Remember, marketing has the last word when a product is finally released
for sale. Also, manufacturing variations also play into the whole
picture. I wouldn't be too concerned with anything less than 2:1.
Suppliers can claim anything. Take a look at the gain figures quoted by
the many suppliers of CB antennas. They are outrageous and have no
connection to reality!!!
Dave - W?LEV
On Sat, Jul 16, 2022 at 8:06 PM Siegfried Jackstien <
siegfried.jackstien@...> wrote:
if in manufacturers smith is shifted in the inductive area ... how can
he claim an swr 1:1 and 50 ohms??
just thinking? (i have not seen the plots)
dg9bfc sigi
Am 16.07.2022 um 18:20 schrieb KENT BRITAIN:
Hi Doug, having done quite a few RFID antennas, that 1 to 1 is rather
optimistic.
One thing to consider, do you have any other metal within a foot or so
of the antenna? You can easily see a pair of pliers passing a foot or so
from the loop.
Good luck with your project, Kent WA5VJB
On Saturday, July 16, 2022, 11:00:36 AM CDT, Douglas Butler <
sherpadoug@...> wrote:
I have a 125 kHz RFID antenna consisting of a coil and series tuning
capacitor. The manufacturer supplied plots of the SWR and Z of the antenna
showing a nice 50 Ohm 1:1 SWR at resonance. I have tried to replicate
these plots using my newly purchased NanoVNA and I get radically different
plots showing a load closer to 25 Ohms and a 2:1 SWR. Measuring the L and
C separately gives about the same readings I get with my HP4801 vector
impedance meter at 125kHz, but it is near the upper frequency limit of the
HP4801 so results are shaky. I calibrated the NanoVNA over the same range
as shown in the manufacturer's plots. My Smith plots are centered on the
horizontal axis like I would expect them to be. The manufacturer's plots
are shifted up to the inductive half of the Smith chart. Both show a nice
resonant dip at 125 kHz.
Am I doing something wrong? Is the antenna manufacturer lying?
SherpaDoug WA1UWP
--
*Dave - W?LEV*
*Just Let Darwin Work*
--
Dave - W?LEV
