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20 RADIO AGE for May, 1924
The Magazine of the Hour
_
ANOTHER VIEW Figure 3. Looking from beneath. See the coupling coii at the left, just inside the vario-coupler? The binding posts you see are as follows: Phones: "B" battery; "A" battery; ground and aerial.
at 27>^ and WDAP at 19. Still lower, KDKA comes in at 12. Now, you may say, doesn't that cover pretty well? Yes, you may tune lower than KDKA and hear several low wave stations. But the slightest touch of the vernier of the left hand dial will tune past a weak station so fast that you'll never notice the station at all
The Second Range At this juncture, let's snap the switch
to the left, where only one-half of the vario-coupler winding is in shunt to the condenser. Now a surprise awaits you On the upper range, WOR and WDAP, for instance, were only &l/2 dial degrees apart. How do you think you might easily tune in stations between those two —like WKAQ, WDAR, WGY and the like? But on scale No. 2 WOR comes in at 9iy2 and WDAP at 68. There are 22>)/i dial degrees between them now! Think what this means in ease of control!
Now you'll find no trouble in getting WHAS of Louisville, for WHAS comes in at 88^ and WOR tunes in at 91>4. Likewise, there is plenty of "room" in between the other stations so that none of them seem to overlap. WTAM, WHAZ and other stations in that neighborhood come through with ease. I am not trying to claim, mind you, that tuning is sharper and that you get less interference on the lower range — but what I do mean is that the dial settings are so thoroughly spread out that you can set the dial at the exactly right position in a jiffy. The other range would do, perhaps, if you had a "vernier of verniers" to control it. But even then you couldn't tell just where the dial was set, because a change of a quarter of a degree would tune a certain station in and out again.
A case in point to illustrate what I mean by ease of control is that of WNAC and WEAN, the Shepard Stores of Boston and Providence, transmitting on wave lengths of 278 and 273 meters respectively. With the ordinary tuner, you'd most likely get both of them at once, or at least hear WNAC and tune right past WEAN without noticing that station at all. Of course, I am assuming that you do not live within local range of those stations and that these are both weak DX stations as far as you are concerned. With range No. 2 of the set illustrated you can tune in WNAC on 26^2 and WEAN on 23^4, giving three degrees of separation. And right between the two. on 25^, comes WRW of Tarrytown.
A movement of a degree on the main dial is a "cinch" when you have a good vernier control, and there are those stations all within five meters and you can tune any one of them in and out with perfect ease. On the usual type of condenser {Continued on page 56)
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T/CKLCR.
ROTOR OF COUPLER
C OuPLiNG COIL
GR/D COAf DENSER
CENTER * TAP
T\
JECOMPARY OR. LARGE WINDING OF COUPLER
3
LEAK
VAR/AbLL CONO.
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TWO PO/NT Jk//TCrt
43
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6
PHOA/ES
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RHEOSTAT
AERIAL GROUND
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A BATTERY
"B" BATTERY
WIRING DIAGRAM Figure 4. The hookup. The antenna coupling coil is being recognized as superior to either single circuits or double tuned circuits for coupling the antenna to the set. Note the tapped secondary — the "kink" which gives the condenser its double range.