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[Linrad] Re: SDR-IQ Birdies - the Solution

At 07:23 PM 10/16/2009, VK2KU wrote:

>Well, well, well - we learn new things every day!
>The lid of the SDR-IQ is NOT electrically connected to the body of the
>Fortunately the circuit board and various cable connections ARE
>grounded to the body of the box.
>The lid is held in place with 8 small countersunk screws - M2.5?
>The lid has been carefully painted, including the bevelled edges of
>the screw holes,
>thus preventing the screws from making electrical contact with the
>The lid itself and the box are of course separated by 2 layers of
>Just to make quite sure that no electrical connection occurs,
>the screws themselves are also black anodized - another insulating
>I removed the paint from the countersunk holes with a hand-held 90-
>degree counterbore bit.
>Then, lacking any other suitable screws or a more suitable tool,
>I spent a happy and fiddly half-hour using a small flat file to remove
>the anodizing from
>the underside of the 8 screw-heads. I also lightly touched up the
>threads to show some metal.
>The result was the almost complete elimination of the offending
>birdies - 99% anyway.
>A bit of aluminium foil as suggested by Leif completely eliminated the
>last traces.
>Every SDR-IQ owner needs to do this!
>73  Guy  VK2KU
The original issue of the SDR-IQ was without enclosure.  As already 
mentioned, I installed mine in a Hammond Diecast box.  Isolating the 
receiver from outside interference was the main reason.  Funny how 
often digital engineers miss the finer points of RF.  Good fix for 
those with the factory enclosure.

73, Ed - KL7UW, WD2XSH/45
  BP40IQ   500 KHz - 10-GHz   www.kl7uw.com
500-KHz/CW, 144-MHz EME, 1296-MHz EME
DUBUS Magazine USA Rep dubususa@xxxxxxxxxxx

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