{"id":2644,"date":"2016-11-19T15:20:56","date_gmt":"2016-11-19T15:20:56","guid":{"rendered":"http:\/\/www.tsgarc.uk\/?p=2644"},"modified":"2016-11-19T15:22:58","modified_gmt":"2016-11-19T15:22:58","slug":"the-hf-antenna","status":"publish","type":"post","link":"https:\/\/www.tsgarc.uk\/?p=2644","title":{"rendered":"The HF antenna…"},"content":{"rendered":"

So, most members should be aware by now that the old 40m dipole has been\u00a0removed and replaced with a new 40m dipole! \u00a0The feedpoint 1:1 balun was also changed for good measure and sealed thoroughly\u00a0for the winter.<\/p>\n

But this is not the end of the work on the HF antenna, that was just task 1 \ud83d\ude09 \u00a0Task 2 consists of\u00a0two activities and is planned for Spring 2017 once it dries and warms a little \ud83d\ude42<\/p>\n

Activity 1 will add elements for 30m and 20m expanding\u00a0the 40m dipole into three parallel dipoles. This will result in a tri-band antenna that is resonant on 40m, 30m and 20m giving us a very useful antenna.<\/p>\n

Activity 2 will replace the coaxial feeder between the radio room and the antenna feedpoint.<\/p>\n

\"TSGARC<\/a>Today we have approximately\u00a02.3dB of loss at 7.1MHz between the radio room and the antenna feedpoint. \u00a0Assuming the coax is in the very best condition (which its not) and it’s RG-58C (Its an RG58 of some sort) this equates to about 54m of coax. \u00a0That’s a 40% power loss on Tx and Rx. \u00a0Replacing this with RG-213 reduces the loss to 0.9dB or a 19% power loss. \u00a0An improvement of 1.4dB or 20% doesn’t sound much and its not but consider the situation at 14MHz. \u00a0With RG-58C there is 3.2dB \/ 53% loss but using RG213 the loss is 1.3dB or 26%.<\/p>\n\n\n\n\n\n\n
Frequency<\/strong><\/td>\nRG-58C<\/strong><\/td>\nRG-213\/U<\/strong><\/td>\nUltraflex-10<\/strong><\/td>\n<\/tr>\n
7.1MHz<\/td>\n2.2dB<\/td>\n0.9dB<\/td>\n0.5dB<\/td>\n<\/tr>\n
10MHz<\/td>\n2.7dB<\/td>\n1.1dB<\/td>\n0.6dB<\/td>\n<\/tr>\n
14.2MHz<\/td>\n3.2dB<\/td>\n1.3dB<\/td>\n0.8dB<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Coax loss per 54m\u00a0<\/strong><\/p>\n

To put this differently. \u00a0The transmitter places 100W max into the feeder at 7MHz, 10MHz and 14MHz. \u00a0With RG-58 the antenna receives: 60W, 54W & 47W respectively. \u00a0Replacing with RG-213 results in: 81W, 77W & 74W. \u00a0Using a better coax and one that does not cost \u00a0much more than RG-213 the situation can be improved further. \u00a0The overall difference of using something like Ultraflex-10 over RG-58 is definitely worth having and that is why activity 2 is so important.<\/p>\n

The completed parallel dipole antenna will remain in its current location supported by the trees at either end. \u00a0But supporting the end of the antenna elements will require two attachment points instead of the one we have today. \u00a0Investigation has showed this is not a significant obstacle.<\/p>\n

Thanks to Peter, G3LDO for the above diagram taken from his excellent book Backyard Antennas<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"

So, most members should be aware by now that the old 40m dipole has been\u00a0removed and replaced with a new 40m dipole! \u00a0The feedpoint 1:1 balun was also changed for good measure and sealed thoroughly\u00a0for the winter. But this is … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":7,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[5],"tags":[9,8,17,27],"class_list":["post-2644","post","type-post","status-publish","format-standard","hentry","category-news","tag-antenna","tag-dipole","tag-g0rvm","tag-tsgarc"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t