Wednesday, 31 July 2013

Simple RF signal meter with LEDs

The simple but effective circuit presented here converts an RF input signal into a visible LED indication. Only discrete components are used. The circuit can be used as field strength analyser or RF Wattmeter when a 50 ohms resistor is connected between ground and HF (J1). Calibration required. Of course you can add extra LED stages in case you want to extend the range. The second picture shows how the circuit can be build on a very small piece of vero-board.



RusJet Yak-130 amazing model

Somewhat off-topic  but this YouTube movie amazed me. This type of model building reached a new level. Look at the pilot of this Yak-130, he is really moving the control stick. Look at the miniature avionics. Primary Flight Display and Nav display are really working. Even the part- and serialnumbers are duplicated on the components. Strobelights and nav light are full operational.
In 2011 during the 9th Jet World Masters championship, this model RusJet Yak-130 was recognized as a limit of accuracy and a standard in its class. This model managed to receive a highest static score ever been achieved. That was a climb to new peaks...

International Space Station Bouncing

DJ5KAR and PA3FXB have succeeded in the first ISS Bounce lately. In principle similar to EME (Moonbounce), however with some differences:  The ISS is much closer to the earth and it moves with a higher velocity. Anyway, both ham’s succeeded in the first ISS Bounce ever (in the 23 cm segment).  The limited reflection area of the ISS required more EIRP than when doing an EME excercise.  The earth antennas had a diameter of 3 meter.  The doppler effect was another difficulty to solve. On the VHF-band the doppler shift should have been 5 kHz up / down. Using the 23 cm band (1.2 GHz), however , resulted in a shift of 60 kHz (!)



Tuesday, 30 July 2013

Coding of Japanese transistors

Do you also have lots of Japanese transistors in your junkbox with hard-to-understand coding ?
Those codes might not be so difficult to understand. You might be richer than you think and this article can help you finding a useful application for those forgotten semi conductors.

Most Japanese transistors have been coded according to the JIS, which stands for “Japanese Industrial Standard”. The JIS looks as follows:  Number – 2 characters – Serial number – Suffix
The number is one less than the total amount of contactwires. (A standard transistor with base, collector and emitter has a 2 as a start for the coding. Examples; 2SA1187, 2SB646, 2SC733)

The two characters refer to the application as follows:
SA: PNP HF transistor
SB: PNP AF transistor
SC: NPN HF transistor
SD: NPN AF transistor
SE: Diodes
SF: Thyristors
SG: Gunn devices
SJ: P-channel FET/MOSFET
SK: N-channel FET/MOSFET
SM: Triac
SR: Rectifier
SS: Signal diodes
ST: Avalanche diodes
SV: Varicaps
SZ: Zener diodes
The serial number is in the range 10 till 9999. The optional suffix indicates that the semi conductor has been approved by various Japanese authorities.

Note: Since most common transistors have a code starting with 2S, this part is often omitted;  A 2SC733 can be found as C733.
Also be aware that the internet is your best friend in order to find out with what type of transistor you are dealing with. For example I found some transistors with code C1921. I searched for 2SC1921 and found

Here I discovered I owned some transistors from Hitachi designed for hi voltage video circuit applications.

Monday, 29 July 2013

Measuring RF Power with EB91 tube

Measurements of RF power are usually performed while making use of a diode (either Si or Ge). A fault in the measurement is introduced, when using silicum diodes, because of the voltage drop of 0.7 Volts. (With Ge diodes about 0.4 Volts). This disadvantage does not exist when using a rectifier tube. In the circuit below the rectifier tube EB91 is used.
The circuit can be used till RF powers of appr. 50 Watts. When measuring larger RF powers with a diode, the  max. tension of the diode can be exceeded thus introducing an inaccuracy in the measurement. This disadvantage does not exist when using a rectifier tube. Of course 6.3 Vac must be available for the tube’s filament. A Philips EZ80 or EZ81 should work fine in a similar circuit. The measuring device must be calibrated before it can be used.


Sunday, 28 July 2013


Sometimes one can be lucky. On the local fleemarket in Zoetermeer, some years ago I bought for some euro's a pcb of which I tought it contained interesting components. Of course this pcb ended on my junk pile in the corner of the attic and I forget about it. Till some days ago I searched for SMD components for the prescaler of the frequency counter. I re-discovered the pcb and found it is a real goldmine.
It contains 4 times a NE602 smd ic, 8 opamps LF353, some NE604, xtals and lots of SMD capacitors and resistors. Also coils and an UHF tuner is present. Must have been a pcb from a CATV device I guess.
Anyway, I am glad with all the new components. Removing the SMD capacitors for the prescaler was succesful.

PSK31 QSO on 30m with Italy

Yesterday late in the evening I could still detect signals in the digimode segment of the 30m band (10.140 MHz). PSK31 is my favorite digimode for over 5 years. It was a few weeks ago I made a PSK31 contact. Danili, IZ1OVH, from Genova Italy responded on my QRP (5 Watts) CQ. An eQSL-card immediately followed after a succesful QSO.

Saturday, 27 July 2013

Good ATV repeater reception

In spite of a lot of rainfall today (we were surprised by local lightning and heavy rainfall about noon) the reception of the local ATV repeater PI6ZTM at 10.5 GHz was still fine.

                                        PI6ZTM received on LNB without dish on my attic roof

Rain is a known attenuator for EM-signals in the GHz range. Apparantly the PI6ZTM signals on 3 cm were not influenced that much. The signal is quite strong at my QTH. Repeater antennas are about 60 meters high on a building "The Blankaard" about 5 km from my QTH. Therefore it is not a real challenge to receive the ATV repeater.

Heavy rainfall above the mid of The Netherlands (including Zoetermeer) this afternoon.


Electron August

Today the "Electron" of August 2013 arrived. The "Electron" is a Dutch magazine for ham's. Always a joy to read it. This time the magazine contains following interesting articles: Build a videogenerator, set-up of a medium wave AM broadcast transmitter, minicomputers (Arduino, Rasberry Pi, PICs) for radio amateurs and a simple interface for spectrum analisers.

Friday, 26 July 2013

2 eQSL cards received

This morning I found two eQSL cards in my in-box. One from Zacharias SV3GLL from Greece (SSB qso 2 days ago on 20m) and the other from a Short Wave Listener (SWL); YL-RS-01, Alex from Latvia. The last  is my first card from a SWL who reports  a 12m band QSO. I do not make many contacts on the 12m WARC band (24 MHz).
eQSL is an easy and nice method to exchange QSL cards in a digital way. I use it for over 5 years now; no post stamps required. If you are interested have a look at 
But of course the paper cards remain the real stuff !

Building frequency counter in progress

Today I did some drilling work on the case of the frequency counter. The case is an old housing of a PC power supply of which I removed all components. The case has been painted grey and black; cheap solution and I think the result is acceptable. I refuse to pay 15 euro's for a simple casing. 
In the end this counter should be able to measure frequencies up to 2 GHz. I am still waiting for the components of the prescaler (The MB506 and 3 7490 dividers). The design of the pre-scaler can be found on my second posting on this blog. 
The main design is from India. Have a look here: 

Previous year I built the PIC16F628A version and this counter works fine till frequencies of about 50 MHz.

Inside the counter
Front view

Magnetic loop antenna with coil tuning

Richard, PE0RIG designed a magnetic loop antenna some time ago with an original method of tuning:
A small ferrite core inside a coil realizes the magnetic loop antenne to be tuned.
No expensive vacuum glass capacitors - which are often used in this type of antennes - are required. The antenna is designed for the 80m band and is constructed in a way that portability is garanteed.
Two fixed value high capacitors (120 pF / 10 kV) are used; this type of capacitors can easily be found and are not expensive. 

Richard has used this antenna with SSB RF powers up to 100 Watts and that is a lot for this type of antennas. I would keep great distance from this antenna while using this amount of power. (Magnetic) fieldstrengths are enormous  in the near field of this antenna. Take care !

The complete story:

This article was published earlier in the "QRP Nieuwsbrief 132, December 2009" 

Thursday, 25 July 2013

Homebrew variable capacitor

A year ago I made this 20...200 pF variable capacitor. It is used in a magnetic loop antenna for 80m. The plate distance must be large enough to withstand the high voltages that exist at the magnetic loop antenna's top (levels of over 1 kV are easily reached).

The static plates are made of pieces unetched PCB. The variable plates are aluminium. This capacitor works fine in my magnetic loop antenne. I have been able to made some QRP contacts on 80 m with it without the use of a long wire antenna. Still handcontrolled. Remote control would be a nice improvement.

Den Helder is calling

In spite of the high temperature in my attic (still over 25 degrees C) another nice voice  radiocontact this evening was with Maarten, PD1MZ from Den Helder. We had a chat on 40m, 7087 kHz in LSB. Nice to hear that Den Helder did not change that much. About 25 years ago I worked for the Dutch Royal Navy and had to visit Den Helder a few times a year so it was good to hear that the navy vessels are still there. I used 15 Watts and Maarten about 40 Watts to establish the link. Den Helder is about 90 km away from my QTH Zoetermeer.
Below you see the antenna configuration of Maarten;

Easy 20 mtr contact with Greece

During a few minutes spare time I was able to start-up my FT450 this afternoon.
Tuned in on 20 meters and was able to make a short QSO with SV3GLL, Zacharias.
RF power out was 10 Watts into my G5RV junior antenna at 14.150 MHz. Good signals from Greece and of course I was given a solid 599 as well :-)

Sporadic E-layer propagation opportunities

Yesterday, lots of possibilities to realize a sporadic E link were present.
In the picture below you see the 50 MHz (yellow), 70 MHz (orange) and 144 MHz (red) QSOs which were realized around noon.

2.4 GHz pre-scaler

I was intrigued by the design of a simple 2.4 GHz pre-scaler for a frequency counter as designed by F4DCI. The circuit divides the input signal (up to 2.4 GHz) by 1,000. In this way frequency counters with a limited upper range can be used to analyse EM-signals in the GHz range. The MB506 has been configured as 64 divider. 3 type 7490 ic's work as 2 1/2 dividers. In this way the circuit divides by 1,000 (64 x 2.5 x 2.5 x 2.5).
The MB506 chip can be bought at Kent Electronics in The Netherlands (provence of Zeeland) (euro 6.50) ;

                This prescaler will be part of the frequency counter being built at this moment


My first internet blog

Dear visitor,

This is my first attempt to create a blog.

I have the intention to enter some interesting information now and then which has any relation with radio communications. Hope to gain some experience with internet blogs and entertain anyone with interest in radio.

In the garden, Zoetermeer 2013

                                                    At work, Schiphol Oost, 2011

                                           Behind dad's 19-set, Culemborg, 1968

73, Ron