On 3/19/24 18:09, Robin Szemeti via Emc-users wrote:
TWT's are still widely used for satellite uplinks ... a typical broadcast
uplink will be a pair of 400W tubes at around 14GHz .. one running to the
antenna, one running to a dummy load, ready for instant changeover. The
bigger tubes will run 750W.. There are no affordable solid state devices at
those power levels at those frequencies. Surplus TWT's occasionally appear
on the surplus market.
They are also highly prized by radio amateurs for "moonbounce" .. the path
losses involved in bouncing a signal off the moon to another station are
"significant" ... you generally want all the power you can get. The moon is
quite far away and oddly enough, spheres of dust and rock with a fairly
random surface are not exactly great reflectors ...
On Tue, 19 Mar 2024 at 21:49, Dave Matthews <n36...@gmail.com> wrote:
We had some training on traveling wave amplifier tubes, referred to as TWAT
tubes back in Nike Hercules tech school in 1977.
Dave
ex MOS 22L
On Tue, Mar 19, 2024 at 4:35 PM gene heskett <ghesk...@shentel.net> wrote:
On 3/19/24 14:15, Robin Szemeti via Emc-users wrote:
I purchased a couple of large travelling wave tube amplifiers in an
auction. I phoned the US company to ask about schematics and a manual
...
"can we have the serial numbers please?" ... "sure ... " "great and
what
date did you sign the ITAR agreement?" <click brrrrr...>
I had a student following me around in his spare time in the 70's who
got interested in moon bounce, finally did it on 2 meters with an array
of log-periodic antennas rigged on servo mounts to track the moon as it
came above the horizon. I understand the losses on 2 meters were a
hundred thirty db +, but that array was bigger than his house and wind
demolished it so I expect he went to a higher frequency so the arrays
were a more manageable size. Don't know what became of him as I left
the area in favor of the Chief's chair at a bound to fail NM tv station.
Market wasn't big enough and my salary was bankrupting them. It went
bust and the assets sold to a bigger station a couple months after I
left. But they were on the air all but about a day during the time I was
there. No trace of the station site in the sand above the San Juan River
the last time I checked on GE 30 years ago. An NBC bonus station, bonus
meaning we got the network signal for free, but also didn't get paid for
the commercials aired. NBC was then hosting the MDA thing over the long
labor day every year. And I was there making sure everything was working
for the 15 minute cutaway for local station efforts, when a greyhound
buss with KISS painted all over it pulled into the parking lot, unloaded
there gear and volunteered to spend the rest of the day playing for
Jerry's kids. I got handed their mixing console. Told which jack to get
a line out and I could mix to suit me. So I can say I spent an afternoon
mixing for KISS when they were just getting started. I left a couple
months later, walking away from a $20,000 bath in real estate amoung
other things, wandered into a station in Redding ca, hired instantly
based on the CET after my name, and before I'd found all the light
switches the then Chief had a heart attack and took 18 months off. He
eventually came back and it was plain my chance of officially getting
the job I was doing, was null, so I left. I sign on to Key systems, got
sent to WTSF in KY, spent a year teaching their golden boy all about
klystrons. So I next went 150 mi NE to WDTV where I finished out my
working years, lost my wife she couldn't stand WV, married a local old
maid school teacher 3 years later. Good neighbors, place paid for 26
years ago. Lost my 3rd to COPD 4 years back. I'm here till I ain't.
I've done pretty good for an Iowa farm kid with an 8th grade education,
I quit school at 14 and went to fixing tv's when they were new. Been
chasing electrons to make them do useful work since. So if someone
mention a 2A3 vacuum tube I know precisely what they are referring to.
If some of what I write sounds off the wall, I've probably BT & DT.
Take care all. and stay well.
Its been an interesting ride, I was doing things with tubes when
transistors were invented..
I presume they've been disposed of in unsalvagable condition... Like if
glass, smashed into small pieces by a 16 lb sledge. If they ever trace
them to you, pix of the destruction may help. But not if ceramic body's
instead of glass. Any dust from destroying them is lung cancer seed.
Very 100% dangerous. Do not break, grind or file.
And that auction has been advised of its illegality. It is a tech
similar to klystrons but with a more distrituted and much broader band
applications that because of ITAR has faded away into a technical info
vacuum. I've not heard of a twt since the cold war warmed up in the late
50's and we started building ICBM's in everybody's back yard. I was
there, help build 3 titan ones in the middle of nowhere South Dakota.
On Mon, 18 Mar 2024 at 17:45, gene heskett <ghesk...@shentel.net>
wrote:
On 3/18/24 11:28, Todd Zuercher via Emc-users wrote:
Gene,
Well 2 things I've observed since posting that, Todd. the pix is
identical for a 3 kilohertz version on amazon for about the same
price,
once adjusted to us dollars . So I'm wondering if aliexpress added an
extra 0, they rarely know what they are selling anyway.
And since it showed up on amazon too, I'm wondering if the ITAR rules
have been relaxed.
Here is the highest HP rated amazon offering. 15kw 20hp for about
$1200:
<
https://www.amazon.com/Mollom-220V-15KW-20HP-Frequency/dp/B0CQBZ4FZN/ref=sr_1_52?crid=30GVV1U3R7JUA&dib=eyJ2IjoiMSJ9.5mKofR2CvOgdLO3tCtLjmKysBbvC8T8oTt4SNyV7-PqBQ6UsvOrsvyppX7rBUpjT2IZZ2mAWKRkL0H1nJj5MGcPBTDsP2EbqZePAsB09iFXxVTemY7Dr4c-fOZHZLdaaBQulJLMrOYJl5bQBZyyubX0LkNc-DuFlyrVam8hlnFXUx5O0mASax2WBIToQk1TnTgzTo9aSvbn0kcp1wxgKUbqJsSefz-wM0iZmaooVN5zTcqmgr8SzJWLCsHsviwy3aYCLB0dDN-JFW7Rw6Cp1GUTSqURhr6UCPywhkuSnYI0.1sKFN_5H6kH9Ju3mlK1mAlKX2LaJ6eM0Et-7LWB83CI&dib_tag=se&keywords=high+speed+high+horsepower+vfd&qid=1710778937&sprefix=high+speed+high+horsepower+vfd%2Caps%2C82&sr=8-52&ufe=app_do%3Aamzn1.fos.765d4786-5719-48b9-b588-eab9385652d5
I'd think that could run your 4 pole motor at 800hz just fine. UNK and
unstated in the adv is the control range so I would scale the 3k range
so max from the controller would only get you the rated speed at the
motor. But I don't have to tell you that, you've been dealing with
those
sorts of problems with that machine for long enough this ought to be
the
best answer. Sometimes this is self limiting, higher frequencys run
into the motors inductance, coil current falls and the motor actually
slows down, my Sheldons max usable speed while running a 70 yo motor
that never saw a vfd until me is about 200 hz as the coil current is
under an amp at 200 hz. 3.7 amps at 60 hz. OTOH it can run it at 5hz
long enough to finish the job and still lay my hand on that motor w/o
discomfort from the heat.
As for needing a new one, the usual failure is going to be the line
stage filter caps which often will have a note in the docs someplace
to
the effect that they should be replaced at 5 year intervals, however
the
smaller ones that don't have braking resistors are actually 4 quadrant
controllers, meaning a quick reversal will overvolt those filters for
a
few milliseconds as they do the reversal, they suck that power out of
the motor stopping it, storing it as overvoltage in those filters,
then
as soon as the new direction is applied use that stored energy to spin
the motor back up in the other direction, so the overvoltage is not
present long enough to damage them, but actually contributes to
maintaining the "forming" of those caps so they live longer. The 1.5
hp
rated el-cheapo clone running the 1 hp in my Sheldon lathe is now
around
9 years old and can still reverse that motor and its 40lb 8" 4 jaw
chuck
in under 1/3 second at 100 revs. Overshoot at 100 revs is .24 turns
from
100 rpm to stopped. And the shop lights don't blink. Its all in the
.hal
file if interested. No circuit breakers in any danger of tripping as
all
the excitement is in the vfd and doesn't involve the wall power. Just
give me a yip.
These aren't toy's, they can kill, so give them the respect such
killers
deserve. But I don't have to tell YOU that.
Take care & stay well Todd.
In all honesty I wouldn't mind knowing more about your VFD source you
say you want black listed. I'm so sick of trying to track down high
speed
VFDs that I'm almost tempted to pay the machine manufacturer's
ridiculous
3X normal retail list price markup the next time we need a new one.
We
occasionally have needed a replacement VFD capable of running about a
15kw
4pole router spindle at up to 24krpm (that is 800hz output, most
drives
seem to max out at or are limited to 500-600hz output.) The last time
we
tried to order a new drive with these specs it was put on back order
for
more than 1 year before we canceled the order. (We canceled after the
delivery date had been pushed back 3 months for the 5th time.) Then
we
bought a used one off of ebay. (Tracking down a used drive on ebay
with
documented proof of the correct high speed firmware, when the sellers
have
no clue, is also another annoying trick to perform.)
That is what we get for doing unusual things Todd, Goes with the
territory. The trick is getting the info needed to make an informed
decision from someone who has NDI what those numbers represent. They
simply don't speak the language. And it can be very frustrating.
Todd Zuercher
P. Graham Dunn Inc.
630 Henry Street
Dalton, Ohio 44618
Phone: (330)828-2105ext. 2031
Cheers, Gene Heskett, CET.
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law
respectable.
- Louis D. Brandeis
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Emc-users@lists.sourceforge.net
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.
Cheers, Gene Heskett, CET.
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
_______________________________________________
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users
_______________________________________________
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users
_______________________________________________
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users
Cheers, Gene Heskett, CET.
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
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