We have moved…Post #4754


Effective 30 December 2014, “KH6JRM’s Amateur Radio Blog” has moved to a new URL.

The blog title remains the same.

The new URL is http://kh6jrm.net.

Thanks for your patience and understanding.  Reconstructing a blog after a mysterious hacking incident is never pleasant.  But, with the new blog running successfully, things are returning to “normal.”

Happy Holidays from my family to yours!

I’ll see you on the new site (http://kh6jrm.net).

Aloha es 73 de Russ (KH6JRM).

Free antenna tutorial – KB6NU’s Ham Radio Blog


Free antenna tutorial

november 7, 2014 by dan kb6nu leave a comment

For a limited time, Rohde & Schwartz and the IEEE Communications Society are offering a free tutorial on Antenna Basics. Here’s a description of the tutorial:

In this tutorial the basic functionality of an antenna is explained. Starting with Hertz’s antenna model and a short introduction to the fundamentals of wave propagation, the important general characteristics of an antenna and its associated parameters (e.g. antenna gain, radiation pattern, bandwidth or VSWR) are explained. A more detailed explanation of the functionality of some selected antenna types (e.g. dipole or monopole) is also given.

Speaking will be Maik Reckeweg, Product Manager Antennas, Rohde & Schwarz GmbH, Munich, Germany, responsible for all the company’s monitoring, measurement and communications antennas.

The video is kind of dry, but I think Reckeweg does a pretty good job of discussing antenna basics. The video is also accompanied by a white paper that delves into these topics a little more completely. Overall, there’s a bit more math than in most amateur radio discussions of antennas, but this makes the discussion a little more comprehensive.

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filed under: antennas

via Free antenna tutorial – KB6NU’s Ham Radio Blog.

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Thanks to Dan Romanchik (KB6NU) for this tip.  For a limited time, you can download an excellent video tutorial and white paper on “Antenna Basics” from the IEEE Communications Society and Rohde & Schwartz.  Although there’s some sophisticated math in the presentation, the information is easily digestible.  Download a copy of this well-organized tutorial for your reference library.

For the latest Amateur Radio news and events, please check out the blog sidebars. These news feeds are updated daily.

Aloha es 73 de Russ (KH6JRM).

SARL 5 MHz propagation research project


Page last updated on: Saturday, November 1, 2014

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SARL 5 MHz propagation research project

The 5 MHz propagation research project show unexpected results.

One of the most interesting findings is the inconsistency in the results of Near-vertical-incidence sky wave propagation (NVIS).

Comparing a communications path between two amateur stations, ZS6KN and ZS6KTS (a distance of 51 km) it is interesting to note that in June 2014 there was a good communications path from just after 05:00 until approximately 16:30 after which the signals disappeared. The pattern for July was the same, but signals were considerably stronger than during August and September.

During September, a strong dip in signal strength can be seen. The other interesting observation from the graph is that propagation “opens” earlier and closes later as we go into summer which indicates variations in the ionisation of the D layer of the ionosphere as the sun rises earlier and sets later.

Not enough data has been collected to make any meaning full conclusions. If the path was a pure ground wave, the signals would have been more or less constant throughout the day and night.

The article will be published in the November/December edition of EngineerIT and is already available on the web. You can find the link on http://www.sarl.org.za, click on propagation research. You will find links to the article as well as a report of the first six months.

The South African Radio League

via SARL 5 MHz propagation research project.

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The South African Radio League (SARL) has found some unusual results from its recent test cycle of the 5 MHz band.  According to SARL officials, there was much inconsistency in Near Vertical-Incident Skywave Propagation (NVIS) and the discovery that 5 MHz “opens earlier and closes later as we go into summer…, indicating a variation in the ionization of the D Layer of the atmosphere.”  The SARL notes that is hasn’t collected enough data “to make meaning full conclusions.”

For the latest Amateur Radio news and events, please check out the blog sidebars.  These news feeds are update daily.

Aloha es 73 de Russ (KH6JRM).

Weird antenna behavior – KB6NU’s Ham Radio Blog


Weird antenna behavior

november 1, 2014 by dan kb6nu leave a comment

Two years ago, I put up a 20m, end-fed half-wave antenna. It wasn’t a terrific performer, but it worked OK, and I was able to make contacts on 20m.

Basically, it’s a 33-ft. piece of wire connected to a matching network, made up of a toroid and a capacitor, as shown in the figure at below. The inductor is a toroidal inductor, and the capacitor is made from a length of RG-174 coax, as shown in the figure below.

A month or so ago, the antenna started acting funny. While transmitting, the power would fluctuate, not wildly, but noticeably. Thinking it might be the coax, I took my dummy load outside and connected it to the coax, but that checked out OK.

The next step was to check the matching unit. I had built the matching network in a waterproof box, or so I thought. When I opened the box, there was water inside it. Water had apparently gotten in around the screws holding the SO-239 to the box. I dried it out, replaced a rusty nut and bolt, and when I put it back together, sealed up the SO-239 with silicone.

That still didn’t do it, though. I was still getting the erratic behavior. Today, I practically rebuilt the entire antenna, aside from rewinding the toroid and making a new coax capacitor, but it’s still acting weird.

I guess my next step is to make a new capacitor. I suppose some water could have wicked up into the braid, compromising it. That seems kind of far-fetched though. At this point, I’m open to any other ideas you guys might have.

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filed under: antennas

via Weird antenna behavior – KB6NU’s Ham Radio Blog.

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Dan is asking for your help in diagnosing the weird behavior in his end-fed half-wave antenna.  Somehow, his antenna is radiating fluctuating amounts of power, despite Dan’s efforts at replacing parts of the matching network and checking to see if his coaxial feedline was alright (it checked out fine).  The source of the problem could be a failed capacitor in his matching network, but I’m not certain of that. Perhaps the RG-174 coax he used in the capacitor has a short or some water “wicked up” inside the coax shield.  If you have a solution to Dan’s problem, drop him an e-mail.

For the latest Amateur Radio News and Events, please check out the blog sidebars. These news feeds are updated daily.

Aloha es 73 de Russ (KH6JRM).

TC2M Broadband HF Antenna


Page last updated on: Tuesday, October 28, 2014 Share on facebookShare on twitterShare on emailShare on printMore Sharing Services3. TC2M Broadband HF Antenna. Martin Ehrenfried G8JNJ has developed an omni-directional antenna with a claimed bandwidth of 2-30 MHz at less than 2.5:1 SWR.  View the TC2M site at http://www.tc2m.info/Read the construction article at http://www.tc2m.info/TC2M%20HF%20Vertical%20G8JNJ.pdf 

via TC2M Broadband HF Antenna.

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This antenna appears to be a kind of “cage” antenna (minus the other half) often seen in broadband 80 meter dipoles.  There are a few AM broadcast antennas that employ a variant of this antenna, such as the folded monopole antenna.  At one time Barker & Williamson made something called a TFTD antenna that closely resembled a folded dipole. This antenna was used by the U.S. military to give broadband HF coverage. Martin’s (G8JNJ) TC2M looks fairly simple to make and gives a reported 2.5:1 SWR from 2 to 30 MHz.  This antenna looks interesting.  It might be worth the time to make one.

For the latest Amateur Radio news and events, please check out the blog sidebars.  These news feeds are updated daily.

Aloha es 73 de Russ (KH6JRM).

HamTV reception with a low gain antenna | Southgate Amateur Radio News


Page last updated on: Friday, October 17, 2014

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HamTV reception with a low gain antenna

Tonino Giagnacovo IZ8YRR conducted an experiment with a low gain antenna during the commissioning of the Ham Video system on the International Space Station (ISS) earlier this year

He has written a 10-page article on his experiment which can be read at

http://www.ariss-eu.org/HAMTV_IZ8YRR_1.pdf

Read more about the ISS Ham Video system on the ARISS-EU site at

http://www.ariss-eu.org/

via HamTV reception with a low gain antenna | Southgate Amateur Radio News.

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Great article by Tonino Giagnacovo (IZ8YRR) on low gain HamTV antennas on board the International Space Station (ISS).  Sometimes, simple is best.  This post also connects you to a more extensive article about the ISS Ham Video system.

For the latest developments in Amateur Radio news and events, please refer to the blog sidebars.  These news feeds are updated daily.

Aloha es 73 de Russ (KH6JRM).

Why radio hams should consider 3D printing | Southgate Amateur Radio News


Page last updated on: Thursday, October 16, 2014

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Why radio hams should consider 3D printing

Mike Grauer, Jr, KE7DBX, asks radio amateurs to think about how 3D printers can be used in home construction

He says:

As a member of the ham radio community, I have always been fascinated by the maker mindset which has existed since the early days of radio. From making radio equipment from scratch, to kits and even modifying commercially available equipment, the maker movement and radio go hand in hand.

The 3D printing community shares many traits with the ham radio movement. At the heart of it all is making, creating and inventing.

And just like ham radio operators, those involved with 3D printing are constantly learning new technical skills that can be used in other areas of our lives.

Read the full story at

http://www.inside3dp.com/ham-operators-consider-3d-printing/

 

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via Why radio hams should consider 3D printing | Southgate Amateur Radio News.

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Nice essay on the traits shared by amateur radio operators and those following the “maker mindset.”  Mike Grauer, Jr. (KE7DBX) makes an excellent case for having these two groups of “makers” share more ideas and common interests.  At the very least, 3D printing can duplicate hard to find parts for classic radios, such as dial pointers, cabinets, knobs, and toggle switches.  3D printing can also be used for experimental projects by both groups of enthusiasts.  Aloha de Russ (KH6JRM).

For the latest Amateur Radio news and events, please check out the blog sidebars.  These news feeds are updated daily.

Aloha es 73 de Russ (KH6JRM).

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