Welcome to PA0SIM´s home page



Triggered by the magic of radio I started as a SWL in 1973. Helped by Peter PA0AP (SK). Got my full license in 1975.

My main ham radio interests are radio technology, shortwave propagation and CW.

Doing practically 100% CW on HF (AGCW #2867, FISTS #18854, NTC #59), mainly rag-chewing, some DX-ing (DXCC) and now and then a contest (e.g. PACC). Always using QSK.

CW represents the essence of radio communication and all its aspects, analog and digital.


Operating with the excellent FTDX5000 equipped with a very good APF for reading CW signals in the noise. Antenna for 80m-10m is a 24 meter long doublet at an average height of 7 meters, using an open line feeder and the auto tuner CG3000 with a current balun at input and output.

Two orthogonal small broadband active receiving loops and two phase coherent SDR receivers are used for one mouse click noise cancelling, stereo diversity noise reduction and for measuring propagation polarization behavior over frequency.

Update May 2020: now using the WebSDR Maasbree and doing what professionals have been doing for a long time, receiving at a quiet remote location.

Why: I have lost the battle with local QRM. In the Netherlands we are losing the battle.

At the end of the day with a xdB higher noise level you lose xdB in SNR.


The information on my internet site is a result of the ever increasing level of man-made noise on the HF bands.

Man-made noise level is inversely proportional to the level of civilization. Any noise: acoustic, electromagnetic or light:

Man-made noise level × level of civilization = Constant


I am now (Dec. 1 2018) retired as a mixed signal electronic developer/engineer from Océ - A Canon Company.



There are five sections:


1) Analog section (partially published in Electron 2004)

Some examples of what can be found on this route

- dual loop antenna system

- balancing and closed loop antennas

- broadband small loop amplification update Dec. 2018

- broadband small loop amplifier update March 2022 of 2018 and 2003 design

- noise canceller / phaser / QRM killer update March 2019 of 2006 design


2) Digital Signal Processing section (published in Electron 2006 and QEX 2006)

Some examples of what can be found on this route

- effective directivity by DSP

- two phase coherent Software Defined Radio’s (two Elecraft K2 receivers as SDR)

- ideal phaser/noise canceller in DSP (e.g. for phased array’s)

Some audio samples:

- enhanced stereo reception by DSP

- CW APF filter optimized for weak signal reception


3) Finding Signals in the Noise using two Antennas section (published in March/April 2019 issue of QEX)

            - One mouse click Noise Cancelling (Noise Cancelling Lezing Veron A31/A22 in Dutch)

            - Stereo Diversity Noise Reduction

            - Measuring propagation polarization behavior over frequency

            - GNU Radio implementation of Noise Cancelling (added April 2019)


4) XO Mode Propagation section



5) CW bug section

            - Learning to play the bug

            - Bug debounce circuit



=== >   Link to all my published ham radio articles < ======




73 es cu on the band,


(I do only paper QSL!)


Contact: PA0SIM








Permission is granted to use the information and the software on this website for private, non-commercial use only. If you use the information and the software provided by my pages for non-commercial use, please make proper reference to the source of the information.

Using the information and the software provided by my pages for commercial use is only allowed after my explicit and personal permission.

I will not accept responsibility for any damage to your equipment through the use of this information and the software or as a result thereof.



Last update: June 13, 2022