, or LDR. Think about it. All around you has collapsed. Weather, earthquake, fire, terrorism, loss of civil order (which often follows all other forms of disaster). 

You need to communicate, not among yourselves (you've got that covered with handheld radios), but with family members, friends and emergency response personnel well outside of the impacted zone. You need a reliable radio that has enough capability to provide assured communications and can survive extended use in an austere environment - outdoors, in inclement weather, subjected to rough handling. Reliability trumps capability, but there are some things we can't live without. Let's look at the operational requirements.
  1. Long-haul voice and digital communications - a minimum 300 mile reach on each mode under current solar cycle conditions
  2. Direct interface with a computer via USB or wireless (WiFi, Bluetooth)
  3. Integrated soundcard interface for digital modes (no external soundcard hardware)
  4. Either integrated Automatic Link Establishment 2G (ALE2G) or the ability to operate in 'quiet scan' mode when driven by an ALE software application (PC-ALE, Ion2G)
  5. 50% duty cycle operations - can run long duration digital mode operations without overheating or component failure
  6. Provision for integrated battery power (either internal or in an attached and integrated case)
  7. Minimum 100 watt output on external power sources / 20 watt output on integrated battery power with 6 hours of 50% duty cycle operation from each power source
  8. Internal antenna tuner capable of handling a 10:1 impedance mismatch
  9. Wide-band TX on HF (the 'MARS mod')
  10. IP67 rated for water and dust protection (includes the microphone or handset)
  11. The radio, integrated battery, microphone, power and computer connection cables and documentation must fit in a Pelican 1520 or equivalently sized protective case
No Amateur radio on the new or used market meets all these requirements. A few do come close. However, to meet all of the requirements I've laid out you'd need to turn to the high end MILSPEC manufacturers such as Harris, Barrett and Codan, This means using off-the-shelf equipment from any of the 'big three' (Icom, Yaesu, Kenwood) amateur radio manufacturers will require some compromise.

The easiest requirement to meet is #1 - a 300 mile reach. Just about any radio on the market that has a 10 - 100 watt output will meet this requirement. Ten watt QRP rigs like the Elecraft KX series, the Icom IC-705, the CommRadio CTX-10, the Xeigu 5100, the Lab599 TX-500, and even the Yaesu FT-818 (6 watts max) can reliably reach out 300 miles, particularly on low power digital modes. Of course, the more TX power the the greater likelihood that you'll reach where you need to reach. One hundred watts of output can provide a much greater assurance you'll be able to make contact. A last ditch radio shouldn't be an exercise in QRP operations. As Tim the Toolman Taylor would say, "More power!"

The hardest requirement to meet, and one that NO current Amateur radio HF rig meets, is #10 - IP67 rating. Virtually all rigs on the market - new and used - are wide open to water and dust. I know some of you are screaming "What about the new Lab599 radio?!" Fair question. Clearly, the Lab599 TX-500 looks like it's fully sealed, and the manufacturer touts its weather resistance. But it's not IP67 rated. In fact, it doesn't carry any IP or other industry standard rating for environmental protection, which I find odd. Still, reports from the field so far seem to be good, and nobody reports any issues with water or dust ingress. So we'll say that the TX-500 likely meets the IP67 standard, but it also falls woefully short in other areas.

Some of the requirements are, I think, fairly obvious - sound card interface, internal tuner, integrated battery. But why the need for things like ALE capability and wide band TX? Let's start with wide band TX. When things go south I'm not going to be too concerned about staying within the Amateur radio band segments. I'm going to want the ability to come up on the HF frequencies used by DHS, FEM, SHARES, MARS, etc. Many Amateur radios on the new and used market can be modified for wide-band transmit. Most require a simple hardware mod (remove some diodes or create a solder bridge across some open pads), but I particularly like how Elecraft handles it for the KX line - it's just a simple firmware update. 

What about ALE - Automatic Link Establishment? Amateur radio operators don't play around all that much on ALE. There is a small and dedicated Amateur ALE community (hflink.com), but most Amateurs don't see a fit for ALE in how they operate. However, ALE is in wide use in the commercial, federal and military communications spaces, and is becoming increasingly important in the MARS and DHS SHARES communities. ALE simply adds another layer of assurance to any communications plan. When not actively communicating during a disaster event, you can run an unattended ALE monitoring and sounding session to better determine what frequencies work best at any given time. Many commercial and military HF radios have ALE built into their firmware. The best example I can give is the Icom F8101, a commercial mobile HF radio that does see some sales into the Amateur radio community. The F8101 has ALE G2 built into the firmware. You simply program the ALE frequencies you want to scan into the radio, and off you go. But no Amateur radio I'm aware of offers embedded ALE. The best we can hope for is driving a suitable HF rig using one of two ALE software options running on a connected computer - Ion2G or PC-ALE. What makes an Amateur radio 'suitable'? A suitable radio is one that operates in what's referred to as the 'quiet scan' mode when operating split mode. The quiet scan mode bypasses the band filter relays during scanning. You don't hear the constant 'clack-clack-clack' as the filter relays engage during the scanning process. Since many of these relays are mechanical, they can actually be worn out by the scanning process. A number of modern rigs (but not all) use diode switched filters instead of mechanical ones, and can be used for ALE even if they don't have 'quiet scanning' capability. This includes a variety of Kenwood, Yaesu and Icom radios (check the HFLink website for more details). In theory any modern Amateur radio can work on ALE if you are willing to put up with the noise. I'll do an in-depth discussion of ALE in a later post.

The last consideration is portability. You need to be able to carry the complete setup - radio, mic, cables, documentation - in one hand. The Pelican 1520 has proven to be an ideal size - large enough to accommodate most radios but easy to carry in one hand. Any hardened case of equivalent size will do, but keep in mind that this case also helps mitigate the fact that Amateur radios are not environmentally protected. The case becomes a surrogate IP67 rated enclosure, protecting against moisture, dust, shock, etc. It pays to buy quality. Pelican cases are actually industry rated for protection against moisture and dust intrusion. The Harbor Freight knock-offs, not so much.

When I started to write this post several months ago I really didn't have an ending in mind. The concept of the last ditch radio was just rattling around in my head and I wanted to get things down to see if I could turn it into a post. I've returned to the topic several times since, and finally decided it was a topic worth maturing out into a formal post. Part of it was my recent writing on hardened laptop and tablet computers. Part was my continuing investigation of ALE. Part was some recent world events like the volcano eruption near Tonga in the Pacific and the devastating tornado outbreak in Kentucky this past December. Mother Nature and human nature will have their way, regardless of the measures we take. It's up to us to be prepared.

In looking at my personal radio arsenal I've got several good candidates. Nothing I own comes close to fulfilling all the requirements, but one radio I own comes close. The Icom IC-7300. It checks most of the boxes:
  • As a 100 watt rig it has no problem meeting the 300 mile voice and digital requirement
  • Computer interface via USB is a snap
  • It has a built-in sound card interface
  • From the factory it runs in the quiet scan mode for use on ALE
  • It has a built in antenna tuner. The tuner only handles up to 4:1 impedance matches, but as long as the antenna is close to being resonant on the operating band the internal tuner handles it just fine. Otherwise I have to insert a more capable external tuner into the mix
  • It has the factory wide-band transmit 'MARS' modification (done by the retailer)
  • The radio, microphone, cables and documentation fit into a Pelican 1520 case. It's a snug fit, but it fits

Of course there's no integrated battery or power supply, and the radio is wide open to dust and moisture ingress. It needs to be used in a protected environment. But the same is true for every other Amateur radio I own - and it's the same for almost every Amateur radio on the market. For power, I have portable battery power systems (20 & 30 amp hour) that each will power the radio for up to 10 hours on 30 watt output. I can run on one while recharging the other. If band conditions are good I can crank the TX power down and improve battery run time,. If conditions are bad I can crank up the power as needed and just live with the fact that I'll need to charge my batteries more frequently.

Of course, a radio is useless without a power supply and an antenna and, if you are working digital modes, a computer. I've covered computers and operating systems for Amateur radio ad-nauseum, but power and antennas still need discussion. I'll cover those in upcoming posts.

But for today your assignment is to take a look at your personal radio arsenal and pick one that could  serve tomorrow as your LDR, and think about how you'd configure it, support it and protect it for the last ditch communications mission. Get to work. Spring storm and hurricane seasons are just around the corner.

W8BYH out

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