T EVIS i - AmericanRadioHistory.Com
T EVIS i - AmericanRadioHistory.Com
T EVIS i - AmericanRadioHistory.Com
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impedance" and is an import ant consideration<br />
in designing stacked arrays.<br />
Impedance considerations be( ome increasingly<br />
important when vre stack<br />
antennas because the connect rig rods,<br />
acting as quarter -wave transformers,<br />
tend to multiply impedance errors.<br />
This difficult concept of impedance is<br />
of prime importance to deign engineers<br />
who must master it if they<br />
are to create antennas that skill operate<br />
over wide ranges of fret uencies,<br />
that will stack into two- or 'our -bay<br />
arrays, and that will match closely<br />
300 -ohm line in any combin ttion of<br />
arrays.<br />
Measuring Impedance<br />
At Channel Master, although the<br />
measuring setups for gain and directivity<br />
are similar, different kinds of<br />
impedance testing facilities ere used<br />
for v.h.f. and u.h.f.<br />
The v.h.f. impedance measuring<br />
equipment consists of a modulated<br />
oscillator, an admittance -type bridge,<br />
and a tuned detector and a:nplifier.<br />
The signal from the oscillato- is fed<br />
through the admittance bridge' out to<br />
the antenna being measured 1 Fig. 6).<br />
The mismatch at the antenna will<br />
cause standing waves which are reflected<br />
back to the admittance bridge.<br />
Here, these standing waves a e evaluated<br />
in terms of phase and magnitude<br />
and this information is converted<br />
into impedance. Figures are<br />
presented with both resistive and reactive<br />
components.<br />
The same information is t btained<br />
in the u.h.f. range by use of the<br />
slotted line (Fig. 7). A signal reflected<br />
back along the tram mission<br />
line from the u.h.f. antenna i; measured<br />
on the slotted line. The standing<br />
-wave ratio is converted to impedance<br />
and again this impedance is<br />
analyzed mathematically so that both<br />
the resistive and reactive components<br />
can be obtained. 30<br />
EDISON HAM AWAR<br />
DON L. M ILLICAN of Searcy. At kansas,<br />
has been n. d winner of the 1952<br />
Edison Radio Amateur award t resented<br />
annually by the General Electric<br />
C palm's Tube Department in recognition<br />
Of outstanding public se .vice by<br />
a radio amateur.<br />
Mr. Dlilliean's honor was bestowed<br />
because he stuck to his rig aln3tn,t without<br />
relief for re than live lays to<br />
bring emergency crews to Scatty; and<br />
the nearby towns of Judsonia and Bald<br />
Knob.<br />
Ile received a trophy emblenlatie of<br />
his efforts at a d r held at t e May -<br />
flower Hotel in Washington. I). C.<br />
Mr. Millican. W51'11I'. took to the<br />
air immediately after the torn ulo hit<br />
Searcy on Friday, March 21st. Ile operated<br />
al 4t eontinuously unt I Monday<br />
afte handling Red Crois messages<br />
and emergency traffic. Ile was<br />
the only link between the stricken<br />
towns and relief opera t'<br />
Ile got his first amateur license in<br />
1948 alt{ gh he has been interested<br />
in radio since boy) I. Ile is now a<br />
junior at Harding- College in 4carcy.<br />
Ile plans to become a missionary.<br />
April, 1953<br />
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125
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