"Field Engineering" or "Jerry Rigging"

[Bluerunner]

What "field engineering" have you done that turned out better than you expected, proved to be very useful or failed miserably?

I salvaged an old 400 watt computer UPS with dead gel cell batteries that were too expensive to replace. I wired it up to two salvaged auto batteries. The original batteries lasted 30 min. The auto batteries last 8 hours. The UPS also filters & stabilizes the crappy voltage from my emergency gasoline generator to give a regulated AC 110 volt sine wave. Most people toss out a UPS rather than replace the batteries which cost nearly as much as the UPS.

I'm sure everyone has had a brainstorm that worked well and everyone can benefit from.

-- Friday, 13 June 2014, 22:13 PM --

After doing a few mods on the Cobra 142 I realized that the PLL just applied a very precise voltage to the VCO (voltage controlled oscillator) for different channels.

I tapped a voltage from the voltage regulator, ran it through a 10 turn potetiometer to the VCO input and had VFO. Put a switch in to switch between the PLL & VFO. Didn't have to change any crystals, cut traces or re-tune any of the oscillator coils. Cost maybe $5 for the pot & switch.

Most radios with the PLL / VCO work the same way.

-- Saturday, 14 June 2014, 22:14 PM --

A 20' section and a 10' section of fence rail with one set of guy wires worked well ( braced to the house at about 10') to elevate my starduster 30'.

I got another 20' section of fence rail and couldn't leave well enough alone and went for 50'. Two sets of guy wires (estimated length by the hypotenuse of a right triangle) pre installed. Got on the roof and attempted to insert the 20' segment and succeeded. while snugging up the guy wires it bent in the middle and came crashing down on my neighbors roof. Just thought I'd mention it so nobody else tries it.

Young & foolish back then. At least I'm not young anymore.

-- Thursday, 19 June 2014, 15:19 PM --

DIY push up pole.

1 3/8" X 10' long fence rail, fits inside a 1 1/4" X 10' piece of EMT conduit, which fits inside a 1 5/8" X 8' Line Fence Post.

Mark the ends VERY WELL to leave about 12" inside the lower tube. If you pull it out you will have a watermelon on a stick kinda thing and everything will come crashing down.

I spliced two of the Line Fence Post together to get an extra 8', supported at the house eves at about 15'.

-- Tuesday, 22 July 2014, 8:02 AM --

I use two lengths of RG8 for my DC power runs from the battery. The shields are connected together ONLY at the battery end and grounded to the chassis.
The center conductors are used to carry the pos and neg 12VDC. Kinda stiff so I solder #12-16 wire on the end to the radio connector. It makes a great linear high frequency bypass capacitor and the shield helps keep noise out of the power supply too.