Archive for category Amateur Radio

Bike Helmet Earbud Iteration

Based on having to seal the rear vent hole of the previous earbud, I did the same for the new one:

Earbud - blocked vent

Earbud – blocked vent

The audio quality was terrible, so I tried another bud with a foam windscreen over the hole and a hole punched in the middle of the double-sided white foam tape:

Earbud - foam over vent

Earbud – foam over vent

The audio remained unintelligible, so I tried an upscale (but still cheap, because surplus) Koss earbud, first without blocking the vents and then with snippets of Kapton tape:

Koss earbud - tape over vent

Koss earbud – tape over vent

The earphone has three slits on each side, but only the middle slit has a hole penetrating the case; it must be a stylin’ thing.

That sounded better, so I’ll roll with it. There’s supposed to be a foam cover over the housing, but those things always get grody and fall off; there’s not much point.

As nearly as I can tell, contemporary earbud designs optimize for volume (dBm/mV) and thumpin’ bass, all to the detriment of actual audio quality. Based on numerous samples over the years, there is zero correlation between price (admittedly, on the low end) and audio quality (admittedly, with my crappy hearing).

I own a pair of very nice (and thoroughly obsolete) Shure E2c sound-isolating ear beetles that sound great (even with my crappy hearing), but I’m unwilling to chop them up for the bike headset …

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Bike Helmet Boom Mic: Assembly

After building the mic mount, another dab of epoxy mounted the length of AWG 10 wire I said I wouldn’t use:

Bike Helmet Mic Boom - rod epoxy

Bike Helmet Mic Boom – rod epoxy

The whole point of the complex mount is to expose the two noise cancelling holes on the back of the electret element:

Bike Helmet Mic - electret element rear

Bike Helmet Mic – electret element rear

Add heatstink tubing over the entire length of the boom wire, use more black cable ties, shape another foam ball:

Bike Helmet Mic Boom - installed

Bike Helmet Mic Boom – installed

And it worked on the first try, not that there’s much to it.

Yeah, that’s the HDR-AS30V camera mount up top: dork mode in full effect.

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Bike Helmet Boom Mic: Housing

The last time around, this involved silver soldering the boom wire directly to the mic housing. This time, I filed a fishmouth in the smaller tube and epoxied it to the tube that’ll hold the mic capsule:

Bike Helmet Mic Boom - housing

Bike Helmet Mic Boom – housing

The smaller tube is a loose slip fit for #10 copper wire, but that’s really too heavy for the boom. I’ll probably nestle #12 wire inside another tube and epoxy that whole affair in place.

The mic capsule tube needs a rounded notch filed in one end to accommodate the wire.

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Monthly Image: Hudson River Boating

Much of the boat traffic on the Hudson consists of barges shuttling bulk commodities between the Atlantic and the Port of Albany. I think this is a crude oil barge, based on the Christmas Tree plumbing that was more visible when it passed under the Mid Hudson Bridge:

Walkway and Barge - from Mid Hudson Bridge

Walkway and Barge – from Mid Hudson Bridge

We crossed the Walkway Over the Hudson westbound, where a work crew was tending a crane. That’s how they do repair and inspection:

Walkway Inspection Crane - from Mid Hudson Bridge

Walkway Inspection Crane – from Mid Hudson Bridge

The Hudson River has far fewer power boats than in years gone by, probably due to their gallon-per-minute fuel consumption:

Power boat on Hudson River - from Mid Hudson Bridge

Power boat on Hudson River – from Mid Hudson Bridge

It was a fine day for a ride:

KE4ZNU - APRS track 2014-06-30

KE4ZNU – APRS track 2014-06-30

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3D Printed Things I’ve Designed: Brag Sheets

The whole reason I got a 3D printer in the first place was to make things that would otherwise be too difficult or tedious by hand or on a CNC mill. Most of the things I make look like brackets and I don’t do sculptures … this stuff solves problems!

Being able to go from “I need a part shaped like that” to holding the thing in my hand a few hours (or, for complex designs, days) later is empowering. Being able to adjust a dimension by changing the source code and “recompiling” to get a new part is wonderful.

These five slides from the presentation show my answers to the question “Why would anyone want a 3D printer?” Clicky for more dots.

Things I Designed - 1

Things I Designed – 1

Things I Designed - 2

Things I Designed – 2

Things I Designed - 3

Things I Designed – 3

Things I Designed - 4

Things I Designed – 4

Things I Designed - 5

Things I Designed – 5

You can find those and more by searching for OpenSCAD source code.

They go along with the sheets of solid models.

, ,

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Plastic Stress in Polarized Light

Here’s what the (cracked) faceplate of the FC1002 Frequency Meter looks like, through polarizing filters that reveal the internal stress.

A circular polarizer screwed on the lens:

FC1002 Frequency Counter - faceplate - circular polarizer

FC1002 Frequency Counter – faceplate – circular polarizer

A sheet of linear polarizing film held in front of the lens:

FC1002 Frequency Counter - faceplate - linear polarizer

FC1002 Frequency Counter – faceplate – linear polarizer

For reference, none of the other instrument faceplates on the bench show anything other than uniform gray, with one exception that points directly to the plastic injection point.

I’d say this plate cracked due to unrelieved internal stresses and not anything I did or didn’t do.

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FC1002 Frequency Counter Battery Pack

The main reason for taking the FC1002 frequency counter apart was to replace the failed quad-AA NiCd battery pack. Rather than buy new cells with tabs, I recycled some low-discharge “ready to use” NiMH cells from the heap. Back in 2009, they looked like this:

Tenergy RTU Pack A Tests - Aug 2009

Tenergy RTU Pack A Tests – Aug 2009

Nowadays, they’re a bit less peppy:

Tenergy RTU - 2014-01 - loose cells

Tenergy RTU – 2014-01 – loose cells

The red blooper shows that you can’t trust a smart fast charger to get the right answer; it concluded that pair was fully charged. After the discharge test and an overnight C/10 charge, they regained as much enthusiasm as they’ll ever have.

They have slightly less capacity than in 2009 and also a somewhat lower terminal voltage. That shouldn’t matter here, as the frequency meter has a power supply to take care of that problem.

Although I’ve sometimes been able to (quickly!) solder directly to ordinary AA cells, a trial run on a defunct RTU cell showed that wasn’t going to work on whatever variety of steel they used, no matter how much I scuffed it and despite using aggressive flux that normally blends silver solder onto stainless steel.

Fortunately, the top half of a four cell case fit exactly in the space available, so I used woven copper fabric tape inside the case to interconnect the cells, then lashed everything together with the obligatory Kapton tape:

FC1002 Frequency Counter - battery pack

FC1002 Frequency Counter – battery pack

That cracked faceplate isn’t the nicest thing to confront, but it’ll suffice until I get more motivation:

FC1002 Frequency Counter - repaired

FC1002 Frequency Counter – repaired

I’ve misplaced my stack of Round Tuits again…

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