{"id":16,"date":"2026-10-28T00:05:27","date_gmt":"2026-10-28T00:05:27","guid":{"rendered":"https:\/\/k0axx.net\/?page_id=16"},"modified":"2026-10-28T01:23:03","modified_gmt":"2026-10-28T01:23:03","slug":"relay-sequencing","status":"publish","type":"page","link":"https:\/\/k0axx.net\/?page_id=16","title":{"rendered":"Transmit\/Receive Relay Sequencing"},"content":{"rendered":"<p class=\"k-kicker wp-block-paragraph\">TECHNICAL NOTE \/ PROTECTION \/ CONTROL<\/p><p class=\"wp-block-paragraph\">A high-power weak-signal station cannot safely treat an antenna relay and a preamplifier as independent accessories. Their control timing must ensure that transmit power cannot reach the LNA or receiver.<\/p><h2 class=\"wp-block-heading\">A fail-safe sequence<\/h2><ul class=\"wp-block-list\"><li><strong>Before transmit:<\/strong> disable or bypass the LNA; switch the receive path out; move the antenna relay into its TX state.<\/li><li><strong>Confirm switching:<\/strong> allow relay contact movement and any required settle time.<\/li><li><strong>Enable RF:<\/strong> only after the path is safe, permit amplifier drive and transmit RF.<\/li><li><strong>After RF stops:<\/strong> withdraw drive, let RF decay, return relays to RX and restore LNA power last.<\/li><\/ul><h2 class=\"wp-block-heading\">No universal delay fits every system<\/h2><p class=\"wp-block-paragraph\">Mechanical switching times, RF hang-time, amplifier behavior and control-voltage transients differ. Design the sequence around data sheets and direct measurement. Make sure a stuck relay, broken cable or lost DC power cannot silently place the LNA in the transmit path.<\/p><h2 class=\"wp-block-heading\">Isolation and power handling<\/h2><p class=\"wp-block-paragraph\">Verify relay specifications at the band and power level actually used. DC coil rating, RF connector type, port isolation and insertion loss are separate requirements. A relay adequate on 50 MHz may be unsuitable at 1296 MHz.<\/p><p class=\"k-callout wp-block-paragraph\">This is design guidance, not an approved high-power wiring diagram. Include a positive transmit inhibit, RF exposure assessment and lightning protection appropriate to the installation.<\/p><h2 class=\"wp-block-heading\">Marshall K5QE: original primary source<\/h2><p class=\"wp-block-paragraph\">Read <a href=\"https:\/\/www.pnwvhfs.org\/conference\/2016\/pdf\/Marshall-K5QE-Sequencing-Presentation-v2.pdf\" target=\"_blank\" rel=\"noopener noreferrer\">On the Dark Side of Sequencing \u2014 Marshall Williams K5QE (2016, 23 slides)<\/a>. Marshall explains that the sequencer must ultimately control when the transmitting chain is allowed to produce RF. Simply using rig PTT to activate a relay downstream can leave the RF source transmitting before the contacts have settled.<\/p><h2 class=\"wp-block-heading\">Bench-test both transitions<\/h2><ul class=\"wp-block-list\"><li>Key the sequencer with RF drive inhibited; scope or time-stamp each output and relay-auxiliary contact.<\/li><li>Confirm receiver\/LNA protection and relay settle <em>before<\/em> the transverter and amplifier are permitted to generate RF.<\/li><li>On unkey, verify RF is completely removed <em>before<\/em> the relays return or preamp power is restored.<\/li><li>Test emergency release, lost-coil supply, partial connector removal and stuck-PTT behavior.<\/li><li>Use hardware transmit-inhibit and physical interlocks where feasible; software timing alone should not be the only protection.<\/li><\/ul><p class=\"k-callout wp-block-paragraph\">Do not copy a relay delay or wiring arrangement blindly from an example. Measure timing, power handling, isolation and fail-safe behavior with your actual hardware; high-power RF can damage equipment or cause injury.<\/p><p class=\"wp-block-paragraph\">Other talks and conference records appear in the <a href=\"\/marshall-k5qe\/\">K5QE presentations archive<\/a>.<\/p>","protected":false},"excerpt":{"rendered":"<p>TX\/RX interlocks, preamp protection, relay travel and sequencing principles, with K5QE primary-source references.<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-16","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/k0axx.net\/index.php?rest_route=\/wp\/v2\/pages\/16","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/k0axx.net\/index.php?rest_route=\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/k0axx.net\/index.php?rest_route=\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/k0axx.net\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/k0axx.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=16"}],"version-history":[{"count":1,"href":"https:\/\/k0axx.net\/index.php?rest_route=\/wp\/v2\/pages\/16\/revisions"}],"predecessor-version":[{"id":56,"href":"https:\/\/k0axx.net\/index.php?rest_route=\/wp\/v2\/pages\/16\/revisions\/56"}],"wp:attachment":[{"href":"https:\/\/k0axx.net\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=16"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}