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TemCell Woes

B

Blarp

Jan 1, 1970
0
In our company we make stuff that must meet EMC requirements. Usually
the radiated emissions are the most challenging. We have these checked
in accredited test houses, which are expensive.

So we try to pre-check the products to see if there is fair chance of
success.

We have no OATS or anechoic room, so we make do with a logper antenna
in an empty office room. The ambient radio smog is making this
virtually impossible nowadays.

I recently bought a secondhand 3m TemCell, intending to use it the
wrong way around (not immunity, but unwanted radiation).

After reading up on the matter I became convinced that it should be
possible to get at least a fair -albeit uncalibrated- impression of
the radiated spurious of the EUT.

Not so however. If a EUT with known radiation characteristics is
placed in the TemCell, all I see is a Flat line on the spectrum
analyzer. I might as well have connected a dummy load. Even with a
preamp I see nothing.

Connecting the same spec on the same setting on the antenna, the
screen lights up. And the EUT does radiate..

Question:

Anybody else out there doing what I do? Am I expecting something that
is not there? Does a TemCell not work both ways (reciprocal)?

Or is the cell just broken...and do I need to tear it open for
repairs?

Thanks in advance!

Best Regards, Rene
 
M

Martin Riddle

Jan 1, 1970
0
| In our company we make stuff that must meet EMC requirements. Usually
| the radiated emissions are the most challenging. We have these checked
| in accredited test houses, which are expensive.
|
| So we try to pre-check the products to see if there is fair chance of
| success.
|
| We have no OATS or anechoic room, so we make do with a logper antenna
| in an empty office room. The ambient radio smog is making this
| virtually impossible nowadays.
|
| I recently bought a secondhand 3m TemCell, intending to use it the
| wrong way around (not immunity, but unwanted radiation).
|
| After reading up on the matter I became convinced that it should be
| possible to get at least a fair -albeit uncalibrated- impression of
| the radiated spurious of the EUT.
|
| Not so however. If a EUT with known radiation characteristics is
| placed in the TemCell, all I see is a Flat line on the spectrum
| analyzer. I might as well have connected a dummy load. Even with a
| preamp I see nothing.
|
| Connecting the same spec on the same setting on the antenna, the
| screen lights up. And the EUT does radiate..
|
| Question:
|
| Anybody else out there doing what I do? Am I expecting something that
| is not there? Does a TemCell not work both ways (reciprocal)?
|
| Or is the cell just broken...and do I need to tear it open for
| repairs?
|
| Thanks in advance!
|
| Best Regards, Rene

According to this site (http://www.temcell.com/tc5060.html),
Yes, you should be able to pick up any radiated emissions (RF) from a
DUT.
Did you try rotating the DUT? otherwise it sounds like bad connectors.

Cheers
 
B

Blarp

Jan 1, 1970
0
Also is the TEM Cell good for the frequency band you are concerned with?
May be operating below cutoff..

Thanks for all answers so far...The Cell is rated up to 300 MHz, and
the EUT I selected (because it was emasured in a testhouse before, and
has known radiations) - happily radiates in the 100MHz .. 1 GHz range.

I would not be amazed by a dropoff above 300 MHz, but a flat line..

@ Martin: Yes, I did rotate the EUT any witch way.. Had representative
wiring connected. In free air (using the logper antenna) it (the EUT)
even "outradiates" the considerable local radio smog.

I think I indeed need to check the connectors and such.

Thanks! - Rene
 
B

Blarp

Jan 1, 1970
0
Or using the wrong impedance 'N' connector.

....but it's a BNC...

After the Xmas holidays I will check if the septum has broken loose
from the connector - should have done that in the first place I
guess..
 
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