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Legal Ham radio on 828kHz

The OMs Chris DL1CR, Ben DK6OT and Juergen DF9OA have been dealing with Ham radio on the medium wave 630 m for some time. The idea came up to activate the QRG 828 kHz for the Maker Faire as part of an “event broadcasting”. The frequency choice is no coincidence, because until the beginning of 2015 there was a local station in Hanover. Meanwhile, all AM stations in Germany are completely shut down.

In order to use this AM radio frequency, it first requires the approval of the responsible officials BNetzA. This was granted surprise, but only with the allowed ERP of 100mW with an assumed efficiency of the antenna of 1%.

The transmission technology is built around a Direct Digital Syntheziser (DDS) of the type AD9850. An Arduino microcontroller controls everything, a microphone input with compressor and an MP3 module for the pause signal provide the modulation signal. A 5W-PA with harmonic filter and fitting means will (hopefully) reach the allowed 100 mW ERP.

Pause sign in AM https://youtu.be/3UrnGWDxwco

As a small highlight, our technicians, Chris have come up with shift of +/- 100 Hz with CW signals. This is not heard with a normal AM receiver, so do not bother. However, if you have a proper AFU-RX and set the receive QRG and bandwidth correctly, you can hear the CW. The signal (read: key pressed) is sent to 828 kHz + 100 Hz. 828 kHz - 100 Hz then represents the pause. Normally, the BNetzA prescribes a frequency constancy of the carrier of + - 10 Hz. The request to extend it to + -100 Hz to enable the CW broadcast was unbureaucratically complied with.
We will also run the station during the night of 17 to 18 August and probably also in the night of 18 to 19 August and are looking forward to receiving reports!

Frequency Shift Keying in CW https://youtu.be/WmW5eyIxiQ8

Based on our experience at 630m, the range of the CW signal with interference-free reception could be well over 100km.

AM transmitter

Reception reports are very welcome!

Matthias Wendt, DL9MWE

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So, next Monday, 12.8. it is time. From 13:00 utc we install the antenna and go from about 14:30 utc clock for one or two hours on the air.
Frequency: 828kHz
Location: Garden of the Congress Center in Hannover
Transmitting power: 5W
ERP: 100mW (or more) :slight_smile:
Modulation: AM, FSK
estimated range: max. 30km in AM, much more in FSK

Our project has literally hit big waves:
Magazine “Die Welt”: https://www.welt.de/wissenschaft/article198078079/Comeback-Mittelwellen-Programme-in-Hannover-und-Muenchen.html

The regular operation begins with the construction of the Fair Maker Faire on Friday, 16.8. from 16:00 and ends on Monday morning, the 19.8. This means that the transmitter is also operated overnight.

Of course, we are looking forward to receiving reports!

Chris, DL1CR

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In preliminary tests we were able to record the AM signal at a distance of 65km, albeit only slightly. The CW was signal "loud ‘n’ clear. https://youtu.be/fuIfCgnNXD8

73 Chris

Short report: The AM signal could be properly heard in the city, in the car radio while driving in front of Neustadt a.Rb. partly and in Leveste with aerial (20km) in the noise.
The CW signal went very well in Wolfenbüttel (60km).

It is still interesting, whether we are also heard at night by sky wave. Stay tuned!

Chris

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So, since 17:30 loc is the 828kHz in Hannover again off air.
We thank you again for the many feedbacks in the local area and of course for the odx reports in AM about 63km (Wolfgang DF4AY) and 560km in CW (Christoph OE2CRM). I’m just reading that the Max in Holland has heard about 268km in CW.
Here is a short video from our broadcasting location at Maker Faire in Hannover.


Wilfried has received your last words with his tube rx in 20km distance.
https://youtu.be/mfYXUhJqOA4

73 Chris