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Graham McIntire 2026-04-18 17:40:32 -05:00
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@ -4,35 +4,39 @@ date = 2026-04-18
draft = false
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How can microwave contacts be made non-LOS is a question I've had for a while now.
From running a WISP I'm very familiar with point-to-point microwave links. However,
amateur radio operators have been making NLOS contacts for years when they technically
shouldn't work at all.
How to make microwave contacts non-line-of-sight (NLOS) is a question I've had for
a while now. From running a WISP I'm very familiar with point-to-point microwave
links. However, amateur radio operators have been making NLOS contacts for years
that technically shouldn't work at all.
As an example, this is the elevation path between my QTH and an [NTMS beacon on top of Texas
Women's University's dorm building](https://prop.w5isp.com/beacons/dddca785-c3e7-45f8-8f9f-edc748f881d6):
As an example, this is the elevation path between my station and an [NTMS beacon on top of Texas
Woman's University's dorm building](https://prop.w5isp.com/beacons/dddca785-c3e7-45f8-8f9f-edc748f881d6):
![Path profile](/images/path_profile.png)
This lead to a deep rabbit hole to investigate why contacts work some times and HOW they work.
There are already known propagation methods such as EME (moonbounce) or rain / meteor scatter,
however it's also possible to form ducts within the lower levels of the atmosphere with favorable
conditions. An easy to understand demonstration is why sometimes ships appear like they're floating:
This led to a deep rabbit hole to investigate why contacts work sometimes and HOW they work.
There are already known propagation methods such as EME (moonbounce), rain scatter, and meteor
scatter, but it's also possible to form ducts within the lower levels of the atmosphere with
favorable conditions. An easy visual analogy: ships sometimes appear to float above the horizon.
![Atmospheric ducted ship](/images/atmospheric_ducting.jpg)
This is because there's a duct with favorable conditions for refracting visible light -- the same
thing happen for microwave.
This is because there's a duct with favorable conditions for refracting visible light — the same
thing happens with microwave signals.
At one of the [NTMS](https://ntms.org) meetings, KM5PO presented about this same thing and had used
claude to write out some client-side pages to help predict and analyze the propagation. It was based
on limited data, but did an okay job guessing at why the propagation worked.
At one of the [NTMS](https://ntms.org) meetings, KM5PO presented on this exact topic and had used
Claude to write some client-side pages to help predict and analyze the propagation. It was based
on limited data, but did an okay job guessing at why the propagation worked. That talk is what
kicked off this project.
Fast forward a few weeks and I've now build an elixir/phoenix app at <https://prop.w5isp.com> that
collects and processes everything. For a quick import of some known contacts made, I imported all
of the ARRL 10 GHz and up contests as well as the 222 MHz and up contests.
Fast forward a few weeks and I've now built an Elixir/Phoenix app at <https://prop.w5isp.com> that
collects and processes everything. For a quick import of some known contacts, I pulled in results
from the ARRL 10 GHz and Up and 222 MHz and Up contests — VHF/UHF/microwave events where stations
log long-distance contacts on those bands.
With known contacts in place, it was time to backfill them with data, including:
With known contacts in place, it was time to backfill them with data. To predict ducting we need
atmospheric data at fine vertical resolution, so the app pulls from a mix of weather models,
surface observations, upper-air soundings, and terrain:
### Atmospheric
* HRRR (NOAA 3 km) — hourly f00–f18 propagation scoring hot path; native hybrid-sigma levels for fine-grained duct detection
@ -58,17 +62,20 @@ have now been backfilled with this information. Feeding all of this in to Claude
[algorithm](https://prop.w5isp.com/algo) that understands and can predict future conditions based
on weather data.
This algorithm gets turned in to code, and then we can fetch HRRR data hourly, amend with ASOS
when available and feed it through the algorithm to determine if any given area's atmosphere is
favorable to propagation. Our predictions are still estimated and may not have any bearing on
reality.
This algorithm gets turned into code, and then we can fetch HRRR data hourly, amend with ASOS
when available, and feed it through the algorithm to determine if any given area's atmosphere is
favorable to propagation. The predictions are still experimental and not yet validated against
enough real-world contacts to be trusted.
Now our mission is to continue collecting as many verified contacts on 50 MHz and up and enrich
to refine our prediction model gradually over time. Another sub-project is automated beacon
monitoring. Any NLOS beacon that can be automatically monitored continuously provides an enormous
amount of data to train our model with since both points are known.
Now our mission is to continue collecting as many verified contacts on 50 MHz and up (the bands
where ducting and other exotic modes are most useful to amateurs) and use them to refine the
prediction model gradually over time. Another sub-project is automated beacon monitoring. Any
NLOS beacon that can be monitored continuously provides an enormous amount of training data,
since both endpoints are known and fixed.
The effort to expand has been growing and we now have help from a senior meteorologist in Lubbock,
Tx and many hams helping submit verified contacts. If you'd like to help out, we need as many
contacts during non-contest times as possible and future automated beacon monitoring. You can reach
me at my first name at my last name dot me (it's in the footer.)
The effort has been growing and we now have help from a senior meteorologist in Lubbock, TX and
many hams submitting verified contacts. If you'd like to help out, we need as many contacts as
possible during non-contest times — contest weekends concentrate activity into a few days, but
the model needs samples spread across all conditions. We also need volunteers for future
automated beacon monitoring. You can reach me at my first name at my last name dot me (it's in
the footer).