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
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
SolderSmoke Podcast 147 is available for downloading:
October 29/30 2012
Hurricane Sandy on the way
Thanks for birthday wishes
Einstein — a very nice fellow with a bit of the Knack
Rocket project update
808 key chain cameras (thanks for the Amazon support!)
Audio output transformer for Barbados Barebones RX
Mighty Midget RX — breaking it, fixing it (with help from friends)
Freq counter connection to Tek scope
Halli S-38E — How to avoid electrocution?
The HQ-100’s anti-drift alarm clock
Book Review: “Instruments of Amplification” by H.P. Friedrichs (5 Soldering Irons!)
BANDSWEEP: 20 meter SSB via DC receiver on hurricane day
Report on outcome of the hurricane — inverter saves the day (really the night)
MAILBAG (a big one).
Short but interesting demo of antenna static discharge – good motivation. Take precautions!
Link to Youtube video
On one of the QRP lists I get, there was a link to K7HV’s quest for DXCC with an Argonaut at QRP power. Here is a link
to videos of each contact, 1-92 so far.
Update: Sept. 25, 2012 – total now sits at 101.
You’ll have to work extra hard on this quiz because it’s not a “multiple guess.” Some answers may require a little calculation, some may require exercising the memory banks — and all will require a little head scratching.
Do the quiz