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Fox Hunt and Beacon
FOX HUNT / BEACON is a programmable shortcut action with two complementary modes built for ARDF (Amateur Radio Direction Finding), the "fox hunting" or radio-orienteering discipline:
- Fox Hunt is a receive-only signal-strength aid used to home in on a hidden transmitter.
- Beacon turns the radio into the hidden transmitter and repeats a Morse identifier on a timed cycle.
The feature opens in Fox Hunt mode. Press either side button while the controls are unlocked to switch between Fox Hunt and Beacon.
Note
Where this page mentions
UP/DOWN, use the equivalentLEFT/RIGHTkeys on UV-K1. The active navigation layout followsSetNav.
Warning
Beacon starts transmitting immediately when it is selected. Before entering Beacon mode, verify the active TX frequency, power, antenna,
F Lock,TXLock, identification requirements, and the regulations applicable in your country. Do not leave an unattended beacon transmitting where autonomous or periodic transmissions are prohibited.
About fox hunting (ARDF)
In ARDF, several low-power transmitters (the "foxes") are hidden in the field and competitors use a directional receiver to find them. In the classic IARU format there are five foxes sharing one frequency. Each fox transmits for 60 seconds in turn, so the cycle repeats every 5 minutes and each fox is silent for the 4 minutes (240 seconds) while the other four are on.
Every fox sends the same MO prefix followed by a rising number of dits, so you can tell which one you are hearing by counting the final dits:
| Fox | Sends | Morse | Final dits |
|---|---|---|---|
| 1 | MOE |
-- --- · |
1 |
| 2 | MOI |
-- --- ·· |
2 |
| 3 | MOS |
-- --- ··· |
3 |
| 4 | MOH |
-- --- ···· |
4 |
| 5 | MO5 |
-- --- ····· |
5 |
A separate finish (home) beacon marks the end of the course. It sends MO (-- ---) and, unlike the timed foxes, transmits continuously. This firmware offers MO as an identifier but still runs it on the normal transmit/silence cycle rather than a true continuous carrier (see TX window and idle interval); a short IDLE makes it near-constant.
On the 2 m band the foxes send a tone-modulated CW identifier (A2A). This firmware transmits it on FM: by default the carrier stays up while the 1000 Hz tone is keyed on and off for each Morse element (MCW / F2A). A second keying mode (CARR) instead interrupts the carrier itself for each element, matching the carrier-interrupted pattern many foxes use in the field — see Keying mode.
This feature lets one radio play either role: Fox Hunt to search, or Beacon to be one of the transmitters. With several radios you can lay out a full course — set each one to a different fox (MOE, MOI, MOS, …), one to the MO finish beacon, or use the CALL identifier for a properly identified beacon on the amateur bands.
Assigning the shortcut
Assign FOX HUNT / BEACON to one of the customizable shortcuts:
F1ShrtF1LongF2ShrtF2LongM Long
Trigger the assigned shortcut to open Fox Hunt on the currently selected VFO. See Button functions for the complete list of programmable actions.
Fox Hunt mode
Fox Hunt displays the calibrated received level in dBm, an S-meter value, held peak (PK) and minimum (MN) readings, and the recent signal trend. The current RX frequency and battery state remain visible.
The signal scale runs from S0 to S9+40. The main gauge can be either:
- a 13-level staircase covering
S1throughS9, then+10through+40 - a smoothed scrolling signal history covering approximately the last
18 seconds
The trend arrow and signed dBm difference compare the current level with the level measured roughly one second earlier. An upward arrow means the signal is increasing (you are getting closer); a downward arrow means it is decreasing.
Fox Hunt controls
Every setting has its own number key, and each press cycles to the next value, wrapping back to the start at the end. To go the other way, short-press F first: an F appears in the status bar and the next number key steps that setting backwards through its cycle instead. The reverse arm lasts for one key press; any other key cancels it. This is the same F + number scheme used in Beacon.
UP and DOWN provide direct attenuation control without first selecting setting 3.
| Control | Action |
|---|---|
1 |
Toggle between the S-meter staircase and the signal-history graph |
2 |
Cycle audio: silent → Geiger-style beeps → received station audio → silent |
3 |
Cycle receiver gain: ATT 0 → ATT 6 → ATT 15 → ATT 27 → BYP → BYP+ → ATT 0 |
UP / DOWN |
Increase or decrease attenuation by one step; these remain available while locked |
F then 2 or 3 |
Step audio or attenuation backwards through its cycle; an F shows in the status bar while armed |
M |
Reset the peak (PK), minimum (MN) and trend references |
Hold F for approximately 0.5 seconds |
Lock or unlock the Fox Hunt / Beacon controls |
| Either side button | Switch immediately to Beacon mode |
EXIT |
Leave Fox Hunt / Beacon and return to the normal radio screen |
Finding the fox
Direction finding with a handheld relies on watching how the level changes, not its absolute value:
- Attenuation is the key tool as you close in. When a nearby transmitter drives the meter to full scale you lose the ability to tell "closer" from "farther"; add attenuation with
3orUPto bring the reading back into the middle of the scale so small changes stay visible. The normal steps areATT 0,ATT 6,ATT 15, andATT 27, followed by the deeperBYPandBYP+front-end-gain settings. - Body scan is how you get a bearing without a directional antenna. Hold the radio against your chest and turn slowly through a full circle: your body shields the antenna when it faces the transmitter, producing a clear minimum (null) in one direction. Reset with
M, sweep once, and read the bearing where the level dips. - Peak (
PK) and minimum (MN) hold keep the strongest and weakest levels seen since the last reset. They bracket a rotation — the deeperMNsits belowPK, the sharper and more reliable the null. Reset both withMbefore each sweep. - Trend shows whether the signal is rising or falling over the last second — useful while walking a bearing.
The signal-history graph (1) also shows the shape of a rotation directly: the valleys in the scrolling trace are your nulls.
In Geiger audio mode, the beeps become faster and higher-pitched as the received level rises. In station-audio mode, the received audio is routed to the speaker. Both audio modes remain silent below approximately -120 dBm to avoid continuous noise-floor output.
About BYP and BYP+
BYP and BYP+ are convenient labels for close-range gain settings; they do not activate a hardware LNA-bypass switch. Both keep the final PGA gain low and reduce gain earlier in the BK4829 receiver chain. BYP+ applies the deepest reduction.
The displayed dBm value is not compensated for the selected gain setting, so it intentionally drops when changing to a deeper step. Use readings comparatively while staying on the same step rather than comparing absolute values across two different steps.
After every gain change, the firmware waits briefly for the RSSI detector to settle, then resets the peak, minimum, trend, and signal-history references to the new level. This prevents an old high-gain peak or an artificial graph cliff from carrying into the new range.
Fox Hunt / Beacon keypad lock
Hold F for approximately 0.5 seconds to toggle the local keypad lock. A padlock appears in the status line. This lock is shared when switching between Fox Hunt and Beacon, but it is separate from the radio's normal SetLck keypad setting.
While Fox Hunt is locked, every control is ignored except:
UPandDOWN, which remain available to adjust attenuation during the final approach- another long press of
F, which unlocks the controls
While Beacon is locked, all ordinary controls are ignored, including during an active transmission. Hold F again to unlock. The lock is temporary and is always cleared when Fox Hunt / Beacon is opened again; it is not saved with the other settings.
Beacon mode
Beacon uses the active TX VFO frequency, output power, and transmit configuration. As soon as Beacon mode is entered, the radio keys up and repeats the chosen identifier for the whole TX window, then goes silent for the idle interval, and starts again.
Fox identifier
The FOX setting selects what is transmitted:
FOX |
Message | Notes |
|---|---|---|
MOE … MO5 |
MOE, MOI, MOS, MOH, MO5 |
The five standard IARU ARDF foxes |
MO |
MO |
The ARDF finish/home beacon identifier |
CALL |
<CALLSIGN> MOE |
Your callsign followed by MOE — an identified beacon for the amateur bands |
<CALLSIGN> comes from Message Line 1, which can be edited with the dedicated Fusion CHIRP driver. Letters are converted to uppercase; letters, digits, and / are supported, and unsupported characters are removed. If the line is empty or contains no supported characters, CALL falls back to a bare MOE.
Use the pure MOE … MO5 and MO identifiers for ARDF practice or casual "hide the radio" games (for example on PMR); use CALL when you must identify with your callsign on the amateur bands. The default is CALL. For a finish-beacon feel, select MO and set a short IDLE so it repeats almost without a gap — note that this is still a cyclic transmission, not a true continuous carrier.
The Morse identification uses a 1000 Hz tone at approximately 12 WPM (the slow, beginner-friendly pace typical of ARDF foxes). By default (TONE keying) the FM carrier remains active for the whole window while the tone is keyed on and off for the Morse elements; the CARR keying mode interrupts the carrier itself instead — see Keying mode.
TX window and idle interval
Two timers shape the cycle:
TX— how long the identifier is repeated each time the beacon keys up.- default
30 s, range5 sto60 s, step5 s
- default
IDLE— the silent time after the window, before the next transmission.- default
30 s, range5 sto240 s, step5 s
- default
The full period between two transmissions is TX + IDLE. To reproduce a classic ARDF fox, set TX = 60 s and IDLE = 240 s (on for one minute, silent for four).
During transmission the top line shows the seconds remaining in the current window, counting down live. During the silent phase the screen shows IDLE with the countdown to the next burst.
Keying mode (TONE / CARR)
The TONE / CARR setting selects what is switched on and off to form the Morse elements. Both modes send the same 1000 Hz identifier on FM; they differ only in whether the carrier is present between elements:
| Mode | What is keyed | On the air |
|---|---|---|
TONE (default) |
The tone only | The FM carrier stays up for the whole window and the 1000 Hz tone is keyed on and off (MCW / F2A). The carrier is present even in the gaps between elements. |
CARR |
The carrier and the tone together | The carrier is switched on only during each dit and dah, and off in every gap, so the signal disappears completely between elements (carrier interruption). |
TONE is the standard behaviour and matches earlier firmware. CARR reproduces the carrier-interrupted keying that many real ARDF foxes use in the field: because the signal vanishes between elements, a hunter has only short bursts on which to take a bearing, which makes direction finding harder and more realistic. A carrier-interrupted signal is also copyable on a plain AM receiver, whereas a continuous-carrier FM signal is not.
Note
CARRkeys the power amplifier directly, without envelope shaping, so each element produces a small key click and a little more spectral spread thanTONE. This is inherent to carrier keying on this hardware and is more noticeable at close range. UseTONEwhen you want the cleanest signal.
Set the mode with key 4; it is saved with the other settings.
Beacon controls
The four settings map to the number keys in the order they appear on screen, and all of them can be changed at any time — during transmission as well as during the silent interval. As in Fox Hunt, pressing F before a number steps that setting backwards through its cycle (the F indicator shows in the status bar while armed) — a real time-saver on the long IDLE range:
| Control | Action |
|---|---|
1 |
Cycle the TX window: 5 → 60 s, then back to 5 |
2 |
Cycle the IDLE interval: 5 → 240 s, then back to 5 |
3 |
Cycle the FOX identifier: MOE → MOI → MOS → MOH → MO5 → MO → CALL → MOE |
4 |
Toggle the keying mode: TONE ↔ CARR |
F then a number |
Step that setting backwards through its cycle (handy for the long IDLE range); an F shows in the status bar while armed |
Hold F for approximately 0.5 seconds |
Lock or unlock all Beacon controls, including during TX |
M |
Stop the current transmission and begin a fresh silent interval; during the silent phase, restart the IDLE countdown |
| Either side button | Return to Fox Hunt (interrupts the current transmission if necessary) |
EXIT |
Leave Fox Hunt / Beacon (interrupts the current transmission if necessary) |
A TX or IDLE change applies to the next window or silent phase; a FOX change applies to the next repeat of the identifier, so switching fox mid-transmission never corrupts the message in flight. A TONE / CARR change takes effect from the next Morse element, so it is safe to toggle at any time, mid-transmission included.
Pressing M while transmitting is a quick way to yield the frequency without leaving Beacon: it cuts the identifier short, drops the carrier, and starts a full IDLE silence before the next burst. Pressing M during the silent phase simply restarts that countdown, so M always means "stay silent for the full IDLE time, starting now".
Transmission protections
Before every Beacon burst, the firmware checks the normal transmit restrictions for the active TX VFO:
- the
F Lockfrequency plan and the VFO/channelTXLockpermission - low-battery and over-voltage conditions
- whether the selected modulation permits transmission
If transmission is refused, Beacon displays the corresponding radio status, such as TX DISABLE, BAT LOW, or VOLTAGE HIGH, then returns to Fox Hunt mode.
Fox Hunt and Beacon both continue running through normal inactivity periods, so SetOff does not put the radio to sleep or return it to the main VFO while either mode is active. The normal backlight timeout still operates. Battery level is refreshed during idle operation and the transmit checks are repeated before every Beacon burst.
Saved settings and Air Copy
The following Fox Hunt / Beacon settings are stored in external flash:
- attenuation level
- staircase or signal-history gauge
- audio mode
- fox identifier
- Beacon
TXwindow - Beacon
IDLEinterval - Beacon keying mode (
TONE/CARR)
Changes are saved automatically and restored the next time the feature is opened. They are also included in an Air Copy Settings transfer. A full factory reset clears them.
The temporary Fox Hunt / Beacon keypad lock is not stored or copied.