Am 16.08.2011 22:14, schrieb wolf_dl4yhf:
Hello Tom,
Yes I use a UHF link, but "only" for VLF, single channel, covering
500 ... 20000 Hz. The dynamic range is somewhat limited as you can
see on the VLF stream's detail page: http://abelian.org/vlf/detail.php?stream=vlf6&page=0
But if strongs sferics are occasionally clipped (in the
transmitter) doesn't hurt that much for this application.
One important thing was getting rid of the stereo encoder /
decoder, which I had used in the first setup (it was a cheap
"HiFi" wireless headphone in the 864 MHz band, which didn't
deserve its name. Analog stereo wideband FM, but noisy as hell).
Getting rid of the stereo-stuff (tap the rx after the FM
discriminator) gave a better performance, and no aliasing effect
caused by the strong Navy transmitters in the vincinity of the 19
kHz pilot (there is no 'sharp lowpass' before the stereo modulator
which would have cured some of the problems).
The currently used stream is still analog, using a modified FM
wideband TX (which was once a cheap AM transmitter), and a
wideband RX. Today I'd go for a digital system, something with a
16-bit ADC on the TX, and 16-bit DAC on the RX side. Not sure if
the "bluetooth HiFi wireless headphones" sold today would be up to
the job. For example, the Sennheiser RS 170 (digital, without
compression, but datasheet not very detailed).
73,
Wolf .
Hello Wolf,
thanks for zour info and the hints! I'll keep them in mind when
fetching my pliers and fireing the soldering iron ...
73,
Tom, DK1IS
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