Sunday, March 28, 2010

Medium Wave DX-ing

When I rediscovered the radio hobby 4-5 years ago my main interest soon become medium wave DX-ing. It means that I like to try to listen for local AM stations mostly from America. It could be sports, news, music or other kind of stations. In south and central america it become a little more challenging as the language is usually Spanish. One might wonder what´s the fun of that. I think it´s a great hobby in many different ways.

It could be technically challenging both with receivers and antennas. One of the most common medium wave dx antennas is the Beverage antenna . It´s basically a wire that goes horizontally  in the direction of the desired area (North America for example) and is usually put in the trees in the woods, for at least a couple of hundred meters.But you could of course get lucky with simpler antennas. During the Winter I´ve been able to receive some stations even with a portable radio with ferrite antenna.

The American radio stations are spaced 10 kHz apart compared to the Europeans that are 9 kHz apart. You can see the carriers of both European and American stations in the image above.

Another aspect is language and geography. Sometimes you never know where the conditions will take you. In one minute you are in Cuba and then you are in New York, as an example.

The third aspect is hunt and collect. It´s always fun to receive a new station that you have not heard before. You can also send a letter to the station and ask for a confirmation that you heard the station, but that´s something that I don´t do any longer as the stations are usually not interested at all to receive a letter from a geek in Sweden...

I haven´t been listening to the medium wave during the last months (when it´s been very good conditions!) mostly due to that fact that I can´t devote as much time to the hobbies as I want, and the little time that has been there was used to study for the ham radio license.

But you might wonder how  an American AM station sound like when it´s received in Sweden? Here´s some examples of a few stations that are not that uncommon:

680 WRKO Boston MA "This is Boston's talk station AM 6-80 WRKO"

1070 KNX Los Angeles CA "This is KNX 10-70 AM and HD"

1190 WLIB New York NY "Your praise and inspiration station"

Saturday, March 20, 2010


Lennart SE5X, is a friend in the DX listening club that has helped me with different areas of the radio hobby. The plan was to have my first QSO with him, but he came second. So I was very pleased when I received my first ham radio QSL card with the post some days ago from him. Thanks Lennart! 

Saturday, March 13, 2010

First QSO

Ok, now it´s done. First QSO completed. I did check in to the local club net a while ago, but today I heard SM5DVP call CQ on the nearby Echolink node SL5ZYT-L on 145.275 kHz that I happened to monitor. I answered and had a nice chat with him. He was in Eskilstuna connected over Internet and I used my newly purchased  Wouxun KG-UVD1P . It´s a nice radio with very good value for money I think. I will buy another battery and BNC connection so I can connect it to some other antenna later on. I want to try out satellite communication. Talking about Echolink I have signed up and validated my call sign. I will try it later on to see if it´s any good.

Wednesday, March 10, 2010

Colt receiver part 1

I found a book as an E-book at the university library: Radio and Electronics Cookbook that was published by the Radio Society of Great Britain in 2001. I have skimmed through it briefly and it seems to cover both some  radio theory and some interesting projects. I do have a lot of  "maybe" and "should be" projects in my head (that I will cover in later blog posts) and now I think I decided, apart from getting the softrocks built (as they are already on my desk), I would like to build a hardware defined receiver.  A very basic one to really try to understand how a radio works.

In this book, I found one called the "The Colt 80 m receiver" that I liked, because it´s built in modular steps and quite thoroughly explained. It starts with the audio amplifier and then adds mixer (NE602) and VFO to become a direct conversion receiver. The last part is to add an IF stage to become a superhet.

What worries me a bit is that I can´t find any reference to this design when I google it. Or maybe blogs and so on wasn´t that common 2001 and earlier or this design is named something else elsewhere? A bigger problem is the availabilty of parts. Variable capcitors to be used in a VFO can´t be bought new, but I´ve have asked around in the club and I think that will be solved.

Then there are some specific inductors from Toko:
  • Toko KANK3334
  • Toko KANK3333
  • Toko YHCS11100AC (tuned inductor)

For the two first ones I have found a guide at the GQRP club (that I by the way have joined; Sprat is a great magazine), so I can make those inductors with toroids. But the last one, I have no clue. Any ideas someone? There´s also a part number for a crystal filter, but I think I can use another one for 455 kHz.

We will see if there will be a part 2.

Monday, March 1, 2010


To be able to build my amateur radio equipment I have to solder electronic components. That´s a basic fact. :-) My experience so far with soldering has been coax cables and wires from torroids to be soldered to connectors, that is impedance transformers for receiving antennas . For that task a very basic soldering pen has been used.

But if I want to be able to solder small components I have to have something better. I started bidding on nice ones I saw on auction (Weller etc) but they all came up on level I didn´t think it was worth spending. Probably they all are alot better than the one I bought. Time will tell. The one I found cost 600 SEK (~80 US dollar) on the local store Kjell & Co, but it´s atleast equiped with temperature control and the tips can be changed over to smaller ones.

You can see an ancient modem on the bench in the top image for practicing. When I feel compfortable with my soldering skills I will move over to build the Softrock Lite II for 30 meters or maybe I start with an FM receiver kit I got laying around. Before I can get to the SMT components I think I have to get hold of some nice flux.