Equipment information:

Silver Marshall Inc. Round the World Four Receiver
Silver Marshall Inc.
Model: Round the World Four
Date: 1928
Category: Professional music equipment
Group: Receiver
                                    rT''lIK unquenchable rumors that tele-

1	vision is here in form simple enough ini- home
experimentation have led to increased interest, if (hat. be
possible, in -liort wave reception. Jlanv of (lie
experimental television transmissions take plaee on short
waves, such as that from WKNY, New York and WLKX, Boston,
Mass. A short wave receiver was used in these experiments,
and it is certain that no matter whai the form, television
impulses must he tuned in upon receivers of more or less
conventional design, hut of a. higher degree of performance
than is necessary simply for sliort-uave code reception.

The short, wave receiver illustrated and described herewith
provides (his higher degree of performance, plus freedom
from radiation, for (he oscillating detector is isolated
from the antenna by a M i-een-grid H.F. amplilier tube.
While the average three-tube short wave set will haw ample
sensitivity for code signals when in an oscillating
condition, the performance when not oscillating is seldom,
if ever, satisfactory for modulated or telephone reception
(broadcast programs for instance). Tlii-s is because of the
fact, that amateurs, interested primarily in C.W. code
signals heterodyned by an oscillating detector, have taken
little or no pains to obtain the smooth regeneration control
absolutely necessary to satisfactory modulated signal
reception. In the development, of the four-tube set
illustrated, great care was taken to obtain smooth
regeneration control; telephone broadcast, programs weakly
heard, if at all, on ordinary short wave sets are
satisfactorily tuned in on this receiver with considerably
greater strength due to careful design and layout and to
additional amplification provided by the screen-grid R.F.
amplifier (ulie. Tliis R.F. tube (Joes not add a (lining
control, its input circuit being untuned, yet it boosts
telephone signal volume quite a lot, and entirely
eliminates “dead spots” at. which (he set, will not
oscillate, since it. effectively isolates the antenna from
the sensitive detector circuit.

1 S-M 317 or Amsco .00014 tuning condenser. Cl 1 S-M 316B or
Amsco .00035 tickler condenser, C2 1 each S.M. 131-T, 131-U,
131-V, and 131-W coils, L2

1	S-M 512 5-prong soekct	•

2	S-M 277 R.F chokes, LI, L4 1 S-M 275 R.F. choke, L3

1 S-M 818 hook-up wire (25 feetl 1 S-M 734 aluminum
shielding cabinet with terminal strip 1 S-M 255 first stage
A.F. transformer, T1 1 S-M 256 second stage A.F. transformer, T2

3	S-M 311 tube sockets

1 Yaxley 20-ohm midget rheostat, R4

1	Yaxley 500 switch attachment, SV

2	Yaxlcv insulated tip jacks

1 Na-Ald 481XS spring socket for detector

1 Polymet .00015 condenser, C5 1 Polymet .002 condenser, C6
1 Polymet .005 condenser, C4 1 Polymet grid leak mount 1
Polymet 5 megohm grid leak, R3 1 Durham 50,000 ohm resistor, R5

1	Sprague >4 mf. condenser, C3

2	Carter H-10, 10-ohm resistors, Rl, R2

1	Carter H-2, 2-ohm resistor, R6

8 binding posts consisting of 8/32 screw', nut, and
insulated top

2	National type B vernier dials.
An unusual degree of smoothness of regeneration control,
freedom from “putting” and “fringe effect” as the set goes
in(o oscillation is effected by careful circuit and coil
design, notably by using a small coil, which on the lower
waves (particularly around 20 meters and be-
low) provides smoother and sweeter control than (he two,
three, and even four inch short wave coils generally used.
The coils are actually a refinement of the popular “tube
base" or “Scottish” idea which has been found to give such
excellent and economical results. These forms are slightly
larger and longer than the average tube base, by dimensions
sufficient to allow more efficient coils than are possible
on the ordinary tube base (often not available except at the
expense of breaking good tubes). A winding space 1Z" long
and /" in diameter is available, with tickler slot Is" deep
and 1 /16" wide at the filament end. On the bottom of <lie
moulded form are five hollow pins, properly positioned (o
fit any five-prong A.C. tube socket. These coil forms are so
inexpensive that any number of experimental coils for
different wave bands can be wound at little cost, to be
tuned by any size of condenser that may suit the builders’
fancy. In this matter of “builders’ fancy,” however, it is
well to incidentally remark that, while a code receiver can
be (brown together almost any old way and still work,
physical placement of parts and wiring details must, he most
rigidly watched in order to get a good modulated signal

The set illustrated is mounted on (he top and front of a
satin-finished aluminum cabinet, 14" long, f>" wide, and (>”
high, with all parts placed in a simple straight line as in
a schematic diagram, instead of being tied up in a knot
difficult of assembly and “trouble shooting.” Looking at.
the inside of the receiver with bottom and sides removed,
the antenna choke coil is seen at the left; next to it is
(lie screen grid R.F. tube socket, then the screen grid tube
by-pass condenser and plate choke. The 5-prong coil socket
is mounted on the other side of the top, on 1" studs,
directly above the screen grid tube socket and by-pass
condenser. Next is (he grid leak and defector socket, with
the tuning eonden.-er directly in front of them; then the
plate choke, regeneration condenser, two audio tube sockets,
and two S-M Clough-type audio transformers. A 20-ohm
rheostat with switch attachment is placed on the panel to
control detector filament voltage. All binding posts and
speaker tip jacks are mounted on a small bakelite strip at
the rear of the cabinet.

National vernier dials are used. The matter of a good short
wave variable condenser is an interesting one, for few good
broadcast condensers, even of properly reduced capacity, are
good at 20 meters and below, for bearing noises develop to

These manuals are available for the above equipment:

Silver Marshall Inc. -- Round the World Four -- Service and User Manual
File name: Silver-8036-Manual-Page-1-Picture
Manual Type: Service and User Manual
Pages: 5
Size: 998.10 Kbytes (1022056 Bytes)
Language: english
Date: 01 January 1928
Quality: Scanned document, reading partly badly, partly not readable.
Upload date:
MD5: 7274fc5bb1856a05647858fc3d71d538
ed2kID: 833b758fe58205c559281efd33d659f1
Downloads: 2 since 17 September 2016
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