Thanks Dave H., for your candid view and possibly explanation of the
GE/ETO dealings. Erbtec also made some nice looking equipment, as I
was a potential customer in those days, working in industrial RF
power (dielectric heating at 13.56, 27.12 and around 35 and 90 MHz).
Actually it wasn't necessary to go into all the details of it, but I
understand how persistant badgering causes one to need to explain it
better - the woes of email lists, where if one doesn't explain
reality or defend what is truthful, others can continue to make up a
version and post it repeatedly for years. When you ignore it, it
doesn't go away, but continues to confuse people who are just
entering this business. In some ways, the days of RF engineering
excellence have fallen a long way into being like the glass audio
amplifier business, scary thought eh?
Usually contracts such as this OEM agreement get changed for all
sorts of marketing, pricing, legal, delivery, sometimes even for
meeting diabled american business act quotas, minority vendors, you
name it. Technical is hardly the sole reason that contracts get
awarded anymore. I have to go through all sorts of hoops to get
things awarded soley on technical basis, often RF systems are
technically compromised due to business decisions.
An example comes to mind at the CERN particle accelerator in Geneva,
where one of the RF plants for the Super Proton Synchrotron uses a
set of 4 water cooled Seimens RS2004J tetrodes, each suppplying 125
kW CW at 200 MHz, combined to get 500 kW. Then these are combined to
get one MW of CW power. I have some photos I took of the system 5
years ago, with impressive coaxial hardware made by Spinner. However,
when they went out for bid on a second system at a later time,
business reasons (not technical) awarded it to a different vendor,
and they ended up with 16 air cooled 35 kW TV tetrodes
PhilipsYL1530s, combined to get 500 kW, then a second row of the same
for the MW level. The engineers there were not happy to have to
maintain two completely different systems, esp all those air cooled
cavities which get dirty and require regular PM to clean the finger
contacts, etc. However, they have lived with it for years, and now it
comes to haunt them, as Seimens was sold to Thales, and Philips got
out of it, and their tubes became Amperex/Covimag/Richardson parts.
Hams on this site should try and understand this, as some seem lost
in this imaginary world where GE is still run by engineers and has
people who really know RF, like they did when they and RCA were
making transmitters.
I have been reading a boring but very specific and detailled account
of early wireless communications in the US, I think it is called
Continuous Wave. In it there is much to learn about GE and their
contracts dealings, as early as the World War I era. They were trying
to sell Alexanderson Alternators to big stations, and Marconi was
trying to gain exclusive rights to market them. Then stepped in the
US Navy.
Read the book to learn how it played out, and where RCA came from.
Perpetuating illusory realities such as below is self promoting for
the writer, but does nothing to educate RF technicians, engineers,
and hams who read it:
>** Interesting, Dave. I apparently assumed wrongly. My take on the
>issue is that GE knew more about the 8877 failure problem in ETO
>amplifiers than is assumed by some. GE's awareness of the VHF parasite
>problem goes back to 1935, when GE engineer G. W. Fyler wrote about the
>problem in "Parasites in Transmitters" in the Sept. issue of the IRE
>Journal.
>
>....
>The story I got was that GE was concerned with the tube failure rate.
>- After the QST article "Improved Anode Parasitic suppression for Modern
>Amplifier Tubes" was published in October, 1988, I received a
>hand-written letter from Dick Ehrhorn about the article. He concluded
>that if kaput 8877s/8874s from Alpha amps had failed due to
>gold-migration - as per the Oct. '88 QST article - , Eimac would not have
>replaced such tubes under warranty because Eimac knew that gold-migration
>is caused by an oscillation condition, Since Eimac replaced all failed
>tubes, Dick assumed that the tubes failed from a manufacturing defect.
>However, years later, Dick E. apparently began doing his own hi-pot test
>for gold-migration using the W6IHA procedure. Subsequently, Dick sent me
>an e-mail note about having 150 gold sputtered tubes on hand at his
>plant. When I mentioned the 150 figure on AMPS a couple of years later,
>Dick said I was going insane.
> >
And so on it goes....
At 8:17 AM -0500 3/4/03, amps-request@contesting.com wrote:
>One problem is that when I was taking electronic engineering c. 1960,
>there was no course that covered parasites. The only information on the
>subject in the department's library was apparently Fyler's obscure Sept.
>1935 article in the IRE Journal.
The same writer requested this article and/or the 500 KW WLW
transmitter article, which go together from the 1935 IRE journal,
from me a number of years ago.
A few weeks ago, I posted a series of references to parasitesand
flash arcs in tubes, from various journals, some of which were nearly
the same era as the Fyler/GE report on building a 500 kW rig. One was
dated 1932 and it was not by anyone at GE. In 1941 a report was
written which explained failed filament wires based on experiment and
theory, and parasites were not the source, only LC ringing of the B+
circuit after a tube flash arc.
I find it quite odd that an EE department library only had the one
IRE paper on parasites. Even QST was printing articles on using a
resistor and inductor as a suppressor many years ago.
I am not trying to point that parasitic oscillations don't happen,
but that people should not be so naieve (sorry for the spelling) to
believe everything that is posted on the internet! My advice would be
to grab a nice fundamental tube RF engineering textbook like one of
Termans, and read about tubes and RF circuits, then form your own
opinion.
Thanks for the bandwidth,
John
K5PRO
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