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DJ7UA Germany flag Germany

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Picture below shows the summer 2010 holiday QTH in Asturias/Spain; call EA1/DJ7UA. A 15m glass fibre pole supports the home constructed multiband-OCF-dipole. In the background is the Atlantic ocean.

The next one was taken in SM4/ Sweden near Falun in 2005 when bringing the TL922 by boat to the location, a typical red wooden house. Access to that place needs to cross the lake.

Here is DJ7UA operating 2006 from Galicia/Spain using the FT817.


Some details from the latest projects

1. Automatic mobile tuner, designed for 600 Wtts RF 1,8 - 50MHZ, based on 4nec2 studies:


Big capacitor bank with RF-relays, GDR-surplus from the flea market, 11 steps from 9 pF up to 3.6 nF,

one of the 3 HV-RF-relays mounted in the separate coil box in the background


Main unit, C-bank (left) and 7 switched Ls down to 0.1 mikroH at the right hand.

Hope the Gruner relays will do the job...

The metal box at right hand / bottom contains a Z and Phi -detector, made by Hagenuk.

On top you can find the antenna-RF-current probe using a 4C65 core.

Next steps are testing the unit manually outdoor on the roof of the van and creating a tuning strategy, then designing an ATMEGA32 based controller for automatic tuning.

Update 01. May 2012

The Gruner relays died under load in the upper L-stages and were replaced by 3 kV types same type as in the C-bank.

Here you have a parade of the various relays tested so far.

The final sections of the loading coils need Siemens VR411/412, a 10 kV vacuum relay. A pair of relays is used to insulate the coil when unused to reduce stray capacity. Notice the golden metal balls as arcing prevention.
So have a look at the six cylinder machine working in my coil box now!


Update January 2013: yes, it works! Meanwhile does the ATMEGA32 it's job to tune automatically within a few seconds.

An ATEMGA32, a 4x20 LCD display and some toggle switches allow manual and automatic tuning as well.

Controller inside and main tuner unit outdoor ar connected via I2C/CAN BUS technology.

Some of the Gruner Relays have been replaced, at least by vacuum type in the 7th coil step.

Notice the I2C/CAN BUS driven logic unit for communicating with the ATEMEGA controller inside the car at the operator's seat.

A RF-voltage-divider (blue shrink tube at right hand) and probe unit had been added at the RF-output to the following coil box to detect unwanted "high-Z"-conditions f. e. when antenna connection failed or any other dangerous missmatch occurs.

The capacitor bank is now hidden by the main logic unit and located just below.

Update July 2013: Tuner is running since one year now including automatic mode.

A newly designed "DJ7UA FOLDING ANTENNA" (Klappantenne) is on the roof of the motorhome now!


the 4nec2 model

4nec2 Model DJ7UA Folding Antenna


The folding antenna in reality: 3 rods supporting the 3m arial wire, 2 rods glass fibre only, the 3rd one carries a copper braid to lead the RF current from the tuner which is on the roof floor.

The antenna can be erected within 15 s by remote control from the driver's seat even during motion. Top of the antenna exactly meets the German regulations for vehicles in public traffic with a maximum height of 4 m above ground. The system can be folded down when approaching low headroom ways (bridges, trees) .

Don't miss to watch the short youtube videos showing the system in motion (dj7ua channel: "DJ7UA FOLDING ANTENNA (1)" and "DJ7UA FOLDING ANTENNA (2)":


Measurements to reduce noise from Diesel injection

The car (Peugeot Boxer III) engine is a 2.2 l Diesel common rail injection type. Because of the high speed / high current driven injectors a lot of noise reduces the RX-performance. Forget the recipes from the old ham books. There is no way to add capacitors or chokes to smooth the sharpness of the currents in a modern car, because this will ruin the motor management. The only way is to reduce the common mode radiation of 2-wire lines. So I decided to add the following:

1. 4 Ferrite clamps on the 2 wire-feeders of the 4 injectors (left/center), big #31 clamp on the cable harness (right, just below brake fluid container) as common mode chokes

A closer view:

Copper foil wrapped around the harness, as well as low impedance grounding of the hood:

By this measurements the noise level was finally reduced for several s-units and I can receive weak signals now even when I'm on the road.

73, Mario

8403337 Last modified: 2017-10-22 09:36:40, 6441 bytes

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