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.
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.
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.
- Winlink with VaraHF
- P2P Winlink with VaraHF
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.