[hpsdr] hpsdr/pandora grounding concept

[John Ackermann N8UR]

Hi Georg -- here is a link to some work on grounding Alex in the Pandora enclosure; maybe the some comments will be helpful for your setup: http://www.febo.com/pages/hpsdr/alex/alex_grounding/index.html

73,
John

> On Oct 4, 2014, at 12:54 PM, Georg und Brigitte Prinz <getpri at t-online.de> wrote:
> 
> ***** High Performance Software Defined Radio Discussion List *****
> 
> Hi,
> 
> 
> I built an enclosure similar to Pandora box for OZY, Mercury and Alex
> out of aluminium sheets. The cards are powered by LPU and an external
> analog power supply. The Atlas board is screwed to the box via 4
> distance metal adapters. Two additional metal adaptors are placed in the
> middle of the atlas board without screws. No other ground connection is
> made to the box.
> 
> Now I realize that there are several spurs up to -114dBm and more with
> side spurs +/-48 kHz. The noise floor is around -135dBm. Alex is
> terminated with 50 ohms dummy. 
> Another effect is, when shortening the BNC antenna-plug of mercury to
> the enclusure, the spurs are about 10dB up. The connection to Alex is
> still there.
> 
> If I open the enclosure (access plate on top and in front of the cards)
> most of the spurs are down to the noise floor. 
> 
> I guess, that this is an grounding problem, in general. So far, I didn´t
> see any discussion on this subject in the forum at all.
> 
> Did anybody else have similar appearances and how do you recommend to
> ground all components inside the enclosure.
> 
> 
> 73,
> 
> Georg,
> 
> DL2KP
> 
> 
> 
> 
> 
> 
> 
> 
> 
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