Tuesday, 10 December 2019

Fibonnaci and sunflowers


An off topic item this time; a little mathematics from my garden.

One takes a head of a sunflower, let it dry for a while and concentrates on the seeds and their arrangement.



The arrangement of spirals in the head of a sunflower appears to show Fibonnaci numbers:

Number of left hand oriented spirals: 55


Number of right hand oriented spirals: 34

The Fibonnaci Sequence is constructed with the formula F(n) = F(n-1) + F(n-2) and the beginning of the sequence is as follows:

1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144..

Amazing that Fibonnaci numbers seem to appear in nature a lot.

If you divide 55 by 34, you get 1.617… which is very close to the number phi (golden ratio)




Saturday, 2 November 2019

AM Stereo

Now and then I dismantle vintage audio equipment. It is good to see how professionals have designed their equipment. This time I had a closer look at the Denon AM-FM Stereo Tuner UTU-F88. I think it was designed around the '80-s.



I was surprised when I saw a part on the PCB that was allocated to 'AM Stereo'. This part of the PCB was not "bestueckt" (no components).



AM Stereo was never used in The Netherlands as far as I know. In the US however various AM Stereo systems have been  developped.







Thursday, 17 October 2019

PA100KLM

The call PA100KLM was acquired by HAM Operators that participate in the station PI9KLM.

These are (but not limited to) PA0PCV, PA0WBZ, PA0SNY, PA3GDF, PH0PPL, PA2AAP and PA2MCE.
PI9KLM (see www.pi9klm.nl) was founded in 1947 to give radio operating practice to new navigators/radio operators on board KLM aircraft.

After navigators became obsolete (around 1962) the station remained active, and was operated by HAM's that worked and have worked for KLM, the national airline of the Netherlands, founded on October 7, 1919.

In coming period (October, November 2019) KLM has many activities to celebrate the 100th birthday. Being the oldest existing airline in the world, KLM is the first to reach this age.

Therefore the call PA100KLM will be used by the HAM operators of PI9KLM. The transmissions take place from Hangar 12, of KLM's Maintenance facilities at airport Schiphol. The call will be terminated on November 30.

OPERATIONS START ON OCTOBER 7, AT THE CENTURY BIRTHDAY.
Aiming frequencies are 14,250 USB +/- 25 kHz and 7.150 LSB +/- 15 kHz for the time being
LAT/LON@Hangar12 are N 52deg 17min 49sec and E 4deg 47min 32sec - QTH locator is JO22JH(51).


See https://www.qrz.com/lookup for detailed information.

Fokker F2 (early 1920's)
Fokker F2



Boeing 787-10

Wednesday, 16 October 2019

Nice FM Broadcast receiver

Nice small FM receiver (broadcast, 87.5 - 108 MHz) connected to speakers this morning and discovered it has a good sensitivity. 
Antenna: single wire of appr. 80 cm.

Allthough the receiver is designed to interface through a serial link to the outer world, it works fine as stand-alone unit. Power supply voltage 3.3V-5.5V.



Fun for a couple of euro's (You have to deliver your own speakers).

https://www.banggood.com/DSP-PLL-Digital-Stereo-FM-Radio-Receiver-Module-87-108MHz-With-Serial-Control-p-1004778.html?rmmds=mywishlist&cur_warehouse=CN

Monday, 14 October 2019

Butterfly capacitor


Yesterday I had the opportunity to see the making of a butterfly variable capacitor by Gerard, PA2G. This capacitor will be used in concert with a 1.7 meter diameter aluminium magnetic loop antenna. The great distances between the individual capacitor plates allow the use of high voltages (kV range) when the future antenna comes in resonance. I think, this is a nice example of good workmanship.





Speaking about nice mechanics; I added a locomotive to my train collection this weekend: A vintage Marklin DB electric loc Br E 41 (the blue version):



Wednesday, 2 October 2019

PI3DFT

Good signals from SSTV repeater PI3DFT on 144.8875 MHz today.





Thursday, 12 September 2019

Sunday, 1 September 2019

Use of digimodes on 319 THz

I enjoyed building a simple infrared transmitter and receiver.
The circuits are designed around IR LEDs using a wavelength of 940 nm (frequency 319 THz).
On this high frequency it was simple to transmit and receive SSTV pictures, over a long distance of 30 cm, as you can see below:




It is a first trial and a lot can be improved.


Picture transmitted

Picture received

Great fun with this interesting DIY kit (3 euros)


How about using a 5W IR LED ? Or other digimodes. I already used FT8 succesfully (Am I the first using this digimode on this high frequency :-)  )


Thursday, 29 August 2019

PA60HAL

To commemorate the 60th anniversary of the launch of SS Rotterdam, a special call and eQSL for PA60HAL are introduced:


Friday, 9 August 2019

Weather station

The Alecto WS-4800 weather station that I installed provides interesting data about the local weather.




The station consists of an indoor and outdoor unit that communicate over a 868 MHz datalink.

The outdoor unit was easy to install:



The indoor unit provides besides weather data also the local time and date via a DCF77 receiver. Interesting weather parameters are baropressure, dewpoint temperature, pressure trending, windspeed, winddirection, moonphase, rainfall.



https://www.alecto.nl/weerstation-4800