{"id":3193,"date":"2011-07-07T10:52:47","date_gmt":"2011-07-07T14:52:47","guid":{"rendered":"http:\/\/www.engineeringradio.us\/blog\/?p=3928"},"modified":"2023-04-30T11:25:53","modified_gmt":"2023-04-30T15:25:53","slug":"hot-elbow","status":"publish","type":"post","link":"https:\/\/www.engineeringradio.us\/blog\/2011\/07\/hot-elbow\/","title":{"rendered":"Hot Elbow"},"content":{"rendered":"\n

Found this 3-inch rigid elbow to be a little warm when we were removing a dividing wall as a part of an AC upgrade:<\/p>\n\n\n\n

\"MYAT<\/a>
MYAT 3 inch elbow<\/figcaption><\/figure>\n\n\n\n

As measured with my Fluke 62 mini IR thermometer<\/a>, the temperature is 163\u00b0F (72.7\u00b0C) at the clamp and drops down in both directions.<\/p>\n\n\n\n

This is at WEBE and this particular section of the transmission line is running 34 KW into the analog\/digital combiner in the next room. \u00a0The clamps are tight, but you can see a little scorch mark on the stainless steel clamp right over the slot in the field flange. \u00a0That is where there is a gap between the outer conductors, which possibly means the inner conductor was cut slightly too long during installation. \u00a0I suspect this and or a problem with the bullet is causing the heating issue. \u00a0I was never (and still am not) a fan of those field flange-type elbows, I’d much prefer the flanged type with a field flange on the straight line section.<\/p>\n\n\n\n

34 KW is getting into the semi-serious power level for FM broadcasting. \u00a0At those levels, even small impedance mismatches can lead to big problems. \u00a0We have a new elbow, field flanges, and bullets on order. \u00a0Unfortunately, we will have to take the station off the air to replace this.<\/p>\n\n\n\n

\"WEBE<\/a>
WEBE transmitter site with partition removed<\/figcaption><\/figure>\n\n\n\n

This is all a part of an air conditioning project. There was a plywood partition wall between the front and the back of the transmitters which was impeding airflow. \u00a0All of the HVAC contractors who bid on the AC job identified it as a problem that needed to be addressed before the big 5-ton wall-mount AC units were installed.<\/p>\n\n\n\n

Update:<\/strong>\u00a0Replaced elbow last night (8\/4). \u00a0Went off at 10 pm and back on at 10:25. \u00a0Found the inner conductor had been pushed out of place and was off center on the outside (toward the wall side) of the elbow. \u00a0This was an older elbow that did not have the nylon inner spacers on the center conductor. \u00a0The inner conductor was dark purple. \u00a0Before replacement, the elbow was 138\u00b0F (59\u00b0C)\u00a0under full power (34 KW). \u00a0After replacement, it was 97\u00b0F (36\u00b0C) as was the rest of the transmission line. \u00a0At these power levels and frequencies, even small, minor imperfections cause impedance shifts and become issues.<\/p>\n\n\n\n

\"Myat<\/a>
Myat 3 1\/8 inch elbow<\/figcaption><\/figure>\n\n\n\n

I cleaned up and reused the bullets and the outer conductor with scotch brite. I also used more support wires because I believe the elbow was starting to pull apart, which can sort of be seen in the first picture.<\/p>\n","protected":false},"excerpt":{"rendered":"

Found this 3-inch rigid elbow to be a little warm when we were removing a dividing wall as a part of an AC upgrade: As measured with my Fluke 62 mini IR thermometer, the temperature is 163\u00b0F (72.7\u00b0C) at the clamp and drops down in both directions. This is at WEBE and this particular section … Continue reading Hot Elbow<\/span><\/a><\/p>\n","protected":false},"author":4,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[82,214,8],"class_list":["post-3193","post","type-post","status-publish","format-standard","hentry","category-tech-stuff","tag-fm","tag-transmission-line","tag-transmitter-site"],"_links":{"self":[{"href":"https:\/\/www.engineeringradio.us\/blog\/wp-json\/wp\/v2\/posts\/3193","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.engineeringradio.us\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.engineeringradio.us\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.engineeringradio.us\/blog\/wp-json\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/www.engineeringradio.us\/blog\/wp-json\/wp\/v2\/comments?post=3193"}],"version-history":[{"count":5,"href":"https:\/\/www.engineeringradio.us\/blog\/wp-json\/wp\/v2\/posts\/3193\/revisions"}],"predecessor-version":[{"id":11777,"href":"https:\/\/www.engineeringradio.us\/blog\/wp-json\/wp\/v2\/posts\/3193\/revisions\/11777"}],"wp:attachment":[{"href":"https:\/\/www.engineeringradio.us\/blog\/wp-json\/wp\/v2\/media?parent=3193"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.engineeringradio.us\/blog\/wp-json\/wp\/v2\/categories?post=3193"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.engineeringradio.us\/blog\/wp-json\/wp\/v2\/tags?post=3193"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}