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: