The Browning-Drake Receivers of 1924-28
By Bruce McCalley, Gazette Editor

During the mid-twenties a good number of people assembled their own receivers. Some were strictly hone-built, using components purchased individually and using some circuit found in one of the radio magazines. Others purchased assembled components and/or kits which had been designed and proven successful (hopefully). One of the more popular component kits was the Browning-Drake.

The history of the Browning-Drake tuners is interesting. An article authored by Glenn Browning had this to say:
"It was in August of 1923 that Mr. Fred. H. Drake suggested a mathematical treatment of a tuned radio frequency transformer, in order to determine the proper constants necessary for maximum amplification. This theoretical investigation proved to be more fruitful than either of us would have believed, for after choosing the constants predetermined by mathematics, laboratory measurements showed that without a "slot" winding of the primary of the radio frequency transformer amplification could not be obtained. However, with the correct constants and the "slot" winding 90% of the amplification predicted in theory was actually obtained when the transformer was subjected to laboratory test as Harvard University.

"It was noticed by looking over the equations that by adding a coil in the plate circuit of the detector tube signals could be increased ten to twenty times. Accordingly, a set was constructed, using this additional feature, with surprising results. Comparisons made with several makes of sets showed that the receiver was extremely sensitive and selective. Our first impressions, that the set was very good, were later verified by reports from all parts of the country, constantly comparing the receiver with the superheterodyne, so that it is believed that many others have been surprised with the efficiency of the four-tube set besides the writer."

In 1924 Browning and Drake contacted the National Company about manufacturing the coils and condensers for their receiver. At that time National was not really in the radios business but they took on the job and apparently at the same time began changing from making an assortment of toys, gadgets, and some radio parts, into a primarily radio business.

National supplied just the coil/condenser assemblies (along with tuning dials and knobs of various types) for the Browning-Drake receivers, leaving the layout and audio sections up to the individual builders. The success of the design ultimately lead to other firms offering panels and other components for the sets, and eventually almost complete kits.

In 1928 the two separate tuning condensers were ganged together for one-dial tuning. A small "trimmer" condenser was used across the antenna section condenser to allow a bit of fine tuning. The end was in sight, though, and Glenn Browning went on to other designs in cooperation with National, one being the MB29 in 1929 and the MB30 in 1930, both being T.R.F. designs. The MB29 had three tuned stages while the MB30 had four.

Radio magazines in 1924 to 1928 offered many construction articles on variations of the Browning-Drake receivers, all using the same RF and Detector circuit designed by Browning and Drake, but with varying layouts, audio stages, and tubes used.

Once in a while one of these Browning-Drake coil sets shows up at a swap meet but they are not often in good condition and even more often at a pretty steep price. For those who might want to build a set today, the following coil data is taken from a 1926 article in Radio News Amateurs Handbook.

ANTENNA COIL

The input, or antenna coil, consists of 50 turns of No. 20 D.S.C. wire wound on a piece of 3-inch hard rubber or bakelite tubing. This coil is usually tapped in the center so that its use with either, a long or short antenna may be flexibly arranged. Of course, this means the center tap would be used with a long antenna, while the short antenna would be brought in at the high potential side of the coil.

DETECTOR (Regenaformer) COIL

Seventy-seven turns of No. 20 D.S.C. wire should be wound on another piece of 3-inch tubing, which should be about 5 inches long in order to allow for the mounting of the tickler. This winding is the secondary of the Browning-Drake tuned radio frequency transformer and is tapped at the 14th turn for the purpose of neutralization.

The tickler consists of 30 turns of wire, which may be about No. 28 or 30 D.S.C. wound on a piece of 2-inch tubing which is mounted on a rod. This rod may be fastened by end pieces to the variable condenser so as to bring it in proper relation to the coil in order to cause regeneration. Roughly, this tickler coil is about under the last turn of wire.

We now come to the primary, which is the really important and principal part of this receiver. As discussed in this article, through scientific development, it was found advisable to wind this in a slot with very fine wire in order to reduce the capacity coupling between the primary and the secondary. A small wooden disc about 3/8 or. 1/2- inch thick should be obtained with a diameter which will just permit it to slide snugly inside of the 3-inch tubing upon which the secondary is wound. On the outer rim, or tread, of this wooden disc a slot should be cut 1/8 inch wide and 1/8 inch deep. Now 24 turns of No. 30 D.C.C. wire should be wound in this slot in the so-called "jumble" fashion, the arrangement of the turns not being at all critical. When the ends have been brought out and securely fastened in place, the primary is a complete unit. This should be slipped inside the secondary in place so that the slot comes under the first turn. It will be seen at this point that the fit of this wooden disc must be quite snug in order to keep it in place inside the secondary tubing.

The antenna condenser is a .0005 mf. variable, while the regenaformer may be tuned by either a .00035 or a .00025 mf. variable condenser. The fixed condenser in series with the antenna is a .0001. The by-pass condenser of the first audio transformer may be .001 or .002 mf.

Most of the construction articles recommended using the type '99 tube in the RF stage and an '01A as a detector. Later, however, 01A's were used in both stages. Neutralization of the smaller tube (99) seemed easier and the articles went to some length of just what the proper method would be of make the neutralization adjustment.

When the editor was in the radio repair business we always had a '26 tube with either an open filament or with one of the filament pins cut off which we used to make neutralizations adjustments. (Battery-operated sets with '01As or '99s were seldom seen so we didn't have "test tubes" of these types. The procedure was to put the dummy tube in the socket of a working set and then adjusting the neutralizing condenser (remember we didn't have capacitors then) for minimum signal. You did this for each RF stage, one at a time.

Oh, for the good old days!!!!!

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