This weekend I visited the National Safety day in Culemborg.
Red Cross, the Navy, Army and Police showed their skills. Also the DARES was
present. DARES is an abbreviation for Dutch Amateur Radio Emergency Service.
I spoke with PA3GJM, Hans, the regio coordinator of DARES
in Gelderland-Zuid. He explained how, in emergency situations, communication
tru VHF/UHF and Short Wave can be established.
Interesting is the communications vehicle that also contains
equipment to route emergency e-mails via Winlink2000 / PACTOR protocol.
This weekend I installed the Albrecht disconne antenna '"Allband'". It is an omnidirectional discone antenne capable of receiving 25 - 1300 MHz signals. Transmitting is possible from 50 - 1300 MHz (VHF till 300 Watts, UHF till 200 Watts). Antenneheigth is appr. 6 m. above sealevel. In the north, east and west direction I have a clear view. I used Aircell7 coaxial cable to limit the losses on the higher frequencies. I was able to receive various 2 m. repeaters in the neighbourhood ( Goes, Rotterdam, Bergen op Zoom) using a Boafeng BJ-218 VHF/UHF transceiver. First contact with this antenna was with PA0RPA via the repeater of Goes (145.775 MHz, 88.5 Hz CTCSS).
Coming period I will do various trials on various frequencies (50 MHz, 70 MHz, 430 MHz) to get an impression how the antenna performs.
Last months I am not very active in radio homebrew activities. Luckily other radio amateurs are. I visited Hans, PE1DWA, last week and he realized a nice DIY 70 cm Wide Band FM transmitter with an RF output of 5 Watts.
430 MHz ATV transmitter combi; the Local Oscillator is on top
I always thought that either Heinrich Hertz, Marconi or Faraday realized the first radio transmission. But someone was ahead of them;
David Edward Hughes (16 May 1831 – 22 January 1900), was a British-American inventor, practical experimenter, and professor of music known for his work on the printing telegraph and the microphone. His family moved to the U.S. while he was a child and he became a professor of music in Kentucky. In 1855 he patented a printing telegraph. He moved back to London in 1857 and further pursued experimentation and invention, coming up with an improved carbon microphone in 1878. In 1879 he identified what seemed to be a new phenomenon during his experiments: sparking in one device could be heard in a separate portable microphone apparatus he had set up. It was most probably radio transmissions but this was nine years before electromagnetic radiation was a proven concept and Hughes was convinced by others that his discovery was simply electromagnetic induction.
Hughes seems to have come across the phenomenon of radio waves nine years before they were proven to exist by Heinrich Hertz in 1888. In 1879 while working in London, Hughes discovered that a bad contact in a Bell telephone he was using in his experiments seemed to be sparking when he worked on a nearby induction balance. He developed an improved detector to pick up this unknown 'extra current' based on his new microphone design and developed a way to interrupt his induction balance via a clockwork mechanism to produce a series of sparks. By trial and error experiments he eventually found he could pick up these 'aerial waves' as he carried his telephone device down the street out to a range of almost 500 meters.
Hughes wireless apparatus, a clockwork driven spark transmitter and battery (right) and a modified version of his carbon block microphone (left) which he used in his 1879 experiments.
A couple of years ago I have built Le Forty; a 40m QRP transceiver. I received a nice picture from Carlos EA1CGK in Salamanta from his version of Le Forty ('Building in progress'). See also http://lpistor.chez-alice.fr/forty2s.htm
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 banggood.com, are offered in various colours: red, yellow, blue, green and white.
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