BIRDWATCHER - Kirby's Musings

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Birdwatcher is a word which has mostly avoided the internet generation entirely. Birdwatcher is an automated telemetry system with two pilot inputs, an A button and and a B button, and the rest of the inputs were specific telemetry inputs on the aircraft. The A-12 had a Birdwatcher system, as well as the CIA version of the U-2. Both of these aircraft or similar variants (U-2S, SR-71) were transferred to the 9th SRW, 4080th, and other related divisions.

For more information, look to the dead trees.

pdftops filter failed - Kirby's Musings

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If you're reading this, you probably have a problem with Cups and pdftops failing. Install xpdf and some version of libpoppler. This is an unresolved dependency.

Terminal Gibberish - Kirby's Musings

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When your terminal is liberally filled with terminal gibberish, there are a few solutions suggested on stackexchange:

I suggest this:

echo ^V^[c

Alternatively (noobish):

echo <CTRL-V><CTRL-[>c

The actual character being echoed is ^[ followed by the letter c, but to pass control-[. one must type CTRL-V before other CTRL- sequences. Clear as mud, eh?

Thermodynamics or Thermonuclear War - Kirby's Musings

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Law I: You can't win, you can only lose.
Law II: The only way to win is not to play.

In thermodynamics and energy conversion systems, the rules of thermodynamics are immutable. The only variables to implementation are 1) cost of design, 2) labor cost of design implementation, and 3) materials cost of design implementation. These variables all support one equation to calculate a single value: return on investment (ROI), less maintenance cost.

In converting from AC to DC or DC to DC, the fewer the steps, the greater the efficiency. The more transistors act like switches and less like variable resistors, the higher the efficiency. The lower the loss in the transformer or inductor stages, the greater the efficiency. A 90% (0.9) efficient inverter connected in series with another 90% (0.9) efficient inverter results in an overall efficiency of (0.9 x 0.9 = 0.81) 81%. Thus it is most important to make sure that any conversation stage is as efficient as possible to eliminate losses which will invariably appear as heat. This is true of electrical distribution systems, backup power supplies, line-shaft power systems, and belt-powered systems as well.

In a belt-based transmission system, losses can be as high as 5% per stage. Similarly, gear-based transmission systems and hydraulic systems also suffer from losses due to realistic implementation concerns. Multiple stages, lubricants or lack thereof, and turbulence further lower overall efficiency. Thus, while it may be possible to store energy from a solar collector by raising a rail car full of concrete to twice it's height, much energy may be wasted in mechanical gear trains unless a mechanically large gear is used and a small pinion. Even then, one would need a considerable motor/generator to convert from electrical to mechanical.

AT&T Tower Resources - Kirby's Musings

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Free Rigging Guides - Kirby's Musings

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AM Tower Heights by Frequency - Kirby's Musings

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This is a document apparently originating from ERI, Inc, being circulated around the internet on various blogs and sites. AM tower heights listed by frequency for 1/4-wave and 1/2-wave lengths, in feet and meters.

The All-Pass Audio Filter - Kirby's Musings

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The All-Pass Audio Filter is useful for a few reasons:

1) Symmetry of the audio. The human voice is often not symmetrical, and depending on the signaling circuits or transmitter design, it is desirable to limit any sort of inherent DC bias in the transmitted signal. This is an issue for AM and FM transmitters, as well as twisted-pair loops carrying voice communications.

2) Phase correction. The allpass network permits a correction of frequency-dependent phase rotation caused by preceding or following signal processing stages.

In digital signalling networks, these problems are addressed by line coding. The methods of AMI and B8ZS are used in telephony signalling to eliminate a DC bias which would compromise the wire loops and contribute to additional cross-talk coupling, as well as permit the signal to be AC coupled onto a line carrying DC power at -48 VDC or -130 VDC.

Similarly, AX.25 uses Non-return-to-zero inverted (NRZI) to mitigate a similar protocol-based DC bias which would otherwise result from the nature of the data packets. Ethernet relies on 8b/10b encoding in slower forms, and 64b/66b encoding in faster forms to neutralize DC bias as well.
At the moment, this exists as a series of drawings on paper, so this will be a verbose "patent-style" description.

The design is a multi-level dogbone layout, flanked with helical double-track towers on either side which are integrated into the layout route. This permits the middle to support a bench or "desktop" scene in the vertical middle of the entire assembly, multiple flat single or double track "storage racks" connecting from helix to helix from floor level to the top of the entire layout. At the top, it may be desirable to include a multi-track storage yard without adornment. The scene in the middle has the possibility of being multi-level as well, with as many layers as the builder desires in the primary scene. The lower storage compartment should be protected with polycarbonate sheet to prevent accidental contact with locomotives and rolling stock, as well as to maintain a visual sight line with moving trains (consists).

Primary problems to be solved by the implementer are:

  • Power control and routing
  • "Parking" on the flat surfaces.
  • Most of the trackage in the layout design will be installed in the helix, which at a 2% grade, will require a solid mechanical stop to support the train in the helix.
  • Motive power requirements to lift trains through the layout and helixes. This translates directly into more locomotives, higher loads, and high quality locomotives that use both trucks for collecting DC power and delivering torque.

Advantages of this design are that the helixes can be interfaced on the front side or the back side, and the grade differential per level permits interstitial scenes such as a hump yard. One would need to frame or box the area below the upper scene, but this space can be used for mounting lighting to the scene below.

The helixes can be configured in a 1:1 fashion, or crossover at the bottom. They can be built as a left-hand helix and a right-hand helix, or both sides constructed of the same alignment helix. It may be desirable to avoid same-level rail crossings for unattended operation, or operation without intervention.

Minimum radius should be approximately 15", with the twin tracks centered at 1.5" apart. This permits the helix to occupy a space of approximately 36" x 36". It may be desirable to extend the helixes by using a 6" straight section of track or replacing that straight section with a turnout (switch) or using curved turnouts. Since there are two tracks, the inner helix would likely be uninterrupted and provide a path from the bottom to the top for a "long route" unless a block system or interlocking are provided for and a crossing installed in the outer helix track.

As an ordinary bench may be 36" deep, it would be desirable to make the entire structure as wide as possible, say ten or twelve feet, because three feet per side will be used by the helix for a total of six feet of non-layout space. This limits the center scene to four or six feet, which may be sufficient or excessively limiting to some modelers. 

Battery Power Systems Design - Kirby's Musings

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Battery-powered systems are necessarily complex for three reasons: charging, discharging, and heat management. In the world of lithium batteries, this is primarily managed by the BMS, or battery management system.

Panasonic gives excellent battery management advice for dealing with NiCd and NiMH types and the advice is applicable to SLA, VRRH, and other lead-acid battery configurations as well.

Battery heater:

This is a battery heater, which is a necessity in Alaska. The catch with battery management is always keeping them cool when it is warm out, and keeping them warm when it is cool out. The fact that they are primarily lead and have a large amount of thermal mass does not always help. Obviously, passive methods of cooling are good but have to be custom-designed for the application. In the case of NiMH batteries, high temperature at the end of charging is a normal by-product of charging, but should be managed to prevent damage to the cells.

Charging should be structured to state of charge, particularly making sure that each individual battery is charged to it's proper voltage. Strings of batteries mitigate the effects of a shorted cell by minimizing the resulting overcharge voltage. However, a battery going into an open-cell or high-resistance state causes all batteries to be effectively disconnected from the charger or load, rendering a larger capacity of batteries unusable. I recommend that a three-bus approach be used, where battery packs are attached to a load bus using ZVS or other style of buck-boost converter or switch, a charger connected to that load bus, and the battery under charge isolated from the load bus and connected to the charging bus when under charge. This permits a rotating "once a week" charge of each pack, even if the power is out, with a terminal behavior of removing packs from the discharge set as packs are charged for the last time. This way, as few cells as possible are "killed" by being left in an uncharged state unless the load dictates such. Entropy: you can't avoid it.

Discharge should be figured to the chemistry of battery as well. In the case of NiCd and NiMH chemistries, a terminal voltage of 1.0 or 1.1 V per cell may be the lowest that should be permitted. In the case of 12V VRRH or SLA batteries, a terminal voltage of 10.5 or 10.8 volts should be used depending on the current being drawn and the resistance of the wires between the batteries and the load. Once a battery is discharged, it should be recharged as soon as feasible or possible to prevent effective battery death.

Temperature management has two extremes: cold and heat. Even those are relative to the environment of the battery depending on the location of the system in the world. Death Valley regularly has extreme temperatures exceeding 120 degrees F, and the American South may see 90-100 degree F temperatures during a typical summer. Likewise, low temperature extremes are more likely in certain areas than others. These factors shape the design and implementation of a battery thermal management system.

Heat pipes and solid/liquid metal (gallium, indium) cooling systems may be used as pack temperatures approach 90 to 100 degrees F. However, these systems have to be designed not to operate if temperatures are cooler than 70 degrees F as battery capacity starts dropping off below 65 degrees F. Paradoxically, many battery chemistries tend to generate heat as they are discharged which is a benefit to low external temperatures but a caveat when external temperatures are warmer. However, heat-pipe systems may be made of any number of materials, and have correspondingly different behaviors depending on the substances involved. For instance, propane boils at -43.6 degrees F (-42 degrees C), which means it can act as a vapor-phase cooling system if one end of the system is compressed to a liquid state. Likewise, the temperature of the system can be held to a constant as long as a liquid is boiling into a gas state, such as a pot on a stove full of water. This is how a double-boiler manages effective temperature control. In the case of using water, the temperature of the water must not be allowed to drop below 33 degrees F or ice crystals can form at extremes.

Additionally, geothermal contact may be involved in temperature management, using loops of electronegatively inactive, grounded, non-oxidizing metals in well casing, or direct contact with rock outcrops or burial below the soil surface. Depending on the materials involved, these systems can be efficient and/or maintenance free or require periodic maintenance to renew materials or sacrificial anodes. 

In the case of an outside temperature below 55-degrees F, the outside air temperature is lower than the temperature of the ground, which makes contact with ground a good thing. In the case of an outside temperature above 55-degrees, contact with the ground is not desirable because battery capacity decreases rapidly below 65-degrees F.

The other layer of complexity to battery management is that of corrosion. Chemicals in batteries can corrode various metals to different degrees, and it is desirable to prevent some metals from reacting with some electrolytes. Further, some batteries require venting, which may be implemented simply using fans or by using aquarium tubing in others. In general, one should assume that batteries will eventually fail, and in the case of SLA, VRRH, and lead-acid batteries, that either hydrogen and oxygen gas will be vented, or sulfuric acid will be vented or drain into the enclosure. Any nearby electronics will be damaged by the gasses from the batteries.

Yet another area of concern would be the degree to which small rodents of the area find the battery box to be habitable in any and all states of weather.

Another complexity is that batteries should not be placed in parallel unfused lest a battery develop a shorted cell, or several cell failures following a shorted cell. When a 90 Ah battery is rated for 2,000 amps into a dead short, one can be certain that a battery failure will result in the venting of charging gasses and electrolyte fumes while the good battery forces power into the dying battery.

Additionally, serviceable battery types should be serviced on a periodic basis, with distilled water added as appropriate and electrolyte when necessary. Serviceable batteries should be vented and humidity levels managed. Non-serviceable batteries should have discharge and charge rates limited to prevent cell over-temperature or over-pressure.