Tuesday, October 27, 2015

The Capacitor: Not of the Air: by Joe Cerniglia


Joe Cerniglia is our guest blogger here, with his paper on an artifact recovered from the Colonial Village site on Nikumaroro this year. His work exemplifies the kind of careful analysis that's necessary to distinguish artifacts that might have been associated with Earhart and Noonan from those that are not.  TFK

What is it?

In the feral coconut bush north of the Gallagher Highway (the pathway we cut on each visit from the landing to the lagoon beach at what we call Club Fred) and about three meters from the spot where the knee-high metal bin, later known as the Zimmerman Object, was found, lay another much smaller artifact. This artifact is also metallic, box-like, but dark in color, and easily fitting in the palm of one's hand. It has been identified as a bathtub-style capacitor made by the Aerovox Corporation.
The artifact in situ

Reading What it Says

The capacitor bears an inscription:

CP52  B1D F504MK
.5 MFD 600VDC

The top line appears to be a serial number. The second line denotes the manufacturer, Aerovox, and a model number. The last line is interesting. Research has indicated the .5MFD shows the capacity of the capacitor to store electrons, as measured in microfarads. The farad is an SI[1] derived unit of measure of capacitance, named after British scientist Michael Faraday (1791-1867). The 600VDC indicates the capacitor can have input as high as 600 volts direct current.

Brief History of Aerovox

Aerovox Corporation was founded in 1922 as the Radiola Wireless Corporation. At first, Radiola Wireless made radios, but later the company specialized in condensers, also known as capacitors, and resistors, key electronic components in radios and many other electrical appliances. On March 2, 1932, the company changed its name to Aerovox. In October of 1938, Aerovox moved its headquarters from Brooklyn, New York to New Bedford, Massachusetts.[2] By 1972, the company name was subsumed by a subsidiary, AVX, and the company refocused on the new field of integrated circuits.[3]

Aerovox capacitors were the brand of choice for radio manufacturers from the 1920s to the 1960s. Bathtub capacitors, of which this artifact is an example, were typically found in radios for which high performance in varying conditions was important. The 1947 Aerovox catalog stated that this particular style of capacitor meets severe operating conditions encountered in aircraft, police, broadcast, p.a., and other types of communications equipment.

Dating the Artifact with Precision

The description in the catalogs seemed an ideal fit in describing radio components used in a tropical environment, such as Nikumaroro. It also seemed an ideal fit for use on board an aircraft. The next obvious question was whether this particular capacitor might be something connected with Amelia Earhart's radio equipment on board the Electra. To answer this question, we consulted a paper written by TIGHAR radio expert Bob Brandenburg. The paper includes specifications of the capacitors in the Electra's radios. The highest capacitance discussed in this paper is 4000 picofarads (.004 microfarads), far too low to match the artifact's capacitance.[4]

1938 Steward Warner Radio, Model 1865, with
two bathtub capacitors installed[5]
The possibility this was an Earhart artifact, while growing remote, had not entirely been ruled out. There were numerous other electrical instruments on board the Electra that undoubtedly used capacitors. More research was therefore necessary to see if specific data were available on when this capacitor was made.

The subject of this research would again be the inscription, which had, after all, provided more than simply a maker and some electrical specifications. It had also provided a part number: 630B

By fortunate coincidence, a combination of old radio part store catalogs available online, and some original Aerovox catalogs available on eBay allowed us to survey detailed product information from a representative sample of the years in which Aerovox was in business.[6]

The conclusion from this survey is that the capacitor most likely was made no earlier than circa 1947, too late for any connection to Earhart's Electra, which was lost in 1937.
1947 Aerovox Catalog

In the Aerovox catalog for 1947, there is listed a Type 630 - 600 v D.C. Capacitor. It is listed under the more general category of Type 30. Under this listing there is a .5 microfarad capacitor.

The dimensions of the 1947 Type 630 are:
Length: 1 3/4 inch
Width: 1 inch
Height: 7/8 inch

 The Nikumaroro capacitor is a .5 microfarad 600 volt D.C. capacitor, labeled "630B". Its dimensions are:
Length: 1 11/16 inch
Width: 15/16 inch
Height: 13/16 inch

All of these measurements meet the 1947 Aerovox catalog specifications to within 1/16 of an inch.

1947 Catalog page with 630 Capacitor
In examining 1930s Aerovox catalogs and numerous 1930s Aerovox advertisements, we were unable to locate any capacitor that matched the 1947 specifications.

A 1933 advertisement showed that Aerovox was then manufacturing this general type of capacitor, but in 1933 the length of the closest equivalent ran to 2 1/2 inches, much too large. In addition, at 400 volts maximum, the voltage was too low.

1933 Type 60 Capacitor

In 1935, a 600-volt bathtub Type 60 capacitor was advertised, but again the length is 2 1/2 inches and the capacitance is too low.
1935 Type 60 Capacitor

By 1945, Concord Radio Corporation advertised an Aerovox Type 630 capacitor with the correct capacitance and voltage, but at 2 1/16 inches, the length is still greater than that of the artifact.

1945 Type 630 Capacitor

There seems to have been a very brief window around 1947 when the Type 630 Aerovox capacitor was manufactured to the precise length, width, height, capacitance, voltage, and not least of all, part number, of the Nikumaroro capacitor. Only the 1947 Aerovox catalog listing matches all six of these specifications.

To a fair degree of certainty, then, we can assign the date of manufacture of the Nikumaroro capacitor to about the year 1947, perhaps a little earlier or a little later. Even if documentation were to surface, showing that a handful of 630B capacitors with the specifications of the artifact were made in the 1930s, that still would not help to distinguish this artifact from those we know were made in the 1940s.

Loose Ends

There are, however, still a few unanswered questions about this artifact. If the capacitor did not come from the 1930s, as it almost assuredly did not, then who brought it to the island, and why? Its most logical origin and function would seem to have been as a component in the radar equipment from the Coast Guard Loran station, active from 1944 to 1946.

Additional research indicates that this hypothesis, too, may be flawed. We noticed that Concord Radio Corporation's 1945 catalog listed, distinct from the Type 630 capacitor, several "Commercial Grade Capacitors... used by the Army, Navy and commercial communication companies."  None of these bears any resemblance to the artifact. The 1947 Aerovox catalog lists "High-Voltage Transmitter Type D.C. Capacitors" that were specifically made for transmitting, as opposed to just receiving. These are exactly the type of capacitors that would be ideal for a Loran station.
1947 High Voltage Aerovox Capacitor

The bathtub style of capacitor, by contrast, seems to have been manufactured for use in commercially available shortwave radios (see the Stewart Warner example, in the above photo). The Nikumaroro capacitor, therefore, seems most likely to have been something found in someone's personal radio set, not in a commercial-grade installation for the Coast Guard.

The Coast Guard Loran station was dismantled and abandoned in 1946. While it could be that someone from the newly arrived Loran cleanup crew left a personal shortwave radio with brand new capacitors on the island, there are a few other possibilities.

In an email exchange, Tom King commented:

"There were American connections to the Phoenix Islands after the War, right up to the time of the colony's abandonment. There were American anthropologists who studied some of the colonies and their end-times.. I also don't know when the operation on Canton closed down; it may have been '48 or '49 or even later. So I suspect that there were plenty of post-Coastie opportunities for the Aerovox to have gotten there. Well, maybe not 'plenty,' but 'some,' anyhow."

One final mystery is: what does the "B" in 630B stand for? From information supplied by the 1966 Aerovox catalog, it would seem that the letter B signifies that the capacitor terminals were located on the hermetically sealed bottom side. This would make sense. Since the bottom side is mostly absent from the artifact, as are the terminals, and since all bathtub capacitors we have seen had terminals, the logical position for them to have been located was on the missing bottom side.[7]

What We Learned

There are numerous odd artifacts on Nikumaroro, many of them lying on the ground in plain sight. The Zimmerman Object, found close to the capacitor and discussed in Tom King's article below, is a perfect example. The capacitor is another. Most of these artifacts could be anything from anywhere, but unless we collect, catalog and investigate them we will never know. Even after analysis is complete, we may still never know. The effort to run these to ground, what Richard Feynman called "the joy of figuring things out," can still be rewarding, even when the end of all our searching is to say that this capacitor does not show anything one way or the other about the hypothesis of what happened to Amelia Earhart.

The process of "finding out" is a useful training ground in itself for the analysis of future artifacts. At least, it was for me as I look back with fond memories on my visit to Nikumaroro in 2015.

[1] International System of Units (SI), French Système Internationale d’Unités,  international decimal system of weights and measures derived from and extending the metric system of units. Adopted by the 11th General Conference on Weights and Measures in 1960, it is abbreviated SI in all languages.
[2] Decisions and Orders of the National Labor Relations Board, Volume 28, 1941.
[3] Wikipedia article on AVX.
[5] See http://antiqueradio.org/StewartWarner1865Radio.htm
[6] The archive of Allied Radio and Electronics Corporation proved especially helpful in this regard. A nearly complete set of catalogs for this company may be found online at http://www.alliedcatalogs.com/catalogs_main.
[7] Since all Aerovox electrolytic capacitors were hermetically sealed, the bottom should have survived. It is possible this bottom portion was cut away by some curious colonist (or by someone else) at some point in the island's British colonial period. When the bottom portion was removed, it probably released into the Nikumaroro environment a small amount of toxic substances known as PCBs (polychlorinated biphenyls).
See http://www.solacanada.com/UserFiles/File/PCB23_e2.pdf  for the relationship between old capacitors and PCBs. See www.southcoasttoday.com/article/20110331/NEWS/103310343 for efforts to demolish the Aerovox plant and decontaminate the site where it once stood.



  1. Joe Cerniglia, a Mac user, tells me that the images in this piece don't come up on his machine, and asks that this link be used instead: https://www.dropbox.com/s/uhjzk4mscagzq2i/aerovox%20capacitor.pdf?dl=0

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