Elmer G. Osterhoudt
The Modern Radio Laboratories Catalog 

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Small loading coils. No. 28 on the left, No. 29 on the right.

MRL Telefunken Coil.
Elmer related how in 1924 a radio wholesaler named C. D. Tanner came into Elmer's store and sold ELMER a radio.  Elmer bought it because it was very selective. No sooner was Tanner out of sight then the bottom of the radio was off and the circuit checked. It was a Telefunken circuit. Detail Print #58 shows the MRL No. 4 Telefunken crystal set.
Another work of art, and nicely preserved. How long did this take to make? It cost two dollars in 1986, which is the same price for which he sold the much simpler QRM coil shown on Page 1.

$2 in 1986 is $4.50 in 2018. Elmer would have to make and sell six of these AN HOUR at $4.50 each to make an "average income" in 2018. That's 240 coils a week! It's no wonder he never stopped working.

MRL 29-A coil, part #7-193. Not to be confused with the No. 29 Variometer, part #7-194.
This coil seems to be the one used in the MRL No. 29 variometers, but without the inner coil.
Similar to the 29-A. This one may be a No. 10-A.
The coils were numbered according to the radio they went to, so the #10 coil
went with the MRL #10 radio, described in both HB-17 and Detail Print #34


An old wooden box, painted black.
The inside is lined with felt. The hinges are broken and the bottom of the clasp on the front is missing.
The felt has been cut and tacked into the box. On the lid is an MRL address label. The address is 151 Liberty St, San Francisco, CA. This places the date between 1934 and 1938. What was so important about the contents of this box that the owner lined it with felt?


Each coil has a label stating the type of coil, a schematic and the price. The labels were made with fountain pen ink.
The handwriting looks like Elmer Osterhoudt's handwriting.


The bases are repurposed vacuum tube bases which have been cut down with a saw. Each base has two lines cut into the bottom.
The text on the bottoms reads, "LICENSED ONLY TO EXTENT INDICATED ON CARTON."

Why the lines in the base? There's an explanation on page 593 of the Feb 1935 issue of Short Wave Craft.

Also in the box was this. The label says, "SHORT WAVE CHOKE  2 Mhy 25"

Why do these coils have the labels with the schematics and prices on them?
Are these coils the ones that Elmer used as templates in 1936? Were they display samples in his radio store?
Who put them into the felt-lined box, and when?


On the left is the catalog drawing for the MRL antenna coupler. The drawing shows a plug-in coil with the antenna coupler surrounding it. The plug-in coil is the small rectangle at the top of the drawing, as the top projects 1/2 inch from the antenna coupler when viewed edge on.

Included with the coupler was MRL Detail Print No. 11 which gave more information on its construction and use.

$1.50 in the 1983 catalog, $2.50 in 1986.


Mabel's and Elmer's handwriting. Elmer on the right.


Would you buy a headphone cord based on these drawings in the catalog? I did.
MRL-made headset cord, assembled by Elmer in October of 1986.
 Elmer wrote "the cords now cost twice as much, so we make our own. Will last forever - we hope." He charged $3.75. Thirty-three years later the cord still looks new.


This drawing is from "Radio Flyer No. 23", dated 1971. It is one of only four  MRL-made items in Elmer's entire collection of literature that is drawn in perspective. The others are the bracket shown below, an "L" bracket, and the drawing of the MRL One Tube Radio shown on the cover of HB-4.
This drawing is from page F-6 of the 1972 catalog; once again, drawn in perspective. Note that the description states "BRACKET for #10-26." There is no item in the catalog with that part number. It refers to the MRL No.10 and MRL No.26 All Wave Crystal Sets.
Here is an actual MRL battery holder. This photo was taken from a picture of the back of a 1970s MRL No. 10 that was posted on ebay. It's brass bar stock, cut, folded and drilled.

MRL Crystal Set #74

Typical EO two dimensional drawing in the MRL catalog. In 1970 Len Buckwalter wrote an article Mechanix Illustrated describing the construction of a crystal radio. He mentioned MRL in the second paragraph. The result of the article was the MRL #74 Crystal Set Kit.

Full details are found in DP-74, which is the last Detail Print published by MRL.

Note: This is not to be confused with the MRL #1 "Original Radio" described in HB-17.
3D perspective drawing from Mechanix Illustrated, which can be found here.