Hello Group,
I would like to report on the results of implementing the recommendations
offered by many.
We found the wire cloth to be rusty where clamped between the stainless
steel ring and the concrete pad. This no doubt contributed to the 40 ohm
impedance. We replaced a 3 m square of wirecloth surrounding the 1.5 meter
turn-table. We did the acid wash, air blown joint technique. (The air was
more necessary to remove the excess moisture.) With a 1.5 inch tip 500 W
iron, the soldering was quick (.093 60/40 resin core solder was readily
available). We connected the wire cloth to the ss turn-table ring by means
of 5/8" wide tinned copper braid soldered on the ss and on the wirecloth.
(One of our techs found a company that makes flux for ss. It was as simple
soldering to ss as soldering to copper.) We strapped the wire cloth to the
ss ring with 2" long segments every 3" apart. We now have .5 ohm (dc)
impedance from the turn-table to the wirecloth pad.
Our 3 meter measurement is uniform over the 14m x 15 m pad within .8 dB (.8
dB from highest to lowest reading). Unfortunately, the noncompliance at 30
MHz in vertical polarization is still there. Using the formula for a 3
meter site of
NSA=Vd-Vs-Raf-Taf-Cf
where Vd = V direct,
Vs = V site
Raf = Rx ant factor
Taf = Tx ant factor
Cf = mutual coupling factor
Vs appears to be too high by .5-1.5 dB, and about 1.5 - 2.5 dB higher than
previous NSA measurements. Whether the ground was wet or dry, we have
gotten comparable results.
Anyone have any good ideas?
Still stymied,
Don Umbdenstock
Sensormatic
---------
This message is coming from the emc-pstc discussion list.
To cancel your subscription, send mail to [email protected]
with the single line: "unsubscribe emc-pstc" (without the
quotes). For help, send mail to [email protected],
[email protected], [email protected], or
[email protected] (the list administrators).
