The Daring Dufas wrote:
On 9/22/2013 5:17 PM, DerbyDad03 wrote:
The Daring Dufas wrote:
On 9/22/2013 10:17 AM, DerbyDad03 wrote:
The Daring Dufas wrote:
On 9/21/2013 10:53 PM, wrote:
On Sat, 21 Sep 2013 21:50:29 -0500, Dean Hoffman
" wrote:

On 9/21/13 7:22 PM, (PeteCresswell) wrote:
Specially LittleFuse KLK-15 as in http://tinyurl.com/kfs8gje

This thing is almost certainly blown (ohmmeter shows same reading with
or without fuse in circuit)... I'm looking at and looking at it, but
can't see any visible indicator.

There is none, right?

The indicator fuses I've seen have little windows on them.
Example he http://tinyurl.com/q3q65g6

They also make an indicating fuse with a metal plunger that pops out
when it blows. These are usually used in a holder with a sense rail.
The plunger pops out, hits the rail and indicates a blown fuse.
(light, beeper or whatever)


I had fuses like in some surplus gear that had a panel mount fuse holder
equipped with a clear cap having a bubble in it that the plunger popped
up into when the fuse blew. The little tips of the plungers on some of
the fuses were painted red so they would show up more easily in the
bubble but it was easy to tell if the unpainted tips were in the bubble
window of the cap too. I suppose that little fuse would work in a fuse
holder that had an electrical contact to turn on an indicator light. I
had some fuses under the dash in my van that had a tiny LED which would
light if the fuse blew. ^_^

TDD

Have you ever seen a motorized circuit breaker controlled by a 3-strike
relay? We had them in the LORAN-C transmitters I used to work on. These
transmitters were subject to the random arc which would trip the high
voltage breaker in the power supply.

Picture a large circuit breaker above a motor with a shaft the rose out of
the top. When the motor was energized, the shaft pushed the breaker handle
up, energizing the high voltage Power Supply. (25K VDC max, steady state at
15K) the motor would then spin back down retracting the shaft.

Controlling the motor circuit was a mechanized relay with a timer and a cam
that opened and closed the relay contacts. If the transmitter arced and
tripped the breaker, the cam would rotate 1 position, start a 30 second
timer and power up the motor which would close the circuit breaker. If 30
seconds went by with no more arcs, the relay cam would rotate back to its
"normal" position and wait patiently for the next arc. If another arc
occurred within those 30 seconds, the cam would rotate one more position,
power up the motor, close the breaker and once again wait for another arc.
If, within the original 30 seconds a 3rd arc occurred, the cam would rotate
one more position and shut down the power supply.

At that point, if everything else was working properly, other circuitry
would automatically power up the standby transmitter and switch the antenna
coupler to the standby unit, putting us back on air in under a minute.


Were you in The Coast Guard? Those transmitters put out some incredible
power but I seem to recall them being shut down only to wind up being
considered as a backup because of the possibility of GPS being jammed or
knocked out by solar flares. Heck, the government will probably wind up
with some sort of system like it if GPS were to turn out to be somehow
vulnerable. As tall as the towers were for LORAN-C, was lighting a big
cause of the systems going down and switching to backup transmitters? o_O

TDD

I spent a year at USCG LorSta Sylt Germany. Sylt is a resort island in the
North Sea with casinos, all variety of night life and nude beaches. I paid
for it with a year at USCG LorSta Port Clarence Alaska. Night life
consisted of double deck Pinochle, hours upon hours of Cribbage and poker
with the Eskimos when Port Clarence Bay froze over so they could cross it
by snow mobile. I spent my last year as an instructor at the Loran training
center on Governor's Island, NY. My home town was NYC, so they basically
sent me home for my last year.

If I recall correctly, Loran stations across the globe began being shutdown
in the early 90s. Many stations went solid state and unmanned years before
that. All remaining Loran C service was terminated in 2010. I don't know
which, if any, Loran chains are still available as backup for GPS. I do
know that some stations were dismantled and towers taken down.

Check out this video of the tower at Port Clarence.

www.youtube.com/watch?v=u92YYdy6Lak

Lightening hit our tower in Germany, basically melting the antenna coupler
transformer. We were off air for a few weeks while we waited for parts to
rebuild the antenna coupler and final amplifier stage of the transmitter
that was on-air at the time. I don't remember how it worked, but there was
some kind of system that handled most strikes without knocking us off the
air. This one was just too big.

Interesting fact about the construction of Loran stations: Even though the
guy wire system was designed to spin the tower basically straight down
should there be a tower failure, each Loran station was built so that the
closet building to the tower, other than the transmitter building of
course, was no closer to the base of the tower than the tower was high. In
the next-to-impossible case that the tower fell "sideways" it would miss
the buildings.

Since the weather in Port Clarence was an issue, we had a 1/4€� mile
enclosed "hallway" from the main station to the transmitter building. No
heat and very little light, but at least we were out of the weather as we
walked (or biked) to the transmitter building. The inside walls were coated
with ice and there were snowdrifts inside the hallway where the snow blew
through the seams in the walls.


Darn, I lost the pictures I took when I worked at The Kwajalein Missile
Range back in the 1980's during the SDI "Star Wars" program. There were
some cool old and new structures out there for radio and radar use. I do
believe the big satellite dish for the down link had a cryogenically
cooled receiver or components to give it maximum sensitivity. There were
some abandoned old sites that still had the antennas and there was one
big concrete building that was used for the original phased array radar
development for the early warning and ships phases array radars.
I really wish I hadn't lost those pictures years ago. o_O

https://en.wikipedia.org/wiki/Kwajalein_Atoll

TDD

In the 70's working at NASA tracking station, we used loran to track cesium
clock drift. There was a special receiver for that. Loran C and D. The only
other way to measure cesium clock, was for them to bring in a portable
reference.

We also had cooled parametric preamplifier for the best noise performance.
The hydrogen maser was for deep space tracking, and there was another
simple transistor amplifier backup. Most amplifiers can be cooled to get
better noise ratio.

Greg