Friday, 15 June 2018

Radio scale

In the days digital frequency readouts were not available, radio tuning was done while looking at the scale. Names of radio stations were present on the scale;

A nice example is the scale of a Telefunken 876WK receiver from around 1938.

Telefunken 876WK

Friday, 1 June 2018

Home-built TV sets

Around 1948 employees of Philips could buy DIY kits to assemble TV receivers. Two pictures of home-built TV receivers from private collections:

Friday, 4 May 2018

Digital Voltmeter

Geekcreit produces mini digital voltmeters for general purposes. Because the price of such a voltmeter is low (less than 2 euros) you can incorporate the voltmeter into each of your do-it-yourself projects.

Range is about 2.5...30 VDC and the voltmeters, to be found on aliexpress or, are offered in various colours: red, yellow, blue, green and white.

I used one on my 144 MHz transverter:

Friday, 13 April 2018

TV test pattern

Just a nice picture of a TV test pattern from 1956. The era when black/white TV's conquered our continent:

Off topic:

Spot the frog in the pond

Friday, 2 March 2018

Friday, 9 February 2018

Discone antenna

Discone antennes cover a wide frequency range. 
MFJ has introduced a new discone antenna: the MFJ-1868.

It is designed to receive radio signals from 25 - 1300 MHz and to transmit from 50 - 1300 MHz (up till 200 Watts RF power). Interesting because it covers 6m, 4m, 2m, 70cm and the 23 cm band.

A discone antenna is omnidirectional, vertically polarized and has a rather narrow radiation pattern in the horizontal plane. This makes the antenna sensitive in the direction of the horizon. SWR remains below 1:2 for the 50...1300 MHz frequency range.

Interesting if you do not want your garden covered with lots of antennes.

The MFJ-1868 has a vertical whip affixed to the centre in order to extend the low frequency response.

Price of this antenna: appr. $70


Friday, 19 January 2018

LM3886 for lower bands

DIY audio fanatics appreciate this ‘chipamp’ a lot. See for example

                                 LM3886 as 65 Watt audio amplifier

It provides 65 Watts audio into 8 ohms. Audio quality is more than all right. PCB’s with this chip are available for about 10 euro’s (eBay, Aliexpress). 

Bunch of low-cost LM3886 PCB's (10 euro each)

The frequency response curve shows that we are dealing with a broadband amplifier. @ 200 kHz the attenuation is only 1.7 dB !

Frequency response

Therefore, this chip should be able to be used as an RF amplifier for the 2200 m band (135.7 – 137.8 kHz) and lower bands.

A challenge for the designer is of course to adapt the 8 ohms output to the antenna impedance.

Sunday, 24 December 2017

Teylers museum

Some collections are special and deserve to be maintained. 

The collection of Mr. Teyler from Haarlem is such a special collection. This week we visited the Teylers museum and were able to see interesting items such as Leyden jars, 19th century light bulbs, ancient skeletons and the study room of prof. Lorentz.

More info:

Leyden jars

Oval room

Collection 19th century light bulbs

Paint art

Neanderthalers' jaw

Sunday, 10 December 2017

uBITX kit available

A DIY kit for the HF general coverage transceiver uBITX is available:

Off topic:

                                              'Waterbus', view from Zwijndrecht

Friday, 24 November 2017

73 from Banja Luka

A nice eQSL-card was found in the postbox today.
An SSB 6m QSO made August 2008 was confirmed by Vlado from Bosnia Herzegovina:

Off topic: