1 Overview

1.1 Purpose & Key Features

Grid Path Mobile is a browser-based tool designed for microwave rover operators to quickly compute great-circle headings, evaluate terrain line-of-sight, and log QSOs in the field during the ARRL 10 GHz & Up Contest — all from a smartphone, with no app installation required.

Path & Terrain

Great-circle heading A → B and reverse B → A
Distance in km or miles
Animated compass rose with kite-needle
Terrain elevation profile (Open-Meteo API)
First Fresnel zone visualization
LOS obstruction detection with verdict
Earth-curvature correction (k = 4/3 or k = 1)

Contest Operations

Inline QSO logger with ARRL scoring
All 8 contest bands (10 GHz – >241 GHz)
Automatic dupe detection per band
Real-time total score display
ADIF export for submission
Microwave beacon map with headings
GPS location support

1.2 Getting Started

Open grid-path-mobile.html in any modern smartphone or desktop browser.
Enter your current grid square (or tap ⌖ GPS) into Point A.
Enter the remote station's grid square into Point B.
Tap CALCULATE PATH to compute heading and terrain.
Log each QSO using the QSO Log section below the results.

Note The terrain profile requires an active internet connection to fetch elevation data. All other features (heading, compass, QSO logging, scoring) work fully offline.

2 Interface Layout

The page is organized top-to-bottom in a single scrolling column optimized for portrait smartphone use:

Section	Location	Description
Header bar	Top, sticky	App title, font-size buttons (A− / A+), theme toggle (☀/☾)
Endpoints card	§3	Point A, Point B, antenna heights, band, earth model, units
Terrain spinner	Below inputs	Visible while fetching elevation data
Path Results	§4	Compass rose, heading values, path statistics (hidden until first calculation)
Terrain Profile	§5	Elevation cross-section with LOS and Fresnel zone (hidden until calculation)
QSO Log card	§6	Contest score bar, callsign entry, band/mode, LOG button, QSO list

3 Path Calculator

3.1 Point A — My Location

Point A represents your transmit location. It is used for heading calculations, terrain profiling, and as the source grid for logged QSOs. Enter one of the following formats:

Format	Example	Notes
2-char grid	`DM`	Field-level, center of 20° × 10° square
4-char grid	`DM43`	Square-level, center of 2° × 1° square
6-char grid	`DM43CG`	Subsquare — standard for contest exchange
8-char grid	`DM43CG44`	Extended precision
Lat, Lon	`33.27,-111.79`	Decimal degrees, comma-separated

GPS Tip Tap ⌖ GPS to automatically fill Point A with your current location as a 10-character Maidenhead grid (highest available precision). Requires browser location permission. On iPhone, use Safari for best GPS accuracy.

3.2 Point B — Remote Station

Point B is the remote station or target location. Accepts the same formats as Point A. For contest use, enter the 6-character grid square received in the exchange. You can also tap any row in the beacon map to auto-fill Point B with a beacon's grid.

Rover Note As a rover you will update Point A for each new grid square you operate from. Point B remains your intended contact until you need a different heading. The QSO log captures the Point A grid at the moment of logging, so changing Point A later does not affect previously logged QSOs.

3.3 Antenna Heights

Ant A and Ant B set the effective antenna height above ground at each end of the path. These values affect only the terrain profile and Fresnel zone calculation — they have no effect on heading or QSO scoring.

Setting	Typical Use
1.0 m	Dish or horn on a car roof rack (default)
1.5 m	Elevated tripod or portable mast
2.0 – 3.0 m	Fixed tower or elevated installation

3.4 Band Selection

The Band selector determines which frequency is used for Fresnel zone calculation in the terrain profile and which contest multiplier is applied to QSO scores. All eight ARRL 10 GHz & Up contest bands are available:

Selection	Frequency (MHz)	Wavelength	Score Multiplier
10 GHz ×1	10,368.1	3 cm	×1
24 GHz ×2	24,048.1	1.2 cm	×2
47 GHz ×4	47,088.1	6 mm	×4
76 GHz ×8	76,032	4 mm	×8
119 GHz ×16	119,000	2.5 mm	×16
142 GHz ×32	142,000	2.1 mm	×32
241 GHz ×64	241,000	1.2 mm	×64
>241 GHz ×128	300,000	<1 mm	×128

Important The selected band is used for both terrain analysis and QSO scoring. Make sure to select the correct band before tapping LOG — changing the band after logging does not retroactively update existing entries.

3.5 Earth Model & Units

Earth Model

RADIO k=4/3 (default) — Standard radio propagation model. Applies an effective Earth radius of 4/3 × 6371 km, accounting for typical atmospheric refraction. Recommended for all practical path analysis.
TRUE k=1 — Geometric Earth radius, no refraction correction. Use for academic comparison only.

Units

KM / M (default) — Distance in kilometres, elevation in metres.
MI / FT — Distance in miles, elevation in feet. Switching units instantly redraws all results without recalculating.

4 Path Results

After tapping CALCULATE PATH, results appear automatically below the calculator card. Scroll down to view them.

4.1 Compass Rose

The compass rose displays the great-circle bearing between Point A and Point B using a classic kite-needle design:

Green half — forward bearing (A → B). The tip points in the direction you need to aim.
Red half — reverse bearing (B → A, the tail). This is the heading the remote station aims toward you.
N is highlighted in cyan at the top of the rose.
Degree labels appear at every 30°.
Minor tick marks at every 10°.

Field Tip The large green number above the compass is the forward bearing in degrees, with compass direction (e.g., 247.3° WSW). The red number below is the reverse bearing — read it out to the remote station so they can aim back at you.

        Example: A→B = 247° WSW / B→A = 67° ENE
      

4.2 Path Statistics

Below the compass, a statistics grid shows:

Statistic	Description
DISTANCE	Great-circle distance between Point A and Point B
AZIMUTH A→B	Forward bearing in degrees with compass direction abbreviation
REVERSE B→A	Bearing back from Point B to Point A
MIDPOINT	6-character grid square at the geographic midpoint of the path
GRID A	Resolved grid and decimal lat/lon for Point A
GRID B	Resolved grid and decimal lat/lon for Point B
ELEV MIN	Minimum terrain elevation along the path (requires elevation data)
ELEV MAX	Maximum terrain elevation along the path (requires elevation data)

5 Terrain Profile

The terrain profile is a cross-sectional elevation chart drawn along the great-circle path from A to B. Elevation data is fetched in real time from the Open-Meteo Elevation API using up to 200 sample points spaced along the path.

5.1 Chart Elements

Element	Color	Meaning
Terrain fill	Blue-grey gradient	Earth surface elevation corrected for atmospheric curvature using the selected k-factor
LOS line	Green	Straight line-of-sight between the two antenna tips (A and B at their specified heights)
Fresnel zone	Cyan dashed band	First Fresnel zone (F1) radius around the LOS line at the selected frequency. Microwave links perform best when this zone is 60% clear.
Obstruction	Red highlight	Any terrain segment rising above the LOS line — link is blocked here
Antenna markers	Cyan dots	A and B antenna positions with mast height above terrain

5.2 Path Verdict

Below the profile chart, a single-line verdict summarises the path quality:

Verdict	Meaning
✓ PATH CLEAR	LOS is unobstructed and at least 60% of the F1 Fresnel zone is clear. Link should be solid.
△ LOS CLEAR, F1 INTRUDED	Direct LOS is clear but terrain intrudes into the Fresnel zone. Expect some diffraction loss but the link should still work.
✕ PATH OBSTRUCTED	Terrain is above the LOS line. The link is blocked at the reported distance from A. A higher vantage point or different route is needed.

The verdict also reports the worst-case clearance margin and location, frequency used, and k-factor applied.

5.3 Offline Behaviour

If the elevation API is unreachable (offline, poor signal), the terrain profile is skipped and a ⚠ ELEVATION UNAVAILABLE message is shown in its place. Heading calculation and QSO logging are not affected — they work completely offline.

Redraw without Refetch Changing Antenna Height, Band, Earth Model, or Units after a calculation instantly redraws the profile using cached elevation data — no new API call is needed.

6 QSO Log

The built-in QSO log is designed for field use during the ARRL 10 GHz & Up Contest. It stores all contacts locally on the device, computes ARRL contest scores automatically, detects duplicates, and exports to ADIF for submission.

6.1 Logging a QSO

Step-by-step procedure

Set Point A to your current grid square. The My Grid display box auto-fills from Point A.
Set Point B to the worked station's grid square (received in the exchange).
Select the correct Band (including multiplier) for this QSO.
Enter My Call (your callsign; use K6VHF/R format for rover operation). Saved automatically after first entry.
Enter the Worked Station callsign in the QSO entry field.
Select the Mode (CW, SSB, FT8, or Q65).
Tap LOG. The QSO is scored and added instantly to the top of the list.

Before Logging Both Point A and Point B must contain valid grid squares before tapping LOG. If either is empty or invalid, an error message will appear and the QSO will not be saved.

Fields stored for each QSO

Field	Description
Date / Time	UTC date and time at moment of logging (auto-captured)
My Call	Your callsign as entered in the My Call field
Worked Call	The remote station's callsign
My Grid	6-character grid from Point A at time of logging
Their Grid	6-character grid from Point B at time of logging
Distance	Computed haversine distance between the two 6-char grid centers (km)
Band	Selected band label (e.g., 10G, 24G, 47G…)
Multiplier	ARRL band multiplier (1, 2, 4, 8… 128)
Score	Points awarded: distance × multiplier (0 for dupes)
Dupe flag	True if same callsign + same band was already logged
Mode	CW / SSB / FT8 / Q65

6.2 ARRL Contest Scoring Rules

Scoring follows the official ARRL 10 GHz & Up Contest rules:

Scoring Formula Score = Round( Distance_km × Band_Multiplier )
Duplicate contacts on the same band score zero points.

Band	Multiplier	Example: 250 km QSO
10 GHz	×1	250 pts
24 GHz	×2	500 pts
47 GHz	×4	1,000 pts
76 GHz	×8	2,000 pts
119 GHz	×16	4,000 pts
142 GHz	×32	8,000 pts
241 GHz	×64	16,000 pts
>241 GHz	×128	32,000 pts

The same contact on multiple bands counts as a separate valid QSO on each band, provided the exchange is genuinely made on that band. Only true dupes (same call, same band, logged more than once) are zeroed.

6.3 Dupe Detection

Every time you tap LOG, the app checks whether the same callsign has already been logged on the same band in the current session. If it has:

The QSO is still saved (for record-keeping)
The score for that entry is set to 0 pts
The row displays DUPE in red instead of a score
The dupe count appears in the log header

Tip Working the same station on a different band is not a dupe — each band is tracked independently. K6VHF on 10G and K6VHF on 24G are two separate scored contacts.

6.4 Log Display & Full Log View

The compact log list shows the most recent QSOs directly below the entry form. Each row contains:

Element	Description
Date / Time	UTC in MM/DD HH:MMz format
Callsign	Worked station's callsign in cyan
Grid path	MyGrid → TheirGrid (6-char)
Score	Points in large bold green (1,234) or DUPE in red
Band × Mult	Band label with multiplier (e.g., 10G ×1, 24G ×2)
Delete button	✕ — removes the QSO from the log immediately

The log header shows a running summary: N QSOs · TOTAL PTS · ND dupes

Full Log View

Tap ⛶ FULL LOG to open a full-screen overlay showing all QSOs with expanded details. On Android, the device Back button closes this view. On iOS, use the ← BACK button. From within the full log view you can also access Map and ADIF Export.

Deleting a QSO

Tap the ✕ button at the right of any log row to permanently delete that entry. Deletion is immediate — there is no undo. If you accidentally delete a QSO, you must re-enter it manually.

Clearing All QSOs

Tap ✕ CLEAR LOG at the bottom of the log card (or in the full log footer). A confirmation dialog appears stating the number of QSOs to be deleted. This action is irreversible — export ADIF first if you need to preserve the data.

Warning Clearing the log or deleting the browser site data removes all QSOs permanently. Export ADIF before clearing, especially at the end of a contest.

6.5 Contest Score Bar

At the top of the QSO Log card, a Contest Score Bar displays a real-time summary of your overall performance. It reads from the shared contest log key and updates automatically when you switch back to this browser tab or when the log is updated in another tab.

Cell	Shows
Total Score	Sum of all valid (non-dupe) QSO scores
QSOs / Dupes	Valid QSO count, with dupe count in red if any
Active Bands	Number of different bands with at least one valid QSO
Best ODX	Longest single QSO distance in km
Open Contest Log	Link to the dedicated `10ghz-log.html` contest logger

Note — Two Separate Logs Grid Path Mobile keeps its own local log (gp_qsolog) for path-calculation purposes. The Contest Score Bar reads from the shared contest log key (crf_10ghz_log_v1) written by the dedicated 10ghz-log.html page. If you log only in Grid Path Mobile, the score bar will show "No contest QSOs" until you also use the contest logger.

7 Microwave Beacon Map

The 🗺 MAP button opens an interactive Leaflet map in a new browser tab showing all known SoCal / NorCal / AZ microwave beacons plus your logged QSO paths. The map can be opened even when the QSO log is empty — it will still show all beacons.

Popup Permission Required The map opens in a new tab. If your browser blocks popups, you will see a prompt to allow them. Allow popups for this site and tap MAP again.

7.1 Map Elements

Symbol	Color	Meaning
● Large circle	Green	My station — one marker per unique My Grid / callsign combination. Popup shows callsign, grid, QSO count, and total points from that site.
● Small circle	Red	Worked station — one marker per QSO. Popup shows callsign, grid, band × multiplier, mode, UTC time, distance, and score.
◇ Diamond	Orange	Microwave beacon — all 10 known regional beacons. Popup shows name, location, grid, frequencies, and heading/distance from Point A (or from each logged op site).
─── Line	Cyan solid	Valid QSO path (great-circle line A → B)
- - - Line	Faint red dashed	Duplicate QSO path

7.2 Beacon Popups

Tapping an orange beacon diamond opens a popup containing:

Beacon name and geographic location
Grid square
Frequencies per callsign (e.g., WA6MEM/B: 10368.300G)
Heading and reverse bearing from Point A (if entered) or from each of your logged op-sites
Distance in km
⚠ warning icon if the beacon is known to be down

7.3 Known Beacons

Name	Grid	Location	Callsign(s)	Frequencies (MHz)
Palos Verdes	DM03tr	SoCal	WA6MEM/B	10368.300
Mt Frazier	DM04ms	SoCal	N6CA/B	10368.310
Heaps Pk ⚠	DM14kf	SoCal	AF6HP/B	10368.330
San Diego	DM12jv	SoCal	K6QPV/B	10368.360
Mt. Leeson	CM97ae	NorCal	KF6KVG	10367.990 / 24191.975 / 47087.990 / 79919.920
Mt Vaca	CM88wj	NorCal	W6ASL	10368.325
Mt Allison	CM97bl	NorCal	K6MG / N6NU / KF6KVG / AD6IW	10369 / 24192 / 47088 / 80832
Bear Mtn ⚠	DM06ir	NorCal	W6BY/B	24191.990
Stanford	CM87wj	NorCal	K6ML	122400
White Tanks	DM33rn	AZ	W7ATN	10368.375

⚠ = beacon reported down at time of writing. Verify current status before operating.

7.4 Map Tile Mode

When the app is in dark mode (default), the map uses CartoDB dark tiles for readability in low-light conditions. In light mode, it switches to standard OpenStreetMap tiles. The map auto-fits all markers and beacons into view on opening.

8 ADIF Export

Tap ⬇ EXPORT ADIF (in the log card or full log view) to download your QSO log as an ADIF 3.1.4 file (.adi) for submission to the ARRL or import into logging software such as WSJT-X, N1MM+, or Log4OM.

8.1 ADIF Fields Exported

ADIF Field	Content
STATION_CALLSIGN	Your callsign (My Call)
OPERATOR	Base callsign without /R suffix
CALL	Worked station callsign
QSO_DATE	UTC date (YYYYMMDD)
TIME_ON	UTC time (HHMMSS)
BAND	Band label (e.g., 10G)
FREQ	Frequency in MHz (e.g., 10368.1000)
MODE	CW / SSB / FT8 / Q65
GRIDSQUARE	Worked station's 6-char grid
MY_GRIDSQUARE	Your 6-char grid at time of QSO
DISTANCE	Distance in km between grid centers

File Name The exported file is automatically named gridpath_YYYY-MM-DD.adi using the current local date. Save it immediately after export — the download link expires when the page is refreshed.

8.2 ARRL Submission

For ARRL 10 GHz & Up Contest submission, export the ADIF file after the contest period ends and upload it through the ARRL contest submission portal. Verify that your callsign, grid squares, and operating times are correct before submitting. Dupe QSOs are included in the ADIF export for completeness — the ARRL adjudication software handles dupe removal on their end.

9 Data Storage & Privacy

9.1 How Data is Stored

All QSO log data is stored exclusively in your browser's localStorage on your own device. No data is transmitted to any server. The application itself is served as a static HTML file — after the page loads, it operates completely independently of the server.

Key	Content	Where Used
`gp_qsolog`	Full QSO log array (JSON)	Grid Path Mobile only
`gp_mycall`	Your saved callsign	Auto-fills My Call on next visit
`gp_font`	Font size index (0–3)	Display preference
`gp_theme`	"dark" or "light"	Display preference

9.2 Per-Device Isolation

Each physical device and each browser app maintains a completely separate localStorage. Multiple operators using the same URL from their own smartphones will each have their own independent log. There is no synchronization, no shared database, and no way for one device to see another device's data. This is the correct behavior for rover contest operation where each operator maintains their own log.

9.3 Data Persistence

Action	Effect on Log
Close the browser tab	Data preserved
Restart the browser	Data preserved
Restart the phone	Data preserved
Use Private / Incognito mode	Data lost when tab closes
Browser "Clear Site Data"	Data permanently deleted
Uninstall the browser	Data permanently deleted

Best Practice Export ADIF at the end of each operating session, even if you plan to continue later. This protects against accidental browser data clearing or device failure.

10 Display Settings

Three display controls appear in the sticky header bar:

Control	Function
A−	Decrease base font size. Cycles through 4 steps: 100% → 112% → 125% → 140%
A+	Increase base font size. Useful when operating in bright sunlight or gloves.
☀ / ☾	Toggle between dark mode (default, blue-black theme) and light mode (white theme). Light mode is better for outdoor use in direct sunlight.

All three settings are saved to localStorage and restored automatically on next visit.

Field Tip — Sunlight Readability In direct sunlight, switch to light mode (☀ button) and increase font size to A+ or A++ for maximum screen readability. The compass and terrain profile automatically redraw in light-mode colors.

11 Quick Reference

11.1 ARRL 10 GHz & Up Band Multiplier Table

Band	Mult	Freq (MHz)	Score for 100 km	Score for 500 km
10 GHz	×1	10,368.1	100 pts	500 pts
24 GHz	×2	24,048.1	200 pts	1,000 pts
47 GHz	×4	47,088.1	400 pts	2,000 pts
76 GHz	×8	76,032	800 pts	4,000 pts
119 GHz	×16	119,000	1,600 pts	8,000 pts
142 GHz	×32	142,000	3,200 pts	16,000 pts
241 GHz	×64	241,000	6,400 pts	32,000 pts
>241 GHz	×128	300,000	12,800 pts	64,000 pts

11.2 Grid Input Formats

Format	Length	Example	Precision (center)
Field	2 chars	DM	~1,100 km × 550 km
Square	4 chars	DM43	~110 km × 55 km
Subsquare (contest standard)	6 chars	DM43CG	~4.6 km × 2.3 km
Extended subsquare	8 chars	DM43CG44	~460 m × 230 m
GPS / decimal	lat,lon	33.27,-111.79	Limited by input precision

11.3 Common Workflow — Rover Operation

Arrive at grid square → tap ⌖ GPS to set Point A.
Enter remote station grid in Point B → tap CALCULATE PATH.
Point antenna to the displayed green heading.
Read the reverse heading to the remote station.
After contact, enter their callsign, select band, tap LOG.
Repeat steps 2–5 for additional contacts on different bands or to different grids.
When moving to a new grid: update Point A (GPS or manual) → continue.
At end of session: tap ⬇ EXPORT ADIF to save your log.

11.4 Troubleshooting

Issue	Cause	Solution
LOG button shows error	Missing callsign, or Point A/B not set	Ensure My Call, Point A, and Point B all have valid entries
Terrain not loading	No internet connection	Heading and log still work offline; reconnect for terrain
Map popup blocked	Browser popup blocker	Allow popups for this site and tap MAP again
GPS not working	Location permission denied	Grant location permission in browser/phone settings; use Safari on iOS
Score bar shows "No QSOs"	Score bar reads 10ghz-log.html key, not Grid Path Mobile's own log	Use 10ghz-log.html to log contest QSOs, or ignore the score bar
Log lost after clear	CLEAR LOG was used or browser data cleared	No recovery — export ADIF regularly as backup

    CETUS-RF · Grid Path Mobile · cetus-rf.com · Operational Manual v1.0 · 2026

    ARRL 10 GHz & Up Contest Rules · Open-Meteo Elevation API · Leaflet.js Maps

Table of Contents