I have recently acquired a Marconi Wireless Telegraph Co. wavemeter sold as circa 1912 (photos attached). My research has yielded absolutely nothing about this instrument. Jim Kreuzer says he has one like it on display in the Titanic diorama, and that they were made in both England and America, and that it is English circa 1912 - 1914. I've been told by an associate in GB that the little arrows scratched on the knob and panel are typical of WW-I wireless (began on 28 July 1914 and lasted until 11 November 1918). If correct, that might place it a little more recent than 1912.

I am keen to find:

* A photograph of the proper crystal detector (currently replaced with a Formo), so that I may fabricate an authentic replacement

* The wavemeter's model number

* Any other historic information about this type of wavemeter.

Many thanks for any assistance you may be able to offer.

Is that crystal supposed to be there at all? I have a couple of British wavemeters and they use lamps as indicators.

Thank you for your response Alan.

Without any historical information, it's difficult to know much about the original detector. I'm thinking glow lamps may be more appropriate for CW than spark transmissions, as an operator wouldn't be able to hear CW transmissions in headphones without a BFO or modulated carrier. There are some clues however.

There is a hole in the panel partially visible under the detector stand (not the cup), so something else was likely mounted there at one time.

A three-position tap switch is mounted on the right hand corner of the panel. The legend is: 'B', [nothing], and 'M'. My guess is, that the 'B' position connected the battery to the buzzer circuit, or if the original detector was Carborundum, it may have turned on the detector bias voltage. The unmarked position may have selected the panel mounted detector, or been the battery off position. And the 'M' position may have been for selecting a magnetic detector attached through one of the two pair of binding posts. The other pair of binding posts may have been for headphones. Without tracing the wiring, it's difficult to be sure. Plodding forward with research today, I did learn a little more.

I found a photograph of a similar 'Marconi's Wireless Telegraph Co. Wavemeter 1906-1916' (photos attached). It appears to have a Carborundum detector, but it doesn't look original. There are other significant differences too.

I also found some of J. A. Fleming's early writings that may provide a little additional insight:

Wireless Telegraphy for Marine Inter-Communication June 10, 1910

Wavemeter--A wavemeter is provided to enable the transmitting circuit to be correctly adjusted to the
international waves of 300 and 600 metres. It consists of an inductance coil with a fixed number of turns
connected to an adjustable condenser. Across the condenser is shunted a high resistance asymmetrical crystal
in series with a double-head telephone. The condenser is adjusted until signals are loudest in the telephone. A
table affixed to the lid of the wavemeter gives the wavelength corresponding to each condenser reading. The
range of the standard apparatus is 200 to 800 metres.

See also:

Thermionic Tubes In Radio Telegraphy And Telephony; John Scott Taggart

CHAPTER XII.

VACUUM TUBE OSCILLATORS, WAVE-METERS, CAPACITY METERS. AND OTHER MEASURING INSTRUMENTS.
Pages: 336 - 339


So the mystery continues....

Thanks again for any additional sagacious information you may be able to provide.

This extract from Rupert Stanley's 1914 Text Book on Wireless Telegraphy" may be relevant.
Edit: I hadn't noticed that the illustration was of a Telefunken model or I'd have edited it out.

Anan, thank you very much for your insightful and most relevant input. And thank you also for referencing Text Book On Wireless Telegraphy, By Rupert Stanley. Lot's of interesting information in that august tome.

Given the crystal detector in the photograph of Wavemeter No. 59180 above (not mine), with the two vertical clips, and also the instructions on my wavemeter's card (attached), it would seem that the Carborundum crystal detector mentioned in the text you kindly provided operates un-biased, and may indeed be the original design. I hadn't expected that at all. I was expecting something turned from brass. It's certainly easy enough to fabricate that sort of crystal holder from sheet steel, or more likely stainless. (Incidentally, Wavemeter No. 59180 is rumored to be one used by professor Robert Jack who broadcast New Zealand's first radio program November 17, 1921.) However, with a serial number 10,385 higher than mine, and it's arcane added roller-switch, the detector of Wavemeter No. 59180 may not be exactly representative of the original one fitted presumably at Marconi's New Street works on my wavemeter. And there are still the issues of date of manufacture and model number.

So, while the mystery continues, I believe our collaboration is beginning to make some progress toward solving it.

Thank you again for your most welcome and kind help.

I've examined the wavemeter detector mounting hole pattern a bit
closer (through the buzzer door with a light), and this is what I've
found (I hope this ASCII "drawing" appears correctly formatted for
you):


4 ~1/16" Dia. Holes:
|
V

O -------------------
O -------- ^
^ |
| |
7/8" or 0.9" 1-5/16" or 1-1/4"
| |
v |
O -------- v
O -------------------

With about 1/4" between each pair of holes.
(Center-to-center dimensions)

I believe this hole pattern to be original at the time of manufacture.

I have received the attached photographs of MWTCo wavemeter detectors from three knowledgeable associates, none of which appear to require four mounting holes.

So far I've not really seen any detector that might require two pair
of mounting holes, so the search goes on.

The support and camaraderie of the antique wireless enthusiast
community is really quite gratifying and remarkable.

I once had a large wavemeter collection which included one like that shown with the earphones on the left. The two clips, which held a piece of carborundum were typical. The mineral and holder shown in one wm between the clips is from a WW 1 marconi military set.
i would just copy the clips.

will Jensby

The little arrows engraved on the panel and the knob used to mean that the item was originally used by the Government.

Thank you for the information, Will.

I had reached the same conclusion that you did about the two-vertical-steel-strip type of crystal detector mount. And then on closer examination, I found two pair of original mounting holes in the panel where each end of the original crystal holder had been originally fitted. (I made a very rough sketch of the original mounting hole pattern above.) It's pretty clear that each leg of the two-vertical-steel-strip type of crystal detector attached to the panel with but a single screw. So at this point I'm at a loss to find any examples of MWTCo wavemeter crystal mounts from this era that used a total of four screws to attach to the panel.

If historical accuracy is important in restoring this example of one of the first pieces of electronic apparatus ever made, then I think I owe it further research.

Thank you for helping to clarify that.

I received a response on the Antique Wireless Association mailing list from Bill Burns who kindly provided this link: http://en.wikipedia.org/wiki/Broad_arrow#Use_for_British_Government_property. Here's what it says:
So it would appear that the broad arrow marks are not indicative of the age of this piece.

I've attached 2 photos of the exact wavemeter that Will, W0EOM mentioned. It has a Marconi Wireless Telegraph Co of America tag. The 2 detector clips are made out of unplated brass. On the other Marconi Portable wavemeter (Jenkins) I think the clips are quite likely nickel plated brass. Note that the clips on my wavemeter are set diagonally across the corner, whereas the other one and the book picture show the clips parallel with one side. Even though yours has 2 pairs of mtg holes, very possibly it also used 2 spring clips with extra screws used to prevent rotation.

I have also attached 2 photos of another Marconi wavemeter that I have that is missing the detector, but this one has 2 holes spaced 2.25" apart -- and I have no idea of what kind of detector was used. That one is also missing the buzzer and I didn't know what that looked like until saw the photos in this discussion thread. I have never seen 2 early Marconi wavemeters that are the same. There are many variations on placement of the parts and the design of the wood cases on Marconi wavemeters. I wonder if craftsmen assembled the Marconi wavemeters using schematics but with much of the mechanical layout left up to the discretion of the individual craftsman -- maybe using samples, but not detailed drawings. Pure speculation on why there are so many design variations.

Thank you very much for starting this discussion and sharing the photos of your wavemeter.
Larry

Larry, thank you for the information and insight you have kindly provided. Very much appreciated. Your Marconi Wireless Telegraph Co of America wavemeter is in remarkably fine condition. You are fortunate indeed to posess such a remarkably preserved museum quality piece.

There are several other MWTCo wavemeters shown in the Marconi 1996 Centenary catalog reproduction.

There is also an instruction leaflet (French) for a 1906 MWTCo wavemeter on the Museum of the History of Science, Oxford web site. You can search their vast collection with large images too.

The photograph of the wavemeter you provided with the 2-1/4" spaced holes is similar to the one in the photographs I'll attach to this message. At least the holes are similarly spaced.

I've been thinking some more about the four detector holder mounting holes issue. And, given the design of the two vertical strip crystal holder, it is entirely possible that the additional holes may have been provided for adjustment purposes to accommodate larger or smaller chunks of galena or Carborundum. (I presume Carborundum was originally used, as it would seem that a cat's whisker might be required for galena.) Now with the information you provided about the strips being made or brass and possibly nickel plated, I may be able to fabricate a replica crystal holder. Without wanting to impose, it would be good to know the dimensions and thickness of the strips.

I'll have to agree with you about never seeing two identical early Marconi wavemeters. Curious.

Marconi I'm pretty sure never used galena, and I believe always used adjustable bias with carborundum. I'm out of range of reference material here at work, but cerusite rings a bell as Marconi's favored detector when bias wasn't available.

Of course owners could use whatever they liked, and Marconi ship operators could carry their own pet minerals with them, for use as soon as they were out of sight of supervisors.

Larry, Thank you for the link to the early Marconi catalog -- I was not aware of that. I see that on page 44 is a description of carborundum crystals where it says for wavemeters there are "picked crystals" not in cups. As wavemeters are used in close proximity to transmitters being tested, high sensitivity is not needed so biasing the carborundum seems unnecessary. I was aware of the MHS Oxford website and have visited there many times.

The wavemeter you show with the widely spaced holes has a detector on the other side so those holes must be for something else. However, on my wavemeter with those widely spaced holes, there is no other place for a detector. Since Marconi made so many wavemeter variations I have wondered if they ever made ones without a detector but only having a buzzer for use in checking receivers. For the early Marconi stations the TX and RX locations were spaced 10-20 miles apart, e.g Bolinas and Marshalls, CA (where many original buildings are still standing). So it may not be be completely unreasonable to have a dedicated wavemeter at the RX site.

Dimensions of the brass detector clips on my other wavemeter are: 0.020" thick, 0.460" wide, 1.12" high, base 0.40" long. The 45 degree bevel at the top is 0.13" along the bevel. I'm glad to provide this info.

Larry

Thank you for that interesting bit of information, Alan.

The desire to use galena, which requires a cat's whisker, as a detector by the owner of this wavemeter does indeed appear to have motivated the detector modification. That, coupled with the information you provided about Marconi and cerusite, almost ligitmizes the historic modification as evidence of rebellion against Marconi dogma.

It appears that Marconi didn't use galena in his detectors, preferring carborundum and cerusite instead, the latter not requiring a bias voltage.
<http://books.google.com/books?id=kyUyAQAAMAAJ&vq=cerusite&dq=cerusite%20marconi&pg=RA2-PA55#v=snippet&q=cerusite&f=false>

So, it would appear that the previous owner of the wavemeter sought to work around Marconi's galena prohibition, perhaps sometime in the 1920s, by fitting the Formo galena detector.

It just amazes me how so much can be accomplished by a knowledgeable and sincere community of like-minded "brother's of the spark" so to speak. Thank you very much for your help.


Further research:
http://books.google.com/books?id=PkTOAA ... ni&f=false

http://books.google.com/books?id=Ck9IGg ... ni&f=false

http://books.google.com/books?id=kyUyAQ ... ni&f=false

http://books.google.com/books?id=qv1B0W ... ni&f=false

http://www.ebooksread.com/authors-eng/e ... -hci.shtml

http://www.ebooksread.com/authors-eng/r ... -hci.shtml

http://books.google.com/books?id=IMUUAA ... ni&f=false

http://dictionary.reference.com/browse/cerusite

http://franklin-sterlinghill.com/palache/cerusite.stm
Cerusite forms clear white or gray crystals encrusting galena. It
was found as a scarce alteration product of galena at Sterling
Hill. The measured crystals, collected there in 1905, are
prismatic parallel to the brachyaxis (figure 63), with a richly
developed zone of brachydomes. Others are twinned in the ordinary
cerusite habits.

http://dictionary.reference.com/browse/galena

Mike Feher has kindly provided photographs of his wavemeter's detector (Mike owns the Professor Jack wavemeter mentioned above), and this explanation of the four holes used to mount the two-vertical-strip crystal holder:


So, one panel mounting hole was used to attache the vertical strip to the panel, and the other to permit a tab on the foot of the vertical strip to penetrate the panel, so that a connecting wire might be soldered to it. Brilliant! Mystery Solved!

It's not evident at all from observing the crystal mounting strips from the top that they have a solder tab that penetrates the panel. Presumably

ADDITIONAL QUESTIONS:

In my ceaseless quest for ever more information about this wavemeter, I have asked these additional questions of Mike Feher:

1. Does your wave meter have what appear to be galvanized steel
battery holder straps attached to the bottom board? Mine has two
(with associated end-stops/contacts at each battery position?), one
rounded hoop that appears that it was intended for a single cell with
its longitudinal axis parallel with the front, and another wider strap
that looks like it may have held a battery of 4 cells in place with
their longitudinal axes perpendicular to the front. (Photographs
attached) It's also possible that the single hoop may have held one
of those turned-wooden "bottles" that contained spare crystals, as the
contents of that hoop would have been accessible through the buzzer
door. The curious thing is, that there don't appear to be any wired
battery contacts associated with these hoops or anywhere else for that
matter. [Three photographs below]

2. Can you sketch a schematic of the circuit? Mine has been
modified, and it would be good to know how it may have been originally
wired. Does the three position switch with the 'M' and 'B' markings
apply a bias voltage to the crystal when placed in the 'M' position. I
presume the 'B' position energizes the buzzer.