RADIO WAVE PROPAGATION EXPERIMENTS 
SK 
7 
Ficure 3. Sounding techniques for use at the wind speed ranges indicated. 5» 
Temperature and humidity“elements mounted within the radiation shield S are connected through the 3-conductor cable C with slip rings on 
the cable reel R. The meter box (not shown) is connected to the brushes of R. B: 300-g Neoprene balloon. L: light fishline. F: fishline reel. SK: Sey- 
fang 7-ft kite. N: nylon kite line. W: kite winch. HK: Hoffman single cell box kite. Arrangement (D) is suitable for sounding from moving ships; 
its ceiling is limited to about 400 ft by the small lift of this kite. 
loons to somewhat higher wind speeds (from 6 to 10 
mph). The pull of the balloon is taken up by a separate 
fishline, the reel of the fishline being placed windward 
relative to the reel of the cable (Figure 3). 
Jn: wind speeds above about 8 mph kites are used in 
place of balloons. A small folding kite!, standard for 
“Gibson Girl” emergency radio equipment, is easy to 
handle and requires only a light cable, but its ceiling is 
limited to about 400 ft. This type of kite has been used 
successfully for soundings from boats. 
A heavier, 7-ft kite) is well adapted to :and-based 
soundings. It flies at a high angle (55° to 60°) and 
can be put up at minimum wind speeds. At the high 
relative wind speeds encountered in, ship-based sound- 
ings the pull of this kite is excessive and launching cor- 
respondingly difficult. 
Sounding techniques are shown schematically in 
Figure 3. For the kite a braided, waterproof nylon 
line, breaking strength 150 Ib. is recommended. For 
ship-based soundings or conditions where sudden high 
stresses are likely, a 300-Ib test nylon line may be used. 
There seems to be no difficulty in measuring the 
altitude of the captive balloon or kite.** The length 
of line paid out is determined either by counting the 
turns of the reel or by means of markers attached to 
the cable at regular intervals; if the line is off the 
vertical, its mean inclination can be measured with 
sufficient accuracy by a simple hand inclinometer. 
AUTOMATIC RECORDING OF 
METEOROLOGICAL SOUNDINGS* 
A means has been developed for making automatic 
‘Supplied by Hoffman Radio Co., Los Angeles, Calif. 
iSupplied by F. C. Seyfang, Atlantic City, N. J. 
kBy E. Dillon Smith, U. S. Weather Bureau. 
recordings on a Leeds and Northrup Speedomax or 
Friez Cycloray recorder of low-level meteorological 
soundings of temperature and humidity. The design 
of the equipment has been restricted in the sense that 
the standard Weather Bureau-Army-Navy electrolytic 
hygrometer and negative resistance temperature units 
must be utilized; all recordings must be made on the 
existing automatic radiosonde recorders just named. 
GENERAL DrsiGN CONSIDERATIONS 
The existing standardized electrolytic hygrometer 
strip polarizes when direct current is placed on its 
terminals. However, if a reversed direct current is 
placed on the terminals of the strip, this polarization 
tendency is neutralized. This would seem to indicate 
the desirability of placing a low-frequency alternating 
current on its terminals in lieu of the direct current 
commutation principle which generally has been used 
in existing low-level meteorological sounding .equip- 
ment. 
The frequency of the alternating current to be 
placed on the strip will in general be controlled by the 
reactance of the low-level sounding cable. In view of 
this limitation a frequency of approximately 10 c has 
been used. 
The temperature resistor operates equally well on 
either direct or alternating current; therefore, it re- 
quires no equipment design considerations. 
ELECTRICAL CHARACTERISTICS OF HLEMENTS 
Present practice makes the “lock-in” for the tem- 
perature and humidity elements through a resistor in 
series with the elements. However, this technique in- 
troduces errors in the readings both above and below 
that for the lock-in point. Effectively, the slopes of 
the calibration curves are altered, affecting the read- 
ings on the indicators. In view of this situation, it is 
