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

Jim Ford

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 <> Date: 11/27/20 3:54 PM (GMT-08:00) To: 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 <> 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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