Archive for category Amateur Radio

Invisible Asterisk: Except Cops

The signs at every Dutchess Rail Trail grade crossing and access point seem unambiguous:

DCRT - No Motor Vehicles

DCRT – No Motor Vehicles

More specific signs appear at random intervals along the trail:

DCRT - All Terrain Vehicles Prohibited

DCRT – All Terrain Vehicles Prohibited

You can’t see it, but every sign includes an invisible asterisk introducing the invisible clause “Except Cops”:

DCRT - Sheriff ATV Convoy

DCRT – Sheriff ATV Convoy

Back when the Dutchess County deputy sheriffs rode huge ATVs that occupied nearly the entire paved trail and bulldozed everybody out of their way, I had the temerity to ask why they weren’t riding bikes. The deputy sheriff told me, rather condescendingly, that they had to be prepared for anything and that there had already been incidents.

These little ATVs aren’t quite so imposing and, more likely, also fit on the new bridges and between the bollards, which may explain everything.

I’ve seen what might be their best use case, although ambulances can attract your attention without an ATV escort:

DCRT - Sheriff ATV Leading Ambulance

DCRT – Sheriff ATV Leading Ambulance

Straight up, I have no objection to police patrols on the rail trail.

do object to the official mindset that simply adds an invisible exception to any inconvenient rule.

As I see it, the root cause of the militarized police and extralegal government activities we’ve seen across the country in recent years boils down to “That law / regulation / rule does not apply to us, because we are the government.”

I can ride the length of the DCRT and back in about two hours, averaging 12 mph, without getting particularly sweaty in the process; the track in that link shows a three hour ride that includes the HVRT and a Walkway scrum, plus the ride from and to home. A police ATV can’t go much faster than that on the trail, even with lights and sirens, because oblivious pedestrians keep getting in the way.

If an officer on a bike can’t keep up with me, then something has gone badly wrong with the job requirements for becoming a deputy sheriff.

As far as “being prepared for anything” goes, the cargo capacity of those little ATVs rules out a bunch of hardware that fit in the big ones: anything seems an elastic concept. A bike can carry enough equipment for many incidents; my tool kit weighs more than some bike frames, the packs have plenty of room to spare, and there’s always the trailer option. I doubt genuine Mil-Spec assault rifles would come in handy on the rail trail.

It’s also not clear why an officer on a bike can’t call for the same backup as an officer on an ATV: those buggies lack fancy VHF antennas, so they’re using a hand-held radio or phone. The 5 W amateur radio on my bike, through a mobile VHF antenna on a crappy ground system, can easily reach local amateur radio repeaters and APRS nodes. Many pedestrians seem absorbed with their phones, so getting microwaves into and out of the trail doesn’t pose much of a problem.

Cops-on-bikes present a much less aggressive aspect than cops-on-ATVs who ignore the rules that apply to the rest of us.

They could do it differently, as the department has both bikes and ATVs.



Eroded PTT Cable

While installing new underseat packs (about which, more later) on my Tour Easy, I discovered a bight of PTT cable had been touching the top of the chain:

Eroded PTT cable - Tour Easy

Eroded PTT cable – Tour Easy

The gentle ripples to the right of the worn-through section seem particularly nice; you couldn’t do that deliberately if you had to.

This section of cable should have been taped to the upper frame bars. It’s hidden under the seat, just in front of the rear fender, and between the under-seat packs, so it’s basically invisible from any angle.

Soooo, that probably explains a bit of the intermittent trouble I’d been having with the PTT switch, although most of it came from the corroded switch contacts.

Rather than replace the whole cable, I cut out the eroded section, spliced the conductors, and taped it firmly back on the tubes.


Tour Easy: Push-to-Talk Switch Rework

The handlebar-mounted PTT button for the amateur radio on my bike once again went toes-up, most like due to the accumlation of road dust and rainwater over the years. Rather than replace the switch, which would require peeling off a massive glob of hot melt glue and resoldering the wires, I just carved the tops off the rivets holding the cover in place, pried off the cover, and removed the button to reveal the top of the switch dome:

Handlebar PTT switch - corroded dome

Handlebar PTT switch – corroded dome


The dome flexes outward to contact the (rather crusty) terminals on either side, so all the action happens under the dome.

A lineup of the plastic button, the inverted dome, and the cover plate:

Handlebar PTT switch - components

Handlebar PTT switch – components

The top and bottom of the dome show some grit: that’s where it contacted the switch terminals.

Wiping the crud out of the switch body, scrubulating everything with contact cleaner, and putting it all back together restored the switch to working order. There’s (once again) a snippet of Kapton tape over the cover holding it in place, but I don’t expect this to last very long:

Handlebar PTT switch - kapton cover

Handlebar PTT switch – kapton cover

But it works well enough for now …


Sony HDR-AS30V vs. ExFAT vs. Ext2 Times: Total Bafflement

I’d like to overlay a timestamp on still images extracted from Sony HDR-AS30V camera videos, ideally including the frame number, to record exactly when the incident occurred. Movie players use relative time, with 00:00:00 at the beginning of the file, so we’ll need either the file timestamp or the timestamp recorded in the image’s Exif data, plus the frame number modulo 60 (or, shudder, 59.94 for NTSC).

The ExFAT format used on 64 GB MicroSD cards stores the file’s creation time, its modification time (writing data), and the most recent access time (reading data). That’s similar to the Linux ext2/3/4 filesystem time and unlike plain old FAT, which omits the access time.

The various FAT formats store local time, with no regard for time zones, Daylight Saving Time, or anything else. Linux stores times as UTC and converts to local time on the fly. This has catastrophic consequences for getting any of this right.

It helps to have alias ls='ls -h --color=auto --time-style=long-iso' in your .bashrc file.

The HDR-AS30V has a year-month-day calendar, a 24-hour clock, a Time Zone value, and a separate DST on/off setting.

Turning DST on adds 1 hr to the Time Zone value, turning it off subtracts 1 hr. That has the side effect of changing the clock time: not what I expected. You must, therefore, set the TZ first, then DST, then the clock, which does not follow the menu’s natural order of things.

The camera sets file timestamps as it creates the files, but Linux also meddles with the values while displaying them. Some doc suggests that Linux regards FAT file timestamps as UTC and applies DST correction, which seems to match what I see. There’s a mount option (-o tz=UTC) that seems to have no effect, as well as an undocumented time offset (-o time_offset=60) that also has no effect.

Setting the TZ to GMT+0 (Sony uses GMT, not UTC) for simplicity, setting the clock to the correct local time, and twiddling DST shows that:

  • Rebooting (remove /insert battery) doesn’t change anything
  • Metadata in file = clock setting – DST setting (-1 on, +0 off)
  • MP4 / THM file create / modify times = always clock +1 hour
  • MP4 / THM file access times = as create / modify until next Linux access

Under those conditions, with the clock set to (locally accurate) 1908, UTC+1, and DST off, then the Exif timestamp metadata for a movie created at that time look like this:

exiftool /mnt/part/MP_ROOT/100ANV01/MAH00036.MP4 | grep -i date
File Modification Date/Time     : 2014:09:01 20:08:09-04:00
File Access Date/Time           : 2014:09:01 19:10:14-04:00
File Inode Change Date/Time     : 2014:09:01 20:08:09-04:00
Create Date                     : 2014:09:01 19:08:03
Modify Date                     : 2014:09:01 19:08:08
Track Create Date               : 2014:09:01 19:08:03
Track Modify Date               : 2014:09:01 19:08:08
Media Create Date               : 2014:09:01 19:08:03
Media Modify Date               : 2014:09:01 19:08:08

The corresponding filesystem values:

ll /mnt/part/MP_ROOT/100ANV01/
total 146M
... snippage ...
-rwxr-xr-x 1 ed root  14M 2014-09-01 20:08 MAH00036.MP4
-rwxr-xr-x 1 ed root 8.5K 2014-09-01 20:08 MAH00036.THM

ll -c /mnt/part/MP_ROOT/100ANV01/
total 146M
... snippage ...
-rwxr-xr-x 1 ed root  14M 2014-09-01 20:08 MAH00036.MP4
-rwxr-xr-x 1 ed root 8.5K 2014-09-01 20:08 MAH00036.THM

ll -u /mnt/part/MP_ROOT/100ANV01/
total 146M
... snippage ...
-rwxr-xr-x 1 ed root  14M 2014-09-01 19:10 MAH00036.MP4
-rwxr-xr-x 1 ed root 8.5K 2014-09-01 20:08 MAH00036.THM

The THM file contains a 160×120 pixel JPG thumbnail image taken from the first frame of the corresponding MP4 file. For longer movies, it’s more obvious that the MP4 file creation date is the start of the movie and its modification date is the end. The maximum 4 GB file size of corresponds to exactly 22:43 of 1920×1080 movie @ 60 frame/sec (the metadata says 59.94).

The +1 hour offset in the file create / modify times comes from the FAT timestamp being (incorrectly) adjusted by the Linux DST setting. When exiftool reads the MP4 file, that resets its access time to the actual time as seen by Linux, thereby crushing the bogus FAT time.

Doing the seemingly sensible thing of setting the camera to have the correct local time (roughly 1930), the correct time zone, and the correct DST setting produces this jumble:

exiftool /mnt/part/MP_ROOT/100ANV01/MAH00037.MP4 | grep -i date
File Modification Date/Time     : 2014:09:01 20:33:15-04:00
File Access Date/Time           : 2014:09:01 20:33:14-04:00
File Inode Change Date/Time     : 2014:09:01 20:33:15-04:00
Create Date                     : 2014:09:01 23:33:11
Modify Date                     : 2014:09:01 23:33:14
Track Create Date               : 2014:09:01 23:33:11
Track Modify Date               : 2014:09:01 23:33:14
Media Create Date               : 2014:09:01 23:33:11
Media Modify Date               : 2014:09:01 23:33:14

ll /mnt/part/MP_ROOT/100ANV01/MAH00037*
-rwxr-xr-x 1 ed root  11M 2014-09-01 20:33 /mnt/part/MP_ROOT/100ANV01/MAH00037.MP4
-rwxr-xr-x 1 ed root 8.2K 2014-09-01 20:33 /mnt/part/MP_ROOT/100ANV01/MAH00037.THM

ll -c /mnt/part/MP_ROOT/100ANV01/MAH00037*
-rwxr-xr-x 1 ed root  11M 2014-09-01 20:33 /mnt/part/MP_ROOT/100ANV01/MAH00037.MP4
-rwxr-xr-x 1 ed root 8.2K 2014-09-01 20:33 /mnt/part/MP_ROOT/100ANV01/MAH00037.THM

ll -u /mnt/part/MP_ROOT/100ANV01/MAH00037*
-rwxr-xr-x 1 ed root  11M 2014-09-01 19:34 /mnt/part/MP_ROOT/100ANV01/MAH00037.MP4
-rwxr-xr-x 1 ed root 8.2K 2014-09-01 20:33 /mnt/part/MP_ROOT/100ANV01/MAH00037.THM

The only correct time in that mess is in the next-to-last line: the access time for the MP4 file. Every other timestamp comes out wrong, with the internal metadata values being off by +4 hours; that suggests the camera sets the internal timestamps to UTC.

As nearly as I can figure, the only way to make this work requires setting the clock to the local time, TZ to UTC+0, and DST off. That will screw up the filesystem timestamps, but at least the Exif metadata will be correct, for some value of correct.

The camera’s GPS receiver depends on the clock for its initial synchronization. I don’t know how the TZ and DST settings affect the clock’s correctness for that purpose.

I do not know if / how / when the displayed times have been altered by the programs that display them.

I think exiftool can extract the times from the internal metadata and fix up the filesystem times, but that’ll take more tinkering.

Sheesh & similar remarks…


Cycling the Hudson Valley: 2014

Seven days and 300 miles of pedal pushing:

KE4ZNU route - 2014-07-28 through 2014-08-04

KE4ZNU route – 2014-07-28 through 2014-08-04

We rode north to the start of the Cycling the Hudson Valley ride in (wait for it) Hudson, rode south while crossing the Hudson six times, then I rode north from Da Bronx while the other 100 riders proceeded south to the tip of Manhattan and the finish line in Brooklyn. Mary, alas, drove the last few days to avoid aggravating a tender tendon.

While everybody else had a touristing day in Hyde Park, we slept in our own beds for two nights.

Everything you need to know about modern bicycle touring:

Cycling the Hudson Valley - Charging Station

Cycling the Hudson Valley – Charging Station

The straight line along the right side of the map, from just below the New Croton Reservoir to Hopewell Junction, represents data loss from riding in a valley, plus knocking the coaxial power plug out of the battery pack where the South County Trail becomes one with Rt 100 / Saw Mill River Road for a few miles.

That last day had plenty of hillclimbing, even on the rail trail, but with a rewarding section of Rt 52 that drops 500 feet in a mile; I hit 41 mph while passing under I-84.

A good time was had by all!


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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