feat: amplifier band-follow — answer the amp's frequency polls

On its CAT/AUX connector an ACOM is the MASTER: it polls a transceiver and
changes band from the reply, so nothing can be pushed to it. internal/catemu
answers those polls on a second serial port, in ACOM command set 5 (Kenwood /
Elecraft): FA;, FB;, IF; and ID;, and nothing else — a wrong-length reply is
worse than none, it desynchronises the amp's parser for the following poll.

Also offered for SPE. Some amps do not poll at all but read the radio↔PC CAT
line in parallel; those never hear a responder, so an optional unprompted send
(500/1000 ms) covers them.

The TX frequency is what is sent: in split the amp must be tuned where we
transmit. Frame lengths are pinned by tests — the failure they guard against is
silent and only shows up as an amp that mistunes.

Untested on hardware.

frontend/src/components/SettingsModal.tsx

@@ -627,7 +627,10 @@ function ADIFMonitorPanel() {
 }
 
 // AmpUI mirrors the backend AmpConfig — one configured amplifier.
-type AmpUI = { id: string; name: string; enabled: boolean; type: string; transport: string; host: string; port: number; com_port: string; baud: number };
+type AmpUI = { id: string; name: string; enabled: boolean; type: string; transport: string; host: string; port: number; com_port: string; baud: number;
+  // Band-follow (ACOM): a SECOND serial port on which OpsLog answers the amp's
+  // frequency polls, pretending to be a Kenwood-format transceiver.
+  freq_out?: boolean; freq_com_port?: string; freq_baud?: number; freq_broadcast_ms?: number };
 
 // RelayAutoPanel configures automatic control of the Station Control relay boards
 // from the rig's frequency / band (PstRotator-style). Each relay carries one rule:
@@ -2811,6 +2814,7 @@ export function SettingsModal({ onClose, onSaved, initialSection, onMainPaneChan
     });
     const addAmp = () => setAmps((l) => [...l, {
       id: '', name: '', enabled: true, type: 'spe13', transport: 'tcp', host: '', port: 9008, com_port: '', baud: 115200,
+      freq_out: false, freq_com_port: '', freq_baud: 9600, freq_broadcast_ms: 0,
     }]);
     return (
       <>
@@ -2927,6 +2931,62 @@ export function SettingsModal({ onClose, onSaved, initialSection, onMainPaneChan
                   </div>
                 )}
 
+                {/* Band-follow, for any amp that takes its band from a transceiver
+                    CAT link (ACOM and SPE both do) — never PowerGenius, which is
+                    driven over its network protocol. A SECOND serial port,
+                    separate from the metering one above. */}
+                {!isPGXL && (
+                  <div className="border-t border-border/60 pt-3 space-y-3">
+                    <label className="flex items-center gap-2 text-sm cursor-pointer">
+                      <Checkbox
+                        checked={!!amp.freq_out}
+                        onCheckedChange={(c) => patchAmp(i, { freq_out: !!c })}
+                      />
+                      {t('amp.freqOut')}
+                    </label>
+                    {amp.freq_out && (
+                      <>
+                        <div className="grid grid-cols-3 gap-3">
+                          <div className="space-y-1 col-span-2">
+                            <Label>{t('amp.freqPort')}</Label>
+                            <div className="flex items-center gap-2">
+                              <Select value={amp.freq_com_port || '_'} onValueChange={(v) => patchAmp(i, { freq_com_port: v === '_' ? '' : v })}>
+                                <SelectTrigger className="h-9 flex-1"><SelectValue placeholder="— COM —" /></SelectTrigger>
+                                <SelectContent>
+                                  {wkPorts.length === 0 && <SelectItem value="_" disabled>No ports found</SelectItem>}
+                                  {wkPorts.map((p) => <SelectItem key={p} value={p}>{p}</SelectItem>)}
+                                </SelectContent>
+                              </Select>
+                              <Button size="sm" variant="outline" className="h-9" onClick={() => ListSerialPorts().then((p) => setWkPorts((p ?? []) as string[])).catch(() => {})}>
+                                <ArrowDown className="size-3.5 rotate-90" />
+                              </Button>
+                            </div>
+                          </div>
+                          <div className="space-y-1">
+                            <Label>Baud</Label>
+                            <Input type="number" min={1200} value={amp.freq_baud ?? 9600}
+                              onChange={(e) => patchAmp(i, { freq_baud: parseInt(e.target.value) || 9600 })} className="font-mono" />
+                          </div>
+                        </div>
+                        <div className="grid grid-cols-3 gap-3">
+                          <div className="space-y-1 col-span-2">
+                            <Label>{t('amp.freqBroadcast')}</Label>
+                            <Select value={String(amp.freq_broadcast_ms ?? 0)} onValueChange={(v) => patchAmp(i, { freq_broadcast_ms: parseInt(v) })}>
+                              <SelectTrigger className="h-9"><SelectValue /></SelectTrigger>
+                              <SelectContent>
+                                <SelectItem value="0">{t('amp.freqPollOnly')}</SelectItem>
+                                <SelectItem value="500">{t('amp.freqEvery', { ms: 500 })}</SelectItem>
+                                <SelectItem value="1000">{t('amp.freqEvery', { ms: 1000 })}</SelectItem>
+                              </SelectContent>
+                            </Select>
+                          </div>
+                        </div>
+                        <p className="text-[10px] text-muted-foreground">{t('amp.freqHint')}</p>
+                      </>
+                    )}
+                  </div>
+                )}
+
                 {amp.enabled && amp.id && <AmpStatusCard id={amp.id} />}
                 {!isPGXL && !isACOM && (
                   <p className="text-[10px] text-muted-foreground">

frontend/src/lib/i18n.tsx

@@ -170,7 +170,7 @@ const en: Dict = {
   'gen.showBeam': 'Show the antenna beam heading on the Main map',
   'gen.startEqEnd': 'QSO start time = end time', 'gen.startEqEndHint': '(matches LoTW when you call a while)',
   'gen.showQsoRate': 'Show QSO rate in the header', 'gen.showQsoRateHint': '(QSOs/hour, projected from the last 10 / 60 min)',
-  'gen.lookupOnBlur': 'Look up the callsign only after leaving the field', 'gen.lookupOnBlurHint': '(not while typing)', 'amp.hint': 'Configure one or several amplifiers — each panel card has a dropdown to pick which one it shows.', 'amp.none': 'No amplifier configured yet.', 'amp.namePh': 'Name (e.g. SPE left)', 'amp.remove': 'Remove this amplifier', 'amp.add': 'Add amplifier',
+  'gen.lookupOnBlur': 'Look up the callsign only after leaving the field', 'gen.lookupOnBlurHint': '(not while typing)', 'amp.hint': 'Configure one or several amplifiers — each panel card has a dropdown to pick which one it shows.', 'amp.none': 'No amplifier configured yet.', 'amp.namePh': 'Name (e.g. SPE left)', 'amp.remove': 'Remove this amplifier', 'amp.add': 'Add amplifier', 'amp.freqOut': 'Send the frequency to the amplifier (band follow)', 'amp.freqPort': 'CAT/AUX COM port', 'amp.freqBroadcast': 'Also send unprompted', 'amp.freqPollOnly': 'No — answer the amplifier only', 'amp.freqEvery': 'Yes, every {ms} ms', 'amp.freqHint': 'OpsLog pretends to be a transceiver on this second port, in Kenwood format: set the amplifier to that command set (set 5 on an ACOM) at the same baud rate, and put it in OPERATE — in standby it acknowledges but does not switch band. An amplifier that POLLS (ACOM) needs nothing more; one that only LISTENS to the CAT line of the radio hears nothing unless you also turn on the unprompted send.',
   'gen.groupDigital': 'Group digital modes as one (DXCC-style)', 'gen.groupDigitalHint': '(matrix badges + cluster: FT8/FT4/RTTY… count as a single Digital mode; off = each digital mode is its own slot)',
   // Password encryption
   'gen.pwEnc': 'Password encryption',
@@ -563,7 +563,7 @@ const fr: Dict = {
   'gen.showBeam': 'Afficher le cap de l\'antenne sur la carte principale',
   'gen.startEqEnd': 'Heure de début du QSO = heure de fin', 'gen.startEqEndHint': '(correspond à LoTW quand tu appelles un moment)',
   'gen.showQsoRate': 'Afficher le rythme QSO dans la barre du haut', 'gen.showQsoRateHint': '(QSO/heure, projeté sur les 10 / 60 dernières min)',
-  'gen.lookupOnBlur': 'Rechercher l\'indicatif seulement après avoir quitté le champ', 'gen.lookupOnBlurHint': '(pas pendant la saisie)', 'amp.hint': 'Configurez un ou plusieurs amplificateurs — chaque carte de panneau a une liste déroulante pour choisir lequel afficher.', 'amp.none': 'Aucun amplificateur configuré.', 'amp.namePh': 'Nom (p. ex. SPE gauche)', 'amp.remove': 'Supprimer cet amplificateur', 'amp.add': 'Ajouter un amplificateur',
+  'gen.lookupOnBlur': 'Rechercher l\'indicatif seulement après avoir quitté le champ', 'gen.lookupOnBlurHint': '(pas pendant la saisie)', 'amp.hint': 'Configurez un ou plusieurs amplificateurs — chaque carte de panneau a une liste déroulante pour choisir lequel afficher.', 'amp.none': 'Aucun amplificateur configuré.', 'amp.namePh': 'Nom (p. ex. SPE gauche)', 'amp.remove': 'Supprimer cet amplificateur', 'amp.add': 'Ajouter un amplificateur', 'amp.freqOut': "Envoyer la fréquence à l'amplificateur (suivi de bande)", 'amp.freqPort': 'Port COM CAT/AUX', 'amp.freqBroadcast': 'Envoyer aussi sans être interrogé', 'amp.freqPollOnly': "Non — répondre seulement à l'amplificateur", 'amp.freqEvery': 'Oui, toutes les {ms} ms', 'amp.freqHint': "OpsLog se fait passer pour un transceiver sur ce second port, au format Kenwood : réglez l'amplificateur sur ce jeu de commandes (le jeu 5 sur un ACOM) à la même vitesse, et mettez-le en OPERATE — en veille il acquitte mais ne change pas de bande. Un amplificateur qui INTERROGE (ACOM) n'a besoin de rien de plus ; un amplificateur qui se contente d'ÉCOUTER la liaison CAT de la radio n'entendra rien tant que l'envoi spontané n'est pas activé.",
   'gen.groupDigital': 'Regrouper les modes digitaux en un seul (style DXCC)', 'gen.groupDigitalHint': '(badges de la matrice + cluster : FT8/FT4/RTTY… comptent comme un seul mode Digital ; décoché = chaque mode digital est un slot distinct)',
   // Chiffrement des mots de passe
   'gen.pwEnc': 'Chiffrement des mots de passe',

frontend/wailsjs/go/main/App.d.ts

@@ -6,6 +6,7 @@ import {main} from '../models';
 import {cat} from '../models';
 import {profile} from '../models';
 import {acom} from '../models';
+import {catemu} from '../models';
 import {antgenius} from '../models';
 import {award} from '../models';
 import {awardref} from '../models';
@@ -344,6 +345,8 @@ export function GetActiveProfile():Promise<profile.Profile>;
 
 export function GetAlertEmailTo():Promise<string>;
 
+export function GetAmpBandFollowStatus():Promise<Record<string, catemu.Status>>;
+
 export function GetAmpStatuses():Promise<Array<main.AmpStatus>>;
 
 export function GetAmplifiers():Promise<Array<main.AmpConfig>>;

frontend/wailsjs/go/main/App.js

@@ -638,6 +638,10 @@ export function GetAlertEmailTo() {
   return window['go']['main']['App']['GetAlertEmailTo']();
 }
 
+export function GetAmpBandFollowStatus() {
+  return window['go']['main']['App']['GetAmpBandFollowStatus']();
+}
+
 export function GetAmpStatuses() {
   return window['go']['main']['App']['GetAmpStatuses']();
 }

frontend/wailsjs/go/models.ts

@@ -1442,6 +1442,10 @@ export namespace main {
 	    port: number;
 	    com_port: string;
 	    baud: number;
+	    freq_out: boolean;
+	    freq_com_port: string;
+	    freq_baud: number;
+	    freq_broadcast_ms: number;
 	
 	    static createFrom(source: any = {}) {
 	        return new AmpConfig(source);
@@ -1458,6 +1462,10 @@ export namespace main {
 	        this.port = source["port"];
 	        this.com_port = source["com_port"];
 	        this.baud = source["baud"];
+	        this.freq_out = source["freq_out"];
+	        this.freq_com_port = source["freq_com_port"];
+	        this.freq_baud = source["freq_baud"];
+	        this.freq_broadcast_ms = source["freq_broadcast_ms"];
 	    }
 	}
 	export class AmpStatus {