Differences

This shows you the differences between two versions of the page.

--- oarc-sota-day-antennas [2022/05/29 13:13] – [VHF/UHF Antennas] m0smu
+++ oarc-sota-day-antennas [2025/04/03 19:46] (current) – m0kvi
@@ Line 2: / Line 2: @@
 ]]
-====== Antenna Ideas ======
+====== Antennas ======
 The primary goal for any SOTA antenna is to be lightweight while also being somewhat efficient. Typically setups use low power (unless you have strong arms!) so we want to get the best out of them.
@@ Line 22: / Line 22: @@
 You can, of course, buy these pre-made or in kit form from various retailers as well.
 ===== VHF/UHF Antennas =====
+==== Beam Antennas ====
 At this wavelength beam antennas become small enough to bring up hills. Yagi antennas for 2m are not uncommon, and the Moxon is an excellent design, but for the vast majority of people a vertical antenna may be fine.
@@ Line 29: / Line 31: @@
     * http://www.antentop.org/w4rnl.001/mvhf.html
     * https://reflector.sota.org.uk/t/home-brew-2m-moxon-fairly-lightweight/13123
+==== Vertical Antennas ====
 Popular vertical antennas include coax dipole types, 1/4 ground plane antennas with some radials, or j-pole/Slim Jims made from ladder line. A mast of some kind is useful to get them up high for better line of sight to the horizon.
+=== Slim Jim ===
+A Slim Jim is a small, robust, roll up antenna that can be bought ready-made or [[https://m0ukd.com/calculators/slim-jim-and-j-pole-calculator/|easily home made]] from ladder line, a length of coax and a connector for your radio. The default velocity factor on the calculator page is for bare copper which is too high for insulated ladder line - 0.8 to 0.89 is a closer estimate. The feed point can be weak so either make sure it is aligned with the centre support material or don't strip the insulation completely. Combined with an collapsible pole that can be strapped to a fencepost or supported on a ground spike makes for an effective - though single-band - antenna setup.
   * Links to vertical antenna plans
-Dipole antennas of various types are also popular for portable VHF/UHF expeditions, and some people use them to good effect on SOTA trips.
+==== Dipole Antennas ====
+Dipole antennas of various types are also popular for portable VHF/UHF expeditions, and some people use them to good effect on SOTA trips. Coax dipoles are included here, but some people would probably put them as a vertical. We’ll leave that debate and whether all vertical antennas are actually dipoles for an antenna theory class, though.
-  * Links to dipole antenna plans
+  * https://vk1nam.wordpress.com/2019/07/21/sota-lightweight-portable-2m-70cm-dipole-antenna-update/ - a lightweight dual-band dipole with integrated toroidal choke
+  * https://vk2zoi.com/articles/dual-band-half-wave-flower-pot/ - excellent design, easy to make and both Simon-M0SMU and Vic-EI7IYB have made versions.
@@ Line 43: / Line 54: @@
 Here’s some recommendations for masts and supports.
-  * SOTABeams do extensive poles and guying systems.
+  * [[https://www.sotabeams.co.uk/|SOTABeams]] do extensive poles and guying systems.