Do you have a passion for homebrew portable HF antennas and antenna impedance matching devices, commonly known in the radio amateur community as Antenna Tuning Units (ATU) or in parts of the northern hemisphere as Aerial Matching Unit (AMU)? …then read on else leave this page now. The term ‘Tuning Unit’ is far from the truth, an ATU is a mechanical device comprising of one or more variable capacitors and a variable or multi-tap inductor. The sole purpose of an ATU is to transform the impedance of an unknown or known antenna feed point (where the impedance is not 50 ohms) to 50 ohms, suitable for connection to a solid state transceiver antenna socket. An ATU doesn’t ‘tune’ an antenna.
One of my hombrew HF SOTA antenna options is a 27.2 metre end fed long wire antenna, I chose 27.2 metres as the length is non-resonant for radio amateur HF bands 80, 40, 20 and 17m. Being a non-resonant length the feed point shouldn’t exhibit a very high impedance thus placing the End Fed wire antenna impedance within range of my homebrew T-Match ATU. The antenna length may be longer but not shorter. If you are interested in non-resonant End Fed antenna lengths, take a look at VK6YSF Long Wire antenna page http://vk6ysf.com/longwire_antenna.htm. The next longest length I may try is 33.5 and later 38 metres.
For SOTA purposes, my HF SSB operating frequency interests are 3.6, 7.1, 14.31 and 18.14 MHz (80, 40, 20 and 17m respectively), with the exception of summer where on some occasions 50 MHz (6m) is a viable option for long distance contacts around Australia, these are generally limited to days of sporadic E propagation. Why 80, 40, 20 and 17m? well that’s where the majority of VK SOTA and Parks home chasers have their HF antenna arrangements set up. Remember as the activator you have accepted the risk of being on a mountain top and due to local environmental factors you may be on a summit for a short period say 15 to 30 minutes, in that time you need transmitting frequency options. It’s unwise to rely on a single band for a four unique callsign qualification. BTW not every activator limits their activation to only four unique contacts alas some do. If you are faced with an impending storm, you accidentally set up next to an ant’s nest or the return journey back to you car is five hours away, then you may not have time to share the summit points with a bunch of enthusiastic SOTA chasers 🙂 When time permits I offer the summits points to as many chasers who have the time to call me, that includes offering the summit points to DX chasers in particular our friends in New Zealand (ZL) 🙂 To do so you need a choice of bands which offer a range of propagation distances, hence the addition of 14 and 18 MHz.
So how does the end fed long wire antenna, some may say an inverted L, perform in the real world deployed on a summit where the ground is hard and rocky? This is not the ‘simulated’ world of End Fed antenna critics who sit in front of their computer screens creating hypothetical antenna models to prove their dislike of End Fed antennas. I find it odd that the keyboard warriors take every opportunity to discredit the humble End Fed? Back to the real world which consists of people like me who choose to experiment with a range of practical antenna solutions for a range of environmental factors found at a summit. Yes I do have three (3) homebrew portable linked dipole antennas and yes each linked dipole performs like any other inverted V dipole, however there are times when an End Fed antenna is well suited to a particular type of summit and it’s environmental surrounds. Besides, to be honest, it’s nice not to have 12 metres of RG58AU coax in my backpack.
I have just returned to Canberra having spent five days in VK3 where I activated 3 summits using the 27.2 metre End Fed Antenna fashioned as an inverted V. See diagram below. Ideally the far end should be as high above the ground as is possible, try a tree branch if one is within reach. The transceiver is an Icom IC-703 QRP 10 watts output. What are the results?
27 metre End Fed Long Wire Antenna with three counterpoise wires connected to the ATU ground terminal.
The results speak for themselves, using HF frequencies I qualified each summit and in doing so I made a number of DX chaser contacts. Considering we are all dealing with the solar minimum the results are good. See SOTA log extracts below.
On 80 and 40m the antenna is at a height above ground which promotes NVIS propagation out to 500 km. On 40m the propagation is also out to 1000 km to VK5 while on 20m the propagation is beyond 1000 km reaching 2300 km to ZL. Two separate sporadic E openings on 20m demonstrated the capacity to work short skip between 200 and 500 km.
17 December 2018 – Mt Big Ben VK3/VE-105
|01:17z||VK1VIC/P||7MHz||SSB||Tony S2S VK1/AC-040 S59 R59|
|01:19z||VK1DA/P||7MHz||SSB||Andrew S2S VK1/AC-042 S59 R59|
|01:21z||VK3PF/P||7MHz||SSB||Peter S2S VK3/VG-080 S57 R45|
|01:22z||VK2IO||7MHz||SSB||Gerard S59 R55|
|01:23z||VK3HP||7MHz||SSB||Grant S59 R33|
|01:26z||VK1DA/P||3.5MHz||SSB||Andrew S2S VK1/AC-042 S55 R51|
|01:33z||VK4TJ||14MHz||SSB||John S55 R54|
|01:34z||VK5IS||14MHz||SSB||Ian S57 R52|
|01:35z||VK3SQ||14MHz||SSB||Geoff S58 R57|
|01:45z||VK3SQ||7MHz||SSB||Geoff S59 R55|
20 December 2018 – Mt Donna Buang VK3/VC-002
|02:56z||VK3PF/P||7MHz||SSB||Peter s56 r57 S2S VK3/VE-167|
|02:59z||VK3SQ||7MHz||SSB||Geoff s58 r56|
|03:00z||VK7XDM||7MHz||SSB||David s58 r53|
|03:13z||VK5IS||14MHz||SSB||Ian s58 r54|
|03:14z||VK1MCW||14MHz||SSB||Bill s58 r55 sporadic E|
|03:15z||VK4TJ||14MHz||SSB||John s55 r51|
|03:17z||VK2IO||14MHz||SSB||Gerard s59 r53 sporadic E|
|03:18z||ZL1BYZ||14MHz||SSB||John s55 r42|
|03:27z||VK3SQ||3.5MHz||SSB||Geoff s59 r56|
22 December 2018 – Mt Burngoogee VK2/RI-016
|02:14z||VK1MA||7MHz||SSB||Matt s59 r58|
|02:16z||VK5CZ||7MHz||SSB||Ian s55 r52|
|02:17z||VK3GTV||7MHz||SSB||Col s59 r59|
|02:19z||VK3SQ||7MHz||SSB||Geoff s59 r56|
|02:19z||VK5IS||7MHz||SSB||Ian s57 r52|
|02:20z||VK2IO||7MHz||SSB||Gerard s59 r44|
|02:21z||VK1RX||7MHz||SSB||Al s59 r49|
|02:23z||VK3FXBR||7MHz||SSB||Ben s58 r59|
|02:24z||VK5FANA||7MHz||SSB||Adrian s51 r52|
|02:28z||VK5WG||14MHz||SSB||Nev s59 r58|
|02:31z||VK4SYD||14MHz||SSB||Rob s58 r55|
|02:34z||ZL1BYZ||14MHz||SSB||John s59 r53|
|02:36z||VK3SQ||14MHz||SSB||Geoff s55 r53 sporadic E|
|02:37z||VK5IS||14MHz||SSB||Ian s59 r58|
I will continue to experiment with this End Fed wire antenna from SOTA peaks and just for fun I may try a 33.5 metre version.
If you are interested in homebrew HF antennas, why not give the humble End Fed a shot? Ignore the desktop warrior critics 🙂