Tuesday, 12 April 2022

8 meter band

Lately there is quite a lot of attention for the 8 m band (40 MHz). Transmissions are done from Ireland, UK  and Denmark for example.



This band could be interesting to explore for various reasons:

The 8-meter band shares many characteristics with the neighboring 6-meter band. However, as it is somewhat lower in frequency it does display the better propagation mechanisms via the F2 layer normally seen at  HF. Also sporadic E-propagation is common on this band in summer.

After I performed the MARS modification, my FT-450 is able to receive 40 MHz signals. Of course the FT-450 input filters are not designed for this frequencies.

I am working on a 8 m bandpass filter / pre-amplifier for the FT-450 to increase the sensitivity for this band. 

Hopefully I will be able to tune in into 40.680 MHz - to receive FT-8 signals - soon.

First results;

                                                      Passive band filter under test

                                                             nanoVNA showing filter characteristic


Saturday, 2 April 2022

Hardware

 For more than 10 years I have a piece of hardware in my junkbox that waits for an application:

It is an old school mechanical tuning device, most likely obtained from 'green' radio equipment. The tuning knob drives, tru a variety of gear wheels, a 100 Kohm potentiometer.

The only (German) inscription present says "Funk.stat.18.T"


This beautiful piece of mechanical art waits to be incorporated into a homebrew VFO (for example).

Off topic:


My QTH Zuidzijde, locator JO21dq from above. Photographed by a collegue in a Robin DR400, March 2022




Wednesday, 2 February 2022

Earth's thermal radiation

As a radio amateur I am interested in all sorts of electromagnetic radiation. That includes thermal radiation in the infrared spectrum as well. Lately prof. William Harper visited The Netherlands with a remarkable presentation on climate. I was intrigued by one of his graphs:



The picture shows us the outgoing thermal flux spectrum from earth. 

If there were no greenhouse gases, the (uv/visible/thermal) radiation going to space would be the area under the blue (Planck) curve.
The green curve is the computed spectrum with all the greenhouse gases present except for CO2. 
The black and red lines are the energy fluxes for the CO2 concentrations for 400 ppm (part per million) and 800 ppm respectively.

When doubling the earth's CO2 concentration from 400 to 800 ppm, the outgoing flux will decrease from 277 W/m2 to 274 W/m2. A change of 3 W/m2

IPCC fully agrees with this model. However, the dispute is ongoing whether the 3 W/m2 change will raise earth's average temperature by 1.4 degrees C (Happer) or 4.7 degrees C or even more (IPCC).

It looks like the greenhouse effect of CO2 is already more or less saturated. Doubling CO2 concentration probably does not make much difference.

More on this subject:






A 40 minute YT-video from David Siegel shows the same graphs (and more..)


More:

Saturday, 22 January 2022

Royal KMM typewriter

Yesterday I found a pretty nice old school mechanical typewriter in the second hand stuff store ("Kringloopwinkel"). It is a Royal KMM 'workhorse' typewriter. KMM stands for Key Set Tabulator, Magic Margin, Machine. Its original design dates back to 1939, pre WWII.

It is produced in 1947 by the company Royal, which had its headquarters in New York City and its factory in Hartford, Connecticut (USA). I found that millions of this typewriter had been produced and have been spread all over the world.

The one I bought shows severe marks of use, but a first trial indicates that most functions are still in tact.



I know this device does not need a battery and has nothing to do with radio. Sometimes I just like old mechanical stuff. But hee, doesn't the QWERTY keyboard look familiair to our PC keyboards ? (Yes, it does !).

On YT,  I found a nice movie from Joe Van Cleave who explains the typewriter functions in a clear way:


https://www.youtube.com/watch?v=pjn-XG_WgMQ


Anyway, I will be busy coming weeks trying to restore this incredible machine as much as possible in its original state (where can I buy the ink ribbon ??)


Tuesday, 14 December 2021

Geminides

This is a screenshot of Meteor Scatter (MS) signals received yesterday:


Strong signals from S59A in JO21dq ! 

As you can see I used the MSK144 mode on 50.280 MHz. Ftol was set to 200.
I did not manage to make an MS QSO.





                                                        Geminides
Off-topic:

Nieuwendijk; ferry to Tiengemeten



 

Thursday, 28 October 2021

Airband receiver

It is not difficult to receive nearby AM aircraft transmissions in the VHF airband (118 – 136 MHz). The aircraft transmissions use a bandwidth of 8.33 kHz. 


Dutch coastguard Do228


Since the ‘old fashioned’ modulation AM is used, a simple detector (e.g. Schottky diode) can demodulate the airband waves. The schematic below shows a simple receiver that enables you to receive (strong, nearby) AM transmissions. Not a lot selectivity, so you may receive more transmissions on various frequencies at the same time..


 

More info about this design:

http://techlib.com/electronics/aircraft.htm

 

I was intrigued by a similar design - using PNP transistors - a long time ago. It was a design from the book “Jongensradio” from 1967. I never built it. 




Sunday, 26 September 2021

Doggerland

No, Doggerland is not a new DX entity. 

Doggerland was the land between England and Holland/Belgium/Denmark appr. 10,000 years ago. The Northsea has taken its place nowadays.


Doggerland, abt. 10,000 years ago

Past years the Northsea has shown to be a gigantic storage of fossils. Fossils from The Netherlands, with Doggerland as origin, can be found on the Dutch beaches, in particular Maasvlakte2 and the Zandmotor (near Kijkduin). The sand used for those beaches comes from the Northsea floor and contains fossils.
I have visited Maasvlakte2 a couple of times and have found some small bones of mammals from the Pleistocene.

Interesting to know is that the Northsea level rise was 5 - 10 cm a year those days. Past 100 years the Northsea level rise is appr. 1.5 mm (millimeter) a year.

I got in contact with Kommer Tanis, a fisherman who lives in Havenhoofd, close to where I live on Goeree-Overflakkee. Kommer is a fossilhunter and has been collecting fossils for the past 40 years. Between the fishes he catches, sometimes there are fossils. Kommer has a nice fossile collection at home. In his workshop he prepares the fossils.


The big bones are mammooth bones


Mainly horse bones / yaws


Mammooth yaw with 3 enormous teeth



Kommer has a small shop where he sells some of his fossils. The above picture shows part of a deer antler which I took home (Estimated 12,000 years old).

If you want to get in contact with Kommer Tanis, you can e-mail him: tanisfossils(at)go6tanis.nl





Saturday, 11 September 2021

UHF amplifier under test

Last FT8 EU contest on 70 cm I participated with my homebrewed 50 Watt UHF amplifier. The amplifier uses an MRF186 in the final stage to boost the 5 Watt RF signal coming from the 28-432 MHz transverter. The amplifier seems to work well. I was able to make 25 QSO's during the evening (PA, ON, F, DL and G stations). Best DX was with Richard G7KHV in East Yorkshire (IO93vw) over 392 km.

FT8, 432 MHz signals



Amplifier under test


Housed in old Onkyo receiver case





Sunday, 22 August 2021

LPF for 70 MHz

The RF output of my 28 - 70 MHz transverter shows an irritating 3rd harmonic at 210 MHz. 

I found a simple Low Pass Filter for 70 MHz at dutchrfshop.nl 

The filter should be able to handle RF powers up to 150 Watts.

4 ATC capacitors and 3 coils is all you need:


Arranged on a PCB as follows:



Some finetuning using the nanoVNA shifted the dip @ 70 MHz;


Next step is to test the LPF with the transverter..

Off-topic: Old QSL card