Now active via the International Space Station

I happened to set my 2m receiver to the APRS (Automatic Packet Reporting System) frequency of the International Space Station (ISS), 145.825 MHz, and lo and behold stations in Central and Southern Europe started to appear. This is not rocket science, but for me it's a first. (Well actually the ISS is a kind of rocket ...)

Here in Oslo, using the local APRS service, I can also receive Swedish and Danish stations when conditions are good, but never Spain, Italy, Greece, Romania, Ukraine, Russia or Turkey. When a message appeared from NA1SS itself, the station onboard the ISS, I felt that I had really nailed it (see image). But ISS had more in store for me.

Latest firmware for AP510 APRS tracker is superb

I got my AP510 APRS tracker a little more than a year ago. It kind of worked, but not very well in my car. But after the tracker got a new firmware dated 3 Nov 2015, it has become so much better. Now I can say that it is really useful.

AP510 with original short antenna
and telescopic antenna

Apparently, the Smartbeacon function didn't work properly in earlier versions of the firmware. With some good debugging and error reporting by KC5EVE, Mark, working with the software developer for the AP510, BG6QBV, the annoying errors now seem to be gone. This is all documented in the Yahoo AP510 group.

I have fitted mine with a 16-45 cm telescopic antenna and even when attached to one of the rear headrests in my sedan, the 1 Watt of output power tracks very well.

The map below shows a drive from Telemark, about 100 km west of Oslo, to Oslo with as good coverage as one can expect given the valleys and the availability of APRS digipeaters especially in the western part.

Note the missing tracks east of LA5PPA-1 which are due to a 3.5 km long tunnel,
Strømsåstunnelen, between Drammen and Mjøndalen.

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 DK7XE, DJ7OO (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.

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.

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:

• "Car keys in the 70 cm band" (with more documentation of hardware and software)
• "Not so busy 70 cm ISM band"

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:

• "Car keys in the 70 cm band"
• "Video of busy 70 cm ISM band due to car key fobs"

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:

• "Not so busy 70 cm ISM band" showing the status on a late Monday night
• "Video of busy 70 cm ISM band due to car key fobs"

The best of the Baofeng handhelds

How do the cheap Baofeng handhelds compare? I have had the Baofeng UV-5R since I bought it from the 409shop in April 2012, but recently I noticed that the UV-B5, UV-B6, and UV-82 have appeared on the market also. If I should need another handheld transceiver for VHF/UHF, is there any advantage in getting any of the other models?

I prepared the following table in order to highlight differences and similarities. Bold characters signify an improvement for what I conceive to be typical radio amateur use.

GSM phone power control and signalling

When you measure the energy out of a GSM cell phone at the moment of initiating a call, you get the picture to the right. It shows the first 15 seconds.

For the first 3.5 seconds there is the signalling between the phone and the base station. Then the connection is established, but after some time (at 4.2, 5.6, 7.5 and 9.5 seconds) one can see how the phone turns the power down, according to the commands it gets from the base station.

Half a year of APRS temperature monitoring

My APRS-based temperature monitor has now worked flawlessly for half a year. APRS stands for Automatic Packet Reporting System so it can send much more than temperature data, the chief usage is really for GPS position reports.

But I just needed a temperature monitor and here are the readings for December. As one can see, there were no days with temperature above freezing. At 800 m elevation in the mountains of Telemark in Norway, this is not unexpected for this time of year and makes for good skiing!

I use a Quanzheng TG-25AT handheld with a quarter-wave whip antenna on 144.800 MHz. Its signals reach the LD3GT digipeater at 1845 m above sea level. Although I don't have direct line of sight, the low power (1 Watt) setting is adequate as the distance is only 10 km. The APRS-beacon is an OpenTracker USB set up for transmission every 15 minutes. An external DS18S20 temperature sensor which measures the outside temperature is connected to the 1-Wire® bus of the OpenTracker USB.

Thanks to the infrastructure providers: The Tønsberg group of NRRL (LA1T) who operate the LD3GT digipeater, probably the one with the largest coverage in Southern Norway (Gaustadtoppen). Thanks also to the various operators who receive packets from LD3GT and pass them on to the internet, and thanks to aprs.fi for processing and displaying the data on their excellent web site!

Visiting 409shop in Hong Kong

A stop-over on my way from Sydney to Oslo gave me the opportunity today to visit Apliu street in Hong Kong. This is where all the electronics products are found. As I had purchased a Baofeng UV-5R from them before it was fun to stop by the 409shop as well. Their address is on their web site, and the word "showroom" really made me expect something larger than what I found. It turns out to be just one small store among hundreds of others in this street.

I bought a handheld frequency counter, Yaege FC-1, and a better antenna, Nagoya NA-666, for the UV-5R and got a good deal - I like to think that it is because I presented myself as a previous internet customer.

On the other side of the street there was another store with communications equipment as well, Yee Fu Technology Shop, where I bought a 13.8V/20 A switch mode power supply, HK Products Electronics SPS-200MA.

It even had a noise-offset control which I have come to appreciate in my other power supply, the Alinco DM-330MV. It is particularly nice to have on 160 m. How they avoid Alinco's pending patent on this feature is something I don't know. There seems to be several other supplies on the market with this feature also, such as the Watson Power-Mite-NF (NF for Noise offset Function), so maybe Alinco's patent application hasn't been granted?

Altoids Projects

Press image for magnification

I like to build small electronics projects and like many others I have found the small Altoids tins to be excellent enclosures. 

These tins are inexpensive, well shielded, easy to work with, and least but not least they enable you to make experimental circuits that are sturdy enough that they can be reused later.

Pictured here is a collection of projects I have built over the years with the hope that  they may inspire others.

Mobile Phone Conversion

Several fellow hams in the Asker and Bærum district have converted Mobira (Nokia) MD50 or MD59 Talkman NMT-450 phones from 1985-1988 to the 70 cm band. LA7TM, Nicolai, has played a central role in the conversion, based on the work of Finnish hams who pioneered the conversion and made their experiences and their software available. We then made some changes to the software. These changes are now included in the official Finnish version.