My SHIELDING is wrong?

I have electrodes to be tested their characteristics
Here is a picture of them,
https://picasaweb.google.com/lh/photo/UY9fJGfk2iayEBafvniVbg?feat=directlink

And I connected them to USRPs via SMA-SMA cable
https://picasaweb.google.com/lh/photo/0wJ84tU_Y0veX6svcWBeMw?feat=directlink

However, there is a problem!
I want to know characteristics of just CIRCLE part, except a rod part.
In my experience, this rod part acts as an antenna! Thus, I cannot
figure
out exactly

So, I make a shield around the rod part. This shield is made with
Aluminum
foil which is used for cooking.
https://picasaweb.google.com/lh/photo/kMx24c0PLaQdhfo2-t00MQ?feat=directlink
And I expect that the rod part rarely sense electromagnetic wave and
thus
only the circle part can receive a signal

The result is like this:

Result without SHIELDING
https://picasaweb.google.com/lh/photo/JBWG6A0NzhbLgcto44_B0w?feat=directlink
Result with SHIELDING
https://picasaweb.google.com/lh/photo/H9RItzjpfemHy-OR2eQhQg?feat=directlink

That’s very weird.
As my knowledge, if there is SHIELDING, the sensitivity of an antenna
should
get worse.
But, in my experiment, this SHIELDING helps communication!
I have any idea of it. I got confused

Did I make shielding wrong?

On 14-03-11 12:31, Songsong G. wrote:

So, I make a shield around the rod part. This shield is made with
Aluminum foil which is used for cooking.
https://picasaweb.google.com/lh/photo/kMx24c0PLaQdhfo2-t00MQ?feat=directlink

I cant see a electrical connection between the foil and the shielding
solder pads from the connector.

Is there any? If not, you should make one.

Gr. Sim

Thank you for your answer

So, does you mean that I have to connect foil with ground pin of the
connector?
It seems to make sense…
I’ll try it

Thank you so much

2011/3/14 Sim IJskes [email protected]

On 14-03-11 12:49, Songsong G. wrote:

Thank you for your answer

So, does you mean that I have to connect foil with ground pin of the
connector?
It seems to make sense…
I’ll try it

Make sure you make no short between shield and pad, by measuring with
ohm meter.

Also, if you are going to use this on living beeings, make sure you have
good medical class isolation from the mains power. For your USRP and PC
and everything connected to it.

Please seek adequate professional advice.

Gr. Sim

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