24 December, 2014

Getting ready for 60 meter

I have never had any contacts on the 5 MHz or the 60 meter band. But I guess it's time for that now.

Both my K2 and my K3 support it and about 40 countries now have access to this band according to K1ZZ in his column "It seems to us" in this month's QST.

As a first test I ran my 0.2 W Ultimate 3 GPS-controlled WSPR transmitter over night and the image shows the result. I am using an 80 m long loop skywire antenna (horizontal loop) tuned to 60 m.

The results were encouraging with the best DX being UR5VIB in Ukraine at a distance of 1887 km. By the way, considering that it is 1093 km to LA9JO in the north of Norway, one sees the distortion in the map projection used for the Google map.

I have also operated the antenna as a vertical (about 8 meters) with top-hat loading by tying both feed-line conductors together and feeding it against a ground plane. The result is quite similar. The article by Dave Fischer, W0MHS called "The Loop Skywire" in QST November 1985 is the reference for both uses of the loop. The article starts out with this catchy phrase: Looking for an all-band HF antenna that is easy to construct, costs nearly nothing and works great DX? Try this one! This matches my experience exactly as this antenna has been instrumental for my 8 band DXCC.

14 December, 2014

Waiting for an AP510/AVRT5 APRS tracker

I just ordered an AP510/AVRT5 APRS tracker and am anxious to get my hands on it to try it out. I like the small size and the fact that it is self contained - no external wires are needed to have a fully functional tracker for the automatic packet reporting system APRS: But is it useful or just a toy?

The specifications from the Amazon.co.uk site are (adapted from Chinglish):
  • SainSonic AVRT5 APRS Tracker VHF with GPS/Bluetooth/Thermometer/TF Card, Support of APRSdroid
  • GPS module: SIRF3 module, high sensitivity, fast positioning, stable power.
  • GPS antenna: 18mm x 18mm active GPS antenna, built-in LNA amplification, Star Search, locate quickly.
  • VHF Module (1W): The latest 1W VHF transceiver modules, small size, high stability for all types of wireless data transmission.
  • VHF antennas are individually matched to transmitter to ensure that the standing wave ratio is proper and the emission is efficient.
I also signed up for the Yahoo group AP510 AVRT5 APRS.

What attracted me were the reviews given by DK7XEDJ7OO (German), and APRS.facile.fr (French) and the descriptions at Radioddity and Sparky's blog,

It is evident that the 2. harmonic suppression leaves something to be desired, that the antenna is inefficient, that the programming interface isn't the easiest to deal with, and that it can be hard to set the frequency for people in countries such as Norway with PC's set for "," rather than "." as the decimal point. Hopefully I can figure out ways to deal with all these and also other issues that may show up.

12 December, 2014

Congratulations to Logbook of the World

Congratulations to the ARRL Logbook of the World (LOTW) which just reached 100 million confirmed contacts. This is the same as an impressive 200 million QSL cards out of about 630 million uploaded contacts on LOTW.

LOTW was established way back in 2003. This was only 2 years after I got my license. Since I have never enjoyed much to fill in QSL cards I embraced LOTW very quickly. I have to say though that I will of course respond with a paper QSL for those who ask for one.

But LOTW has been my primary means of confirming contacts for a decade. My DXCC was confirmed with LOTW.

Now at the same time that LOTW is celebrating 100 millions confirmations, I am celebrating 8 bands with 100 or more contacts all confirmed via Logbook of the World. This is on all bands from 3.5 to 28 MHz and has been my goal for many years. The last confirmation came from the TC0A contest station in Turkey on 80 m after last month's CQ World Wide CW contest.

I consider myself lucky to have reached 100 confirmations even on the elusive 12 m band which we all know will shut down soon not to reopen again until the next solar maximum in about 11 years time.

But as the saying goes "The journey is the reward", so what to do next as a radio amateur?

23 November, 2014

Milestone in blogging

Today the number of hits on my blog just exceeded a quarter of a million. When I converted my old web pages to a blog I didn't really expect this many readers, so I thank you all for each and every hit on one of my 106 blog posts.

I have been blogging here since May 2011. But I have actually 23 posts which are older than that as I copied posts from my old web pages and gave them the original date of publication. The oldest post actually dates back to 2001 and is the first modification I published for my Elecraft K2. That was the year when I got my ham radio license

These are the most popular posts:
  1. How to make a very cheap VHF receiver (2011)
  2. The best of the Baofeng handhelds (2013)
  3. QRPp: Ultra low power operation with the Pixie (2011)
  4. Scratchy Tivoli Model One (2013)
  5. Temperature compensation for an Arduino ultrasonic distance sensor (2014)
  6. A regenerative receiver for the 40 m band (2011)
These pages (not posts) are also among the most popular ones:
  1. General modifications applicable to any Elecraft K2
  2. Unofficial Guide to Elecraft K2 Mod's
One thing I have learnt is that hands-on articles are the more popular ones, and they don't necessarily have to be on ham radio topics.

05 September, 2014

So you want to play with a Pixie 2?

My own surface mount version of the Pixie2
Here's a guide in table format to minimalistic single-band amateur radio transceivers. The Pixie 2 and related kits are fun to build, yet they perform well enough to be used, although with some effort, for real contacts.

The idea of using the power amplifier transistor as a mixer seems to come from George Burt - GM3OXX - whose five transistor FOXX was described in 1983 in SPRAT. The basic design of the oscillator, PA/mixer and the simple keying has been more or less unchanged since Oleg Borodin - RV3GM - described the four transistor Micro-80 in 1992 in SPRAT. Then Dave Joseph - WA6BOY - replaced two of those transistors with the LM386 audio amplifier in the Pixie 2 (QRPp 1995). Most later versions are variants of these designs.

Here's the table of Foxx, Micro 80, and Pixie 2 kits:

20 August, 2014

Digital Signal Processing

The Norwegian-language "The road to the international radio amateur license" came off the press this June. It is based on the RGSB International Amateur Radio Examination Manual from 2006, which RSGB graciously allowed us to use.

But the translation has been adapted on several topics. One example is the chapter on propagation due to the need in our country for more emphasis on propagation in polar regions and in mountainous terrain. Another is a completely new chapter on digital signal processing.

15 August, 2014

New gadget measures negative resistance

If you are like me, you appreciate electronic gadgets with dials and displays. So when I discovered this "USB detector",  I thought to myself that I really always wanted to know the voltage as well as the current consumption of my USB devices. And since it is more or less impossible to connect a multimeter, this is exactly what I need.

The device fully satisfied my curiosity. Actually one surprising result was that the charger for my Samsung Galaxy Note 8 has a negative output resistance.

07 August, 2014

WSPR on 5 bands

For the first time ever I have been spotted on all the five bands that my Ultimate3 QRSS/WSPR kit (G0UPL design) is transmitting on. This is after 2-3 days of transmitting.

Right now I am using the beacon for discovering if the bands should open up on 24 and 28 MHz. The other three bands, and especially the 14 MHz band, serve as references to tell me that the transmitter is working. My antenna is not so optimal so I would be surprised if I am spotted far outside Europe. It is an end-fed 5 m long half wave vertical dipole which isn't too bad for 28 and 25 MHz, and probably not very good at all on 21, 18, and 14 MHz.

02 August, 2014

Nice radio-related stamp

A few weeks ago I had one of my rare visits to the post office. As I was waiting, I saw a display of a new series of stamps and I just had to buy the one shown here. What caught my attention was not really the artist, but rather the Kurér portable radio.

The stamp was of course not about the radio but was issued in commemoration of the 100 year anniversary of the birth of Alf Prøysen. The English Wikipedia page has this to say about him:

20 June, 2014

Disappointment with Spice and the QRP-er's favorite, the LM386

The trusty old LM386 audio amplifier from the 70's is still used a lot in low power and portable equipment. Recently some ultra high gain circuits have been recommended that I wanted to simulate with Spice. I started with the datasheet examples for checking the quality of the model. The result was surprising.

In the data sheet one can find a minimum parts circuit, a high gain circuit, and a bass boost circuit:
Gain = 20 (26 dB), minimum parts
Gain = 200 (46 dB)
Bass Boost

30 May, 2014

Temperature compensation for an Arduino ultrasonic distance sensor

161.3 cm
27.0°  347.7 m/s
Ultrasonic distance sensors can find the range out to 2-4 meters and are popular in e.g. robotics. Here I look at how the accuracy can be improved by compensating for the variation of speed of sound with temperature. It actually varies quite a lot in air and around 0 C it is:

      c = 331.3 + 0.606 * T

where c is in m/s and T is in C. The formula is good to up to at least +/-30 C. There is also a dependence of humidity, but as it is so small it is neglected here.

The equation can be analyzed for sensitivity (a little bit of differentation, you know). The result is that a two-way range measurement creates an error of 1.8 mm/C/m. That means that with a 4 degree C error, the deviation will be 14.4 mm at a range of 2 meters. Not a lot, but more than the wavelength which is 9 mm at 40 kHz. Considering how easy it is to compensate for, then why not give it a try?

19 May, 2014

Nice, watery CW signals from Alaska

 Great circle path between Anchorage and Oslo
Here's what a transpolar signal sounds like (click here to listen) and looks like (below). This one has traveled from Anchorage, Alaska to Oslo, Norway.

The characteristic sound of a CW signal that has passed over a moderate geomagnetic disturbance (Kp = 2) isn't too hard to recognize with a little practice. There is also some static on this short recording as we had a local thunderstorm coming in with the first summer days here.

The great circle distance between the two cities (actually their two airports) is 6446 km as illustrated by GPSVisualizer. Anchorage and Oslo are about at the same latitude, 61° N and 60° N, respectively. As they are at longitudes 149° W and 10° E, there is a difference of 159 ° - almost 180 ° - and this means that the signal almost passes directly over the North Pole, although a bit hard to see on the projection used in the map.

03 May, 2014

Practical Wireless with the LM386 unleashed

"Improving the LM386 Audio Amplifier" is the title of always inspiring Rev. George Dobbs G3RJV's column in this month's Practical Wireless. George talks about the basic amplifier with a voltage gain of 20 (26 dB) and how it is straight forward to increase gain to any value up to 200 (46 dB). The article then shows how it can be built dead-bug style.

Then he goes on to talk about various ways to improve the circuit such as for hiss reduction and even higher gain. In that connection he also mentions my article "Unleashing the LM386" from SPRAT in the Autumn of 2003. That circuit was an enhanced version of the high-gain circuit of Kazuhiro Sunamura JF1OZL. Basically it increases the gain to up to more than 70 dB, enough for it to drive a loudspeaker. My circuit also adds bandpass filtering. All this is achieved by adding only 5 passive components to the basic amplifier. The circuit was recently revisited in SPRAT by Johnny Appel SM7UCZ. He added a 40 dB Darlington pair preamplifier for even further gain.

The bandpass filtering (not low pass as the article says) is due to the series resonance of 100 uF and 1 mH which happens at about 500 Hz making it a nice CW filter.

24 April, 2014

Pulled out my dummy load tonight

Press image for a better view of the dummy load
Testing a transmitter means the use of a dummy load. Trying to be considerate, I don't want to cause unnecessary interference with my signals. So when I want to test my Ultimate 3 QRSS/WSPR kit I also pull out one of my dummy loads.

It measures just 9-10 mm across and is the size of a BNC connector. It is simply one of the many Ethernet terminations that I have lying around. Its built-in 50 ohm resistor is rated at something like 0.25 W. Considering that the kit outputs something like 200 mW that should mean that there is enough margin and no forced air cooling or liquid cooling is required.

06 April, 2014

Bletchley Park, Enigma, and GB3RS

Enigma (Photo: R. Holm)
Bletchley Park, northwest of London (between Oxford and Cambridge), is one of the best known British sites from WW2. Its fame goes back to the breaking of the legendary Enigma cipher machine and its successor, the Lorenz cipher machine.

In order to perform this work a large effort in the development of early computers took place here. They include the mechanical Bombe for breaking the Enigma, and the valve-based Colossus for breaking the Lorenz.

The Bombe was reconstructed through a 13 year effort that resulted in an Engineering Heritage Award in 2009.

27 March, 2014

I think we have a pile-up ...

TX6G on the Austral Islands of French Polynesia is calling for EU stations on 14026 kHz CW. I hear him well at level S7, but the pile-up stretches up to almost 14033 kHz. 

What can a small gun do to get through? 

26 March, 2014

Fantastic Conditions on 10 and 12 m

This last month has seen some of the most fantastic conditions I have ever experienced. Especially the higher bands have given world wide coverage. I haven't had that much time to operate from home, but despite this I have gotten many first. My recent verifications on the Logbook of the World testify to that.

Let's all hope it will last!

19 March, 2014

Proposal for a fourth ultimatic mode: First paddle priority

The ultimatic mode is an alternative to the iambic mode for sending Morse code from a dual lever paddle. When pressing both paddles the last one to be pressed takes control, rather than the alternating dit-dah or dah-dit of the iambic mode.

In the K1EL Winkeyers there are actually three ultimatic priority modes. This is shown in the table below that comes from page 9 in the specification for the command for setting the PINCFG Register. (K1EL CW Keyer IC for Windows Winkeyer2 v23 10/5/2010). This is a de facto standard for interfacing to and controlling a keyer, as an example it is used in the K3NG Arduino Open Source Morse keyer.

K1EL has defined bits 6 and 7 for setting this up by remote command. I propose that the last possibility, '11', presently undefined and unused, be used for a new mode. This mode is "First paddle priority" meaning that the last paddle which is pressed is ignored. It can also be interpreted as an emulation of a single-lever paddle. I and others have found that helpful in eliminating errors when keying. See for instance "Single Paddle operation with Iambic paddles" by Larry Winslow, W0NFU, in QST, October 2009 and the Iambic to Single Paddle kit from WB9KZY or my earlier blog post "Single-lever and ultimatic adapter".

My proposal is that the bits for the ultimatic mode be used like this:
  • 00 - Last paddle priority, i.e normal ultimatic
  • 01 - Dah priority
  • 10 - Dit priority
  • 11 - First paddle priority or Single Paddle Emulation (New)

Related posts:

10 March, 2014

Non-English display for the K3NG Arduino Morse keyer

German, Swedish, Danish, Norwegian, Finnish, and some Spanish characters in the display are now supported by the K3NG Arduino Open Source Morse keyer. I have worked with OZ1JHM, Hjalmar and K3NG, Anthony, in order to implement this using the 8 custom-designed characters of the LCD display (based on the Hitachi HD44780). This should satisfy the call I had for such support here on this blog last year: Which non-English Morse characters are the most important ones?

Here are examples using the phonetic alphabets of these languages.
  1. For Norwegians and Danes - Æ, Ø, Å:
  2. Norwegian: Ærlig Østen Åse

    Danish: Ægir Ødis Åse

25 February, 2014

Show off your project in a clear top tin

We all want to package our electronics projects in some nice enclosure. An Altoids tin is often used - and I have used that a lot myself. But for slightly larger projects, the tin shown below is a better alternative. In addition it has a clear top, so displays can be viewed and the nice layout of your electronics can be admired. 

20 February, 2014

Worst snow winter since 1958 and an indoor Yagi antenna

Norway has had its fair share of precipitation this winter. Along the coast most of it has been in the form of rain. But that is different in the mountains. Our cabin at 800 m above sea level is now about to disappear in the snow and we can hardly see out of the windows anymore. This is a result of having had to shovel the snow off the roof three times so far this winter. And there is yet more to come.

They say that one has to go back to the winter of 1958 for more snow than we have had this winter, and we are still only in February. The snow has also given us an unexpected problem. Our digital TV signal is now gone.

04 February, 2014

Ultimate QRSS kits

I'm a great fan of Hans Summers (G0UPL) and his effort in launching kits for various slow speed modes. In fact I have all three generations of the Ultimate QRSS kits up and running. That includes the original single-band kit (30 m in my case, bottom in picture), as well as number 2 and 3, the multi-band kits.

The latest version, in the middle of the picture, has a nicer two line display, and it can also be fitted with a relay board. It makes it possible to jump between up to 6 different bands.

18 January, 2014

Single-lever and ultimatic adapter

Photo @LA3ZA 
Here's an adapter that emulates both a single-lever paddle mode and the ultimatic mode. It is meant to go between a dual-lever paddle and an iambic keyer. The adapter has been implemented in an AVR Butterfly in C and it is compatible with Morse keyers such as the one in the Elecraft K3 and the K1EL WKUSB. The single-lever emulation is probably the most novel part and it is meant to make it easier to practice single-lever keying on a dual-lever paddle.

09 January, 2014

Video of busy 70 cm ISM band due to car key fobs

The audio in particular should make it clear how busy the frequencies around 433.92 MHz are:

Data recorded from an RTL-SDR USB dongle with the SDR# program using the Apowersoft Free Online Screen Recorder.

Related posts:

06 January, 2014

Not so busy 70 cm ISM band

Yesterday's post entitled "Car keys in the 70 cm band" showed a very busy band around 433.92 MHz with up to 10 simultaneous transmissions. That snapshot was taken on a Sunday afternoon at 16:32 local time. Here is a much less crowded snapshot taken with the USB SDR-RTL dongle under the same conditions as the previous blog post. The difference is that this is from late Monday night at 23:34 local time:

Press image for a larger view

There are only three bursts of about 1 second length here. This shows that the activity in the band varies a lot and in my mind strengthens the case for believing that the main contribution is from car keys. But of course, one cannot be certain without decoding the bursts. That is possible for weather stations, as shown by Gough Lui in the article "RTL-SDR: 433.92Mhz ASK/OOK Decoding of Various Devices with rtl_433". The bursts can easily be heard if the receiver is set for Wide FM, as shown in the settings of SDR# in the image above.

Thanks to all viewers who have made the former blog post the most popular on my blog for this week. Thanks also to the RTL-SDR blog which gave it publicity in the blog post "Looking at the 432 to 438 MHz ISM band".

Related posts:

05 January, 2014

Car keys in the 70 cm band

The 70 cm amateur band covers from 432 to 438 MHz in Norway and radio amateurs have primary status. Secondary users are among others remote controls for keyless entry systems for cars since it is an ISM (Industrial, Scientific, Medical) band also.

I wanted to see how much traffic the secondary users generate. I used my RTL-SDR dongle with RTL2832U and R820T chips that I bought on Ebay for less than 10 US$ almost a year ago. The antenna was a roof mounted HL-B61N vertical (1.7 m long). This is the output of the SDR# program:

Press image for a larger view

It is clear that this band is pretty busy! No wonder that amateur repeaters have had to move their input frequency away from this frequency range. 

The waterfall covers 10-12 seconds and there are up to 10 transmissions simultaneously. The nominal frequency is 433.92 MHz and there are emissions from 433.75 - 434.05 MHz. I live in a suburban area with about 1 million people, but I imagine that I only pick up a small part of the remotes in this area since the car key transmitters are very weak. Anyway it demonstrates both the versatility of the cheap software defined receiver dongle, as well as how busy the band is. 

Related posts: