Sunday, 29 September 2013

Aircraft reflections on 4m

When analyzing WSPR signals in the 4 m band, signals can be spotted that are near the carrier wave of WSPR signals transmitted by other stations. These "ghost signals" are caused by aircraft reflecting the WSPR signal. Because the aircraft are moving a dopplershift is introduced.
This morning I caught a WSPR signal from PA0TBR on 70.0926 MHz with an aircraft reflection. I used the nice program SpecLab to have a close look at the signals:

The dopplershift between the carrier and the signal on the right (coming from the aircraft) is approximately 50 Hz. With this you can calculate the speed of the aircraft:

v= 50 * ((300/70.0926)/2) = 107 m/s = 385 km/h

Above you see a screenshot of WSPR March 2012. Measured dopplershift here was about 90 Hz which represents an aircraft speed of 695 km/h. A normal speed for an airliner jet at cruizing altitude.

More info:

Friday, 27 September 2013

Australia on 28 MHz

This morning there appeared to be a very good radio path on 28 MHz between Europe and Australia. As you can see below, many WSPR signals from Europe reached VK5EI in the south of Australia, Adelaide:

                                 WSPR activity on 28 MHz, morning September 27, 2013

I was lucky to be one of the European stations who achieved to reach Joe, VK5EI in Adelaide ("Adelheid", QTH locator PF95he); a surprising 15930 km with 5 Watts.

Would this have been sporadic E propagation or were F-layers involved in this multi-hop path ? I do not know.

                                       Adelaide (South-Australia), city of churches

Saturday morning September 28, results were even better:

VK7AB, Glenn from New Norfolk Tasmania appeared on my screen (17.058 km). For me a new distance record on 10 meter band. Also Rob, T6RH, from Kabul, Afghanistan and Richard VK6XT, Broomehill (14.428 km) showed that the propagation conditions were surprisingly good:

                                         Saturday morning 28 September, WSPR 28 MHz

Thursday, 26 September 2013

Green radio

Since a couple of years I have a SEM35 in my shack. This is an ex-army radio with a frequency range of 26 till 69.95 MHz. It provides 1 Watt RF output power and the rig can only be used in FM mode.
The rig accepts a DC input voltage between 14 and 28 Volts DC.

                                                      SEM35 radio

The SEM35 produces loud clicks ("kloenk")  when selecting a different frequency. In spite of the low output power I have been able to make some local contacts on 10 and 6m with this set.

I modified the handset by introducing an electret microphone. This improved the audio quality significantly.

The SEM35 can be found in the surplus shops for under 100 euro.

 SEM35, designed for portable use in spite of heavy battery pack (total weight 17.5 kg !)

Friday, 20 September 2013

Digital LC meter

One of the selfmade tools I frequently use is a digital LC meter.  With this device it is very simple to determine the value of an inductor or capacitor. I built this nice design in 2011 according to the description on this website

The required HEX-file for the PIC can also be found here.

In an earlier version, an external comparator LM311 was used. With this design the internal comparator  of the PIC16F628A is used.

Saturday, 14 September 2013

New QSL cards

Last wednesday I went to the meeting of the local ham club,, and was surprised to find about 25 QSL cards of some past QSO's.
Some of them are very interesting. I scanned four of them:

                            First contact on 4 m (70.2 MHz, SSB) with Estonia; Hellar in Tallinn

                         First 10 m contact (28.120 MHz, PSK31) with Liechtenstein, Waldemar

                First (confirmed) 10m contact with Israel, RTTY contact during Holyland Contest

                         7 MHz, LSB QSO with Lionel from the Channel Island Guernsey

Friday, 13 September 2013

The 4004 processor

With the recent launch of the iPhone 5S with its 64 bit A7 processor it is good to remember that the chip race all started with the 4 bits 4004 in 1971.

The Intel 4004 is a 4-bit central processing unit (CPU) released by Intel Corporation in 1971.
It was the first commercially available microprocessor. 
The first public mention of 4004 was an advertisement in the November 15, 1971 edition of Electronic News.
Packaged in a 16-pin ceramic dual in-line package, the 4004 was the first commercially available computer processor designed and manufactured by chip maker Intel,  which had previously made semiconductor memory chips. 

The chief designers of the chip were Federico Faggin and Ted Hoff of Intel, and Masatoshi Shima of Busicom. 
The 4004 employed a 10 µm process silicon-gate enhancement load pMOS technology and could execute approximately 92,000 instructions per second; 
a single instruction cycle was 10.8 microseconds. The original clock speed design goal was 1 MHz however 740 kHz was the max clock speed realized.

The Intel 4004 was designed by physically cutting sheets of Rubylith into thin strips to lay out the circuits to be printed,  a process made obsolete by current computer graphic design capabilities

Some tech data:
Semiconductors: 2300 transistors
Maximum clock speed was 740 kHz
Instruction cycle time: 10.8 µs(8 clock cycles / instruction cycle)
Instruction execution time 1 or 2 instruction cycles (10.8 or 21.6 µs)
Separate program and data storage.
Contrary to Harvard architecture designs, however, which use separate buses, the 4004, with its need to keep pin count down,
used a single multiplexed 4-bit bus for transferring: 12-bit addresses
Instruction set contained 46 instructions (of which 41 were 8 bits wide and 5 were 16 bits wide)
Register set contained 16 registers of 4 bits each Internal subroutine stack 3 levels deep.

If you have a 4004 in your pile of junk, you are a lucky guy. 4004's sell at auctions for over $1,000 these days !

Tuesday, 10 September 2013

23 cm bi quad antenna

On the website of DL5NEG I found an interesting 23 cm antenna; it is a bi quad antenna which can be homebrewed with the use of 1mm diameter cupperwire.

The antenna is discussed here:

The antenna should have a gain of 10 dBd, which is not that bad compared to difficult yagis.
Maybe it is worth a try to build it during a rainy weekend. A simple improvement can be made by using another type of 50 ohms coaxial cable. Instead of RG58 for example Aeroflex can be used. Little bit more expensive but less RF attenuation

                                             23 cm bi quad antenna

                                  Dimensions, calculated for 1296 MHz

Saturday, 7 September 2013

Late eQSL from Norway

I was surprised to find an eQSL from Morten, LA9DFA in my inbox.
On the 'new' ham 4 m band (70.202 MHz) we made an SSB QSO July 2012 during periods of good sporadic E propagation. QTH locator from Morten: JP60ea, distance from Zoetermeer is almost 2000 km.
 I made this QSO with homebuilt 4m transverter providing 15 Watts RF and simple inverted-V antenna inside the house (attic).

Friday, 6 September 2013

QRSS experiment in 2009

While cleaning up my harddisk I ran into some pictures from a QRSS experiment I did in 2009/2010. QRS means " lower your speed "; with QRSS it is meant that really slow modulation methods are used.

Here you see the screenshot of the grabber of I2NDT who received my 500 mW signal on 10.140 MHz in Borgema, Italy, QTH locator JN45tq.

You can see my callsign in the screen followed by morsecode.
I recall I made a simple X-tal oscillator on 10.140 MHz. The X-tal oscillator was followed by a simple ATU and that was my QRSS beacon. The signal from the oscillator was frequency modulated with a varicap connected to the X-tal. A variable DC voltage was applied to the varicap. This DC voltage was created by a PIC16F628A which contained the code for my callsign and waveform that contained the CW code.

A picture from a UK grabber in JO01ho from G6AVK shows the 30m 500mW signal easily crossed the North Sea.

This is the grabber from PA1GSJ, Joachim, on short distance from my QTH (Iess than 15 km). This time an experiment with 1250 mW. Modulation performed by the program SpecLab. Frequency stability is poor as you can see by the sloped text. Here you can get an idea of the speed of the signal; the screen covers an elapsed time of more than 15 minutes.

At that time I was amazed what was possible with QRP power (and less). Now, with the presence of WSPR (Weak Signal Propagation Reporter or "Whisper") and smart modes like JT-9, I learned that worldwide communications can be established with (far) less than 5 Watts.

Sunday, 1 September 2013

Heard in Japan on 18 MHz

The WARC 18 MHz (17 m) band can give surprising results.
I was amazed that my 5 Watt WSPR signal on 18.106 MHz reached Japan this afternoon.

JA2KCT, Ryosei Aimiya from Shimoina picked up my small signal. QRB was an estonishing 9269 km.

In the past I have made a couple of QSO's with Japan but it is certainly not a regular DXCC and therefore for me a special event.

Domo Arigato, 73 !