[hpsdr] Pandora & Shielding

[Sheldon Hands]

Message
------------------------------I plan to run my hpsdr with an amplifier at full legal limit.  I also want to be sure to maximize receiver performance.  Therefore, I've been concerned that there may be the need to have the boardset well-protected, from an RF point-of-view, from the external environment.  

First of all, does anyone have practical experience with the importance of grounding and shielding (or not) for hpsdr?-----------------------------



It´s taken me a while to sort all the tx RFI problems at typically 1KW output. I´m not sure that all the things I did were necessary but they possibly add up to sensible precautions in a good installation.

1) Merc/Pen/Ozy on the Atlas in a box with slots in the back plate  just big enough for the connecters. Atlas bolted to box on metal spacers.

2) Merc and Penny coax cables in miniature Teflon microwave cable with 2 passes through  stack of 3 small ferrite torids (43 or 67 Material) close to backplane entry

3) Mic and headphone cable wrapped around ferrite toroid again at back plane entry. 1nF 1206 SMD across Electrect insert pins (cheap Skype headset)

4) Added missing filter components on ATX SM PSU mains in and removed all unused connectors and leads on Low voltage output. Added stacked beads on 12V 5V etc outputs and parallel 10nF and 1nF to ground. Ran output to Atlas in shielded cable.

5) My install uses my own design intermediate amps (2x2SC1969 to 2XMRF454) and  LPF/HPF driven by the Penny open collectors in a separate die cast. Relay supply is filtered and relays decoupled by 10nF

6) All antennas run on 600 ohm open wire with Gunella  cross coupled baluns and about a yard of coax into the shack. I added a choke balun at the tuner input on some 50mm ring cores (think they were Phillips 2C4 )

7) Do not attempt to use PC powered speakers.They are impossible to RF proof. Best to strip the amp out and place in a metal enclosure 

Hope this is of some help.

Shel C1IZU
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