MIL-DTL-15370J
If the previous equation in 4.7.10 is changed so that Po represents the "reflected power" rating of the coupler, one
obtains the correct value (0.50 W) for one component of this total power. The equation would then be
P = Pr /antilog(α/10), where
α = coupling factor and Pr is the reflected power. But one should also allow for the 0.12 W component. Since this is
essentially the coupled power reduced by the directivity factor, and since the coupled power Pc = Pi / antilog (α/10) for
input power PI, the term to be added is Pc / antilog (d/10). Instead of the antilog function we prefer using powers of
y
10, so, since for any x = antilog y, log x = y and 10 = x = antilog y, we get
[ -α/10 ]
[ -α/10 ]
[ -d/10 ]
P = (Pr) (10
) + (Pi) (10
) (10
)
where P is power.
Pr is reflected power.
Pi is input power.
α is coupling in dB.
d is the directivity.
as the equation that should replace the one previously used in the specification. With Pr = 2 W, Pi = 50 W, α = 6 dB,
and d = 20 dB (the M15370/10-001 values), this gives P = 0.62 W as found above.
This discussion neglects phase shifts; the two signals could be out of phase such that they do not add scalarly as
done herein.
(For more information please contact Mr. William Di Pasquale, 435 Moreland Road, Hauppage, NY 11788.)
6.8 Tin whisker growth. The use of alloys with tin content greater than 97 percent, by mass, may exhibit tin
whisker growth problems after manufacture. Tin whiskers may occur anytime from a day to years after manufacture
and can develop under typical operating conditions, on products that use such materials. Conformal coatings applied
over top of a whisker-prone surface will not prevent the formation of tin whiskers. Alloys of 3 percent lead, by mass,
have shown to inhibit the growth of tin whiskers (see 3.3.14). For additional information on this matter, refer to
ASTM-B545 (Standard Specification for Electrodeposited Coatings of Tin).
6.9 Environmentally preferable material. Environmentally preferable materials should be used to the maximum
extent possible to meet the requirements of this specification. As of the dating of this document, the U.S.
Environmentally Protection Agency (EPA) is focusing efforts on reducing 31 priority chemicals. The list of chemicals
and additional information is available on their website at https://www.epa.gov/osw/hazard/wastemin/priority.htm.
Included in the list of 31 priority chemicals are cadmium, lead, and mercury. Use of the materials on the list should
be minimized or eliminated unless needed to meet the requirements specified herein (see section 3).
6.10 Changes from previous issue. The margins of this specification are marked with vertical lines to indicate
where changes from the previous issue were made. This was done as a convenience only and the Government
assumes no liability whatsoever for any inaccuracies in these notations. Bidders and contractors are cautioned to
evaluate the requirements of this document based on the entire content irrespective of the marginal notations and
relationship to the last previous issue.
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