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Патент USA US2122183

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June 28, 1938.
F. scHwARzER
`
m5221183
METHOD OF AND ARRANGEMENT FOR'STEPWISE TUNING OF ELECTRIC CIRCUITS -
Filed April 8, 1936
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June 28, 1938.
2,122,183
FL scHwARzERf
METHOD oF AND'ARRANGEMENT FOR' sTEPwIsE TUNING 0F ELECTRICv CIRCUITS
Filed April 8„ 1956
2 sheets-sheet 2
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connec feo’
INVENToR
15d/m
ß//î
„
TORNEYS
Patented June 2s, 1938
UNITED STATES PATENT OFFICE
2,122,183
METHOD 0F ANDI ARRANGEMENT FOR
STEPWISE TUNING OF ELECTRIC CIR
CUIT‘S
Fritz Schwarzer, Berlin- Schoneberg, Germany>
Application April 8,A 1936, Serial No. 73,380
In Germany
5 Claims.
April 11, y1935
(Cl. Z50-40)
My invention relates to a method of and ar
rangement for stepwise tuning of electric circuits,
such as may be employed for instance in adjusting
the frequency of electric circuits in the radio
and kindred arts.
It is already known to provide devices especially
for tuning high frequency communication circuits
with Step-wise adjustable tuning elements which
operate by two or more selective procedures, and
by which stepwise ñrst coarse steps and then
within such coarse steps ñne steps are ad
justed. With such arrangements preferably
different fixed capacities are selectively con
nected into or out of circuit. In such a case, as is
15 well-known, considerable difliculties are en
countered in utilizing the same equal fine fre
quency step arrangement for all coarse steps 4and
to obtain within allcoarse steps the same uniform
division of the fine frequency steps. Therefore,
20 in such cases additional, separate expedients had
te be used heretofore in order to obtain 'approxi
mately equal frequency steps when the same fine
step arrangement is used for all coarse steps` `In
some of the well-known arrangements of this
character the practical construction still en
counters considerable diñiculties. For instance,
the original dimensioning of the different step.
values is very difiicult.
Since in such arrange
ments indirectly also those condenser electrodes
30
act as series capacities which are not connected
in circuit at the time, these _indirect capacity
effects must‘be taken into consideration and in-`
cluded into the calculation, not only when the
system is first calculated, but, in dimensioning in
_) the assembly each condenser electrode to a
.
series connection of a similar ñne step result
in the required line variation of each coarse fre
quency step at the same ñne frequencyinterval.
My invention is illustrated in the accompany
ing drawings in which
Fig. 1 represents diagrammatically the method
of arranging the different capacities for coarse
and nne step adjustment, and
Figs. 2 and 3 represent a constructive form of 10
such an arrangement of- which Fig. 2 represents o
a sectional elevation onl line 2_2 in Fig. 3, and
Fig. 3 a sectional elevation on line 3-3 in Fig, 2.
' First, the method of connection will be ex
plained with reference to the circuit diagram Fig. 15,
1. The tunable circuit, which may for instance
be a portion of a circuit arrangement for a ther
mionic tube T, consists of an inductance L'and of
a number of condensers, of which in the present
case always three simultaneously partake in the
tuning. These condensers are taken from three
groups which together constitute the coarse and
fine step tuning system, and which in this figure
is arranged as a decimal system. The conden
sers Ca to Ck together with the condensers of
group Cm to 01k constitute the coarse steps (which 25
may for instance be 100 kilocycles apart) and
the condensers C1 to C10 represent the fine steps
(which may be for instance 10 kilocycles apart).
The connecting means for effecting the coarse and
fine condenser connection which is required for 30
the different steps is represented by the sliding
elements a: and y assumed in this diagram as
sliding contacts. The leads u and w represent the
common low potential and ground connections of
one side of the condensers of the coarse group Ca 35
to Ck’and of the condensers of the fine group C1
definite value, the total indirectly acting capacity ' to C10,- and the lead 'urepresents- the common con
nection of the low potential side of all condensers
in progressively dimensioning the different ca
Cia to Cik which side may be connected in series
pacity step values of the system the already di
of the remaining electrodes also varies, so that»
40
4
5
mensioned steps change in their effect upon the
by step tuning arrangements which involve a simi-v ` over the two condensers of the two coarse step
lar problem and the invention suggests a solu- . groups, appertaining to that step, ata certain
tion by which the above-mentioned disadvan-- ratio which can easily be calculated, the addi
tages are avoided. According to the invention a
tional selective series connection of the fine step
combination of parallel and series connected condensers brings about within all coarse steps
capacities are used whereby the coarse steps are
the same fine frequency intervals. In order to 50
produced by assembling the total- capacity of
each coarse step from at least two parallel con
nected capacities. Each ñne step is then pro
duced by individual series connection of the se
lected condenser of a fine step condenser group
with only one of the constituent condensers of the
55
selected coarse step. With such an arrangement
the relative values of the constituent elements of
each coarse step are dimensioned so that on one
hand the desired coarse capacity step is produced,
60
with any selected fine step condenser. The fine ‘10.
steps, it will be noted, are thus connected for each
system so that correct and permanent values can'- Y . coarse step in seriesrwith-only a portion of the
not be fixed.
total coarse step capacity. If now the total
The invention refers in particular to such step - coarse step capacity of a given step» is distributed
and on the other hand the additional selective Y
prove this assertion it is only necessary to con
sider the two extreme cases. If for instance in' a
given coarse step the constituent capacity portion
Ca is made to equal zero, the condenser C15 must
include the entire capacity necessary for the
frequency appertaining to that step. If m such
55.
a case the fine steps are added in order to make
fine adjustments these fine steps are thrown in
series with the total coarse capacity, and con
siderable variations in the uniformity of the steps
60
2
2,122,133
will occur when this is tried in the different coarse
quency step we have the equation according to
steps. If, on the other hand, the capacity C13 is
made to equal zero, the entire required coarse
capacity must be embodied in Ca. The addi
tional series connection of fine steps, with C_ia
Equation 3:
equal Zero, would in this case not produce any' ’
capacity variation at all. From these extreme
cases it appears that for each coarsefrequency
¿g for» the first coarse and second ñne step:
(21av '
C2.
. E_CalLcaa-cz’
and so forth.
Thus ten equations are derived for each coarse
step a suitable intermediate value, located between
10 zero and maximum capacity musteXist foreach
step with the unknown values Ca, C10, C1, C2, C3, l0
of the two constituent capacities of each coarse ' C4, C5, C0, C7, C3, C9, C10. If for practical reasons
step, for which the addition ofthe same set‘of fine' Athe values Ca and C15 (of C1 and C10) are assumed,
step series capacities will result in similar `>iîre _ all other unknown values in thc ten equations can
quency intervals in each coarse step.
15
be calculated, which when combined according
to the invention produce ten equally spaced fre
quencies, constituting 4the small steps, for in
`
The manner in which these capacitiesV can be
calculated in practice is as follows:
stance 10 kc. each.
According to the invention, the total capacity
20
._
_
are determined, the values of CP and Cs can be
determined for each coarse step likewise on the
basis of Equation 3. For instance for the second
coarse step and ñrst fine step we have the equation
combined, we have the resulting value `_
_K_2_~
For the second
cuit elements is for the moment disregarded, since
it can be easily correctly added to Vthe parallel
capacity Cp.
.
1
» coarse
step,
i
'
l
i
'
l
step
“
v
___Clb'clo ' andsoforth for
f0102
0111+ C10’ the remaining
-
coarse steps.
circuit then becomes dependent only upon the
capacity of the circuit (Thomson’s formula). The
Thus for each coarse step, the desired' fre
quency range can be determined (for vinstance 100
frequency, .according to this formula, -Would
kc.) .
then be.
Y
Since, however, each coarse step is divided
into ten fine steps according to the above equa
tions, it follows that a change by one fine capacity
Ü
35
step will produce at least substantially, if not 35
exactly, the desired fine frequency step (for in
whereby
stance'lO kc.) .
K=
.
_
21m/.ï
Y
,
_
We have thus a value for Ca
K2
2.
,
First, the desired stepyalues for the- coarse
andV ñne capacities _are entered into a table in
relation to one another. 'It may here be assumed 45
,
If now the »value for CR, derivedrfrom Equation 1,
is substituted in Equation 2, VWe obtain
3'-
..
the preceding mathematical deductions.
.
CF?
E;
'
For calculating a set of coarse and ñne capaci
ties in designing a step by step tuning device ac
cording to the present invention, one would pro 40
ceed as follows in substance in accordance with
.
40 in other words, #Kurepresents a constant which is
solely dependent upon L.
v
50
C1b‘C1 .
‘ tenth iìneï2 :Cb
,
If we further assume that the inductance ofthe
` circuit is constant, the frequency ofthe oscillatory
30
20
fbl12- b C15-l~ q1’
" The capacity of the circuit wires and other cir
25
'
Thus after the capacity values of the ñne steps
CR of the circuit is composed for the> coarse steps
of a parallel capacity Cp, a series capacity Cs and
a ñne step capacity CF." vIf ¿these capacities are
that the desired intervals ofthe fine step group
amount to about 9 kc. each.
CS'CF
The diiïeren'ces be
tween the coarse steps 'are not exactly 90 kc. but
f2_CP+CS+CF
slightly differ from one another for the purpose
Now in further calculating the values >for a of Yequalizing inequalities in the distribution of
practical condenser, according to the invention, a ` the wave lengths of the several transmitters over 50
table of the required frequency steps ismade, for the given frequency range. Thus, Vthe following
instance as follows:-Table I results, in which the‘top row represents
Fine f frequency steps
55
fal, fa2, fa3, fa4, fa5, faô, fa7, faS, faQ, falO
Coarse
fbl, fb2, . . .
.
. .-
.
. .
frequency
.
.
.
.
.
.
Y
Y
-
.
.
.
.
.
.
steps
.
.
.
.
.
.
.
.
.
.
.
.
fblO
60
UWe can then set up the following equations. For
instance for the ñrst coarse and ñrst fine fre
60
the fine steps `1-10 and the rows A-K represent
the coarse steps in. kc.
TABLEI
65
Frequencies in kc.
0
70
75
9
3
65
7v t
0
5
4 ’
3
2
1
F
901
`1054
970
1003
079 Y
1072 v
933
1031
._ 997
1090
1000
1099 __
1015>
1103
1024
1117
1033
1120
1042
1135
K
1
1140
1233
132s
1155
1247
1037
1104
1250
1340
1173
1205
1355
1132
1274
1304
1191
1233
1373
1200
1292
1332
1209
1301
1391
1213
1310
1400
1227
1319
1409
H
o
11
1419
1510
1000
1423
1519
1009
1437
152s_1013
1440
1537
1027
1455
1540
1030
1404
1555
1045
1473
1504
1054
1432
1573
1003
1491
1532
1072
1500
Y 1591
1031
11
D
o
1091
1700
,1731
1790
»
'
1709
1713
1727
1799 1
1303
`1317 l
1730
1745
c1320
_1335
_
1754
1703
1772
B
1344»V
1053
-1352
A
70
75
3
2,122,183
If thiscondition is entered in Equation I, we
have
Il.
CK"
Then the capacities 'appertaining to each fre
quency are calculated.
The smallest tuning ca
pacity for the given circuit was assumed to be 135
cm. with which is coordinated the highest fre
Assuming that the capacities of a coarse step 5
quency to which the given circuit can be tuned,
are known, the line steps are
namely, 1862 kc. (A-1, Table I). These cal
culated -values are then entered into the> following
Table II.
HI
’
F_ GS(CR- GP)
-
--(iq-_(CRHQÜ)
10
10
TABLE II
Capacities in cm.
15
0
9
506- 81
421. 32
356. 39
305. 39
265. 40
232. 45
205. 27
182. 83
163. 69
147. 56
8
497. 45
414. 21
350. 86
300. 99
261.84
229. 53
202. 85
180. 79
161. 95
146. 08
7
488. 34
407. 30
345. 45
296. 70
258. 34
226. 66
200. 47
178. 78
160. 26
144. 62
479. 48
400. 53
340. 17
292. 49
254. 92
223. 85
198. 13
176. 81
158. 58
143. 18
6
5
470. 86
393. 94
335. 0l
288. 37
251. 58
221. 09
195. 83
174. 88
156. 93
141. 77
4
462. 47
387. 52
329. 97
284. 33
248. 28
218. 38
193. 57
172. 96
155. 31
140. 37
3
454. 3l
381. 23
325. 04
280. 40
245.06
215. 72
191. 34
171.08
153. 71
139.00
446. 37
375. 14
320. 21
276. 52
241. 9
213. 1
189. 16
169. 24
152. 14
137. 65
1
438. 62
369. 16
315. 49
272. 74
238.8
210. 49
187. 02
167. 42
150. 59
136. 31
F
431. O7
363. 32
310. 89
269. 04
235. 7
208. 02
184. 90
165. 63
149. 06
135. 00
K
I
H
G
F
E
D
C
B
A
20
If two fine steps are known, the values Gs and
GP are to be calculated for all coarse steps as
follows
For the further calculation there should be de
ducted froln the foregoing calculated values a
constant value representing the capacity dis
tributed over the whole circuit, which value in
the present case is assumed 80 cm.
2
C
Thus, the
G _1_ G5147a
“_
actual tuning capacity values result which are
entered in the following Table III.
P
30
GS.;- 1_9“a
GSF,
Cb- GP+__GS+
Fb
35
TABLE III
35
Capacities in cm.
0
40
425. s1
341. 52
270. 59
225. 99
185. 40
152. 45
125. 27
192. 59
s3. 69
07. 55
9
417. 45
394. 21
270.55
220. 99
181. 84
149. 55
122. 85
100.79
s1. 95
60. 08
s
7
40s. 34
327. 90
265. 45
215. 70
178. 34
145. 69
120. 47
98. 79
s0. 25
54. 02
399. 4s
52o. 53
250. 17
212. 49
174. 92
143. 85
118.15
99. s1
7s. 5s
59. 1s
9
39o. 89
313. 94
255. 01
20s. 37
171. 58
141.09
115. s3
94. 9s
75. 95
91. 77
5
4
582. 47
907. 52
249. 97
294. 35
168. 28
las. 58
119. 57
92. 95
75. 91
99. 37
a
574. 91
901. 25
245. 04
209. 39
165. 06
155. 72
111.
91.
75.
59.
For the further calculation, the following addi
tional designations are introduced:
s55. 37
295. 14
24o. 21
195. 5_2
161. 90
155. 10
109.16
89. 24
72. 14
57. 05
2
358. 62
289. 15
2.25. 49
192. 74
158. 80
150. 54
107. 02
87. 42
70. 59
55. 31
l
351. o7
285. 92
239. 99
189. 04
155V 76
129. 02
104. 90
85. 99
59. 05
55. 09
40
F
1;
l
H
G
F
n
D
o
B
A
45
If these equations are solved according to their
unknown, we have
‘
55
55
The capacity of the capacity combination C
provided with the index of the coarse step (A-K)
and the ñne step- (1-0)
60
The parallel capacity GP with the index of the
coarse step (A-K)
I.
GSF
CR- GP ¿om
For practical reasons the condition was re
quired that the values of largest individual ca
pacities should be approximately all of the same
order
75
60
.
The series capacity Gs with the index of the
coarse step (A-K)
The capacity of the ñne step F With the index
of the ñne step (1-0)
The fundamental equation on which the fur
ther calculation is based is
70
50
GFK: GSK: Fo
Thus, all equations for the division of the
capacities are determined.
'
65
The numerical evaluation was made as fol
lows. First, after the coarse step K, the ñne steps
yF1 and F0 were calculated.
From the values ob
- tained were then determined the parallel-and
70
the series capacities for the coarse step H (GPH,
GSH) and thereafter definitely the line steps
Fl-Fu. From the ñne steps F9 and. F2 the coarse
steps A-J are calculated. In order to determine
the deviations. on the step K, the capacity GFK 75
4
2,122,183
was 'increased a corresponding amount.` Thus,
the following values were obtained:
The idea involved in such 'an arrangement as
Vshown in Fig. 1 may be embodied in a practical
apparatus in the manner shown in Figs. 2 and 3. -
GP
10
Gs
Referring to these figures, the three diiTerent
F
20` 811
32` 672
55. 53
61. 686
86. 832
98. 41
46. 735
63. 298
69. 357
78. 678
111` 49
126. 330
83. 357
107. 691
137. 261
90. 722
106. 33
127. 23
174. 877
222. 701
285. 85
157. 81
204. 605
284. 54
143. 264
162. 81
185. 61
212. 585
244. 99
284. 54
groups of condensers above-mentioned are ar
ranged separately on three circular carriers Z, m,
n, of suitable dielectric material, for instance
ceramic material of well-known type, and- so_that
the high potential electrodes of condensers C6 to
Ck are located on the side plate Z, facing plate m, 10
the high potential electrodes of the condensers C111
to C111 are arranged on the side on plate m facing
plate Z, and the high potential electrodes of con
densers C1 to C10 are mounted on the front side
of platen. These individual electrodes may con
sist of suitable metal, such as silver, and may be
In order to determine the deviations, all ca
pacities are combined according to the system
described hereinbefore, and the resulting values
attached to their respective carrier plates by
are entered in the following Table IV.
spraying or other suitable means.
Their exact
TABLE IV
Capacities in cm.
:1
l...
20
0
9
8
7
6
5
4
3
2
1
F
428. 12
341. 709
276. 387
417. 496
334. 210
270. 86
407. 53
326. 969
265. 451
398. -18
320. 033
260. 17
389. 40
313. 372
255.011
381. 138
306. 979
249. 98
373. 336
300. 847
245. 042
365. 952
294. 876
240. 234
358. 968
289.160
235. 491
352. 379
283. 570
230. 912
K
J
H
225.175
220.990
216.853
212. 746
208.676
204.645
200, 650
196.680
192.750
188.878>
G
185. 086
152. 114
124. 949
102. 499
83.366
67. 27
181. 840
149. 530
122. 85
100. 79
81. 95
66. 08
178. 571
146. 914
120.723
99. 030
80. 483
64` 84
175. 296
144. 267
118. 554
97. 226
78. 972
63. 55
172. 011
141. 587
116. 340
95. 371
77. 406
62. 217
168. 724
138. 878
114. 085
93. 468
75. 791
00. 829
165. 427
136. 136
111. 781
91. 511
74. 119
59. 38
162. 115
133. 353
109. 424
89. 492
72. 38
57. 87
158. 795
130. 540
107. 020
87. 42
70. 589
56. 31
155. 490
127. 704
104. 574
85. 293
68. 736
54. 681
11
E
D
o
B
A
The differences 2 between the required values
and the actually resulting Values are entered in
the following Table V.
25
30
areas may be iinally adjusted by grinding or
scraping away surplus portions, a method of ad
justment,V well-known in the manufacture of 35
TABLE V
Capacities in cm.
40
0
9
8
+1.31
+0.39
+0
_0. 21
_0.30
_0.34
_0.32
_0. 83
_0. 32
_0. 29
+o. 046
:1:0
i0
i0
:1:0
+0
i0
:t0
:t0
i0
_0.81
_0.33
:1:0
+0. 15
+0. 23
+0. 25
+0. 25
+0. 25
+0. 22
+0. 22
7
6
_1.30
_0.5
io
+0. 26
+0.38
+0.42
+0. 42
+0. 42
+0. 39
+0. 37
_1. 46
_0.57
:to
+0. 31
+0. 43
+0. 5o
+o. 51
+0.49
+0.48
+0. 45
5
4
_1. 33
_0. 54
+0. 01
+0. 32
+0. 44
+0. 50
+0. 52
+0. 51
+0. 48
+0. 46
8
_0. 97
_0.38
:1:9
+0` 26
+0. 37
+0.42
+0. 44
+9. 43
+0. 41
+0.38
2
_0.42
_0.26
+0.02
+0. 16
+0.21
+0. 25
+0. 26
+0.25
+o. 24
+0. 22
1
+0.35
:1:0
:1:0
+0. 01
i0
i0
:80
i0
:60
:1:0
+1.31
+0.35
+0.02
_0. 16
_0. 27
_0.32
_0.33
_0.34
_0. 32
_0.32
E
40
K
J
H
G
F
E
D
o
B
A
ceramic condensers. The three carrier plates are 50
mounted in parallel to one another at suitable
distances apart and are fixed in a frame 0». To
plates Z, m, and n on the side where the high po
The largest capacity deviation exists at the
Value K6, amounting to 1.46 cm. This would cor
respond With a frequency diiîerence of 1.56 kc.
The greatest frequency diiïerence exists, on the
other hand, in the step A, since here the greatest . tential electrodes are located are ñxed respectively
relative capacity difference appears. At A5 the the conducting contact stars in, q, T, the shape
error is +0.46 cm. or +2.95 kc.
of which is shown with respect to the star r in
In the following Table VI are entered the tun
Fig. 2. The arms s- of each of these stars con
ing deviations in kc. Errors below 0.5 kc. are de
stitute yielding tongues, as shown in Fig. 2, which
noted by 0, since they may be neglected for all
practical purposes.
protrude severally'over the sector-shaped high
potential condenser electrodes, as shown in both
TABLE VI
Frequency deviations i711 icc.
65
0
70
9
8
7
6
5
4
3
2
1
F
_1. 25
0
0
0
+0.75
o
+1. 25
+0. 75
+1.50
+0.75
+1.50
+o. 75
+1.00
+0. 5
0
0
0
o
_1. 5
_0. 5
K
J
0
0
+0.75
+1. 0
+1.25
+1.50
+1.75
+1. 75
0
o
o
0
o
o
0
0
0
0
_0.5
_0. 75
_1.00
_1. 00
_1. 25
_1. 25
0
_1.5
_1. 0
_1. 25
_1. 50
_2.00
_2.00
_2.00
0
_0.75
_1. 25
_1.50
_2. 00
_2.25
_2.50
_2.75
0
_0. 75
_1. 25
_1. 50
_2.00
_2.50
_2.75
_3.00
0
_0.5
_1. 0
_1.25
_1. 75
_2.00
_2.25
_2.50
0
0
_0` 5
_0. 75
_1. 00
_1. 25
_1. 50
_1. 50
0
0
0
0
0
o
0
o
o
0
+0.75
+1.25
+1. 5o
+1.75
+2. 00
+2.25
H
G
F
E
D
o
B
A
65
75
2,122,183
figures, and which are provided at these over
lapping portions each with a silver contact point t.
As may be further noted from Fig. 2, the contact
stars p, q, 1‘ are mounted eccentrically with re
spect to the circular carriers Z, m, n on which
latter the condenser electrode ñelds are arranged
in eccentric sector fashion with different areas.
The low potential counterelectrodes for the
electrode sectors on carriers l, m, n constitute
li) closed metallic rings u, u, w, indicated in Fig. 1
with correspondingly similar letters, which in that
figure are meant to include the low potential con
denser plates as well as the interconnecting leads.
The switching elements .r and y in Fig. 1 corre~
spond in Figs. 2 and 3 to the rotatable arms n: and
y, together with the pressing balls e1, z2 respec
tively, of which ball .22, is made of insulating
material for purely constructive reasons. Arm
œ is mounted insulated on the rotatable shaft a1
which carries at one end a hand knob d'2.
This
arm constitutes one of the terminals of the entire
vcondenser arrangement which is connected, as
shown in Fig. 1, to lead x’ which is in turn con
nected to the high potential end of the ínductance
L. In Fig. 3 this connection is merely indicated.
by an arrowed line with the legend “To 91”’. l The
contact arm 'J is mounted on the hollow shaft
h1 which is vcarried on shaft a1, and shaft b1 is
provided with a hand knob be. Of course, in
ISO place of these hand knobs any other suitable driv
ing means for these two shafts may be used in
accordance with the mechanism in which the
condenser system may be mounted.
If now for instance arm œ is rotated by oper
C: La ating its hand knob a1, the contact ball 21 car
ried by that arm will press oppositely located
tongues of stars p and q, between which arm
:r is mounted, outwardly as soon as it encounters
these tongues and thereby press these tongues
40 with their respective contact tips t against their
oppositely located condenser electrode sectors.
In this manner two appertaining condensers of
the two- coarse groups Ca to C1; and. Cm to C11;
are connected in parallel, the same as if in Fig.
45 1 the slide :I: had been moved for instance into
the position shown in that figure. If now by
rotating arm y into the desired position, its con
tact ball 22 will press tip t of the particular tongue
of contact star r which it encounters against
50 the oppositely disposed line step condenser sec
tor of the fine step group C1 to C10, and thereby
connect a particular ñne step condenser in se
ries with the previously selected parallel con
nected coarse step condenser of group Cia to Cik.
For instance, as shown in Fig. 1 the slide y may
connect the fine step C4 in series with the con
stituent condenser C1@ of the total coarse capac
ity step Ce, Cie.
For simplicity of illustration the carrier plate
60 n shown in Fig. 2 in front elevation is provided
with only eight sectors C1 to Cs instead of us
ing the decimal system shown in Fig. 1.
This
is, of course, only a matter of design.
The essential advantage of the arrangement
65 shown for instance in Figs. 2 and 3 is that with
in the capacity groups no separate connections
are necessary.
Aside from the modifications
shown and described hereinabove numerous addi
tional modifications of this arrangement may be
70 made within the scope of the present invention,
involving a mixed series and parallel connection
of capacities as tuning elements in oscillatory
circuits or the like, for obtaining uniform or
approximately uniform frequency steps. For in
stance, according to the invention it is also pos
5
sible to arrange a third group of condensers which
constitute a further subdivision of the fine group
C1 to C10, and which permit within that group
stepwise adjustments from kilocycle to kilocycle.
I claim:
l. Means for stepwise tuning an electric cir
cuit by capacity variation at substantially uni
form frequency intervals, comprising a group ofl
individual coarse step capacities and at least.
one group of selected individual ñner step capac 10
ities constituting the substeps for the coarse
capacities, each of said coarse capacities being
divided into two parallel-connected individual
constituent capacities at «such a ratio with re
spect to the fine step capacities, that each se 15
lected ñner step capacity, when connected in se
ries with one of the constituent capacities of
any selected coarse step, produces the same ñne
step frequency intervals, whereby the same group
of finer step capacities can be used as substeps 20
for each coarse step capacity to produce substan
tially the same nner stepI frequency intervals
for all coarser capacity steps.
2. Means for stepwise tuning an electric cir
cuit by capacity variation at uniform frequency 25
intervals, comprising a group of individualcoarse
step capacities and -at least one group of indi
vidual ñner step capacities constituting the sub
steps for the coarse capacities, each of said coarse
capacities being -divided with respect to the finer 30
step capacities at such a ratio into two parallel
connected individual constituent capacities that
each selected finer step capacity, when connected
in series with one of the constituent capacities
of any selected coarse step, produces the same 35
fine step frequency intervals, a contact spring
for each constituent capacity of each coarse step,
and means for simultaneously actuating the con
tact springs of the constituent capacities of the
selected coarse step to connect said capacities in 40
parallel into the circuit, a contact spring for each
finer step capacity and means for actuating the
spring of the selected finer step capacity to con
nect it in series with one of the constituent ca
pacities of the selected coarse step, whereby the
same group of ñner step capacities can be used
as substeps for each coarse step capacity to pro
duce substantially the same ñner step frequency
intervals for all coarse capacity steps.
3. Means for stepwise tuning an electric cir 50
cuit by capacity variation at uniform'frequency
intervals, comprising a group of individual coarse
step capacities and at least one group of indi
vidual fine step capacities constituting the sub
steps for the coarse capacities, each of said coarse 55
capacities being divided with respect to the finer
step capacities at such a ratio into two parallel
connected individual constituent capacities that
each selected finer step capacity, when connected
in series with one of the constituent capacities 60
of any selected coarse step, produces the same
fine step frequency intervals, a disc ofy dielec
tric material having one of the electrodes of one
set of constituent capacities of all coarse steps
mounted on one side in sector fashion and car
rying on the opposite side an annulus of con
65
ductive material representing the other electrode
in common to all first-named sector electrodes,
a second similarly constructed disc of dielectric
material having the electrodes of the other set 70
of constituent capacities mounted on it in simi
lar sector and annulus` fashion, said discs beingv
spaced >apa-rt and fixed in parallel `to one an
other so that the sectors of the constituent ca
pacities of each coarse step are located opposite 75
6
2,122,183
one another, contact means rotatable between
said discs for connecting the constituent sec
tors of the selected coarse step simultaneously in
parallel into the circuit, `a third disc of dielec
tric material constructed similar to the previ
ously mentioned. discs and having the electrodes
of the fine step capacities mounted on it in simi
lar sector and annulus fashion, and contact
means rotatable over the sectorized portion of
said disc for connecting the selected ñne ca
Y pacity in series with one of the constituent ca
pacities of the selected coarse step, whereby the
same group of fine step capacities can be used
as substeps for each coarse step capacity to pro
duce substantially the same ñne step frequency
intervals for all coarse capacity steps.
4. Means for stepwise tuning an electric cir
cuit by capacity variation at uniform frequency
intervals, comprising a group of individual coarse
2,0 step capacities and at least one group of indi
vidual fine step capacities constituting the sub
steps for the coarse capacities, each of said coarse
capacities being divided with respect to the fine
step capacities at such a ratio into two parallel
25 connected individual constituent capacities that
each selected flnerstep capacity, when connected
in series with one of the constituent capacities
of any selected coarse step, produces the same
fine step frequency intervals, a disc of dielectric
material having one of the electrodes of one set
of constituent capacities of all coarse steps
mounted on one side in sector fashion and carry
ing in the opposite side an annulus of conductive
material representing the other electrode in com
35 mon to all ñrst-named sector electrodes, a second
similarly constructed disc of dielectric material
having the electrodes of the other set of con
stituent capacities mounted on it in similar sec
tor and annulus fashion, said discs being spaced
40 apart and fixed in parallel to one another so that
the sectors of the constituent capacities of each
coarse step are located opposite one another, a
star-shaped contact spring ñxed on each disc and
having each of its arms extending over one of
the constituent electrode sectors on said disc,
and means rotatable betweenl said discs for simul
taneously actuating the contact arms for the
constituent capacities of the selected coarse step,
to connect said capacities simultaneously in par
allel into the circuit, a third disc of dielectric ma
terial constructed similar to the previously men
tioned discs and having the electrodes of the ñne
step capacities mounted on it in similar sector
and annulus fashion, a star-shaped contact spring
ñxed on said disc and having eachV of its arms ex
tending over one ofthe sectors of the ñne step
capacities, and means rotatable over said arms
for actuating the contact arm of the selected fine
step to connect the selected fine step capacity in
series with one of the constituentcapacities of
the selected coarse step, whereby the same group
of ñne step capacities can be used as substeps for
each coarse step capacity to produce substan 20
tially the same ñne step‘ frequency intervals for
all coarsev capacity steps.
5. Means for stepwise tuning an electric circuit
by means of a plurality of ñxed capacities serv
ing as coarse tuning steps, each capacity being
divided at a suitable ratio into a plurality of
parallel-connected portions, and a plurality of
capacities serving as fine tuning steps, said tun
ing means comprising means for connecting the
two parallel portions of a selected coarse step 30
into the circuit and means for connecting into
the circuit for each selected coarse step one of
the fine step capacities in series with one of the
constituent portions of the selected coarse step,
to produce for each tuning step a definite total Y
capacity resulting from a plurality of capacities
in mixed series-parallel connection, the relative
values of the parallel connected portions of each
coarse step being dimensioned with respect to
the fine step capacities so that the same nner
step capacities produce in all coarse steps sub
stantially the same ñne step frequency intervals.
FRITZ SCHWARZER.
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