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ANOTHER MRL No. 2? |
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MRL No. 2 |
Morgan crystal set
Page 92 |
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| There seems to be
a clone of the No. 2 Crystal set in the book "FIRST RADIO
BOOK FOR BOYS" by Alfred P. Morgan,
Copyright 1941.
The picture from Morgan's book is on the right.
Alfred P. Morgan wrote over 15 books on radio. Would he copy Elmer's circuit into one
of his own books? |
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They certainly look similar. Which circuit works better?
I tried it both ways. The fact is, the Morgan circuit doesn't work
at all. The problem is the variable capacitor in series with the
coil tap selector. A person named Hue Miller emailed and wrote that there is a mistake in the Alfred P. Morgan
circuit. |
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All modern AM radios need a "BS" detector and switch!
The term "BS" or "Bullsh*t" didn't become popular till after WWII.
Morgan's book is copyright 1941.
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Here are two examples of the MRL No. 2
coil. The one with the fiber rings at the ends is the
oldest, but they both show signs of the celluloid shrinking
from age.
The coil form is 2" in diameter by 4.5" long. The coil is 90
turns of #22 cotton covered wire. The coils are tapped at
turns 5, 10, 16, 23, 40, 50, 61 and 73.
What formula did Elmer use to determine the taps? Did he
calculate the inductance of each tap and determine the
frequency the coil will resonate at depending on the
position of the variable capacitor? |
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It seems he used a ruler! The coil is tapped
at 1/4, 1/2, 5/8, 3/4, 1½, 1¾,
2, and 2½ inches. |
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Another MRL Advertisement |
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| In November of
1958, "Electronics Illustrated" magazine announced
they were accepting classified ads. Elmer wasted no
time. This MRL
advertisement appeared in the very next issue. |
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If you saw this in the catalog, what do you think it
would actually look like? |
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It's a beautiful, hand-made, low loss, high-Q,
transparent celluloid coil form. 2" in diameter x 4.5" long.
According to an advertisement in Radio magazine, the first 2"
celluloid coil forms were sold in July of 1934. |
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| The 2XM coil form is the
heart of many of the crystal set kits and plans in Elmer's
literature. The cost in 1972 was 45¢.
In 1985 it was a dollar. An MRL-made mounting bracket
was included. This bracket was not sold separately in the
catalog. |
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MRL No. 18
Diode-Transistor Set |
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Catalog entry for the No. 18 and an actual No. 18
built in 1980. |
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MRL No. 26
Diode-Transistor All Wave Set |
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Catalog entry for the No. 26 and an actual No. 26
built in 1978 by Sloane Freeman. |
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Another MRL No. 26, this one built by Don Holdaway.
That brass switch looks new! |
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MRL No. 10 All-wave
Diode-Transistor Set |
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Catalog drawing for the #10 and an actual #10 built 50
years ago.
The kit came with all the parts, a 4.3 volt battery and a
copy of DP-34. It sold for $8.50. |
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Rear view of
the MRL Number 10 shown above. This was built in 1971.
On the left is the battery holder, but the battery and connecting wires
are missing. |
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The 4.3 volt Mercury battery is so rare I can't find a
picture of one.
According to the catalog, the battery holder will
fit an AA or a 4.3V mercury. |
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MRL VARIOMETER |
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Here's another
drawing that is ambiguous, as is the statement "has never
been listed in CAT." How can it not be listed in the catalog
if you're looking at it in the catalog? Obviously, it was
only intended for the first catalog to list the variometer
but the line stayed in for all the other catalogs.
What is it? What does it look like in real life?
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| The
catalog hints we should get DP-44. Here is the
variometer in DP-44, drawn actual size in the
publication. Unfortunately, Elmer's drawing
shows it as viewed perfectly down from the top. It looks like two rectangles in a square inside a
circle. |
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The square and the circle are cylinders! |
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The rectangles are coils!
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Two different sizes. |
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The coupling between the coils is varied by
turning the inside coil.
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Another MRL masterpiece! How many of these
would he have sold if he had put a picture of one in the
catalog? If you scroll back up and look at DP-44 again,
you'll see he has a picture of a "1920 - 1930 Low -
Loss Variometer" next to his drawing. Why
didn't he use a photo of his own variometer?? |
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MRL TRANSISTOR AMPLIFIER |
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This is an unassembled kit from 1986. If you
purchased it already wired, a 9V battery was included. |
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The most interesting aspect of
the kit is the box! Elmer made a wooden box, then
covered it with wood grain Contact Paper. How long
did that take? Why didn't he paint it
with the same paint as the front panel?
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An explanation of the box, from MRL Data
Sheets Vol. 6 |
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Look at the underside of the front panel in the
middle picture. We've just solved the mystery of what Elmer calls "Compo." It's
Masonite!
Note: In HB-5, Crystal Set Construction, page
3, Elmer stated that "Compo." is Masonite. However, HB-5
wasn't published till 1956 and he had been calling it
"Compo." for two decades prior, |
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| Misprint in the February 1959
edition of Popular Electronics. Fortunately it only ran for
one month. |
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In 1971 Elmer
and Mabel moved to Reno, Nevada.
A year later they were back in California. |
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Why would Elmer and Mabel move to
Reno, Nevada? In 1984 Elmer wrote
that years previous Mabel would sometimes go to Reno
for a week. During that week he'd go into the shop
at 6AM and write a handbook.
Apparently, there was some draw to Reno for Mabel,
perhaps family, but who knows? So Elmer, who lived
almost his whole adult life near the coast of California, moved
MRL to the dessert of Reno, Nevada. Actually, it was
only a two hour drive from where they lived in
Sacramento CA.
I guess something didn't pan out and before you knew
it, they were in Garden Grove, CA. The trip from
Reno to Garden Grove is over 500 miles and would
have taken all day. Every time they
moved, they moved seven and a half tons of MRL with
them. |
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