Sunday, 2 February 2020

PA for 70 cm transverter

From BG7SGM, I ordered a PA module for 70 cm:
It is capable of delivering appr. 20 Watts RF at 70 cm. The module uses a M57704H.

I installed the module in the 28 - 432 MHz transverter:

A good heatsink is required. For the first time I used the repeater shift mode of the FT450. For 70 cm repeaters, in The Netherlands the repeater shift is 1.6 MHz. I also had to insert the CTCSS frequency of 88.5 Hz. I made a short QSO with PA0WBS via the Rotterdam repeater (430.300 MHz out). 

A quick measurement showed that the transverter delivered 15 Watts RF. Now, the challenge is to work in digimodes and see what is possible (FT-8 in particular).

See  and eBay for more RF products from BG7SGM (use google translate!).

Thursday, 9 January 2020

First FT-8 signals transmitted on 432 MHz

Yesterday I transmitted my first FT-8 signals on 432.176 MHz. PA3EWP received those signals:

At the moment of transmission the 28MHz-432MHz transverter delivered 2 Watts only.

Monday, 6 January 2020

28 MHz - 432 MHz transverter

I started to work on a transverter that converts 28 MHz (10 m band) to 432 MHz (70 cm band). I use a FT450 to process the 28 MHz signals. At 432 MHz the transverter is capable of delivering about 5 Watts RF. A Power Supply Unit from an old PC was used for the 12V/12 Amp and 5V/20 Amp electrical power supply .

Frontview transverter

The transverter and control board I used were purchased in the Ukraine. See and also ebay.

                                           Transverter board

Control board with 50 ohms/10 Watt load

First results are promising. I could listen to repeater signals in FM. I hope it will be possible to work with digimodes later on. I will consider adding a PA stage to increase the RF output (to 10..20 Watts).

Friday, 3 January 2020

Kilrock Radio

On Medium Wave I discovered 'Kilrock Radio'. 

They broadcast rock music from the '50-'80s. This is a small radio broadcast station located near Dordrecht. They transmit with 100 Watt RF power on 1287 kHz. I discovered that they can be received on my car radio receiver on various locations in Zeeland and Zuid-Holland. In the evening/night they are often 'overruled' by a Spanish station.

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


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 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.

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 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).

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):