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


stevenhorii
 

Yeah, I think smartphones can also triangulate off of cell towers. I have
had the experience with my in-car GPS of driving in a new housing
development that was likely not in the map database the car had. It showed
me in the middle of a field. My funniest experience with GPS was when I
returned from a trip to Berlin. I was trying to use what is really an
automotive GPS for walking around the city. I had loaded my location and it
showed it correctly on the map, but it would simply not update correctly
when I was walking around the city. I put the unit away until I got home.
The next time I used it, I took it with me from where I was living in
Maryland to Los Angeles on a flight. I turned it on for the first time
since using it in Berlin and when I put in my uncle's address in LA and it
spent a LOT of time calculating the directions. It came up with "drive 5400
miles east to I-405 South" as the first direction. I then had it reset to
the local position (I must have told it to use my last known destination as
the start) to get the right directions. I got a laugh out of that.

On Fri, Nov 27, 2020 at 8:41 PM Jim Ford <james.ford@cox.net> wrote:

In addition, smartphones use Wi-Fi and other comms methods to navigate.
Much superior to those TomTom boxes that only used GPS.JimSent from my
Verizon, Samsung Galaxy smartphone
-------- Original message --------From: stevenhorii <sonodocsch@gmail.com>
Date: 11/27/20 3:54 PM (GMT-08:00) To: TekScopes@groups.io Subject: Re:
[TekScopes] (OT) Where to go for 70s IBM hardware? I'm looking for a
terminal. Jim,Yep. I'm pretty sure the navigation system in my car uses GPS
primarily butmust have a dead reckoning system as it shows me where I am
when I amdriving through an underground tunnel. The system updates as soon
as theGPS signals are again available, so there are sometimes funny jumps
fromshowing me somewhere off the highway to back on it. GPS-aided
inertialseems to be the way many navigation systems are being designed.On
Fri, Nov 27, 2020 at 6:46 PM Jim Ford <james.ford@cox.net> 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 <sonodocsch@gmail.com>>
Date: 11/27/20 1:04 PM (GMT-08:00) To: TekScopes@groups.io 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:>
http://usdynamicscorp.com/literature/general/AN-003%20USD%20Spin%20Motor%20Excitation.pdfI>
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 <
madyn@dragonworks.info> 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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