Technical Blog

ham radio coverLearn how to build projects for the ham shack or about new technology in Ham Radio. Posting of articles requires a user login ID with publishing rights.  Send an email to the WEB admin to request publishing rights for your account.

 

 


 

Home RFI Solution

RFIFor those who have struggled with RFI at the home station here is my solution to the interference.

 Over the past few years I have had an annoying set of evenly spaced tones that interfered with my 2M, 6M and UHF reception at home. The noise could be heard for about 100 ft from the house and then dropped off quickly. RF suppressors on the cables did not reduce the noise source.

My final solution proved to be replacing my 4 port Ethernet switch which was located near my radios. The low cost plastic case switch (LinkSys 10/100 5 port SW) was replaced with a another low cost switch with a metal case (Netgear FS10). I still have some interference on 6M but I also have another Ethernet switch downstairs that may be an additional source for 6M interference.

March Tech Demo

 

 

 

 

 

 

 

 

 

Will Jourdain AA4WJ from ICOM USA (left) was interviewed by Tim Duffy K3LR (right) on YouTube.  Check out the interview at https://www.youtube.com/watch?v=2DJ3buSKANI.

 

Will Jourdain will be our March Tech Demo presenter via Skype.  He will discuss what’s happening at ICOM and answer any questions we may have, so come prepared. 

 

The Tech Night will be at Olathe City Hall, in rooms 1310, 1320, 1330, on March 17, 2017 from 19:00-21:00.

Kit Building - K0NEB January 2017

K0NEBKit Building Expert Joe Eisenberg K0NEB presents at SFTARC Tech Night - 1/20/2017

Joe Eisenberg made the trip from Lincoln to present "Kit Building" for the SFTARC Tech Night meeting. Joe is well known in the local Kansas City/Lincoln area and around the world as being the "Cat in the Hat" person at ham events. He is also the Kit Building editor for CQ magazine.

From Joe's QRZ page he explains his adventure in ham radio and the electronics hobby.

"I have been licensed since 1969 and am currently the Kit Building Editor for CQ Magazine. There is nothing better than sitting down at the bench with parts sorted and ready to be stuffed into a circuit board! My Elmer was Leo Meyerson, W0GFQ, who started me in radio at an early age in Omaha, Nebraska. I am available to speak on Kit Building for your hamfests, conventions and meetings. I can also put on group kit building events as well. Building a kit as a group can be a fun and educational experience. See you on the air!"

During his presentation Joe mentioned a number of companies that you can get kits from and here are some of the ones highlighted:

  • Nightfire Kits (vakits.com)
  • QRPme.com
  • Velleman
  • Elenco
  • 4sqrp.com
  • QRPkits.com
  • Elecraft
  • qrpguys.com
  • hamgadgets.com
  • banggood.com

There are many good suppliers so get that soldering iron going and try some of them. Some of the most interesting kits include CW keyers, component tester (R,L,C) and low speed scope. Some of the kits are based on the Arduino processor and others aren't.

Some of the kit building equipment that was suggested is a good soldering iron preferably one that you can control the tip temperature. Xtronicusa.com is a local company in Lincoln that has a good one. The right kind of solder is important and he mentioned 63/37 0.031 or 0.025" rosin core, no clean as a preferred one that he uses. If you are mounting surface mount parts you might use solder paste and cure it with hot air or a heat plate that has temperature control so its not too hot for the parts. Also to store kits or parts Joe mentioned the Plano 1354 Tackle/Tool Box is available from many stores and in a variety of colors. It has several drawers to hold parts or boards.

Joe finished the presentation with some of his video creations of picture taken at various ham events and then set to music. The final days of Hara Arena in Dayton which has been the home for the Dayton Hamvention event for more than 50 years is changing location and there was a nice video remembering the arena location.

Many thanks to Joe for a fine presentation and sharing of his knowledge.

Wire Antennas

The following Dipole description was taken from the General Class license manual, pg 7-2 and 7-3 with permission from the ARRL.

 

“Dipoles are the most fundamental antenna.  It is a straight conductor that is ½ wavelength long with its feed point in the middle.

 

A dipole radiates strongest broadside to its axis and weakest off the ends as shown in the diagram below.  The current in a half-wave dipole is highest in the middle and zero at the ends.  Voltage along the dipole is highest at the ends and lowest in the middle.

 

The feed point impedance (the ratio of RF voltage to current) of a center-fed dipole in free-space is approximately 72 ohms, but it varies widely depending on its height above the ground.

 

In free space, ½ wavelength in feet equals 492 divided by frequency in MHz.  At resonance, a ½ wave dipole made of ordinary wire will be shorter than the free-space ½ wavelength for several reasons.  First, the physical thickness of the wire makes it look a bit longer electrically than it is physically.  The lower the length-to-diameter (l/d) ratio of the wire, the shorter it will be when it is resonant.  Second, the dipole’s height above ground also affects its resonant frequency.  In addition, nearby conductors, insulation on the wire, the means by which the wire is secured to the insulators and to the feed line also affect the resonant length.  For these reasons, a single universal formula for a dipole length, such as the common 468/f, is not very useful.  You should start with a length near the free-space length and be prepared to trim the dipole to resonance using an SWR meter or antenna analyzer.”

 

Learn more at the February 17, 2017 Tech Demo from 7-9 pm at the Olathe City Hall, or check out these “how to” information resources.  Either way, enjoy learning about simple wire antennas.

 

The ARRL web site has a nice “For the Beginner” article on how to build a dipole.  You can find it at http://www.arrl.org/files/file/Technology/tis/info/pdf/0683033.pdf.  And, of course, you can find most anything on the Internet.  Here’s one http://www.wikihow.com/Build-Several-Easy-Antennas-for-Amateur-Radio.