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Dynamic range measurements
- Subject: Dynamic range measurements
- From: Leif Åsbrink <leif.asbrink@xxxxxxxxxxxxxxxxxxxx
- Date: Mon, 2 Jun 2003 10:23:31 +0200
For those of you who plan to come to the Scandinavian VHF-UHF meeting this
year. Do not forget to bring your 144 MHz transceiver:)
I will bring equipment for rx dynamic range and tx purity measurements
and I am interested in getting data for many different radios.
As you may know I am working with Linrad (Linux Radio) and wideband
signal processing in the computer. With the new technology, old
standards may be inadequate to judge how useful a radio is.
An A/D converter is more or less ideal all the way up to the saturation
point where it abruptly fails completely while a "good old analog"
receiver can be used even if it is subjected to signals that cause
severe intermodulation - one just has to avoid certain frequencies.
For these reasons one has to extend the comparisons of IP3 and
BDR to wider frequency ranges. Comparing a 5kHz and 20kHz is
inadequate, data is needed at larger frequency separations also.
Another thing is that published data in QST come from measurements
that are defined in a way that does not give the information one
really looks for. The FT1000D (March 1991 QST) is listed as BDR
(blocking dynamic range) larger than 154 dB. It means the receiver is
not blocked even with 0.1W at the antenna input. With a more
conventional definition for BDR, the ratio of strongest and weakest
signals the receiver can manage simultaneously, the dynamic range
is 97 dB for the FT1000D at 20kHz. The relevant phenomenon is
reciprocal mixing and not blocking......
The meeting will be held in JO49XI close to Oslo
from June 6 to 8.
If you do not plan to visit the Scandinavian VHF/UHF/SHF meeting
this year, there will be another meeting in the very southern part of
Sweden in August. I will bring all the equipment to this meeting
also - and probably also some equipment to check HF rigs.
The main purpose of my participation in these meetings is to
demonstrate Linrad and the WSE converters:-)
Leif / SM5BSZ