Beyond LOS (Line of sight)

In preparedness, we can often rely too heavily upon VHF and UHF Communications, with lightweight and portable handheld radios. Let’s discuss how to mitigate the potential failure point.

One Communications plan includes VHF UHF handheld radios. Either the analog Baofeng type, DMR radio, or other digital protocol. These radios are excellent for short-range communications on VHF and UHF. Where they fail is beyond line of sight communications, or in heavily congested urban areas, where their reliability is reduced.

Scenario

Repeaters are down, the Internet is out. Your group has unexpectedly spread beyond Line-of-sight (LOS), and your fallback Rally Points are compromised!  How communications with the entire group will be re-established, is a question that usually goes unanswered!

Beyond line of sight means your VHF UHF radios no longer work, because you’re out of range of one another. VHF & UHF radios rely upon LOS for their effectiveness. Even the clever marketing of the “high power” radio, won’t defy the laws of physics. That extra power could be helpful IF it was put through an effective antenna.

Extending our VHF or UHF range can be achieved without infrastructure, by using yagi antennas. Although this type of antenna can help radically increase the range of VHF and UHF signals, it also adds to the amount of equipment we carry.

Fallback plan

NVIS has no infrastructure requirements. It is reliable on 160, 80 (mostly night), 60 (day & night), and 40 meters (mostly day into early evening and again in the early morning). The most effective man-portable antennas for NVIS are OCF, Fan or half wave dipole antennas placed horizontally, no more than 1/8 wavelength above the ground (full wave horizontal loops are also effective). A tuned, attached or detached reflector underneath the radiating element, will also help performance. There is no exact configuration that always works! So testing various configurations will give you the best examples of what works for you. Just keep in mind, that NVIS works best when both stations are set up for NVIS communications.

NVIS allows communications from 0-350 (approx) miles in all directions. It doesn’t require much power, especially when using narrow bandwidth data modes.

HF NVIS is used to fill in coverage gaps in a primarily VHF/UHF comms strategy. Although real-time voice is possible, my test results suggest the mode is best utilized, with Asynchronous Messaging over a narrow data mode. This provides the most efficient use of the gear, power reserves & available time.

Although I haven’t specifically done a video on asynchronous data modes and nvis, I have put together a playlist of videos relating to both of these topics.

Asynchronous Emergency Communications | OH8STN Ham Radio:

There are several applications allowing effective Asynchronous communications.

  • JS8Call
  • VaraAC
  • Winlink with VaraHF
  • P2P Winlink with VaraHF

Conclusion

If your group communication plan is heavily reliant on VHF and UHF radios, consider a fallback plan using HF NVIS. It will require gear investments, routine training, and the intention to reinforce a traditional VHF UHF Communications strategy. The benefits outweigh the pain! If your group finds itself forced into an unplanned withdrawal, NVIS may be the only way, to safely coordinate a new Rally Point. Remember, without a functioning repeater, the internet, or LOS, that brand new digital radio will at best, become a boat anchor.

Food for thought!


Lots of effort goes into these posts. Researching each component, software application, strategy, pragmatic field testing. When you see these posts, the mistakes and blunders have already been filtered out. If you find any value in that, share this post and/or buy me a rootbeer.

73
Julian oh8stn
YouTube http://www.youtube.com/c/oh8stn
Buy me a rootbeer: https://paypal.me/oh8stn/2usd

Spread the love

7 Comments

  1. We just had a club member help with coms for a 200 mile race around Mt Rainer (Washington state) and they used NVIS, winlink, and of course some repeaters where they could. Super cool. I then suggested he bring his set up to the next town event where the club has a booth.

  2. Good stuff, Julian! Asynchronous Communications (messaging) via NVIS should definitely be practiced and used for VHF and UHF, but In the quiver of capabilities don’t forget to also practice VHF / UHF SSB.

  3. Hey Julian,

    Thanks for all you do – I have been a follower since the earliest battery builds!

    Question: Why do you steer towards JS8Call over infrastructure-free modes like FSQ or THOR?

    I do know the modulation/signal benefits of JS8Call, but my understanding is that it requires precise time-sync. Perhaps your scenario planning is different, but if the internet and power is down I do not expect to be able to rely on GPS. They require continual maintenance from the ground, can be cut off at any time, or limited to Mil/Gov only.

    As I’m sure you know, some FlDigi modes don’t have this limitation. Given that we all have limited time to train, and our comms groups can only juggle so many modes and different software, wouldn’t it make more sense to focus on one of those for keyboard-to-keyboard chat?

    Thanks!

    • Excellent question.
      The time sync issue is the single irritating thing about JS8Call. Fortunately, it was improved by the implementation of a time delta. The tie delta allows operators to sync their start and stop times based on the other signals on frequency. JS8Call will even tell you how fast or slow off delta our station is.
      With that said FSQ is very nice but requires much more output power to be effective, compared to t0 JS8Call, FSQ doesn’t have very good weak signal decoding capabilities, or range of speeds slow, normal, fast, turbo, allowing various types of extremely sensitive to extremely fast (adaptive) mobes available. Using normal mode, 10 watts and a dipole are enough to be heard across the EU and other continents.

      The asynchronous and Store-n-Forward capabilities of JS8Call are amazing features. One does not need to sit in front of the station, to send or receive a message. JS8Call is a network (literally). Most other modes are designed for the operator to sit there waiting for a message to come in. In a real disaster, there are surely more critical things to do. So my radio should be able to manage the collection or transmission of a message for me, even if I leave the keyboard.
      There is another tool recently released called VarAC. It uses the VaraHF modem which also has very good weak signal performance. It is a work in progress but has asynchronous messaging and store-n-forward capabilities planned like JS8Call. It has no time sync requirements, and can be left idle as part of the network. Ultimately, it is the networking functionalities I’m after.

      About FLDigi. It is too much IMHO. It tries to be everything but ends up doing nothing well. The FSQ implementation is OK at best, but better than the authors’ own published apps (to be fair). I used the FLDigi FSQ implementation, WEFax, PSK, Olivia, … but was never happy with the FLDigi GUI. I love the concept, but prefer tools which are designed to do one thing very well.

      Thanks fo the awesome question.
      73
      Julian oh8stn

  4. Julian,
    Thanks for your detailed reply on JS8 vs the FlDigi modes. That all makes sense.

    I recently tried VarAC for the first time and it was AMAZING. It was SO EASY even compared to JS8Call, much less trying to get FLDigi to work.

    My only complaint is that it does not have a viable group-chat option yet. (I know you can use monitor mode). I am hopeful that will be developed.

    Either way I plan to focus on VarAC mostly going forward.

    P.S. just FYI I’m having a lot of trouble with your WordPress comment system – sometimes comment doesn’t post and I get “nonce” failure” notice. I am unable to reply to your last comment on Firefox or Chrome (via Fedora). and something with the CSS around the comment form hides all the other required fields (name, etc) – can only get to them by tab. You can delete this part, but thought you would want to know – I couldnt find an email address for you to let you know.

Join the discussion

This site uses Akismet to reduce spam. Learn how your comment data is processed.