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Патент USA US2404333

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July 16, 1946.
2,404,333 -
Patented July 16, 1946
Harry Whalley, Darwen, and CharlesV Walter
,Millen Sale, England, _assignors .to Metro
politan-Vickers Electrical Company Limited,
London, England, a company of `-Great Britain
Application December 16, 1943, Serial No. 514,478
In England August» 8, ‘1941.
1 claim.
(c1. 25o-¿20) t
' 1
` This invention relates >specifically to so-cv'alled f
far as possible from the wavebands covered by the
The invention is based on the above consider
ations which are given in greater detail in the
following statement which includes further con
panoramic radio receivers the nature of which
was described in “Electronics,” June, 1940 `and
wherein, inbrief,._a waveband `or it may be any
selected one vof av plurality rof wavebands, is
scanned from end. to end by the `automatic vari
ation of a tuning parameter at arate comparable
In general a satisfactory panoramic receiver
shouldhave a high sensitivity to enable- the maxi
mum number of signals to be observed, b the
’ with. thefrequency 'of .the persistence, of vision, the
output or outputs due to any received >radio trans
missionsA which’may-v be taking place within the
waveband being indicated as resonance or peak
components perpendicular to atime base wave
selectivity should be high to give adequate disn
crimination between adjacent signals, consistent
with thetuned circuits being kable to respond at
band component on the screen of a cathode ray
the rate of time base sweep and of scanning syn
tubeî the time base component being provided syn
chronously with the scanning such as by means of
a saw-toothtype of oscillation generator. Pro
vision can-be madewhereby _any selected one of
the `,thus indicated transmissions can be tuned
into manually and its modulation listened to or
recorded or` otherwise indicated, that is to say, 20
the scanningr of _the waveband can be effected
solely by hand such as through the turning .of a
chronously therewith, cit is desirable at thesame
time thatsecond channel interference’should be
absent or substantially absent; d the process of
scanning should involve the smallest number‘oi
tuning parameters as possible; and e tuning can
be conveniently carried out by electronicrather
than mechanical means.
„ Regarding a above, this involves high overall
gainjwhich isconveniently obtainable by the use .
of an ,îampliñer of standard design operated at, .
for example, 1.6 Irnc. per second or 465 kc. pe-r sec
knob about an associateddial indicating the wave
length. In such a panoramic receiver it has been
convenient for the purpose _of therapidscanning
oiï‘the waveband to‘fffwobble” the'value of cer
tain ltuning components -of the oscillatorsection.
ond. VThis will also satisfy requirement b above
while the consequent use of a superheterodyne cir
cuit simpliñes the requirement d above but it in
of, vafrequency changer valve in ~a superhetero- s
vdyne„circuit„which superheterodyne circuit pref
troduces the difficulty of second. channel interfer
withcorresponding intermediate frequency cir
ence c above'. As an example, a particular re
ceiver may be quoted which was required to cover
, afrequency range of fromfifteen to thirty mega
cuitsi land ,preferably 5 the ,scanning is `effected by
cyclesper second in thirty consecutive bands’each
erably4 has 4¿three stages of `frequency ` changing
aireact‘or valveassociated with the second ofthe
of five hundred kilocycles per secondwidth; such
receiver therefore had to be capable of tuning
oscillators through'lan amplifier as described in
UnitldïStates application _Serial No. 503,277, -ñled
September, 21; «1943-
03 Ur automatically through five hundred kilocycles per '
second on each of the bands at a recurrence fre
»what heejëeée .Celledthe “Single-Span”, «tuning
guency of the order ofrtwenty-iive per second. To
principle in domestic and otherfradio receivers
"achieve _this mechanically with normal input cir
has been proposed but has not apparently come
into cominercialuse.
¿ __
. y
The general- advantages ¿offthesuperheterodyne
receiver over other types are also well known and
its use in a panoramic receiver is highly desir
cuits Wouid haye involved >the use of at least two.~ _
continuously variable timingïdevices such as au
tomatically rotating condensers, as wellgascom
plicated band switching means to cover the neces
sary >number of bands. If the tuning Were to be f
effected electronically such as by means of a re
able, and when panoramic receivers are required
to scan a relativelyvlarge number of wavebands, 45 actor valve, the switching would not be simpli
for instance twenty or thirty, there may be great
fied; therefore a preliminary frequency changing
complexity and expense unless provision is made
stage (it is preceded by a signal’frequency ampli-v
for reducing the number of preset tuning circuits
ñer) was proposed for converting allsignals to a
which have to be changed when the waveband to
frequency band of ñve hundred kilocycles persec
be scanned is altered. In order that the received 50 ond in Width vso that a single automatically var
signals shall have sufficient amplitude at the first
iable oscillator and its associated frequency
frequency changer to override valve noise in the
changer would suflice to produce the panoramic
mixer some signal frequency amplification is gen
sweeps, irrespective of the band to which the
erally desirable. It is, however, also desirable
kthat “image" frequency signals fare removed as
receiver was adjusted.
According to the present invention a panoramic
:ff ;. ifi;
receiver has at least ‘two and preferably three
frequency>r changer stages with aperiodic signal
frequency amplification prior to- the first stage,
radio frequency amplifier stage which is aperi-V
any signal 'frequencyr so that the-"tuned Ycircuitv
elements, preferably condensers only, which have
to be selectively switched to the fixed element of
Acycles* per 'second plusl the'g mid-frequency of the
ity to deal with such high frequencieahelpSJlo.
quency amplifier, sharply tuned to 1.6 mc./sec.
odic, at least Within the band to be scanned. M.
I is the ñrst mixer stage supplied from A_R. F. A.
and from the first oscillator '0.I having a fre
>whilst the first oscillator frequency is high for
giving a first intermediate frequency higher than 5 quency, _in the particular example„o=f 33 mega
band of signals being- scanned.>>y #It'ï
that the scanning is over a band of one-,half'megacycle I. F. A, I is the first intermediate
the receiver for frequency >band changing are re
duced, namely to- those of the oscillator circuit l0Y frequency amplifier, which may include a filter
which responds uniformly over the band, in the
because the image frequency is so high/that it can
" example 33 .mc.i250 kc./sec. and attenuates out
easily be filtered out, or is even inherently elim
inated. The aperiodic signal frequency amplifier 4 .j side it.- M. 2l is the second mixer stage suppliedj
from I,~ F._ A; l Aand from the second oscillator 0.2
does not increase the selectivity and gives only aY
small gain, but it has been’found in the com- l5 the frequency of which, in the example, is lWob- Y
bination above set forth toV give satisfactory per-¿ Y bled between ‘theîlimits of 34.35 and 34.85 mc./
formance in practice and also, due tojits'inabil-> , ' .'isec. „L F. A. 2 is the second intermediate fre
M. 3 is'the third- mixer stage, supplied from I. F. A.
mediate frequency amplifier circuit` preferably 20 2 and from the third oscillator 0.3, the frequency
of which is 2.065 mc./sec. The mixer M.' 3 feeds
' has a' band-pass characteri'sticrcfv adequate ifre
to> they third intermediate .frequency amplifier
quency width which may be, for example,' five
I. F. A. 3 tuned to 465 kc./sec., this amplifier feed
hundred kilocycles per second'so' that the fre
ing to the detector Dwhich is preferably asso
quency wobbling can be done' at the second os-`
iilterout the image frequencies.
The first inter-` -
cillator, ’thus enabling all bands Vselected to have 25 ciated with a limiter L in accordance with UnitedV
States Application Serial No.' l503,280,7‘iiled .Sep
tember- 21, 1943.1y The rectangleB. F. O. Vrepre
In an example olf panoramic receiverîinac
an equal Width.
sents the beat frequency oscillatorfwhich may be '
used for heterodyning a continuous wave signal;
quency rangeof fifteen' to thirty megacycles in
steps of five hundred kilocycles-per second, the 30 in order to obtain an audible beatnote if desired
cordance withV the invention for a signal Vfre-`
The output from theV detector goes, on the one
. first oscillator frequency is `from forty-eight to
hand, to the audio frequency amplifier A. A. su "-`
plying the phones VVlë’h. or loud speaker or otherÍ
sixty-three megacycles per second and the míd-`
frequencyv to Vwhich Ythe intermediate frequency
amplifier is tuned is thirty-three megacycles per
indicating device, and,von the otherhand, to the
second, »the image 'frequency 1 beingV from' eighty-' 35 video’ampliiier V. A., the output of which is taken
to the cathode raytube _represented by the rec
one toninety~six mega'cycles per second.
tangle C.'R_ T. The'time base of the latter is
'Thus fthe' present invention employsr the '_per
seknovrnfsingle span principle in a panoramic »Y . fed from the timeY base generator represented by
the rectangle T. Vl2». G.,ìthe„output of'which is also
receiven'particularly in cases where the frequen-`
cies are s_o chosen that aperiodic signal frequency 40 applied to the second- o'scillaltorl)¿_.2` to wobble the
normally iixedfrequency ó-f the latter in synchro
` ' circuits are permissible and yet second 'channel
nism with-the timebase of the cathode ray'tube
interference is avoided, Whilst the choice of ’band
overa band of 500 kilocycles'. ' '
' ' Í i
to be observed is decided'fmerely by the tuning
of the first oscillator. _The use of )this arrange-`
In _a panoramic receiver, an _input radiofre
ment in conjunction with aïmain'intermediate 45
quency ampliñerstage-aperiodic over the 'range f
Y frequency amplifierV with»_V its .frequencies i chosen
wide frequency band passed Y‘by the »fìr'stinter-à
I '
l ‘
Aof signals to »be received, a first frequency changer
stage variable to select a band of frequencies of Í
appropriately, enables'adequate selectivity, sensi-`
tivity and freedom from second channel inter-`
ference to be obtained,~in-spite of .fthe simple
nature of >the input circuits and the necessarily
substantiallyA constant' Width to be- scanned p and
arranged to convert the selected band to an in
e termediatefrequency -higher than that ofthe re-'v
mediate frequency amplifier.' >It is to be under-`
Vst'oo'd'that wev do' notherein claim per se auto
ceived signal, an intermediate frequency» ampli-‘
fier, a second frequency changer'stage for 'scan-A
ning the band selectedv byY the'ñrst frequency
matically varying the tuning of the> second- osY>-Ã
cillator instead of the first, in a panoramic re'-` 55 changer stage', means for varying the oscillator
' The :accompanying drawing is a block diagramùLA
_indicating a particular panoramic radio receivern
in accordance with the presentïinvention." fÍ _
Starting from the left-hand end of the'diagram 60
the rectangle A. l2.. F.’ AL represents the desirable
frequency of _said secpndïfrequency changer stage
to Veffect panoramic scanning,` and adetector _stage
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