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.

Marti Audio Performance - Kirby's Musings

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Marti makes wideband FM remote broadcast equipment. These are some specifications gleaned from product manuals or sales literature:

sub-audible tone encoder (27Hz, other equipment uses tones at 25, 35, 50, and/or 75 Hz and sometimes in combinations). 
FM compressor/limiter (usually a necessary part of preventing splatter, over-deviation, and excessive occupied bandwidth. Marti may have implemented it as a high-speed limiter or brickwall low-pass filter).
2:1 compander option (These are useful if you have highly dynamic content, but it is required at both ends to be effective. Telephone audio is often compandered; it is the difference between A-law and mu-law signalling. )
Receive Bandwidth: 20-50 KHz, depending on selected frequencies
Deviation: 1.5, 5.0, 7.5 or 10.0 kHz depending upon frequency and filter

Frequency Response:
50 Hz to 3 kHz: ±1.5 dB, 10 kHz Channel BW, 1.5 kHz Dev, 20 kHz filter
50 Hz to 7.5 kHz: ± 1.5 dB, 25 kHz Channel BW, 5.0 kHz Dev, 25 kHz filter
50 Hz to 10.5 kHz: ± 1.5 dB, 36 kHz Channel BW, 7.5 kHz Dev, 36 kHz filter
50 Hz to 10.5 kHz: ± 1.5 dB, 41 kHz Channel BW, 10.0 kHz Dev, 50 kHz filter
S/N Ratio @ 100 µV Input:
10 kHz BW @ 1.5 kHz Dev: 44 dB
25 kHz BW @ 5.0 kHz Dev: 53 dB
36 kHz BW @ 7.5 kHz Dev: 57 dB
50 kHz BW @ 10.0 kHz Dev: 57 dB
THD + Noise:
10 kHz BW @ 1.5 kHz Dev: 2% or less, 50 Hz to 3 kHz
25 kHz BW @ 5.0 kHz Dev: 2% or less, 50 Hz to 7.5 kHz
36 kHz BW @ 7.5 kHz Dev: 2% or less, 50 Hz to 10.5 kHz
50 kHz BW @ 10.0 kHz Dev: 2% or less, 50 Hz to 10.5 kHz
IMD (For 20 dB Signal-to-Noise): 75 dB
Image Rejection: 100 dB

Notably, the Marti doubles the standard deviation of +/- 5 KHz FM radio to 10 KHz. This is because broadcast needs more "headroom"; some NYC STL remotes were used at 200 KHz deviation for 20 KHz audio simply to spread the signal over more spectrum to achieve a greater signal-to-noise ratio. This is the same as process gain in spread-spectrum communications, because "line spectra" -- that is, unmodulated carriers present in the received spectrum -- have less of an individual effect in the recovered audio. A better way to avoid such effects is to switch to a digital format with an acceptable CRC, FEC, or other Error Correcting Code (ECC) to mitigate the errors while using a spectrally dense mode such as QAM256 (8-bits per symbol or baud).  However, the problem with QAM is that one must be able to tell where the bottom of the S/N ratio is, and adjust the range of power dynamically, as well as the upper limits of power. Transmitter power tends to follow a cube-square law in terms of cost per watt, in dB. QAM also requires linear amplifiers, which increases power inefficiency and dissipation.

Durable Transmitter Plant Design - Kirby's Musings

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In a modern transmitter plant, whether broadcast AM, FM, TV, paging, or repeater, a circulator is a valuable part of the installation and often omitted to save costs. The circulator, in combination with SWR bridges, enables a site manager to keep the transmitter on the air during difficulty, as well as prevent minor issues from becoming large ones.

A circulator is valuable for two important reasons. First, a circulator assures that the transmitter will always see a 50-ohm match, within a few percent of that impedance. Second, the circulator prevents mixing products from being generated as a result of rectification and amplification in the last stage of the amplifier. Any amplifier designed to operate as a broadband device is subject to this noise generating effect. The circulator acts to insure the investment in transmitter plant, at the cost of the feedline and antenna in the event of fault.

In the case of lightning and other associated arc-over events in the coax, the SWR bridge provides useful feedback to the transmitter plant controller to temporarily cease transmitting, and/or lower and ramp up transmitter output. For instance, combining these functions with flow and pressure monitoring of the dry nitrogen or dry air being fed into the feedline can immediately identify the cause of failure, and shift the source of pressurization into a higher-flow mode or to a more plentiful source such as an air dryer rather than bottled gas. If dry air is used as the source, or excessive gas flow is noted, the transmitter power can be backed down since the air-dielectric insulation will no longer be as strong or effective as it was when it was dry nitrogen under a few pounds of pressure.

A self-diagnosing transmitter needs four SWR bridges. One SWR bridge should be installed between the transmitter and the circulator, another bridge between the circulator and the feedline, yet another bridge located between the feedline and antenna (equipped with high-voltage clamping diodes), and the fourth bridge sampling the RF to the circulator dummy load.

Useful temperature monitoring points are outside air temperature, temperature at the feedline-antenna junction, the middle of the feedline, the bottom of the feedline, the circulator temperature, the circulator dummy load temperature, the transmitter output temperature, the transmitter input temperature, generator input temperature, generator output temperature, generator body temperature, battery temperature, day-tank and storage tank temperature

If the RF is getting to the antenna and you have a bad match, then the antenna is the problem. If the transmitter has a bad match at the ground, then the feedline and/or antenna are compromised. If transmitter isn't making enough RF into a good match, then the transmitter is experiencing internal problems. The circulator lets you deal with bad stuff happening after it, at the cost of continuing whatever arc welding is presently happening in the feedline without extensive monitoring. The feedline is a great heatsink, so if it gets warmer than the outside air, that is an indicator that something is wrong. A fault at the antenna or in the feedline that is noticed can be mitigated by dropping the RF power level, which keeps the station on the air but may not cover as much contour or footprint on the ground. According to the FCC Parts, the engineer would have to file an STA in the case of a broadcast transmitter but it is not turning $100K of feedline into expensive, oxidized scrap.

Other noteable points of protection inside the shelter and around it:
1. A water shield should be placed over the transmitter to prevent water ingress in the event of roof or other failure. This is largely dependent on electrical codes, but can be the difference between rebuilding a transmitter and resetting one that tripped off.

2. The air conditioner drain line should be fitted with a float switch. For example:

In the event of the switch being tripped, an engineer should be dispatched to the site. To resolve possible false trips, three switches can be placed in physical parallel with each other on the same level, and the combined or individual switches fed into the site controller. If two or three switches trip, one can safely assume that there is an irregularity in the air conditioning drain system.

Depending on the climate and likelihood of entry, the air conditioner drain line should be fitting with a screen, or a series of increasingly smaller screens. Insects and rodents may enter the drain line and nest in the drain line, causing a blockage for liquids. Additionally, molds and fungi may form in the drain liquid and introduce turbulence in the drain line as well.

UPS Battery Management - Kirby's Musings

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Over the years, I've looked at a lot of UPSes and battery-backed power systems. These are my recommendations for power systems where backup is desired, or "clean power" is needed.

1. A 48 VDC sine wave inverter in the 1500 - 2200 - 3000 VA class with a low-voltage shutdown feature
2. a battery bank larger than 25 Ah at 48VDC
3. (2) Schottky diodes large enough to handle the maximum current the inverter can sink, rated for 60VDC
4. A battery charger capable of reaching the equalization voltage (14.4x4), but not used for equalizing.
5. (6) fuses: one from the batteries to the load, one from the batteries to the charger, and four connecting the batteries to each other. 
6. 1F worth of super caps at 60VDC.

The preferred embodiment is such that the charger is connected to the battery pack through a fuse, and the battery pack connected to the anode of the series protection diode through a fuse. The cathode of the diode is connected to the cathode of another diode as well as the positive terminal of the series of supercaps. The anode of the second diode connects to ground, so that any counter-emf current is clamped.

If an APC SmartUPS 2200VA or 3000VA is substituted for the inverter, the supercaps will simulate a battery for the purposes of the UPS's charge and self-test cycles, along with providing a power bypass in the case of restored utility power, or generator power that matches the expectations of the UPS. The batteries may be automatically charged to "full" (13.8x4) once a week by the charger and allowed to float down the remaining six days, unless a UPS self-test cycle occurs. If the battery bank is in the 50+ Ah range at 48V, the effects of the self-test cycles can be ignored.

The advantage of this implementation is that smaller power supplies can be used to put a fraction of the total power required into the battery pack, which can slow the rate of energy reserve depletion. In the first implementation, a 3000 VA (output) power supply made up of four 750 VA modules was used, allowing four 1000VA car inverters to be used to power individual sections or combinations. Additionally, the entire power supply could be used to clean up "dirty power" since the power supply sections were universal can could run from 100 to 250 VAC. More recently built power supplies may also support 380VDC inputs, as the peak-to-peak voltage of 240VAC is 339 V.

The reason for the recommendations are many, and it's mostly addressing the issues present in the APC UPS products.

1) The batteries are severely taxed by the charging, discharging, and self-test cycles of the UPS. The reason why APC's warranty is so short and the cost of replacement so high is that the battery manufacturer will not warranty the batteries, period. You cannot reasonably expect a 7Ah battery to regularly withstand cycles of 30+ A loads being attached and then recovering.

2) The above manifesting in battery failure, it is not unusual for a single cell to short, resulting in the entire chain going up in voltage spread across the remaining cell. Large numbers of batteries in packs mitigates a shorted cell failure very effectively in this way.

3) Individual cell voltages will change over time. In the case of 12V lead-acid batteries, the smallest units are six-cell groups of 12V, so you are stuck with this basic commodity. The voltages in cell differences can add up over time and groups, resulting in less than favorable life expectancy.

4) Cooked, swollen, or leaking batteries do not a happy funtime for electronics make.

On the Care of Batteries:

1) If possible, discharge individually and charge the batteries in parallel or independently. There are limits to this, one gets into the thousands of amps quickly at 1.2VDC for NiMH and NiCd chemistries, or 2.0V when dealing with lead-acid.

2) Charge once a week, don't float batteries. That's old hat. This advice best matches chemistries with high temperatures at the end of charging and high self-discharge, such as NiMH. No surprise, I learned it from the Panasonic NiMH Battery Handbook.

3) If you're using LiPos, use a BMS. LiPos are very much their own animal and the chief reason for letting the battery voltage be what the battery voltage will be and the load voltage being something else entirely (i.e.: 13.8VDC, 120VAC).

4) Not too cold: Batteries will warm due to resistance during discharging events. However, current available will be limited if the batteries are below 60 degrees F.

5) Not too warm: Batteries should not be charged above 100 degrees F unless the manufacturer has provided you with special guidance. More of an issue for people in the American Southwest, freshly discharged batteries, or large packs of NiMH batteries.

6) Control the rate of recharge: It's not a good idea just to dump 1000A into the battery bank after a 1000A discharge unless they are rated for that charging rate. Usually not more than 1/10 C for lead-acid batteries. NiMH and NiCd have different requirements during charging due to specific cell behavior.

7) It's not if batteries fail, it is when. Always assume that they will leak at the most inopportune time and cause the most possible damage at that time. If you put batteries in the same cabinet with the electronics, when the batteries fail, the electronics will corrode in the gasses. It is best to put batteries in a separate, ventilated enclosure away from expensive electronics. NiMH, NiCd, and lead-acid batteries give off different corrosive vapors that are not compatible with each other. These chemistries should be separated from each other. In the case of flooded or other unsealed lead-acid batteries, a spill kit should be nearby, along with a source of distilled water for regular topping of batteries. A battery box or tray should be able to contain any electrolyte that might spill from a broken battery and resistant to the chemicals used in the electrolyte.

This is a lot of information, but applied correctly will result in a backup power plant that achieves or exceeds the warranty of the batteries.

In the case of a large battery plant, it may be desirable to break the plant into battery strings, and individually switch those strings to the load bus, or a charging bus as needed to equalize charging intervals. This can be done with Schottky diodes and MOSFETs in today's world without too much cost since the MOSFETs are either on or off, and the MOSFET's body diode can perform the function of a one-way diode. On the other hand, the MOSFET's body diode may require the use of additional Schottky diodes to prevent the reverse flow of current. Schottky diodes are fast diodes, while the MOSFET's body diode is not known for fast recovery times however that should not be a factor for the reader unless there are large inductances present in the implementation.

Disable PassKey-II on Cadillac Fleetwood - Kirby's Musings

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I was recently introduced to a 94-96 Cadillac Fleetwood, which had a VATS fault which was aggravating the owner. The owner previously tried permanently installing resistors under the dash to allow the VATS system to read a correct resistance value, but for some reason that fix was no longer the cure.These are the steps taken the effectively neutralize the VATS/Passkey system on a 1995 Cadillac Fleetwood that was built in 08/1994 but had a 1995 VIN, and OBD-I. 1995 was the changeover year for the Fleetwood (D-body) to go from OBD-I to OBD-II, so depending on when the car was constructed, it may be of either type.

1) Use C.A.T.S. Flash to download the firmware from the car, twice to assure a proper read.
2) Disable VATS functionality from the car firmware.
3) Upload the firmware to the car.
4) Download the firmware from the car again to verify that the VATS function is disabled.

At this point in the process, the Powertrain Control Module (PCM) no longer monitors or acts on the signals from the Central Control Module (CCM) regarding fuel pump enable. Fuel Pump Enable is a "modulated signal wire", so tying the line to +5V or logic ground will not enable the pump. The service manual contains a simulated oscilloscope trace of a 50% duty cycle square wave. I did not take the time to verify the signal since it was outside of the scope of work (narrowly defined as "Bypass this b**** so I can get to work, homie!").

A core feature of the 1994/1995 LT1 corporate motor implementation present in the Chevy Camaro, Caprice, Impala SS, Buick Roadmaster, and Cadillac Fleetwood is that the fuel pump, injectors, and ignition coil are all under the control of the PCM, while the starter motor is controlled by the ignition switch alone. This means that it is possible to continue cranking the engine until the point of battery failure while the PCM has withheld spark, fuel, or both. Diagnostics of the system approaches ritualistic.

1) When the ignition switch is turned to ON, the fuel pump should run for a few seconds. Even if the fuel pump is weak, this is a good sign that fuel is present in the fuel rail and the PCM has an intent to start so far.
2) Battery voltage should remain above 8 V while cranking.
3) The PCM supplies both fuel (via injectors) and spark.
4) The spark plug gap is 0.050", and the ignition coil can deliver a healthy spark into almost anything -- including you. Use caution in verifying that sparks are being generated. A spare plug wire can connect to the top of the ignition coil and be held above ground to bypass the Optispark distributor.
5) Immediately after a cranking attempt without the engine firing, the odor of gasoline should be notable from the exhaust. Please remember not to smoke in an explosive environment such as unburned exhaust fumes.

The Cadillac Fleetwood further confounds this process because of two additional modules present in few cars. One of those modules is the Theft Deterrent Module (TDM), which receives key fob commands and responds, as well as controlling the horn and lights to create the panic alarm. This module is occasionally found in Buick Roadmasters and Chevy Impalas. Despite the name, the TDM has little to do with actually inhibiting the starting of the vehicle. The other module is the Central Control Module (CCM), which implements most of the functionality present in the Fleetwood's environmental, entertainment, and other systems present only in that car and not shared with many other cars of the model year. The CCM implements the actual checking of the PassKey-II resistor, and controls the Theft Deterrent Relay (TDR).

The Theft Deterrent Relay (TDR) is located on the cabin side of the firewall directly in front of the passenger seat under the dash. Gymnastics may be required to reach this area, so the TDR was left in factory configuration. The TDR is effectively in series with the starter solenoid, but only receives power when the ignition switch is set to START. The control wire for the TDR is Yellow/Black in the 1995 model year, and this wire color is present in the trunk at the CCM.

The Central Control Module (CCM) mounts vertically behind the middle of the backseat and has two connectors along the driver's side: C1 (upper), and C2 (lower). The wire that controls the TDR connects to position D13 of C2. D13 appears to be on the bottom of the connector, if the clamp is located on the top of the connector. The following should be observed as a guide:

D13: Yellow-Black
D14: Light Green
D16: Dark Green-White

Wire D13 can be cut and spliced to a wire connecting to a nearby bolt or self-tapping metal screw and star washer to the body of the car, which completes the ground circuit. This disables what little control the PassKey-II System has to prevent the car from cranking. It is worth noting that the PCM has most of the control of the cranking process, and if the TDR were bypassed (such as holding the starter solenoid down with a screwdriver), the car would likely start. A simple way to test if this change worked is to disconnect the CCM entirely, and attempt to start the car. If the starter solenoid or motor engages, the fix is effective. Then the CCM can be reconnected and the interior reinstalled in the trunk. 

Steel Wire Instead - Kirby's Musings

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In electrical applications, it's not unusual to spend a large amount of money acquiring and installing copper wire, or when that is too expensive, changing to a larger gauge or two and using aluminum wire. Sometimes the cost of aluminum wire is still significant, or there are special needs or reasons as to why steel wire may be favored, such as long spans. Long spans of unsupported wire are often seen in antenna applications as well as power distribution. These spans are typically above 125 feet in height, which is roughly the limit for timber which supplies wooden poles used to support such wires from the ground without impacting the antenna pattern.

From a historical text (free on Google Books, so likely well before 1950):

Example: A cable 3/8"-inch in diameter, made of 7 strands of high strength crucible steel, weighs approximately 295 lbs. per 1000 ft. and breaks under a load of 11,500 lbs. Calculate the actual cross sectional area from the fact that steels weights 490 lbs. per cubic foot; then find the resistance per mile, the ohms per circular mil foot being 115. The volume of 1000 ft. = 295/490 = 0.602 cu. ft., hence the cross section = 0.602/1000 = 0.000602 sq. ft. This equals 0.000602 x 144 or 0.0867 sq. in., which equals 86,700 sq. mils and 86,700 / 0.785, or 110,300 C. M. Resistance per mile = 115 x 5,280/110,300 = 5.5 ohms.

(Journal of Electricity, Jan 1, 1921, p. 30.)

3/8" is between 00 and 000 gauge, so one can see that this is still a large wire for any application used, and being larger than #6, satisfies NEC requirements for power distribution wire sizes.

#6: 0.162" or 13.3 mm diameter for solid rod wire.

Probably just cheaper to buy the cable with the insulation on it, unless it's going outdoors and that's a lot of insulation.