My radio monitoring vehicle

In 2022, I was able to purchase this radio monitoring vehicle, which was formerly used by the "Bundesnetzagentur", the Federal Network Agency to search for signal interference, and I have been using it since then for amateur radio operations, especially for VHF-, UHF-, SHF-Contests. In the following sections, you'll learn a bit about the vehicle and what I do with it.

All About the Vehicle

Here, I’ve gathered everything I know about the vehicle. If you have any additional information, feel free to contact me. I am particularly interested in wiring diagrams and circuit plans.

The Vehicle Itself

The base vehicle is a Volkswagen T5 with a long wheelbase. It was built at the end of 2005 and, after the conversion, was apparently registered with the Federal Network Agency in mid-2006.

The Installation / Conversion for the Federal Network Agency

The vehicle was converted by "Göttinger Sonderfahzeugbau GmbH & Co. KG" in Göttingen for use by the Federal Network Agency. The mast, "L"-shaped furniture, rotating seat, as well as the power supply and network distribution were installed during this conversion.

The mast is a Geroh Type 9 KLp 6/E with a 12-volt motor. It is a 6-element telescopic mast with a length of 9 meters. The total height of the vehicle with the mast retracted increases to 2.76 meters. With the antenna used by the Federal Network Agency, it even reaches 3.5 meters. The azimuth is displayed using an adjustable scale and a laser pointer. The scale must be adjusted to the respective setup direction each time it is deployed.

The furniture was installed in an "L-shape" so that all controls and devices, including the mast control and power distribution, were easily accessible from the ISRI rotating seat in the rear, which can be used even while driving.

The power distribution, which supplies the vehicle via an isolation transformer with shore power, is equipped with an emergency stop for the 230V system. The inverter used is a TransWatt UWS 12-750S "low noise" pure sine wave inverter. The charger for the two Sonnenschein DryFit batteries of type GF 6 180V (6V 180Ah lead-gel), connected in series, is a TransWatt transductor charger, type TLF12-30. The charger operates at 14.2V with a maximum charging current of 30A.

In addition to 230V SchuKo sockets, there are 12mm automotive sockets for 12V, according to DIN/ISO 4165, as well as 3-pin XLR sockets. The 12V circuits are protected by Schurter circuit breakers, model TMT12 221.

As part of the conversion, the vehicle was additionally equipped with a 2KW heater fan for the interior, which could be programmed via a timer. This heating unit was no longer installed when I acquired the vehicle. Only the timer and some stickers remain as reminders of the heater, which could only be operated with shore power.

In this configuration, the vehicle served the Federal Network Agency for almost 300,000 kilometers, before being decommissioned in 2019, after 13 years of service, and sold without the measurement equipment but otherwise almost fully intact.

On YouTube, you can see a similar vehicle in a documentary about the work of the Federal Network Agency:

By clicking on this image, the video
'On the Road with the Federal Network Agency in Bernburg'
from the channel 'Salzlandmagazin'
on the external video service YouTube will open.

My Modifications

One modification that was not done by me was made by the owner between the Federal Network Agency and myself. He was also a radio amateur and reconfigured the furniture inside the vehicle. The "L" shape was turned into a long row on the driver’s side of the vehicle. This allows for multiple people to operate equipment from the vehicle at the same time. It also provides the option to sleep on the floor during 24-hour contests. The sleeping area is 180cm long, which is sufficient for a short rest during contest operations. In that sense, the modification is very advantageous for me compared to the original "L" arrangement.

Since I use the vehicle for amateur radio, and almost exclusively for participating in VHF contests, I’ve made a few modifications to suit my needs. Here are the changes I've already made:

• Replaced the 180Ah lead-gel batteries with two 315Ah LiFePo4 batteries, which together provide me with 630Ah at 13.2V or 8.4 kWh of power
• Replaced the charger with a 40A LiFePo4 charger
• Installed a battery computer AiLi 500A to monitor the battery charge level
• Modified the antenna mount for "Measurement Antenna 2" on the roof to a PL mount

I invest a lot of time and energy in maintaining the vehicle. Since my annual mileage is only 1,000 to 1,500km, much lower than when it was with the Federal Network Agency, my focus is on preventing wear from inactivity. I will continue to regularly protect the vehicle from rust and ensure there is no maintenance backlog.

All About Radio Operation

Here you can find some information about the radio operations for which I use the vehicle. I am a licensed amateur radio operator and primarily use the vehicle for VHF contests. In the next sections, you’ll read more about what amateur radio is and what one does during a VHF contest:

Amateur Radio - What is it?

Amateur radio is a fascinating hobby that connects people worldwide via radio – regardless of origin, religion, or political beliefs. It offers a unique combination of technology and communication, where you can use homemade devices, test new technologies, or even establish radio connections via satellites. Beyond traditional radio conversations, amateur radio enthusiasts can also participate in contests or exchange QSL cards as confirmation of contacts.

Amateur radio is much more than just a hobby – it is a technical playground for radio enthusiasts. With homemade or modified equipment, amateur radio operators can develop and test their own transmitters and antennas. They have access to frequency bands from shortwave to ultrahigh frequency (UHF) and even microwave. Whether it’s voice, Morse code, or digital transmissions, amateur radio offers nearly limitless possibilities to connect with the global radio community.

Technical marvels such as radio communication via satellites or even Earth-Moon-Earth (EME) communication using the moon as a reflector open up impressive perspectives. Amateur radio is not only about communication but also about experimenting with engineering at the highest level. It’s a playground for innovation, where you can experience the laws of physics firsthand.

Moreover, amateur radio often serves as a gateway into technical careers. Many engineers discovered their passion for electronics and communication through this hobby. Amateur radio is, therefore, a perfect combination of creative technology and global networking, which can even save lives in emergencies by providing independent communication channels.

But it’s not just about technology: amateur radio promotes international understanding and friendships across borders. In emergencies, the importance of amateur radio becomes clear, as operators help maintain communication.

This versatile hobby brings generations together and offers countless opportunities to be creative and learn new things. Whether young or old, amateur radio remains an exciting adventure that connects people and technology worldwide.

What continues to fascinate me is how little effort is needed to communicate globally in real-time, and that without any additional infrastructure. Often, a wire thrown into a tree and a small, battery-powered radio is enough to establish a shortwave conversation with someone in South America, Hawaii, or Australia.

Here in the bus, I rarely use shortwave. I primarily use the bus for experiments on VHF. VHF contests are my passion, which I will talk about more in the next section...

What are VHF-, UHF-, SHF-Contests?

VHF contests are competitions among amateur radio operators where the goal is to make as many contacts as possible with other stations within a given time period (usually 24 hours) and to cover as many kilometers as possible. Each kilometer covered between two stations earns both stations 1 point. However, points are only awarded if the exchanged information is correctly and fully received by both sides and entered into a logbook. This logbook—usually kept electronically—is sent to the contest evaluators, where the entries are cross-checked automatically. If everything is correct in both stations’ logbooks, the contact is validated, and both stations receive one point per kilometer covered.

Typically, the following information is exchanged:

• The call sign of the other station
• A signal report (rapport) detailing the signal strength and readability of the signal
• The Maidenhead Locator, a combination of numbers and letters that allows the distance and direction between both stations to be calculated—similar to GPS coordinates
• A serial number, where each station indicates how many contacts it has made (on that frequency band)

Here is an excerpt from my logbook from May 2024 as an example:

* (Report, serial number, locator)

There are seven 24-hour contests held each year. Additionally, there are shorter contests throughout the year, where, for example, the focus may be on being independent from shore power or operating with limited transmission power. Nearly every week, there is a competition where you can test and improve your (homemade) equipment, optimize your station, learn a lot about propagation conditions, or simply enjoy the camaraderie with fellow radio enthusiasts.

How Far Can It Go?

Shortwaves (frequencies from 3 MHz to 30 MHz) can be reflected by the ionosphere and travel around the world if they bounce multiple times between the Earth and the ionosphere. The propagation of very high frequency (VHF) (frequencies from 30 MHz to 300 MHz) and above, however, resembles the propagation of light, as it mostly occurs in a direct line of sight. VHF waves are typically not reflected by the ionosphere but pass through it into space. The higher the frequency, the stronger the attenuation. Currently, I operate from the radio monitoring vehicle on the frequencies of 144 MHz, 432 MHz, and 1,296 MHz.

The range depends heavily on the antenna height, the surrounding environment, and the quality of the equipment. That’s why I try to park the radio monitoring vehicle at the highest possible points, where the terrain ideally slopes gently around the location and there are no large obstacles like buildings. With the current station setup in the bus, ranges of 600 km around the antenna are usually possible. Under good propagation conditions, such as inversion weather or the formation of a sporadic E-layer in the ionosphere, VHF signals can also experience reflection and return to Earth. Through these effects, extended ranges can occur, and with a bit of luck, contacts over more than 1,000 km are possible. You might have experienced something similar if you suddenly received a foreign station on your VHF radio, which you usually wouldn't pick up. Airplanes or dense clouds can also act as reflectors, increasing the range of your signal.

The operating mode (voice, Morse code, or digital) also affects the range. Often, Morse code connections are still possible when voice connections fail. A trained ear and good operating techniques are just as helpful.

My longest contact so far was with the Romanian station YR5C on November 3, 2024, at 08:50 UTC / 09:50 local time during the IARU Marconi Memorial Contest VHF 2024. The contact was made from a location in Halver at 440 meters above sea level. I managed to bridge 1,214 km in CW mode Morse telegraphy.

How does it sound?

Some time ago, I created a video that I recorded during a contest. It gives a good insight into the flow of a VHF contest and the sound of the signals:

By clicking on this image, the video
'That's how a VHF Contest in HamRadio is like - May 2023'
from my channel 'DC6CX'
on the external video service YouTube will open

What equipment do I use?

As of 2024, I am using the following equipment:

• ICOM IC-9700 for 2m, 70cm, and 23cm
• Linear Amp Gemini 2-500 - 500W out for 2m
• Linear Amp Gemini 70 - 300W out for 70cm
• Linear Amp Gemini 23 - 200W out for 23cm
• SSB Sequencer DCW 2004B for 2m and 70cm
• SSB Sequencer DCW 15 SHF for 23cm
• Mast-mounted preamp SSB DB270 for 2m and 70cm
• Mast-mounted preamp SHF MVV 1296VOX for 23cm
• WaveNode WN-2d for monitoring the SWR and output of all amplifiers
• Heil Headset Proset Elite for ICOM with footswitch
• Antenna Amplifiers PA144-432-21-3B Duoband Yagi (2m: 7 elements / 70cm: 14 elements)
• Antenna Amplifiers PA1296-36-3BUT 23cm Yagi with 36 elements
• Mac Mini M1 with 8GB RAM and 256GB SSD, modified tu run on 12V
• Samsung 34" Ultra WQHD Monitor S34J552WQR, which could easyily be modified to run on 12V due to its external power supply
• RUMlogNG as logging software

Changelog

• 06.11.2024 - Updated longest contace from HG6Z (1,006 km on 2 meters, 02.07.2022 20:20 UTC, from JO31LH 180m above sea level) to YR5C (1,214 km on 2 meters, 03.11.2024 08:50 UTC, from JO31SE 440m above sea level).

Image Gallery

To wrap things up, you find a few impressions here:

Overview for the radio monitoring vehicle is available

July 02, 2024 | HamRadio, RadioMonitoringVehicle

The overview page for my radio monitoring vehicle is complete. Here you can find all the information about the vehicle, which was previously used by the Federal Network Agency for interference detection and is now repurposed by me for amateur radio purposes. Currently, I mainly use the vehicle to participate in VHF-, UHF-, SHF- contests.
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