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Hi, Scott.

Bear in mind that PHG data is not describing the same thing as DFS data is, so what they display is not related.

PHG estimates the range an APRS station can send and receive simplex based on the station's transmitter power, antenna height above average terrain (HAAT), antenna gain, and octant of directionality of the antenna. Usually, an APRS station's antenna is an omnidirectional one, so you see a circle centered on the station whose diameter is calculated from the power, HAAT, and gain; if the antenna is directional the PHG approximation circle is offset in the specified octant direction (0, 45, 90, 135, etc. degrees from True North) where the antenna would have the most gain (on the boresite, rather than off to the side or behind the directional antenna).

DFS instead is about how well a station _hears_ one other specific station. There is no generic DFS; the stations participating in the direction-finding have to agree on what station they are reporting about, and if there are two groups of stations in an area both using DFS reports on the same APRS frequency, the display will be somewhat useless.

DFS can be reported in two different ways:

1. If the reporting station actually has a precision directional antenna (beam Yagi or an electronic phased-array) so it can precisely report a station-relative bearing to the target, the NRQ data can be used to specify the bearing to the target from the local station, and quality information about how the target was heard. YAAC can decode received bearing/NRQ data, but is not set up to help in entering such data for transmission. The station must be using the Direction Finding symbol (\/) so listening stations know that NRQ data will be included in the position report. The NRQ data appears after the reporting station's position, course, and speed, then the bearing and NRQ, for example:

010/020/045/123

where 010/020 says the reporting station is traveling on a course of 10 degrees from True North at 20 knots (nautical miles per hour), and its directional antenna is hearing the target at 45 degrees from True North with 1 number of detections, range code of 2, and signal quality of 3. YAAC plots the bearing cone from the reporting station (beamwidth inversely proportional to antenna gain), so you can look for intersections.

2. If the reporting station does not have a precision directional antenna, it can approximate the relative location of the target by reporting the signal strength the target was heard at (in S-units), and the characteristics of the reporting station's antenna (same as PHG without the transmitter power). YAAC will use this information to plot a color-coded (based on the reported S-unit) coverage circle around the reporting station where the target probably is. One reporting station isn't very useful, but if you have a collection of reporting stations, you can look for where the multiple coverage circles are overlapping together and look for the intersection; obviously, this works best if you have several reporting stations in a rough circle around where the target is. Any APRS symbol can be used for the reporting stations.

Note that you will see _nothing_ added to the other map information if there are no reporting stations actually transmitting precision bearing and NRQ or imprecise coverage circles (DFS).

Hopes this helps explain how APRS direction finding is reported and works.

Andrew, KA2DDO
author of YAAC

________________________________________
From: [email protected] <[email protected]> on behalf of Scott Gillins via groups.io <scott@...>
Sent: Sunday, April 27, 2025 10:52 PM
To: [email protected]
Subject: Re: [yaac-users] Direction finding settings don't seem to save in beacon configuration

Thanks for the reply. I have several stations around me that are announcing PHG values, however when I turn on the direction finding layer I expect to see something different on the map. What should I expect to see?

Thanks,
Scott

On Sat, Apr 26, 2025 at 7:17?PM Andrew P. via groups.io<> <andrewemt@...<mailto:[email protected]>> wrote:
Hi, Scott.

Thank you for finding a bug in the beacon configuration panel. It will be fixed in the next build of YAAC.

I'll have to think about your other suggestions. I agree, being able to quickly edit specific DFS values (after observing the RF conditions of the remote signal at the local station) would be useful. I'll have to think of a user-convenient way of doing so.

Andrew, KA2DDO
author of YAAC

________________________________________
From: [email protected]<mailto:[email protected]> <[email protected]<mailto:[email protected]>> on behalf of Scott Gillins via groups.io<> <scott@...<mailto:[email protected]>>
Sent: Thursday, April 24, 2025 1:10 AM
To: [email protected]<mailto:[email protected]>
Subject: [yaac-users] Direction finding settings don't seem to save in beacon configuration

Hey all,

I have been trying to understand some of the direction finding extensions of ARPS. I have specifically been reading from the APRS101 document starting on page 28 for the PHG and DFS data. I believe that I should be able to set this in a beacon settings. This data should then be displayed and calculated if I turn on View->Layers->show direction finding.

I can set some data for DFS in the beacon settings, make sure to save the settings. When I beacon I do not see the data in the packet and when I go back into the settings for the beacon all the DFS options are back to turned off. It does not seem to save things. The PHG settings seem to work.

[cid:[email protected]<mailto:cid%[email protected]>]

Also a nice feature would be to have beacon button have a pull down where you could just hit the button and send what is your default beacon or chose one of the other beacons you have created or maybe a new option under message or query where a new window would open up with the PHG and DFS options and the ability to send a one time beacon with direction finding data.

If anyone has experience with these features I would love to talk with you.

Thanks,
Scott - W2KP