I'm impressed with how closely those two sets agree.
My experience, measuring at 3m and "adjusting" the signal
level for 10m is not the same as MEASURING at 10m. When
the FCC changed the rules from 3m to 10m many of my
clients' marginal equipment went right of compliance.
Increase in signal level? Around 3.5dB
In other words, there should have been a drop of 9.5 dB
when moving the antenna further away. Unfortunately, the
signal only dropped 6dB.
- Robert -
Robert A. Macy, PE .. [email protected]
408 286 3985 . . . .. . . fx 408 297 9121
AJM International Electronics Consultants
101 E San Fernando, Suite 402
San Jose, CA 95112
On Sun, 21 Mar 2004 15:25:44 +0530
[email protected] wrote:
> Dear EMC Gurus,
> I completed my pre-scans for an intentional
> radiator (13.56 MHz)
> in a 3 meters fully anechoic chamber and found that the
> emission are well
> within the Class B limits. The emission @ 108.48 MHz (8th
> harmonic) was
> around 35.8 db, @ 135.6 MHz (10th harmonic) was about 24
> db, @ 162.72 MHz
> (12th harmonic) was about 29 db and @ 244.08 MHz (18th
> harmonic) was about
> 37.5 db. 3 samples were tested and the results were
> similar for all the
> 3.
> But when another sample of the same model was
> tested by my
> counterpart in the 10 meters OATS (at USA) the results
> are differing.
> Emission @ 244.08 MHz is reported about 37.10 db, @
> 162.72 MHz is 31.1 db,
> @ 135.6 MHz is 27.2 db and the device failed to meet
> Class B limits.
> The test setup is very simple and it is just the
> 12 volts d.c.
> output of a variable d.c power supply output connected
> to the device. The
> power supply used by me and by my counter part are not
> same but similar. I
> tried separately with a shielded cable and with an
> unshielded cable and
> the results were almost similar. My counterpart used only
> a unshielded
> cable.
> Now it is great puzzle for us. What is wrong and
> where? Apart from
> the device being tested, the power supply and the cable
> used there are no
> other variables involved in the test set up. What other
> factors we should
> compare between both the testing? I request you all
> provide your valuable
> feedback.
>
> Sincerely
>
> K.Balasubramanian
> Sr.Engineer, Hardware.
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