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Diary Entries

Part Two:
March 1935 - April 1935

(p. 109)

3/1/35 - I had a discussion for about an hour today with Dr. [Vladimir] Zworykin. I described our plans for making single-stage multiplier tubes to reduce input loading.

Last Monday Mr. Nelson came to me asking if he could have a half hour's job done in our workshop, as he was in a big hurry for the job and could not take the time to get it through the Equipment Development Section. I told him it would be all right.

3/13/35 - A lengthy discussion was participated in by Mr. Ritter, Mr. [D. F.] Schmit, Mr. James, and myself concerning plans for research on television projection and pick-up tubes.

3/15/35 – [Leon S.] Nergaard and I visited the RCA Victor plant yesterday. We discussed with Diehl and Schraeder the need for measurement equipment for use at wavelengths less than one meter. They both agreed with me that this work was very necessary; but Diehl did not feel that they were in a position to undertake it because of press of other activities, and suggested that it was in the nature of research and should be done by [Elmer] Engstrom's group. He and I then called on Engstrom to take the matter up with him. Engstrom agreed that the work was very necessary end that he had already been authorized to carry it out, but as we all agreed that the work of one or two men for a year or more would be required, he did not feel that he was at present in a position to undertake it unless he was able to take someone off of other work. The matter was left that he will give me a statement as to what he plans to do, so that I will be in a position to take further action. Nergaard and I arranged with Diehl and Schraeder to supply them with some thermocouples and with some diodes for measurement work, and they will try to extend the calibration of thermocouples to wavelengths of the order of 3 meters.

Diehl and Schraeder showed us their measurement equipment for use at longer wavelengths.

I discussed with [George L.] Beers his work on receivers for 70 to 80 cm wavelength. He informed me that they had found that the input loading of the 954 [electron tube] is very serious at these wavelengths. I told him that this agreed with our experience.

We discussed for a few minutes the magnetron work with Braden and [E. G.] Linder. Dr. [Irving] Wolff was not in.

I called on [R. S.] Holmes, of the Receiver Development Section, and saw their curve tracing apparatus. Turner, working with Holmes, told me their measurement showed a frequency change with plate voltage on a 955 [electron tube] which was in the case of a Hartley oscillator, in the opposite direction to that experienced at low frequencies. I explained this as being due to the change in input capacitance with plate voltage due to change in transit time of the electrons between grid and plate as analyzed by Ferris very recently. The magnitude to be expected from this seemed adequate to account for the change of frequency. Turner seemed thoroughly satisfied with this explanation.

Dr. [Donald] Luck explained to me in considerable detail their new system for transmission by the use of pulses of' very short duration.  He asked me to forward him any comments I could concerning the tube or spark method for transmission. I outlined this system of Dr. Luck's to Mr. Ritter and Mr. Schmit today.

(p. 110) 3/18/35 - I discussed with Nergaard today the limitations of Luck's short-pulse system for radio transmission, and I asked him to make an analysis of it.

I discussed with Zalesak and McClair today the negotiations I carried on with the Heany Laboratories, so that they will be in a position to prepare an affidavit for me to sign describing my activities.

I discussed with H. C. Thompson and Clark the design of the new exhaust apparatus. We agreed that this is substantially complete now and will be turned over to Morrison.

Dr. Miller called me today concerning the semi-conductor work. I made an appointment to discuss this with him Wednesday afternoon, March 20th.

3/25/35 - I discussed with Dr. Shaw today the matter of the effect of ionization in exhaust on the rate of clean-up of gas after exhaust. I told him that I thought a great deal of the effectiveness of a given exhaust schedule depended on this phenomenon. I propose to discuss it further with him some time.

I discussed with T[erence]. M. Shrader the matter of making smaller acorn tubes than at present with a view to finding out how far they will be able to go in ultra-short-wave reception. Shrader felt that it would be possible to make tubes of approximately one-third the present linear spacing giving reception at about 25 cm wavelength.

I told Shrader about Ferris' calculations of the effect of transit time on input capacitance, and about the measurements of the effect of capacitance on frequency change at Camden. I explained to him something of the theory and told him that perhaps they will need to design their future r.f. [radio frequency] tubes with this property in mind.

4/1/35 - Last Friday I spent a couple of hours with Dr. Holst, of the Philips company, discussing the work we are doing, including our work on shot effect, short waves, and input loading. Dr. Holst told me something of the organization of their research laboratory in Eindhoven. which is about as follows as regards radio and vacuum-tube work: there are four groups headed by van der Pol, Osterhuis, DeBoer, and Clausing. Each group consists of, in addition to the group leader, approximately ten research workers, ten assistants, having an education approximately equal to that of our high school, and fifteen to twenty mechanics. Each group has its own workshop and facilities for making tubes. Dr. Holst said that they previously had more assistants for their research workers than they now have, and that their facilities were even more decentralized than at present. He stated that they had also tried to centralize facilities such as the workshop, etc., but found that unsatisfactory.

Dr. Travis, of the License Bureau, called on me today in connection with measurements of input loading. Ferris and I talked with him some time about the work and I showed him Ferris' check between experimental end theoretical values. We discussed Grimes' inability to check Ferris' measurements by his method, and suggested the difficulty was probably due to failure to by-pass the leads of the tube, and to the impedance in the plate circuit of the tube under test.

(p. 111) 4/9/35 - Yesterday I visited the Vacuum Tube Engineering Department of the General Electric Company in Schenectady at the invitation of G. F. Metcalf. Pike first took me through their laboratory and factory, and showed me their work on igniter-type tubes which apparently are largely replacing thyratrons where the current rating is above 25 amperes. Most of these tubes, and the thyratrons also, are now being made in metal-tube structures. In the thyratrons ordinarily the metal container is the shield grid, and in low-voltage diodes it is the anode only in high-voltage tubes do they use any considerable amount of glass. The advantages of the metal tubes are ruggedness, heat dissipating ability, compactness, psychological appeal to the industrial engineer, and eventually, it is hoped, lower cost. In some tubes the leads are made entirely of Fernico wire sealed through the special glass, though the general practice seems to be to use a butt weld with the Fernico only in the portion of the lead sealed through the glass because of the high resistance of the Fernico, about nine times that of molybdenum, and the cost of Fernico. In tubes which need to pass extremely high peak current, the seal is made to a Fernico thimble with the low-resistance leads welded to the inner and outer surfaces of the thimble. Pike showed me tubes made with the anode and cathode in the form of Fernico discs sealed directly to the ends of a glass cylinder. A simple butt joint seems to be perfectly satisfactory.

Metcalf then showed me his work on the receiving-tube metal construction, which is mostly at the present time further development work on the present commercial line. He expects in the immediate future to concentrate on new forms of receiving tubes in metal structures. He states that the glass-to-metal seal can be made with the Fernico by anyone, any girls in the factory, except glass blowers.

Metcalf also showed me a radiation thermocouple made by rolling out two butt-welded sheets of metal, of suitable material for thermocouples, to extreme thinness of the order of the wavelength of red light, and then cutting this up into strips for the thermocouple. The tube was made with a rock-salt window sealed to a silver cylinder by means of silver chloride, the silver cylinder being in turn sealed to ordinary lead glass.

Metcalf then showed me his work on beam tubes. I saw only one sample of tube, and two field plots on the tube and one curve of static characteristics. The tube consisted of a combined focusing and deflecting arrangement so constructed that the deflection was done at low electron velocity and arranged to give small line focus. With beam currents of 1 to 4 milliamperes, deflection sensitivities of about 1800 microamperes per volt were achieved. To accomplish this extreme care in lining up the electrodes was required. The modulation transconductance was low, of the order of 50 to 200. Metcalf has run into the same phenomenon as Harry Thompson has observed of the instability of an electron beam of considerable current passing along a long path. He had observed hysteresis but attributed it to gases present. I offered an explanation of the hysteresis not based on gas. Metcalf described an interesting arrangement for converter tube use in which the sensitivity of the amplifier was to be varied by changing the width of the focus while the signal voltage was applied to the deflector electrodes. I told Metcalf something of the work that Harry Thompson was doing along this general line and described his multiple-beam tubes used for negative-resistance devices, current less positive-grid tubes, and others.

Metcalf told me something of the early work on beam tubes and the origin of the metal tubes. It seems that he was given a group of about a dozen men and (p. 112) told to work on the problem of finding a new kind of radio tube. They tried gas-filled tubes, thyratrons, etc., beam tubes, then eventually hit on the metal-tube idea. Up until that time they were practically ready to go ahead with the beam-tube arrangement. The first metal tube, very similar to the present screen-grid model, was made-up a day or two after the Fernico metal-tube idea was first thought of. Within three months after that the General Electric Company had decided to go ahead with these metal tubes in their next year’s set program. I gathered that this was in the fall of 1934.

I discussed with Metcalf the possibility of our obtaining Fernico in various sizes and the special sealing glass. He assured me that we could obtain numerous sizes of Fernico sheet and rod, as well as eyelets, and that the glass could be obtained from Corning. I told him that we wished to use this only in our experimental work and not on development of metal tubes.

I discussed with Pike and Metcalf the probable future of metal tubes. I said that I did not see that the ruggedness or psychological appeal of the metal tubes was an advantage for the radio tubes, though it was, of course, for industrial tubes, as breakage is no problem in radio application. Any possible manufacturing savings were of no interest to me. The advantages of the metal tubes would have to lie in improved operation of the tubes, or the possibility of new kinds of tubes. As the only tube in the new line of GE tubes which is different from the glass tubes and which takes advantage of the metal bulb as anything other than a container is the "pencil" rectifier, this is the only tube which strikes me as being really worth while. In the future I have no doubt that valuable advantages will be discovered in the use of the metal construction, inasmuch as it offers a new and different type of structure.

4/17/35 - Today Major [Edwin A.] Armstrong, Professor Russell and Mr. Baker, of Columbia University, called on us. I discussed our work on input loading and high frequency measurements with Professor. Russell during the morning, and spent most of the afternoon with Major Armstrong. Kilgore showed him his high power magnetron, and I discussed our latest theory on input capacitance as influenced by space charge, and our high frequency work in general.

Yesterday I discussed with Mr. Ritter the matter of David Langmuir’s interest in our laboratory, and he told me it was all right to go ahead. I also discussed our interest in Hampshire, with the same approval. I pointed out that while we were staying within our budget now, it may be difficult to increase our activities without exceeding it, inasmuch as these activities were not budgeted. I outlined what I considered the new fields of research into which we should get, including light valves, television pick-up tubes, facsimile reproducers, and a study of the effect of positive ions in the region of potential minimum.  It was this last problem which I suggested would be suitable in the beginning for a man like Langmuir.  I told Mr. Ritter of our arrangements for a new exhaust man, and, also told him that I did not think we would need a new mounting girl at the present time. I discussed our need for an additional laboratory assistant beyond the one which will be provided by the change we had discussed before, and received a tentative approval on this. Mr. Ritter asked me to get in touch with [B.] Salzberg’s friend in the factory in this connection.

(p. 113)

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