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Re: LF: Remote Receiving Antenna: UHF-Link

To: [email protected]
Subject: Re: LF: Remote Receiving Antenna: UHF-Link
From: DK1IS <[email protected]>
Date: Tue, 16 Aug 2011 22:55:43 +0200
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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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