E. J. Skudrzyk 229 
Signal fluctuations at 25 and 60 ke have been measured by the Ordnance 
Research Laboratory; Fig. 12.17 is an example of the data obtained during the 
month of July under a wide range of conditions. This figure indicates the fluc- 
tuation of the signal, traveling by way of the direct path and the surface- 
reflection path, as a function of range. The lines indicate the trend of the data. 
a 
[e) 
COMPUTED 60-KC FOCUSING RANGE 
FOR GAUSSIAN CORRELATION FUNCTION 
COMPUTED 25-KC FOCUSING 60 KC 
RANGE FOR GAUSSIAN———= 
CORRELATION FUNCTION 
L 
(e) 
RELATIVE STANDARD DEVIATION (per cent) 
) 200 1400 600 800 1000 1200 1400 1600 1800 
RANGE (yd) 
(a) 
50 
COMPUTED 60-KC FOCUSING RANGE 
= FOR GAUSSIAN CORRELATION FUNCTION 
E 
& 707 compuTeD 25-KC FOCUSING , 
~ RANGE FOR GAUSSIAN——# 60 KC 1 
z CORRELATION FUNGTION ! x | 
= | 2 | 
< 30 ! 4 
ii ; x X yx | 
| 
ied \ Xx I 
< 20 25 Nea 
q o X \ 
Ss Q © ' 
B fc) COMPUTED | CURVES FOR 
! 
$10 Me 43x10 
= X =60KC 
< a = 2.6 YD! 
| 
WwW I 
a 
{ 
200 400 600 800 1000 1200 1400 1600 1800 
RANGE (yd) 
(b) 
Fig. 12.18. Direct-signal fluctuations measured during one day; (a) in January, (b) in March. 
