Friday, February 20, 2015

What's the Difference Between Resistance and Impedance?

I was reading a Facebook discussion today and there was a lot of confusion between resistance and impedance. Someone was trying to measure a speaker with an ohmmeter and didn't understand why his "8 Ohm Speaker" measured less than 8 Ohms. One reply posted this link which I thought was pretty good...

Difference Between Resistance and Impedance

Wednesday, February 18, 2015

W9DUA D-STAR Repeater Update

A few days ago some Sangamon Valley Radio Club members and other friends from the central Illinois area got the gateway computer for W9DUA/R up and running again. The repeater is permanently linked to REF051 so it's tied together with D-STAR repeaters in Decatur and Bloomington. If you have D-STAR capability please tune up the machine nearest you and say hello to central Illinois hams!

5 Million Raspberry Pi Computers

I read earlier today that the Raspberry Pi Foundation reported than over 5 Million Raspberry Pi computers have now been sold. This number supposedly includes only true sales and does not include the number that have been given away for educational and philanthropic reasons.

Tuesday, February 17, 2015

Raspberry Pi and Arduino Tech Night

On Thursday, March 5, 2015 the Sangamon Valley Radio Club is hosting a "Show and Tell" evening that will focus on uses of the Arduino and Raspberry Pi single board computers that you've seen mentioned in Amateur Radio and Maker publications. The meeting will be held at 7:00 p.m. The location is:

American Red Cross Building
1045 Outer Park Dr.
Springfield, Illinois 62704-4408

An specific agenda is not yet finalized. There will be a presentation on considerations for applying devices such as these to an application and several SVRC members will be describing and demonstrating experiments they have been working with on their own. If anyone has an Arduino or Raspberry Pi project of your own you are welcome to bring it and share your story as well.

The SVRC will be supplying some light refreshments at the event. As such, if you are not an SVRC member, we ask that you please let us know that you will be coming just so we can get a rough head count.

There is no charge to attend.

If you plan to attend, please send an email to Roger K9LJB at: so we can plan for the refreshments.

Monday, February 02, 2015

Web Site Update

I've made a few edits to the EMCOMM Email Via Radio In Sangamon County, Illinois page on the main web site. In recent times the Byonics TT4 Tracker/KISS Mode TNC has become one of the dominant TNC types in the Amateur world. Just trying to keep people pointed in an appropriate direction.

Find out more or buy a TT4 at the Byonics web page

Friday, April 20, 2012

eBook Utilities

Do you have an iPad? Kindle? Nook? Another tablet? Besides the obvious things you can do with these handy tools they are a great place to store your own notes, documents, etc. Recently I discovered a program called Calibre which lets you convert between the various eBook formats and can also take an HTML document and create an eBook from it.

A lot of these devices can display PDF files so why bother with making an eBook? Well, the biggest reason is that an eBook can be re-sized, etc. and your documents can have all of the handy features of the other documents you download or purchase.

Check out Calibre, it's worth a look.



Sunday, January 15, 2012


I went back and corrected some typos in earlier posts and edited the first post to include links to the Yahoo Group where the amplifier is discussed and supported. Now, back to the workbench!



Saturday, January 14, 2012

Surface Mount Components

I've made a little more progress on the amplifier. About 10 more capacitors were added before my eyes got tired. I quit before messing anything up.

I got an email asking about using "surface mount" components. There are lots of articles about this technology on the web. This one, What is SMT Surface Mount Technology from Radio-Electronics is a good beginning if you are unfamiliar with it.

The smallest SMT parts used in the WA2EUJ Amplifier are what's called an "1206" package. This designation means that the part is 0.12 inches long and 0.06 inches wide. That seems tiny but other common, but even smaller sizes are 0805, 0603, 0402, and 0201! Realistically, while using anything is possible I suppose, I think the 0805 is the smallest most hobbyists would easily deal with. The 1206 is definitely more "middle aged eye friendly."

There are techniques for hobbyists to use old electric skillets, hot plates, and toaster ovens along with something called 'solder paste' to mount SMT parts. I chose to use a traditional soldering iron and hand solder my board. I don't build a lot of projects that use SMT parts and I didn't want to gear up to do lots of SMT work for this one item.

Below is a photo of one component that's been hand soldered onto the board. It probably has a bit more solder than is necessary but frankly the soldering wasn't so ugly that I'd be embarrassed to share the photo!

My process for hand soldering these components is as follows:
  • First I tin the pads on the PCB with a tiny amount of solder.
  • Next I use a piece of solder wick or a 'solder sucker' to remove the solder from the pads leaving a thin smooth layer.
  • Then using tweezers I set the SMT part across the pads (be sure to observe any polarity on parts like capacitors or diades that have them.)
  • While holding the part down with the tip of the tweezers touch the soldering iron to one end of the part and the solder pad at the same time to re-flow the solder.
  • Go back and add a small amount of solder to each component lead so you have a good electrical and mechanical joint.
This sounds tedious but it really goes pretty quickly once you get into it. Be careful!!! If you drop one of these parts or squeeze it too tight with the tweezers you can easily launch it across the room. 0.08" and 0.05"? It's practically a waste of time looking for it unless your shop is a whole lot cleaner and less cluttered than mine.

That's it. Easy as pie if you take your time. I recommend using one of those magnifiers with a headband while you do this work. In general you should always wear eye protection when soldering. A blob of molten solder in your eye would really take the fun out of a project.



Tuesday, January 10, 2012

Pictures of the Amplifier

Okay, the camera problems are resolved. Here are some initial photos to give an idea of the project.

First up is the PC board made available by the designer...

This heatsink is probably overkill for a 50W amplifier but the designer and most of the other builders have used it successfully. Can an amplifier be too cool?

Finally, here's a sampling of the parts that will be added. Not shown here I have actually started soldering the surface mount capacitors. More on that later.



Monday, January 09, 2012

The Amplifier Construction Begins

Well, good news and bad news.

The heatsink arrived so I can take some real measurements for mounting, etc. and I've started slowly attaching surface mount parts to the printed circuit board. I'm taking pictures along the way however my digital camera has decided to not want to let me have them via the USB port. As soon as I fix that problem or come up with a card reader I'll post some "in progress" photos.



Wednesday, December 21, 2011

New Project: WA2EUJ Amplifier

A couple of years back after a lot of research I took the plunge and bought a Flex 1500 Software Defined Radio. This QRP radio is a really fine machine and I enjoy it very much. Although I also like QRP operation there are times, especially on SSB, that a little more power would be nice.

WA2EUJ won the ARRL Home Brew contest a while back with a neat little 50W amplifier design. He has since updated the design to include filtering for 80-10 Meters and there is a professionally produced printed circuit board available for this updated version. I've decided to build this amplifier and will be documenting it here as a series of posts. I have the bulk of the parts on order and hope to begin as soon as the bench is cleaned off!

Update: January 15, 2012. Several people have asked about where more information can be found on the updated project. Current bill of materials, schematics, etc. are available on the ARRLHBC Yahoo Group. Several other projects are discussed there as well but the files section is a treasure trove of information about the PC board, tuning, etc.



Tuesday, October 04, 2011

The Old Reliable UHF Connector. Is It Really?

One of my favorite blogs is that of KB6NU. He always offers up a good selection of interesting things found on the web and elsewhere. Today he mentioned this article which details some tests done on the common PL-259 connector designated a "UHF". Read more in the 'UHF' Connector Test Results.



Wednesday, August 24, 2011

Exploring USB Devices

The 9-pin or 25-pin D-Sub type serial port connector is going the way of the dinosaurs on most computers these days. Yet, the people who make add-on gadgets such as TNCs, antenna controllers, etc. still crank out products that require a serial port connection. Fortunately a lot of companies make USB-to-Serial converters. Some even make good ones.

I don't claim this is a scientific evaluation by any means. It is just my observation. While any USB-to-Serial converter may work in some cases it is my experience that those with an FTDI or Prolific chipset inside them will always work.

Anytime I buy a new USB-to-Serial adapter I try to buy one that tells me what chipset it uses. Then, if I have a choice, I usually get the FTDI variety mainly because they were some of the first ones I found to work well and they provide good support and information.

But what if you have a device and have no idea what it uses? Knowing the chipset manufacturer may help you troubleshoot a problem. Microsoft has a neat little utility circa 1968 called USB Viewer. It will show you all of the USB controllers and hubs in your system plus in most cases it will identify whose chipset is inside them and even what model chipset in some cases. In the picture below I've plugged in an adapter with a Prolific chipset.

This utility is available free. Download USB View from the FTDI Website

Happy hunting!



Monday, August 22, 2011

W9DUA Repeater... Getting Closer!

Over the weekend we got the RF part of the repeater married back up to the D-STAR Gateway computer. The paperwork is all signed with the repeater site owner, backup power outlets are installed, and data jacks are in place. Once we get a move date with the organization we'll be ready to go on the air from a respectable height!

For the time being W9DUA is on the air but it has a mag mount antenna on the top of the rack cabinet. The range is suffering a bit for the time being.



Wednesday, August 17, 2011

32-Bit Power Comes to the Arduino World

If you've ever wished you could have a little extra horsepower for your Arduino project then this may be just the thing. Digilent Inc. has a new 32-bit chipKIT product. One version features the Microchip PIC32MX320F128 and the other a PIC32MX795F512. Both are MIPS processors. Details are found at the link above including where to download a compatible development environment.

The PIC32MX795F512 on the chipKIT Max32 board supports Ethernet, CAN bus, and full USB 2.0 connections.



Friday, August 05, 2011

Comparing Base Station Antennas

Sometimes you read about something in a book but you don’t really give it a lot of thought. Recently I had a chance to observe the performance of two different antenna types and I can confirm that the design differences can really affect the performance.

On my tower at home I have two dual-band VHF/UHF antennas. One is an Arrow Ground Plane @ 55ft, the other is an Arrow J-Pole @ 45 ft. Both are fed by the same type coax.

One evening I was trying to use the W9BIL D-STAR repeater in Cadwell, IL which is 49.1 miles from my house according to The ground plane is normally used by my Winlink RMS Station and the J-Pole is normally on my shack’s dual band radio.

I was pleased when I was able to key up the repeater operating with the J-Pole although the signal strength meter barely moved. I switched to the ground plane antenna thinking the extra 10 foot or so of height might help a little but to my surprise I could not hear W9BIL at all. I never thought much about the antennas being all that much different and assumed that height would trump anything else.

Some research was in order.

Discounting the difference in height which should have helped if everything else was equal there are two other factors that come into play:
  • Antenna Gain
  • Angle of Radiation

Let’s look at three antenna types: a simple ground plane, a J-Pole which is a 1/2 wave antenna and a 5/8 wave antenna which is another popular style for VHF/UHF.

Antenna Type
Reference Gain
Angle of Radiation
1/4 Wave Ground Plane
1/2 Wave J-Pole
+ 0.85 dB
5/8 Wave
+ 2.35 dB

The lower radiation angle puts more of the power you’re radiating at the horizon. The higher gain means the antenna pattern is also focusing the power in the most desirable direction.

For the curious, going longer than 5/8 Wave tends to hurt your cause. Beyond that length the radiation angle begins to increase.

You may be wondering why I included the 5/8 Wave antenna when I didn’t have one to compare. Well, it turns out several companies like Comet make nice 5/8 Wave antennas for Amateur Radio use at fairly reasonable prices. You never know when an upgrade may be in order!


Sunday, July 10, 2011

D-Star Progress

W9DUA D-Star UHF Gear

The Sangamon Valley Radio Club's new D-Star repeater continues to move forward. The repeater itself won't move to its final location until the end of July/start of August but the gateway is now operating full time and accepting self-registration. If you are a new D-Star radio owner or DV-Dongle user in our area and are not currently registered in the D-Star network please join us!



Monday, July 04, 2011

Web Site Updates

Happy Independence Day to all of you in the United States!

I made a couple of minor updates to the main web site today. First, I got an email from Chris NØTTW telling me that the Programmable ROM I mentioned in my article on updating the KPC-3 TNC is no longer available. Second, I freshened up the listing of programs that are suitable for doing Winlink 2000 email here in Sangamon County, IL.



Friday, July 01, 2011

Watson, Come here! W9DUA D-Star Repeater

Today was a major milestone in the Sangamon Valley Radio Club's D-Star repeater project. We got the controller, UHF repeater, and duplexer mounted in the rack and did some initial configuration of the basic system with a temporary antenna.

Around 4:30pm central time N9UWI and I had a successful digital voice QSO through the repeater.

Next order of business will be to get the gateway computer installed and reguster the system on the US Trust Server to allow Internet linking, etc.



Sunday, June 26, 2011

2011 ARRL Field Day

I spent most of Field Day with the Sangamon Valley Radio Club in Riverton, Illinois. The best way to describe it overall was wet. It rained lightly on and off while we were setting up. Then just before 1pm local time the lightning and thunder began. People operated on and off as conditions permitted. We did have a good time which is important.

Shelter was plentiful. The school at Riverton where we operate makes the cafeteria, restrooms, etc. available. A few people even operated from inside with cables run out the doors to the temporary antennas. The weather may not have cooperated but it was still a day of fellowship and fun.

Don N9ZGE (Left) and Rudy KC9LSM (Right) look on while Don W9EBK tends the grill.

Vicki KC9JPQ


 Roger K9LJB

 Teri K9TLM (Left) and Claudia N9HHE (Right)


There were a lot more club members present, I just didn't get many pictures taken.



Wednesday, May 25, 2011

Kudos to Ameren Illinois

This morning we lost power during a thunderstorm. The repair crew said they thought a lightning strike took out the breaker on the pole with the feed for our house. We lost power around 6:30am. They stopped at the house around 8:00am to say they were out of the part on their truck and had to go replenish their supplies. By 9:30am or so we had power again.

Pretty good service I think.



Friday, May 13, 2011

The Poor Ham's Radial Plate

A lot of discussion around building an HF vertical includes talk of a "radial plate" to attach your radial wires to the ground side of your feedline. There are several commercial offerings that look similar to this one from LDG (S9 Antennas):

These are all well and good but they strike me as being a little pricey for what they accomplish. With a little effort and a trip to the hardware store for a piece of aluminum flat stock you can get enough material to build several for about $10 or less. Fabricate yourself something along these lines:

When I originally sketched this I indicated 2" wide flat aluminum. In fact 1" wide stock or even 3/4" would probably work as well and will be less expensive.


Well, ideas abound on simple solutions to this. My buddy Scott NE1RD sent along a link to show the technique he used on the 40 Meter vertical at his new house. Not only is it economical but you don't have to drill any holes yourself!

Plumber's Strap