WireGuard & rinetd

Protože opakovaně připojuji další dislokované pracoviště a opakovaně hledám ty samé postupy ve svých poznámkách, odložím si zde komplexnější postup a podělím se o svou praxi, která by mohla někoho inspirovat.

WireGuard patří mezí nejprogresivnější a nejpoužitelnější VPN – ten kdo v korporátním prostředí řešil třeba IPSec nebo ještě staré PPTP, případně nějaké obskurní vendorlockované řešení, tak ví jaký je problém aby vše fungovalo všude. WireGuard je velmi jednoduchý na konfiguraci a širokou podporu platforem. Klient existuje jak pro macOS, tak pro Windows, Android i iOS.

rinetd je síťový nástroj na přesměrování TCP a v nové verzi 0.70 i UDP spojení. Používám to místo portforwardingu. V kombinaci s WireGuardem tedy není nutné vystrkovat porty na veřejnou IP adresu, ale stačí se v rámci VPN dotazovat jednoho zařízení, které pak v daném segmentu větší sítě přesměrovává místně dotazy.

Doporučuji zajímavý seriál Petra na root.cz – https://www.root.cz/serialy/wireguard-pro-jednoduchou-linuxovou-vpn/

Konkrétní usecase (třeba): Mám od poskytovatele Internetu zpřístupněné SNMP na WiFi zařízení, kterým jsem připojený skrz jeho síť MAN připojen do Internetu. Směrem z LAN se na zařízení v MAN dostanu, ale z Internetu už nikoliv. Ve virtuálním serveru v Internetu mi běží SNMP monitoring, kterým bych zařízení v MAN síti rád dohledoval.

Příště ukážu svojí konfiguraci rinetd.

3D printable replica of SATCOM / MILSAT antenna AV 2040

In spring 2019 I was asked to build an antenna which should be similar to equipment which is used by US Army and what more it should work.

After some research through sources of US military contracts and pictures there was a hot candidate for MILSAT or SATCOM antenna build: AV 2040 UHF Satellite Communication (SATCOM) Antenna from ULTRALife corporation [1]

There are STL [2] and OBJ [3] files for anyone who would like to print own atenna. The design is for 449,550 MHz but by adjusting lengths of active parts of the antenna it can be tunder in wide range, see below on Fig. 5

Fig.1 – First design in Tinkercad.com
Fig.2 – Detail of RG58 coax cable prepared for soldering SMA connector
Fig. 3 – Detail of SMA connector
Fig. 4 – SWR (Standing Wave Ratio) of antenna
Fig. 5 – The antenna lengths

There are three formulas considering f as frequency in Hz need to be calculated to get three dimensions which are mandatory for best results:

red = (299792458 / f / 2) * 0.92 [meters]
blue = red * 1.05 [meters]
green = 299792458 / f * 0.225 [meters]
Fig. 6 – First bunch of antennas
Fig. 7 – Picture from outdoor testing
Fig. 8- Making of the antenna and QSO on 102 km

IL-2 M3 Sturmovik from 3DLabPrint.com

It all began with an idea to get a 3D printer for home. The original intention of the 3D printer was to print a parts for my antenna designs. Then came up the idea to print something while the printer wasn´t being used.

I got the inspiration from a sub reddit r/3D_printing to print an airplane and later I discovered a great youtube channel of Richard Mrázek where he mentioned the guys from 3Dlabprint which is a company luckily from the Brno in the Czech Republic.

The very first airplane I wanted to print was IL-2 M3 Sturmovik, it was that time the newset airplane in the shop a and the price of $20 was acceptable for some print tests.

The idea becomes reality just instantly. I very appreciate genereated .gcodes for i3 Průša´s printers. You just put the airplane in the basket, proceed paying via PayPal and in a second you are downloading .STL files and pre-generated .gcodes.

Printing landing gear gondolas
Printer corner with huge 2 kg spool of filament.
Pieces prepared for gluing.
Dry setup
Bottom of wing
Wiring RC electronics built inside
Experiments with PU foam for strenghting the wing
PU core of wing
Preflight picture
Our short video with first flight
Original flight video from 3DLabPrint.com

Nordic Activity Contest from the Czech Republic

Inspired by OMs in the Czech Republic who were able to make QSOs with northern stations during the Nordic Activity Contest, I decided to take my portable rig and visit one spot near my home QTH. Unfortunately, the conditions were poor. I only heard two stations but was unable to make QSO with them. At least we started the portable season with grilled meat from a campfire 🙂

Radovič lookout in background of campfire
YL operating campfire
YAESU FT-857d juiced by lead-acid 12V/10Ah battery, YAESU FT-2DR, loogbook and RTL-SDR connected to macbook air with GQRX as scanner.
My Diamond antenna A430S10  and rig with sunset
OK1BT with dinner 🙂

Some useful links:

Security Conference: Legal regulation of weapons in the Czech Republic and related issues of ammunition production

On Friday 22nd March 2019, I was invited as a professional citizen by The Committee on Security to a seminar entitled “Legal regulation of weapons in the Czech Republic and related issues of ammunition production”

CZUB, Radek Musil, Jiří Hynek, Karel Bláha, Radek Koten, Milena Bačkovská, Jan Skalický, Pavel Černý. Source: facebook.com/LIGA.LIBE

Thanks to the Chairman of Committee on Security, Radek Koten many representatives from different fields were invited.

However Mrs. Dana Kovaříková (the chief representative of the European Commision) was invited to give a speech during the main programme, and once again she was unable to attend.

The first speaker was Mgr. Milena Bačkovská (from The Ministry of Interior) who presented information about upcoming changes of Czech Gun Law. She gave more details about all processes and when the amendment should be sent to the House of Commons. The appeal to the European Commison with regards to the European Firearms Directive is still in process so there is no sense of urgency. The New Czech Gun Law will not be implemented before the appeal is solved.

The Director from the Department of Environmental Hazards and Environmental Damages, The Ministry of the Environment, Ing. Karel Bláha, CSc spoked about ECHA which may result in the banning of lead in ammunition. It was said that the toxicity of lead in that form is used in bullets is not an issue. The only opportunity to keep lead in the bullets is to make sure lead is put on the exception list of toxic materials published by ECHA.

RNDr. Jiří Hynek (President of Defence and Security Industry Association of the Czech Republic) spoke about the importance of the Czech weapon industry in context of internal security of the Czech Republic and informed participants about the consequences of accepting the European Firearms Directive or the lead ban could cause.

Special thanks to Radek Musil (Sellier & Bellot) who investigated all
ECHA reviews and papers. Musil reported that the ECHA report was of very poor quality and conlusions from quoted sources were misrepresented. Based on the original study which was noted in the Investigation report, he said there is no danger from the lead used in ammo production. And he also mentioned a suspicious connection between ECHA and Swedish Chemicals Agency (KEMI) which is responsible for starting this campaign.

Mgr. Pavel Černý (police ex-instructor and president of LIGA LIBE) mentioned that banning lead in ammunition could increase annual expenses for gun training more than three houndred percent.

Ing. Jakub Smetánka MPA (vice president of the LEX association) agreed with the gentlemen and lady and presented very interesting statistics about the lead used in ammo and the lack of substitutions. There is no substitue available for .22LR and lead bullets for shotguns.

If you are interested in Gun laws of the Czech Republic go there: https://en.wikipedia.org/wiki/Gun_laws_in_the_Czech_Republic

Flying season has begun

Today we started a new season with our RC models on the airfield. Days are now longer and the Sun provides more energy to the off-grid system which is powered by one standard sized solar panel.

Nominal peak power (Pmax):   225 W
Maximum power voltage (Vmp): 30.2 V
Maxium power current (Imp):  7.44 A
Open circuit voltage (Voc):  36.6 V
Short circuit current (Isc): 8.06 A

For storing captured energy we use Panasonic LC-XB12100P battery with a capacity around 100 Ah and some spare car batteries with the capacity around 55 Ah, thus total capacity is 200+ Ah.

Last year the MPPT tracer 1210a provided 127 kWh and today it juiced the battery to 13.8 V which is considered fully charged.

Maidenhead Locator System

Have you ever wondered how the so-called QTH Locator or WW locator is calculated and what is behind it?

Many HAMs and radioamateurs use it but ask them where their locator came from and not many can tell you. There are plenty of web based applications which overlay Google maps with a locator grid and many of them provide a calculator for conversion from other geographic coordinates to Maidenhead Locator System.

clear all;
close all;

m = mobiledev();
m.Logging = 1;

lat = 50.2727514;
lon = 14.2518494;

alphabet = ['A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','R','S'];

locator = [];
len = 4;

lon = lon + 180;
lat = lat + 90;

lon = lon / 20;
lat = lat / 10;

for i = 1:len
    lon_tmp = floor(lon);
    lat_tmp = floor(lat);
    if mod(i,2) == 0
        locator = [locator int2str(lon_tmp) int2str(lat_tmp)];
        lon = (lon - lon_tmp) * 24;
        lat = (lat - lat_tmp) * 24;
        locator = [locator alphabet(lon_tmp+1) alphabet(lat_tmp+1)];
        lon = (lon - lon_tmp) * 10;
        lat = (lat - lat_tmp) * 10;


Corresponding output:

locator =


And the most amazing aspect is executing .m files on your iPhone. The disadvantage is that an internet connection is necessary for computing via the application.