Friday, 28 March 2014

AM receiver with TA7642

From Kent Electronics l ordered and received some TA7642 Integrated Circuits for 0.75 euro each. These linear circuits in TO92 housing are designed for medium wave AM reception.

The internet provides lots of circuits with the Ferranti TA7642. For example this simple design:

Note: contacts 1 and 3 on TA7642 / contacts 5 and 6 on LM386 swapped

What’s possible with this small IC.  How about (V)LF reception or CW/SSB decoding ?

I found some time to solder the circuit above. To be honest, the results were rather dissapointing. Could receive 2 MW stations and in the evening 4. But there was no good separation of the stations (bad selectivity). I used an SMD version of the LM386. It will be hard to discover it on the photo below.

Thursday, 20 March 2014

Kent Radio Special magazine

One of the nicest electronics on-line stores in The Netherlands is Kent in Zeeland.
Kent has issued its spring Radio Special catalogue.

This time with good information about interesting components like the TA7642 (Ferranti AM receiver), ICL8038 (Function Generator) and Mini Circuit Mixers. Some complete projects are described as well like the DSP receiver.

Have a look yourself at:

Sunday, 16 March 2014

DXCC #129

The postman brought me a nice surprise. QSL from South Africa. April 2011 I made a PSK63 QSO on 28 MHz with Mitch, ZS2DK.

Nice to see the QSO confirmed. This is the first card from ZS and my 129th (confirmed) DXCC.

QTH of Mitch is Port Elizabeth

Friday, 14 March 2014

eAwards provides  global electronic QSL card exchange for amateur radio operators and SWLs.  Since 2005 I am using
This website provides an easy way of swapping digital QSL-cards.
As an eQSL-member you can participate in the eAward program.
There are several eAwards available (e.g. eDX100, ePFX, eWAS).

To my surprise, recently the ePFX300-PSK Award has been introduced.
I have been using the PSK mode often past years since it is an easy and reliable modulation
method for shortwave signals. Apparantly I have exchanged eQSL-cards with radiostations with 342 different prefixes using PSK in the past years.

Another piece of coloured paper to decorate to my "wall of fame" :-)

Saturday, 8 March 2014

First FM QSO with Iceland

Conditions must have been fine yesterday on 10 m. When Odinn, TF2MSN, replied on my  29.445 MHz FM signal I was really surprised. His signal peaked at 5 dB over 9. 

I used 30 Watts RF from a FT-450.
The URL of Odin:

                  Akranes, QTH of Odinn on the west coast of Iceland. Appr. 6500 inhibitants,

Thursday, 6 March 2014

The Shunt Regulated Push-Pull (SRPP)

The SRPP is an elegantly simple circuit, and is really a small output transformerless (OTL) amplifier. It was widely used in TV circuits for delivering significant current into heavy capacitive loads. It was first patented in 1940 by Henry Clough of Marconi, and has returned in many designs since. Interestingly though, it was not referred to as the SRPP until quite recently and instead had a variety of other names like 'bootstrap follower', ‘mu follower’ and 'shunt regulated amplifier'.

Sennheiser HD450

I have used the SRPP principle in a stereo headphone amplifier. The circuit below was made twice (lefthand and righthand channel) and combined with a PSU it forms the amplifier. Allthough the output impedance of the SRPP amp does not exactly match the headphones impedance, the amplifier provides a nice and clear sound to my Sennheiser headphones.

The input comes from a digital source (CD-player, DVD-player or PC soundcard).

                                                       Circuit diagram, 1 channel

                                                     Building in progress, spring 2012