Re: (OT) Where to go for 70s IBM hardware? I'm looking for a terminal.

Harvey White

I suspect that the same "I'm on a road, I must stay on a road because a car doesn't go off a road" algorithm that keeps the fifty foot uncertainty (or so) invisible to the operator.

To test this out, test on a route that takes a diverging exit off a turnpike/freeway/etc.  Don't take that exit and see where the autopilot thinks you're going,


On 11/27/2020 6:54 PM, stevenhorii wrote:

Yep. I'm pretty sure the navigation system in my car uses GPS primarily but
must have a dead reckoning system as it shows me where I am when I am
driving through an underground tunnel. The system updates as soon as the
GPS signals are again available, so there are sometimes funny jumps from
showing me somewhere off the highway to back on it. GPS-aided inertial
seems to be the way many navigation systems are being designed.

On Fri, Nov 27, 2020 at 6:46 PM Jim Ford <> wrote:

FWIW inertial navigation systems and GNSS (Global Navigation Satellite
Systems) are complementary. INS tend to drift over time, and GNSS provide
corrections. Navigation in GNSS-denied or -degraded areas is a whole other
ballgame.Jim Ford Sent from my Verizon, Samsung Galaxy smartphone
-------- Original message --------From: stevenhorii <>
Date: 11/27/20 1:04 PM (GMT-08:00) To: Subject: Re:
[TekScopes] (OT) Where to go for 70s IBM hardware? I'm looking for a
terminal. Harvey and Bill,Yes - I've tried that trick. For small gyros it
works. Gyros with electricspin motors tend to draw the most current at
startup as do most motors.After that, the current usually drops quite a
bit. Some of the 400Hz gyrosuse two-phase power. The usual trick is to put
a capacitor across the twospin motor inputs - it provides the phase lag for
the second phase. I haveNOT tried this, but I have seen some gyros -
usually the small ones thatare about one-inch in diameter and three inches
long and almost always rategyros - that had a phase-splitting capacitor
already soldered in place.This white paper describes a basic 2-phase power
supply for gyro spinmotors:
was fortunate - at a hamfest years ago, I picked up a couple of
AbbottTransistor Labs inverters. These took 24-28 VDC and output AC 400Hz
singlephase at up to about 2 amps. Not enough to run a large gyro, but
enough forthe smaller ones. I even ran a fairly large gyro - a Honeywell
rate gyro -with one of these. They do need a heatsink.I sometimes do an
eBay search for "Behlman Invertron" as they made somevery useful frequency
converters - 115 VAC to variable 400Hz AC. Some werevariable frequency and
some versions also had single to three-phase output.They tend to be
expensive (and heavy for the higher output ones) and Inever managed to find
one at what I thought was a reasonable price. Someversions had
interchangeable plug-in oscillators so you could run evenhigher frequency
AC devices (some gyros use 800 Hz - the Apollo programgyros ran with 800
Hz, 2-phase power). There are currently a couple ofBehlman Invertrons on
eBay, though they are not cheap.If you can find them, some of the WW II and
even early missile (Nike) gyrosran on DC (24-28 v). Those are fun to run
up. However, I've had some forwhich the bearings almost certainly were bad
- they were very noisy whenrunning and spin-down after power was removed
was quite fast. Likely whythey were surplus.Years ago, a surplus dealer on
Canal Street in NYC sold me a WW II Bendixvertical gyro. It was a 400Hz
gyro and he told me I could run it on 60Hz ACby putting a current limiting
incandescent lamp (no choices - there were noLED lamps then) in the power
circuit and running at a lower voltage via aVariac. I did not have the guts
to try it, but I do know those who did andsaid it works, but you will not
get the gyro up to full speed.Messing about with gyros can lead you down a
deep hole much as gettingfascinated by Tektronix equipment and then
desiring to get some (plusspares "for parts" and all the manuals). Now you
can get fairly accurategyros made using IC fab techniques - the MEMS units.
These things live insmart phones and tablets now. These plus GPS have
radically changedinertial navigation. Fun stuff, though.Steve H.On Fri, Nov
27, 2020 at 1:52 PM Harvey White <> wrote:> Hi-fi
amplifier of sufficient output capability driven by a sinewave> generator
sitting at 400 Hz?>> Harvey>> On 11/27/2020 11:52 AM, Bill E wrote:> > Even
though way off the off topic topic (parse that), still a fun> discussion. I
scored a box of 10 real gyros and logic pulled from DC-10s.> Cute little
rate gyro, etc. Problem is, all that stuff takes 28v 400Hz.> Haven't gotten
around to making a power supply for them yet.> >> >> >> >> >> >>>> >>>

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