diff --git a/application/controllers/Callhistory.php b/application/controllers/Callhistory.php
index 3979a2c5e..83d364868 100644
--- a/application/controllers/Callhistory.php
+++ b/application/controllers/Callhistory.php
@@ -21,8 +21,10 @@ class Callhistory extends CI_Controller {
     {
         $user_id = (int)$this->session->userdata('user_id');
 
+        $this->load->model('logbooks_model');
         $data['page_title'] = 'Call History';
         $data['files'] = $this->callhistory_model->get_all_for_user($user_id);
+        $data['logbooks'] = $this->logbooks_model->show_all()->result();
 
         $this->load->view('interface_assets/header', $data);
         $this->load->view('callhistory/index', $data);
@@ -167,6 +169,147 @@ class Callhistory extends CI_Controller {
         redirect('callhistory');
     }
 
+    public function scan_preview()
+    {
+        if (strtolower($this->input->method()) !== 'post') {
+            redirect('callhistory');
+            return;
+        }
+
+        $user_id = (int)$this->session->userdata('user_id');
+        $file_id = (int)$this->input->post('file_id', TRUE);
+        $logbook_id = $this->input->post('logbook_id', TRUE);
+        $logbook_id = ($logbook_id !== '' && $logbook_id !== FALSE) ? (int)$logbook_id : NULL;
+
+        $file = $this->callhistory_model->get_for_user_by_id($user_id, $file_id);
+        if (!$file) {
+            $this->session->set_flashdata('notice', 'Call history file not found.');
+            redirect('callhistory');
+            return;
+        }
+
+        $path = FCPATH . 'uploads/callhistory/' . $user_id . '/' . $file->stored_filename;
+        if (!is_file($path) || !is_readable($path)) {
+            $this->session->set_flashdata('notice', 'Uploaded file is not readable.');
+            redirect('callhistory');
+            return;
+        }
+
+        // Parse every callsign in the file
+        $all_callsigns = $this->get_all_callsigns_in_file($path);
+        if (empty($all_callsigns)) {
+            $this->session->set_flashdata('notice', 'No callsigns found in the selected file.');
+            redirect('callhistory');
+            return;
+        }
+
+        // Look up matching QSOs for all those callsigns
+        $qsos = $this->callhistory_model->get_qsos_for_callsigns($user_id, array_keys($all_callsigns), $logbook_id);
+
+        $preview = array();
+        foreach ($qsos as $qso) {
+            $normalized_call = $this->normalize_callsign($qso->COL_CALL);
+            if (!isset($all_callsigns[$normalized_call])) {
+                continue;
+            }
+
+            $call_data = $all_callsigns[$normalized_call];
+            $proposed_sig = $file->organization_label;
+            $proposed_sig_info = $call_data['exch1'];
+
+            $current_sig = trim((string)($qso->COL_SIG ?? ''));
+            $current_sig_info = trim((string)($qso->COL_SIG_INFO ?? ''));
+
+            // Only propose changes where both SIG fields are currently blank
+            if ($current_sig !== '' || $current_sig_info !== '') {
+                continue;
+            }
+
+            if ($proposed_sig === '' && $proposed_sig_info === '') {
+                continue;
+            }
+
+            $preview[] = array(
+                'qso_id' => (int)$qso->COL_PRIMARY_KEY,
+                'station_id' => (int)$qso->station_id,
+                'callsign' => $qso->COL_CALL,
+                'time_on' => $qso->COL_TIME_ON,
+                'band' => $qso->COL_BAND,
+                'mode' => $qso->COL_SUBMODE !== '' ? $qso->COL_SUBMODE : $qso->COL_MODE,
+                'station_location' => $qso->station_profile_name . ' (' . $qso->station_callsign . ')',
+                'current_sig' => $current_sig,
+                'current_sig_info' => $current_sig_info,
+                'new_sig' => $proposed_sig,
+                'new_sig_info' => $proposed_sig_info,
+            );
+        }
+
+        $this->load->model('logbooks_model');
+        $data['page_title'] = 'Call History - Scan Preview';
+        $data['files'] = $this->callhistory_model->get_all_for_user($user_id);
+        $data['preview'] = $preview;
+        $data['scan_file'] = $file;
+        $data['logbooks'] = $this->logbooks_model->show_all()->result();
+        $data['selected_logbook_id'] = $logbook_id;
+
+        $this->load->view('interface_assets/header', $data);
+        $this->load->view('callhistory/index', $data);
+        $this->load->view('interface_assets/footer');
+    }
+
+    public function scan_apply()
+    {
+        if (strtolower($this->input->method()) !== 'post') {
+            redirect('callhistory');
+            return;
+        }
+
+        $user_id = (int)$this->session->userdata('user_id');
+        $raw_changes = $this->input->post('changes', TRUE);
+
+        if (empty($raw_changes) || !is_array($raw_changes)) {
+            $this->session->set_flashdata('notice', 'No changes submitted.');
+            redirect('callhistory');
+            return;
+        }
+
+        // Validate that every station_id belongs to this user before applying
+        $station_ids = $this->callhistory_model->get_station_ids_for_logbook($user_id);
+        $station_ids_set = array_flip($station_ids);
+
+        $safe_changes = array();
+        foreach ($raw_changes as $change) {
+            $qso_id = isset($change['qso_id']) ? (int)$change['qso_id'] : 0;
+            $station_id = isset($change['station_id']) ? (int)$change['station_id'] : 0;
+
+            if ($qso_id <= 0 || $station_id <= 0) {
+                continue;
+            }
+
+            if (!isset($station_ids_set[$station_id])) {
+                continue;
+            }
+
+            $safe_changes[] = array(
+                'qso_id' => $qso_id,
+                'station_id' => $station_id,
+                'new_sig' => $this->security->xss_clean((string)($change['new_sig'] ?? '')),
+                'new_sig_info' => $this->security->xss_clean((string)($change['new_sig_info'] ?? '')),
+            );
+        }
+
+        if (empty($safe_changes)) {
+            $this->session->set_flashdata('notice', 'No valid changes to apply.');
+            redirect('callhistory');
+            return;
+        }
+
+        $applied = $this->callhistory_model->apply_sig_backfill($safe_changes);
+
+        $this->session->set_flashdata('notice', $applied . ' QSO(s) updated with SIG data.');
+        redirect('callhistory');
+    }
+
     public function lookup()
     {
         if (strtolower($this->input->method()) !== 'post') {
@@ -213,6 +356,75 @@ class Callhistory extends CI_Controller {
         echo json_encode($response);
     }
 
+    private function get_all_callsigns_in_file($file_path)
+    {
+        $callsigns = array();
+        $header_map = null;
+
+        if (($handle = fopen($file_path, 'r')) === FALSE) {
+            return $callsigns;
+        }
+
+        while (($row = fgetcsv($handle, 0, ',')) !== FALSE) {
+            if (empty($row)) {
+                continue;
+            }
+
+            $row = array_map('trim', $row);
+            if (count($row) === 1 && $row[0] === '') {
+                continue;
+            }
+
+            if ($this->is_comment_row($row)) {
+                continue;
+            }
+
+            if ($this->looks_like_header($row)) {
+                $header_map = $this->build_header_map($row);
+                continue;
+            }
+
+            $row_callsign = $this->extract_by_map_or_index($row, $header_map, array('call', 'callsign', 'callsigns'), 0);
+            $row_callsign = $this->normalize_callsign($row_callsign);
+
+            if ($row_callsign === '') {
+                continue;
+            }
+
+            // Strip portable/alternative suffixes to get base call for matching
+            $base_callsign = $row_callsign;
+            if (strpos($base_callsign, '/') !== FALSE) {
+                $parts = explode('/', $base_callsign);
+                // Use the longest segment as the base callsign
+                usort($parts, function($a, $b) { return strlen($b) - strlen($a); });
+                $base_callsign = $parts[0];
+            }
+
+            $name = $this->extract_name($row, $header_map);
+            $exch1 = $this->extract_by_map_or_index($row, $header_map, array('exch1', 'exchange1', 'exchange', 'member', 'membership'), 8);
+
+            if ($exch1 === '' && is_null($header_map)) {
+                $exch1 = $this->guess_exch1_without_header($row);
+            }
+
+            $callsigns[$base_callsign] = array(
+                'name' => $name,
+                'exch1' => $exch1,
+            );
+
+            // Also index by original callsign if it differs (e.g. contains /)
+            if ($row_callsign !== $base_callsign) {
+                $callsigns[$row_callsign] = array(
+                    'name' => $name,
+                    'exch1' => $exch1,
+                );
+            }
+        }
+
+        fclose($handle);
+        return $callsigns;
+    }
+
     private function find_matches_in_file($file_path, $callsign, $file)
     {
         $matches = array();
diff --git a/application/models/Callhistory_model.php b/application/models/Callhistory_model.php
index ac8011d1d..aa1dd0284 100644
--- a/application/models/Callhistory_model.php
+++ b/application/models/Callhistory_model.php
@@ -57,4 +57,115 @@ class Callhistory_model extends CI_Model {
         $this->db->where('id', (int)$id);
         return $this->db->delete('callhistory_files');
     }
+
+    public function get_station_ids_for_logbook($user_id, $logbook_id = NULL)
+    {
+        if ($logbook_id === NULL || $logbook_id === '' || $logbook_id === 0 || $logbook_id === '0') {
+            $this->db->select('station_id');
+            $this->db->from('station_profile');
+            $this->db->where('user_id', (int)$user_id);
+
+            $query = $this->db->get();
+            $station_ids = array();
+            foreach ($query->result() as $row) {
+                $station_ids[] = (int)$row->station_id;
+            }
+
+            return $station_ids;
+        }
+
+        $this->db->select('station_location_id');
+        $this->db->from('station_logbooks_relationship');
+        $this->db->where('station_logbook_id', (int)$logbook_id);
+        $query = $this->db->get();
+
+        $candidate_ids = array();
+        foreach ($query->result() as $row) {
+            $candidate_ids[] = (int)$row->station_location_id;
+        }
+
+        if (empty($candidate_ids)) {
+            return array();
+        }
+
+        $this->db->select('station_id');
+        $this->db->from('station_profile');
+        $this->db->where('user_id', (int)$user_id);
+        $this->db->where_in('station_id', $candidate_ids);
+        $verified_query = $this->db->get();
+
+        $verified_ids = array();
+        foreach ($verified_query->result() as $row) {
+            $verified_ids[] = (int)$row->station_id;
+        }
+
+        return $verified_ids;
+    }
+
+    public function get_qsos_for_callsigns($user_id, $callsigns, $logbook_id = NULL)
+    {
+        $callsigns = array_values(array_unique(array_filter(array_map('strval', (array)$callsigns))));
+        if (empty($callsigns)) {
+            return array();
+        }
+
+        $station_ids = $this->get_station_ids_for_logbook($user_id, $logbook_id);
+        if (empty($station_ids)) {
+            return array();
+        }
+
+        $table = $this->config->item('table_name');
+        $results = array();
+
+        foreach (array_chunk($callsigns, 500) as $callsign_chunk) {
+            $escaped_callsigns = array();
+            foreach ($callsign_chunk as $callsign) {
+                $escaped_callsigns[] = $this->db->escape(strtoupper($callsign));
+            }
+
+            $this->db->select($table . '.COL_PRIMARY_KEY, ' . $table . '.COL_CALL, ' . $table . '.COL_TIME_ON, ' . $table . '.COL_BAND, ' . $table . '.COL_MODE, ' . $table . '.COL_SUBMODE, ' . $table . '.COL_SIG, ' . $table . '.COL_SIG_INFO, ' . $table . '.station_id, station_profile.station_profile_name, station_profile.station_callsign');
+            $this->db->from($table);
+            $this->db->join('station_profile', 'station_profile.station_id = ' . $table . '.station_id');
+            $this->db->where('station_profile.user_id', (int)$user_id);
+            $this->db->where_in($table . '.station_id', $station_ids);
+            $this->db->where('UPPER(REPLACE(' . $table . '.COL_CALL, "Ø", "0")) IN (' . implode(',', $escaped_callsigns) . ')', NULL, FALSE);
+            $this->db->order_by($table . '.COL_TIME_ON', 'DESC');
+
+            $query = $this->db->get();
+            $results = array_merge($results, $query->result());
+        }
+
+        return $results;
+    }
+
+    public function apply_sig_backfill($changes)
+    {
+        if (empty($changes)) {
+            return 0;
+        }
+
+        $table = $this->config->item('table_name');
+        $applied = 0;
+
+        $this->db->trans_start();
+        foreach ($changes as $change) {
+            $this->db->where('COL_PRIMARY_KEY', (int)$change['qso_id']);
+            $this->db->where('station_id', (int)$change['station_id']);
+            $this->db->update($table, array(
+                'COL_SIG' => $change['new_sig'],
+                'COL_SIG_INFO' => $change['new_sig_info'],
+            ));
+
+            if ($this->db->affected_rows() >= 0) {
+                $applied++;
+            }
+        }
+        $this->db->trans_complete();
+
+        if (!$this->db->trans_status()) {
+            return 0;
+        }
+
+        return $applied;
+    }
 }
diff --git a/application/views/callhistory/index.php b/application/views/callhistory/index.php
index 88ecd3335..766f3ecc1 100644
--- a/application/views/callhistory/index.php
+++ b/application/views/callhistory/index.php
@@ -2,6 +2,100 @@
     <h2>Call History</h2>
     <p class="text-muted">Upload N1MM call history files (.txt/.csv), assign an optional organization label (e.g., FOC), and set file priority for matching.</p>
 
+    <?php if (!empty($preview)) { ?>
+    <div class="card mb-3 border-warning">
+        <div class="card-header bg-warning text-dark">
+            <strong><i class="fas fa-search"></i> Scan Preview &mdash; <?php echo htmlspecialchars($scan_file->original_filename); ?></strong>
+            <span class="badge bg-dark ms-2"><?php echo count($preview); ?> QSO(s) with blank SIG fields found</span>
+        </div>
+        <div class="card-body">
+            <p class="text-muted small mb-2">Only QSOs with <strong>no existing SIG data</strong> are shown. Review the proposed values below, then click <strong>Apply Selected</strong> to write them.</p>
+            <form method="post" action="<?php echo site_url('callhistory/scan_apply'); ?>" id="apply-form">
+                <div class="mb-2 d-flex gap-2">
+                    <button type="button" class="btn btn-sm btn-outline-secondary" id="select-all-btn"><i class="fas fa-check-double"></i> Select All</button>
+                    <button type="button" class="btn btn-sm btn-outline-secondary" id="deselect-all-btn"><i class="fas fa-times"></i> Deselect All</button>
+                    <button type="submit" class="btn btn-sm btn-success" id="apply-btn"><i class="fas fa-save"></i> Apply Selected (<span id="selected-count"><?php echo count($preview); ?></span>)</button>
+                </div>
+                <div class="table-responsive">
+                    <table id="callhistory-preview-table" class="table table-sm table-striped table-hover w-100">
+                        <thead>
+                            <tr>
+                                <th style="width:30px;"><input type="checkbox" id="check-all" checked></th>
+                                <th>Callsign</th>
+                                <th>Date/Time</th>
+                                <th>Band</th>
+                                <th>Mode</th>
+                                <th>Station Location</th>
+                                <th>SIG &rarr;</th>
+                                <th>SIG Info &rarr;</th>
+                            </tr>
+                        </thead>
+                        <tbody>
+                            <?php foreach ($preview as $i => $row) { ?>
+                            <tr>
+                                <td>
+                                    <input type="checkbox" class="row-check" name="changes[<?php echo $i; ?>][qso_id]"
+                                           value="<?php echo (int)$row['qso_id']; ?>" checked>
+                                    <input type="hidden" name="changes[<?php echo $i; ?>][station_id]" value="<?php echo (int)$row['station_id']; ?>">
+                                    <input type="hidden" name="changes[<?php echo $i; ?>][new_sig]" value="<?php echo htmlspecialchars($row['new_sig']); ?>">
+                                    <input type="hidden" name="changes[<?php echo $i; ?>][new_sig_info]" value="<?php echo htmlspecialchars($row['new_sig_info']); ?>">
+                                </td>
+                                <td><?php echo htmlspecialchars($row['callsign']); ?></td>
+                                <td><?php echo htmlspecialchars($row['time_on']); ?></td>
+                                <td><?php echo htmlspecialchars($row['band']); ?></td>
+                                <td><?php echo htmlspecialchars($row['mode']); ?></td>
+                                <td><?php echo htmlspecialchars($row['station_location']); ?></td>
+                                <td><span class="badge bg-primary"><?php echo htmlspecialchars($row['new_sig']); ?></span></td>
+                                <td><span class="badge bg-secondary"><?php echo htmlspecialchars($row['new_sig_info']); ?></span></td>
+                            </tr>
+                            <?php } ?>
+                        </tbody>
+                    </table>
+                </div>
+            </form>
+        </div>
+    </div>
+    <?php } elseif (isset($scan_file)) { ?>
+    <div class="alert alert-info"><i class="fas fa-info-circle"></i> No blank-SIG matches found for <strong><?php echo htmlspecialchars($scan_file->original_filename); ?></strong> in the selected logbook scope.</div>
+    <?php } ?>
+
+    <?php if (!empty($files)) { ?>
+    <div class="card mb-3">
+        <div class="card-header">
+            <strong><i class="fas fa-search-plus"></i> Scan Logbook</strong>
+        </div>
+        <div class="card-body">
+            <form method="post" action="<?php echo site_url('callhistory/scan_preview'); ?>" class="row g-3 align-items-end">
+                <div class="col-md-4">
+                    <label for="scan_file_id" class="form-label">Call History File</label>
+                    <select class="form-select" id="scan_file_id" name="file_id" required>
+                        <?php foreach ($files as $f) { ?>
+                        <option value="<?php echo (int)$f->id; ?>" <?php echo (isset($scan_file) && (int)$scan_file->id === (int)$f->id) ? 'selected' : ''; ?>>
+                            <?php echo htmlspecialchars($f->file_label ?: $f->original_filename); ?>
+                            <?php if (!empty($f->organization_label)) { echo '(' . htmlspecialchars($f->organization_label) . ')'; } ?>
+                        </option>
+                        <?php } ?>
+                    </select>
+                </div>
+                <div class="col-md-4">
+                    <label for="scan_logbook_id" class="form-label">Station Location Scope</label>
+                    <select class="form-select" id="scan_logbook_id" name="logbook_id">
+                        <option value="">All my station locations</option>
+                        <?php if (!empty($logbooks)) { foreach ($logbooks as $lb) { ?>
+                        <option value="<?php echo (int)$lb->logbook_id; ?>" <?php echo (isset($selected_logbook_id) && (int)$selected_logbook_id === (int)$lb->logbook_id) ? 'selected' : ''; ?>>
+                            <?php echo htmlspecialchars($lb->logbook_name); ?>
+                        </option>
+                        <?php } } ?>
+                    </select>
+                </div>
+                <div class="col-md-4">
+                    <button type="submit" class="btn btn-warning"><i class="fas fa-search"></i> Preview Changes</button>
+                </div>
+            </form>
+        </div>
+    </div>
+    <?php } ?>
+
     <div class="card mb-3">
         <div class="card-header">
             <strong>Upload Call History File</strong>
@@ -99,3 +193,66 @@
         </div>
     </div>
 </div>
+
+<?php if (!empty($preview)) { ?>
+<script>
+$(document).ready(function () {
+    var table = $('#callhistory-preview-table').DataTable({
+        "pageLength": 25,
+        "order": [[2, "asc"]],
+        "columnDefs": [
+            { "orderable": false, "targets": 0 },
+            { "orderable": false, "targets": 6 },
+            { "orderable": false, "targets": 7 }
+        ],
+        "language": {
+            url: getDataTablesLanguageUrl()
+        }
+    });
+
+    function updateSelectedCount() {
+        var count = $('#callhistory-preview-table tbody .row-check:checked').length;
+        $('#selected-count').text(count);
+    }
+
+    $('#check-all').on('change', function () {
+        var checked = $(this).prop('checked');
+        $('#callhistory-preview-table tbody .row-check').prop('checked', checked);
+        updateSelectedCount();
+    });
+
+    $('#select-all-btn').on('click', function () {
+        $('#callhistory-preview-table tbody .row-check').prop('checked', true);
+        $('#check-all').prop('checked', true);
+        updateSelectedCount();
+    });
+
+    $('#deselect-all-btn').on('click', function () {
+        $('#callhistory-preview-table tbody .row-check').prop('checked', false);
+        $('#check-all').prop('checked', false);
+        updateSelectedCount();
+    });
+
+    $('#callhistory-preview-table tbody').on('change', '.row-check', function () {
+        updateSelectedCount();
+    });
+
+    $('#apply-form').on('submit', function (e) {
+        // Disable checkboxes that are unchecked so their hidden inputs are not submitted
+        $('#callhistory-preview-table tbody .row-check:not(:checked)').each(function () {
+            var idx = $(this).attr('name').replace('[qso_id]', '');
+            $('[name="' + idx + '[station_id]"],' +
+              '[name="' + idx + '[new_sig]"],' +
+              '[name="' + idx + '[new_sig_info]"]').prop('disabled', true);
+            $(this).prop('disabled', true);
+        });
+
+        var count = $('#apply-form input.row-check:not(:disabled)').length;
+        if (count === 0) {
+            e.preventDefault();
+            alert('No rows selected.');
+        }
+    });
+});
+</script>
+<?php } ?>