The London Amateur Radio Club (LARC) announces the availability of a CW course and sessions of kit building. Both should be fun to participate in, if you are interested, then this should be a good way to get better at code, and dust off those kits, it is now time to dig those old kits out of storage and get them built.
Requests for a CW course, to get the participant up to a workable 20 wpm, have been answered. Mitch Powell, VE3OT and long time CW instructor, will begin a CW course on Thursday, January 11th, 2018, starting at 19:00 EST (location to be announced). Several classroom sessions will be supported by nightly on air CW practice sessions. If you don’t have an 80m CW receiver, see the announcement below on kit building. The Koch method of CW instruction may be helpful to you and free software is available at g4fon.net
Kit Building Sessions
Want to learn how to put together a radio kit, but are concerned your soldering or toroid winding skill could use some improvement? Have a kit you started years ago and want to finish someday? Need a simple CW receiver for off air code practice? These sessions, conducted by knowledgeable hams every Saturday morning starting at 10:00 EST on January 13th, 2018, and held at the LARC Club station, will help you get over any hurdles, advise how to build and test any project you decide to tackle. You may wish to build something simple, or something complex, pretty much anything! Type “Radio Kit” into a Google search and see how much choice is out there. Our first session might just be about making an intelligent choice!
Please RSVP your interest in attending these CW and/or Kit Building sessions to Dave McCarter at VE3GSO@gmail.com
We scored 3,170 points in the 2017 Field Day event, 252 contacts, 11 participants, in the ONS section. We participated in the 4A section, 4 transmitters, battery powered. For a full report on the 2017 Field Day, check QST December 2017.
ARRL just announced the ARRL International Grid Chase for 2018. The goal of the “grid chase” is to work as many grid squares as possible. Contest log submissions are required to be done using LOTW, for both parties. For all of the rules, click on the Link below.
Link to Announcements/Rules
Comment: Requiring both parties to log their contacts in LOTW and only then does the contact count towards your grid chase is a major restriction on contacts in this grid chase. QSLs don’t count, only LOTW contact entries count. What percent of those you might contact will actually be in the LOTW program? According to statistics on the LOTW home page, there are 100,000 users of LOTW, this represents a small minority of hams worldwide.
JOTA/JOTI (Jamboree on the Air/Jamboree on the Internet) celebrates the scouting movement on the air and on the internet. This years event happens Oct 20-22. On Saturday October 21, a few of the members of EARS will be attending the event with the Sparta Scouts and Venturers at the Sparta Community Hall and setting up amateur radio stations and attempting to contact other groups with similar setups.
Come on out between 12 and 4 and meet other scouting members and talk to other groups via radio.
EARCHI End Fed Matchbox
An end fed antenna consists of a wire fed on its end, the length of that wire is not resonant with any frequency or frequencies you will be using it on. Lengths of a half-wave or multiple must be avoided. The transformer usually used with an end fed wire is a 9:1 transformer. This transformer converts the impedance at the end of the random wire down to about 50 ohms, a value which any modern transmitter can transfer power to and has been designed for.
Notes from W1SFR:
In the case of the end fed random wire, some lengths are better than others because of the harmonic effect of the length of the wire and how that affects the various band on which you wish to operate. Counter to tuning a length of wire like you would with a dipole, with a random wire you don’t want the length to be harmonic on any band. There are ideal lengths that have been mathematically determined to be best for randon wires. Here they are:
29 35 41 58 71 84 107 119 148 203 347 407 423
I have chosen 35′ as the standard length for my antennas, but you can experiment. I have used up to 84′ and the KX3 will still tune all bands but as the wire gets longer so does the resistance so it becomes harder and harder for the tuner to do its job. At 35′ it’s not too short and not too long and works great in every configuration I’ve tried so far.
9:1 unun transformer:
my 9:1 unun using a T130-2 toroid:
Facebook Group – EFHW Antennas
Steve Ellington N4LQ started up a group on Facebook called End Fed Half Wave Antennas. The purpose of this group is to explore the use of an end fed half wave antenna. An end fed half wave antenna is one of a specific length depending on the frequency that it is to be used on, for example, an end fed half wave antenna for 80 meters is about 130′ long. The length of a half wave antenna is calculated using the following formula: L (ft) = 468 / f (freq in mhz). The end fed half wave antenna presents a large impedance to your rig, so this impedance must be stepped down to a more useful impedance that is closer to 50 ohms. Most radios today expect to see an antenna with an impedance of 50 ohms at the end of it.
End-fed Half Wave antennas (or EFHWs) cover multiple bands without traps, stubs, or resonators. End-fed wires resonate on their 1/2-wave fundamental frequency plus all odd and even harmonics above. By adding a broad-band matching network, the wire’s high impedance feed point is transformed down to 50 ohms across a wide frequency range and, in most cases, you don’t need a tuner to operate. Note that a single-wire radiator may be installed using only one high center or end support, making it fast and easy to set up at home, on the road, or as a “grab-and-go” emergency antenna.
There are many different ways to transform this impedance to 50 ohms. The one that Steve promotes is to use a 49:1 unun and information about this method follows.
The following is a diagram which explains how to construct a 49:1 transformer.
Wound with #14 enameled wire using FT240-43 toroids:
Steve made a video in which he showed the results of antenna tests using various setups.
Video: EFHW Installation Summary or Is your feed line part of the antenna?
Steve’s best test results were with the transformer grounded close to the ground and fed with enough coax to reach the transmitter also grounded. Details are shown in the next two images:
Steve Ellington’s antenna:
133 ft. inverted L with 51 feet vertical. Transformer grounded, very well. Coax on ground 100+ feet to shack, no chokes. Home brew transformer 2 primary 13 sec. mix 52 three stacked cores. 14 ga wire .. swr acceptable …below 2.5 and much lower
Modification for 75 meters:
Here is how to raise the resonant frequency on your myAntennas EFHW-8010 for 75 meter phone operation without affecting the other bands. Simply cut the antenna at the half way point and insert a capacitor. 500pf will put you at around 3700khz. Lower values i.e. 300pf will raise it even higher. I suggest a ceramic disc capacitor rated for at least several KV just to be safe. I have tested and verified this and it works great.
Videos by Steve Ellington N4LQ related to EFHW Antennas:
49:1 Transformer Vendors