DRM-Modification Grundig Concert Boy 80

[Fabien Battesti]

Hello,

I have a Concert Boy 80 and I would like to adapt it to the DRM...
Is it possible ? If "Yes", can I have a copy of the Concert Boy's electronic diagram and the DRM module's diagram ?

Cordially,
Fabien Battesti

[simone]

Hi Fabien,
I don´t mean to discourage you, but I think the performance on SW of the Concert Boy 80 is not great, are you using the normal telescopic antenna?
Also, with some older Grundig models the phase noise caused problems for DRM, so check this first.
Simone

[Fabien Battesti]

Hi,

Thank you for the informations,
I don't use the normal antenna, I have replaced it by the antenna of an old Prima Boy, who is more longer (+70cm). I generally connect it to another antenna or a metalic carcass to improve the reception ("DX Dist." is used).
I don't know how to analyze the phase noise correctly, I carried out a spectral analysis of the frequency of 522 kHz, probably not used in France (no signal) and I have obtained this diagram. what do you think about it?

Cordially,

Fabien Battesti

[richard]

Hi Fabien, I think you at least need a reference carrier to be able to judge the phase noise though.

In my limited set up I just attached a coaxial cable from the mixer output to a 3.5mm jack on the radio. The mixer can be placed in a separate box. Even if it doesn’t work you still have a functioning analogue receiver and can try with another unit. I use a Degen receiver which is quite cheap.

Richard

[Fabien Battesti]

Hi,

I had requested the radio's electronic diagram from Grundig but they did not answer me (I am not astonished !) and as I am not an electronic specialist, I think that I will not modify the radio (it functions very well)… I will rather buy a receiver DRM when they will be cheap and available to the hypermarket of my city…

Cordially,

Fabien

[richard]

Fabien, all is not lost though. Most modern radios use an IC based mixer/demodulator. Identify the chip number and do a search on Google to get the datasheet. Find the intermediate frequency (IF) output from the chip, in this example it is marked ‘MIX OUT’. This should give you the 450 or 450 KHz output you need to feed the DRM mixer module.

The centre cable of a shielded audio lead can be connected from the chip pin to a socket on the radio. The shield of the audio lead needs to be connected to ground (i.e. negative terminal of battery case). The DRM mixer can be connected externally. Hopefully the radio should still function as normal!

Richard