AmateurRadio.com

We have started another intermediate class both in class and distance learning. This course is primarily run on Edmodo. We have run a couple of classes on Edmodo and we think we have the concept correct now. So we have our weekly quizzes set and our 3 week homework assignments all loaded and ready to go.

In class students are also welcomed to join the distance learning students so missing a lesson is no longer such an issue.

Over the coming weeks I will be creating some companion videos showcasing the practical elements of our in lesson activities.

So far we have 5 in class and around 30 distance learning joining us for the next 10 weeks.

Dan Trudgian, MØTGN, is a regular contributor to AmateurRadio.com and writes from Wiltshire, England. He's a radio nut, IT guru, general good guy and an all round good egg. Contact him him here.

It’s always easy to point a finger at others when you encounter noise while scanning the bands. More than often it is yourself who has to take the blame. In my case the switching power supply from my shack laptop is producing a lot of noise and artifacts, especially below 7 MHz. For a long time I had the plan to operate the laptop from my linear power supply and recently I got serious about it. A DC-DC step-up converter was bought for a mere US$7 and the following video shows initial results are very encouraging. The unit runs very cool so I am going to box it up and see if it can handle long operating periods.

Next up: isolating the USB connection. Stay tuned.

Hans "Fong" van den Boogert, BX2ABT, is a regular contributor to AmateurRadio.com and writes from Taiwan. Contact him at [email protected].

 

Earlier this week the Wall Street Journal published an article about the growing prevalence of RFI from unlikely sources.  They quoted Tom Thompson, WØIVJ, of Boulder, Colorado:

Radio hobbyist Tom Thompson of Boulder, Colo., last year tracked a signal using a homemade contraption. After knocking on the suspect’s door, he traced it to ballasts on marijuana grow-room lights. He says he built a filter that the grower agreed to use.

Tom, a retired NOAA electronic engineer, created an entire web page devoted to the grow light ballast filters. According to his page, these ballasts are switching power supplies for high-pressure sodium or metal-halide lamps.

He goes on to describe the problem in good detail:

Typically the light fixture is removed from the ballast by about 25 to 30 feet.  Since this length is about a 1/4 wavelength on 40 meters, it makes a good “antenna” for 40 meters so the RFI may be strongest on 40.  I have heard radiations from these systems up to about 1/2 mile away.  Also, since the “antenna” is so low to the ground, the RFI is mostly vertically polarized which is important when tracking it down.

Check out his page to see how he built a filter that he says reduces the RFI by about 30dB. That’s some good ol’ ham ingenuity!

Matt Thomas, W1MST, is the managing editor of AmateurRadio.com. Contact him at [email protected].

It's been a while since I've had the time to sit down and write a few lines. My recent work and personal schedule has looked like a blackout bingo game. When work interferes with play, that's serious. That said, I have been able to do a few things around the shack. I've been clearing out some of the surplus of QRP radios that have accumulated over the years to make room for more QRP radios. It is, after all, the circle of life isn't it. Buy it, play with it, look at it, sell it and then buy something else to start the cycle over again.

I've also changed up my QRO line-up. I have the FT-5000DX which is a wonderful radio. It does however take up a fair amount of real estate on my, not-so-big, desk. Along with VL-1000 amp, I don't have much room left over. So, I am sending the FT-5000 to my ranch station and replacing it at the home shack with a K3. Not a bad trade. I just received the K3 and am getting comfortable with it. Having owned a KX3 for while, the learning curve is not too steep. There is another agenda here and that is I want to be able to remote into my home station when away and Elecraft has an elegant solution for that. They build a K3/0 which looks just like the K3 but without the TX and RX circuitry. So when remote, you have the same front end to play with. Plug in your key, link up, spin the knobs and away you go. At least that's the theory. I will be setting this up soon and I will report on the progress.

So the circle of life is always with us, which makes life interesting.
Mike Crownover, AD5A, is a regular contributor to AmateurRadio.com and writes from Texas, USA. Contact him at [email protected].

AmateurLogic.TV Episode 64 is now available for download.

Peter sends Tommy and George some Australian treats. See how they react to Vegemite.
George has an introduction into cheaply receiving and decoding digital signals.
Peter brings us the Making of AmateurLogic Downunder.
Tommy builds an Arduino Heads-Up display for use with rigs that have Cat ports and more.

1:16:45 recorded live before an Internet audience.

Download

View in web browser: YouTube

George Thomas, W5JDX, is co-host of AmateurLogic.TV, an original amateur radio video program hosted by George Thomas (W5JDX), Tommy Martin (N5ZNO), Peter Berrett (VK3PB), and Emile Diodene (KE5QKR). Contact him at [email protected].

This weekend I finally got around to sorting out my digital/data mode interface for the Yaesu FT-857D.

To transmit and receive digital/data modes you need to connect the radio audio in/out to the computers sound card in/out, the computer then runs the necessary software to encode/decode the signals. I want to try out WSPR, PSK, JT65 and some SSTV for starters I have spent too long just receiving and decoding...

There are a number of inexpensive commercial interfaces available, but many of them use the same basic design originally intended for eQSO/Echolink operation. I nearly succumbed but I had built an eQSO interface many years ago when using PMR446 and had most of the parts to build another.

I nearly took the easy route and got a commercial one since connecting up some home built circuitry to a £20 hand held is slightly less daunting than plugging it into an expensive rig!  My original interface has been modified and reused over the years and was a bit of a mess, but being brave I decided I could tidy it up and I couldn't really damage anything if I took my time... actually the truth was I discovered I didn't have the necessary optocoupler IC so couldn't build a new one just yet...

A simple internet search for digital/data mode interfaces will bring up a great deal of information, schematics and ideas for home brew solutions. The basics can be found here for example.

The simplest form of interface is just a simple direct lead with the transmitter operating in VOX mode. However levels can be a problem as the line/speaker output from a computer can be too high for a transmitters microphone input. Also connecting a radio to a computer directly can lead to problems with ground loops and interference.

The computer can be made to control the Push-To-Talk (PTT) on the transmitter using a serial port with the software controlling one of the handshake lines (RTS/DTR) Some data mode software support CAT to allow control of the PTT as well as tuning the transmitter, but the serial port method is more universal.

The preferred interface, and the one I had built isolates the computer from the radio by using two audio transformers and an optocoupler. There is no direct connection between the two devices so keeps interference to a minimum.

I could have used the microphone and speaker output on the radio, but the FT-857D has a convenient data connector on the back. This is a 6-pin DIN socket as used by older (PS/2) computer keyboards/mice. Note the diagram shown in the FT-857D manual (as below) is the view as you look at the socket.

FT-857D Data connector as in the manual

The connector has two "data" outputs but they are simply fixed level audio outputs from the receiver. The one of interest for most modes is the 1200 baud output (the 9600 baud output is more akin to a discriminator tap and is only of use for FM packet) There is a data-in (TX-audio) and a PTT control line.

Like many people I initially thought I could cut a lead off a mouse/keyboard and repurpose it, however I discovered most only use four wires and they don't use the necessary pins! You might be lucky especially with older keyboards or alternatively if you have an old keyboard extender cable they usually have all six wires present. Alternatively the plugs are readily available from the likes of CPC/Farnell.

I had a hunt around in a junk box and located a suitable keyboard extender cable. I chopped off the useless end and metered out the pins to identify the appropriate wires. Remember when looking at the plug the pins are swapped left-to-right compared to the diagram which is the socket view.

Well here is the insides of the interface.. and as you can see I completely failed to tidy it up! Not my best work, but I did put it in a new box and I did tape up all those unused wires!

The messy internals of the interface

One annoying issue I had was the audio from the computer wasn't getting to the radio, it worked and scoped out okay when out the box, but in the box it stopped working. I suspected a bad solder joint and redid them all, but still showing the same intermittent issue. I did notice flexing the board slightly out the box cause the fault and soon located a track on the vero-board which appeared to have a hairline crack, I couldn't see anything obvious but a wire soldered along it cured the issue.

It looks better with the lid on..

I soon had it connected up and fired up WSPR

Computer, radio and interface

It was straight forward setting up WSPR to use a combination of CAT for tuning and the RTS PTT control and soon had some encouraging results, in fact these are some of the spots of my 5W signal on 10m/20m and 30m, I was grinning from ear to ear!

10M Spots

20M Spots

30M Spots

I had simply set up the FT-857D for basic USB transmission, however it does have a dedicated DIG mode, the manual refers to setting it up for RTTY/PSK, I very briefly had a go with PSK31 and Digipan and was successfully decoding signals and put out a few CQ calls (again on 5w) but got no immediate response. However checking PSK Reporter later it seems I had been heard by VC3S, OH1FOG and ES1JA maximum distance was around 3260 miles

Looking forward to spending some more time experimenting with the data modes.
Andrew Garratt, MØNRD, is a regular contributor to AmateurRadio.com and writes from East Midlands, England. Contact him at [email protected].