On Tue, Oct 19, 2021 at 08:47 AM, <frikandelmetmayo@...> wrote:
Did some tried to measure a DAB signal already?
I have never measured one, and having never had to design or repair a DAB, I don't really know a lot about them.? However, one of the first things I do when asked about something I don't know a lot about is to consult with somebody that does know a lot about it.? According to Rohde & Schwarz, this is not a particularly easy thing to measure:"The high dynamic range of the signal after the mask filter makes it impossible to check
adherence to the tolerance mask directly using a spectrum analyzer. This is why an
adjustable notch filter is typically used to reduce the useful band power."
Their list of required equipment includes:
"For Shoulder Attenuation and Adjacent Channel Emissions measurements
(3.3.1) using the variant 'after mask filter'
Notch filter to attenuate the wanted signal by 40 dB or more"
Source:
https://cdn.rohde-schwarz.com/pws/dl_downloads/dl_application/application_notes/7bm104/7BM104_1E.pdf
As I said, I'm not the expert on this.? But I'm inclined to accept Rohde & Schwarz's opinion on this.? I'd probably start by building a notch filter to take out much of the in-channel power.? You might try an open quarter wave coaxial stub at the channel center frequency to start with.
Jim Allyn - N7JA