Single Tube Reflex Circuit

This little set gives a surprising volume for a single tube and in addition has no howls and squeals of its own. The experimental set in New York City gave good volume on a loud speaker with the local stations, and was superior to a single tube regenerative set on distance work. While it is a little broad, there was no difficulty in separating WJZ. WEAF, and WOR, all of whom are very close. We believe it is sufficiently selective for most locations, and if extreme selectivity is desired, u series condenser in the antenna circuit will' do the trick.

The important point "in the construction of this set is the choice of proper values for the fixed condensers. It should be noticed that the condenser in the plate circuit has one side connected to the radio-frequency transformer, and that the other side goes directly to the filament of the vacuum tube. The fixed condenser across the audio-frequency transformer has a marked effect on the performance of the set. due to possible variations in aerials and instruments. It is recommended that several sizes, from .0005 to .003. be tried. If the condenser in this position is too large, the set will oscillate: that is, a popping sound will be heard at certain adjustments of the condenser, and there will be noticeable distortion of the incoming signals. If

the condenser is too small the volume will not come up to maximum. A value of .0025 was used in the experimental set.

As this is a radio-frequency amplifier and there is no regeneration to make up for losses, a high-grade variocoupler should be UBed. We found the Sickles variocoupler very satisfactory in this set.

It is rather hard to give directions for tuning, as the controls are to some extent dependent on each other. However, it is not difficult. We called in a gentleman who is only slightly familiar with radio, and with no directions at all he succeeded in tuning in five different stations in less than three minutes.

While this set is primarily intended for use with UV 201-A tubes, very good results were secured with No. 199 and No. 299 tubes, in connection with the Na-ald Adapter.

The adjustment of the crystal detector is not particularly critical. When the crystal is out of adjustment, sometimes oscillation and squealing will start up. When everything is properly connected, a slight readjustment of the ctystal contact will improve reception on distant stations.

The photograph and the circuit diagrams we believe make further directions on this set unnecessary.

the experimental set the following apparatus

was used.

1

Base Board, 6" x 14"

$0.75

1

Condensite Panel, 7" x 14" x 3/16"

2.30

1

Na-ald Coggswell 13 Plate Condenser No.

113 3.50

1

Sickles Variocoupler

______ 4.5(1

1

Thordarson High Ratio Transformer '

4:50

1

Acme R2 Radio Frequency Transformer

3.50

1

.75

I

Inductance Switch

------ 1.20

2

Dubiller Micadons, .0025

-------- .70

fi

Binding Posts

.60

1

Pair Na-ald Phone Tip Jacks

---- .25

1

•Strip Condensite 1" x 5"

20

1 1

1.00

Pacent Crystal Detector

1.30

«25.05

Na-ald De Luxe Socket, No. 400

Price 75c Canada $1.00

Have you ever had the experience—the failure of your set to operate, and, although the filament in the tube lighted, signals refused to come in because the socket clips were not pressing against the plate and grid terminals of your tube? And after finding out that this was the case, it being necessary to hunt for a button hook or other device in an endeavor to bring the socket contacts back Into their proper position? If you are using the No. 400 Na-ald De Luxe, this trouble Is over. The dual-wipe contacts of this socket press on both the sides and ends of the tube terminals. The strips are laminated like an automobile spring to insure continued resiliency. A De Luxe socket, but priced at only 75c! In comparison to the cost of other parts of your set, can you afford to use inferior sockets? Na-ald De Luxe, is becoming the standard of particular set manufacturers.

3% inch DIAL 3 inch DIAL 2 inch DIAL

inch Dial -8 inch Dial

3% inch DIAL 3 inch DIAL 2 inch DIAL

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