i have no idea what you're reading because the terms "5.1," "dip," or "resonance," do not appear anywhere in that post, that is what is misleading.
here is the original post.
"The relative unimportance of low SWR
when feed-line attenuation is low is demonstrated
rather vividly in the following two examples of
spacecraft antenna applications. First, in the
TirosESSA-Itos-APT weather satellites, of which the
entire multifrequency antenna-systems design was
the work of the author, the dipole terminal
impedance at the beacon-telemetry frequency (108
MHz in early models) was 150 - j100 ohms, for a
VSWR of 4.4, reflected power 40 percent.
Matching was performed at the line input, where it
was fed by a 30 milliwatt telemetry transmitter.
(We can't afford much power loss here!) The
feedline and matching-network attenuation was 0.2 dB,
and the additional loss from SWR on the feed line
was 0.24 dB (5.4 percent), for a total loss of 0.44
dB (9.6 percent). On the prevalent but erroneous
assumption that all reflected power (40 percent) is
lost, only 18.1 milliwatts would reach the antenna,
and efficiency, determined on the same erroneous
basis, would be only 60 percent. But 27.1
milliwatts were measured; of the 2.9 milliwatts lost
in total attenuation, only 1.6 milliwatts of it was
from the 4.4:1 VSWR. So the real efficiency would
have been 95.5 percent if perfectly matched at the
load, but reduces to 90.4 percent by allowing the
4.4 VSWR to remain on the feed line. Second, in
the Navy Navigational Satellite (NAVSAT), used
for precise position indications for ships at sea, the
antenna terminal impedance at 150 MHz is 10.5 -
j48 ohms, for a VSWR of 9.8, reflected power 66
percent. Also matched at the line input, flat-line
attenuation is 0.25 dB, and the additional loss from
SWR is 0.9 dB, for a total system loss of 1.15 dB,
approximately 1/6 of an S unit. This is an
insignificant amount of loss for this situation, even
in a space environment where power is at a
premium. Why did we match at the line input?
Because critical interrelated electrical, mechanical
and thermal design problems made it impractical to
match at the load. Line-input matching provided a
simple solution by permitting the matching
elements to be moved to a noncritical location."
Another Look at Reflections Part 1
M. WALTER MAXWELL
here's your original post:
https://www.worldwidedx.com/threads/adjustments-for-resonance.257457/page-4#post-761955
