Month: December 2016

Oddities, Photography & Images

Airliner Over Snow

Poughkeepsie lies under the southbound airliner routes to the NYC airports, so we often see airplanes high overhead. With a few inches of snow on the ground, a sunny day turns them brilliant white against a blue sky:

Air Canada Flight 706 - Embraer ERJ-190 - snow uplight
Air Canada Flight 706 – Embraer ERJ-190 – snow uplight

Feeding “Poughkeepsie NY” into FlightAware produces a map centered over us with (in this case) two candidates, one of which was Air Canada Flight 706, an Embraer ERJ-190. The obvious search produces pictures confirming the ID.

Air Canada’s current livery shows white paint on the bottom, but plain aluminum bodies shine brilliantly, too.

Back when I used to fly, light snow highlighted the networks of stone walls around all the old farms across the Northeast, from back when this area was NYC’s breadbasket. Those days are gone, but the stones remain where those farmers hauled them out of the fields.

 

Home Ec, Machine Shop

Respooling Stainless Steel Thread: The Knack

The comments on my previous stainless-steel thread respooling attempt suggested that I was entirely too much of a sissy, so, when another empty spool appeared, I tried again with more vigor:

Stainless steel thread - second spool
Stainless steel thread – second spool

As before, I put the larger spool on the floor under the lathe and let the thread spill straight off the top toward the smaller spool. This time, I didn’t have a twist accumulating in the loose thread between the two spools:

  • Grab longer lengths of the loose thread
  • Absolutely no slippage between the fingers!
  • Put more tension on the thread at the takeup spool

As nearly as I can tell, the thread still has a slight twist coming off the larger spool, but grabbing longer lengths captures the twist and more tension lays it on the smaller spool. After cutting the thread, what was left had maybe three turns of twist, which was no big deal and obviously hadn’t accumulated.

Seems better: thanks for all the comments!

Electronics Workbench

Fordham FG-801 Function Generator Recalibration

While I had the case open, I checked the FG-801’s calibration:

Fordham FG-801 Fn Gen - circuit board
Fordham FG-801 Fn Gen – circuit board

Look at all those parts!

The raw filtered DC power supplies run a bit high and the output voltages & frequencies were off by a little, but not too much after all these years.

Page 11 of the instruction manual gives the setup and calibration adjustments (clicky for more dots):

Fordham FG-801 Manual - Page 11
Fordham FG-801 Manual – Page 11

Page 12 gives some values that should be true:

Fordham FG-801 Manual - Page 12
Fordham FG-801 Manual – Page 12

For whatever reason, the manual isn’t available on The InterWebs, so here it is for your amusement:

Fordham FG-801 Sweep Function Generator – Instruction Manual.pdf

Electronics Workbench, Machine Shop

Fordham FG-801 Function Generator Power Switch

The power switch in my trusty Fordham FG-801 Function Generator failed with an accumulation of oxidation / crud on the contacts. That’s fix-able, but the switch contained not one, but two powerful springs, and puked its guts all over the floor around the Squidwrench Operating Table. Even with (a preponderance of) the parts in hand, I couldn’t figure out how to reassemble the thing; the only way out was to replace the switch.

The OEM switch had a 0.360+ inch diameter pushbutton that fit into a ⅜ inch hole and, alas, my remaining stock of line-voltage switches had toggle levers and used ¼ inch holes. So I converted a bit of aluminum rod into a suitable bushing:

Fordham FG-801 Fn Gen - new switch hardware
Fordham FG-801 Fn Gen – new switch hardware

The lock washer in the middle started with a much wider tab that I filed down into a tooth for the dent from a #2 center drill. Protip: center drills don’t walk off like twist drills, even when you hand-hold the front panel at the drill press with all the electronics dangling below.

The bushing dimension doodle:

Fordham FG-801 Function Generator - Replacement Switch Bushing
Fordham FG-801 Function Generator – Replacement Switch Bushing

The internal wiring routes the 120 VAC line conductor to the switch, then to the fuse, then to the transformer. I don’t know whether it’s better to have an unfused switch or an unswitched fuse (surely there’s a UL spec for that), but I didn’t change anything. The new switch, being slightly smaller and mounting directly on the panel, required a new wire (the blue one) from the fuse:

Fordham FG-801 Fn Gen - power switch - installed
Fordham FG-801 Fn Gen – power switch – installed

The OEM switch mounted on two round brass standoffs and, wonder to tell, the new switch fit between them!

From the front, the new switch looks like it grew there:

Fordham FG-801 Fn Gen - switch in action
Fordham FG-801 Fn Gen – switch in action

The PCB mounts to the top of the case with one screw and four hexagonal brass standoffs. The standoffs have 6-32 tapped holes on one end and a 6-32 stud on the other; one of those stud had broken off. A 6-32 stainless steel screw secured in a clearance hole with a dab of epoxy solved that problem:

Fordham FG-801 Fn Gen - standoff stud
Fordham FG-801 Fn Gen – standoff stud

I stood it vertically and tweaked the screw to be perpendicular while the epoxy cured.

Memo to Self: The next time around, put a nut on the stud to make sure the answer comes out right. I didn’t do this time to avoid epoxying the nut to the standoff.

Done!

Electronics Workbench, Machine Shop, Software

Loop Antenna Splice Reinforcement

Those solder joints and finicky little wires seem much too fragile on their own:

LF Loop Antenna - complete joint
LF Loop Antenna – complete joint

This should help:

Loop Antenna Splice - assembled
Loop Antenna Splice – assembled

Foam blocks hold the ribbon cable in place and provide a bit of strain relief around the hard plastic edge:

Loop Antenna Splice - hardware
Loop Antenna Splice – hardware

The brass inserts in the bottom block (on the left) got epoxied in place, because they must provide quite a bit of force to clamp the foam. Their larger knurled end sits flush with the outside surface and the smaller end has one thread thickness of clearance below the inner surface.

A last look at the wiring:

Loop Antenna Splice - wiring
Loop Antenna Splice – wiring

I think the preamp must sit at some distance from the antenna to prevent feedback, but that remains to be seen.

The M2’s nozzle accumulated a huge blob of PETG that turned into a giant smear:

Loop Antenna Splice - PETG booger
Loop Antenna Splice – PETG booger

Fortunately, it’s on the inside where nobody will ever see it. If you know where to look, it’s barely visible from the outside.

The solid model shows off the structure a bit better:

Loop Antenna Splice - show view
Loop Antenna Splice – show view

The inside view:

Loop Antenna Splice - bottom
Loop Antenna Splice – bottom

The OpenSCAD source code as a GitHub Gist:

// Ribbon cable loop antenna splice
// Ed Nisley KE4ZNU December 2016
Layout = "Text";
//- Extrusion parameters must match reality!
ThreadThick = 0.25;
ThreadWidth = 0.40;
HoleWindage = 0.2;
Protrusion = 0.1; // make holes end cleanly
inch = 25.4;
function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);
//----------
// Dimensions
Cable = [200,48.0,1.5]; // X = longer than anything else
Splice = [15.0,53.0,5.0]; // epoxy blob around joints
Foam = [15.0,Splice[1],2.0];
CornerRadius = 5.0;
ID = 0;
OD = 1;
LENGTH = 2;
Insert = [3.9,4.6 - 0.1,5.8]; // 4-40 knurled brass insert
Screw = [2.7,5.5,2.0]; // OD = head LENGTH = head thickness
Washer = [3.0,8.0,0.8];
BlockOA = [60.0, // convenient length
Splice[1] + 4*Washer[OD], // clearance around washer on top
2*(Insert[LENGTH] + 2*ThreadThick)]; // insert sets both thicknesses
NumScrews = 2; // screws along each side of cable
ScrewOC = [BlockOA[0] / NumScrews,
BlockOA[1] - 2*Washer[OD],
2*BlockOA[2] // ensure complete holes
];
TextThick = 3*ThreadThick; // depth of text into surface
TextFit = HoleWindage/2; // clearance around text polygons
//----------------------
// Useful routines
module PolyCyl(Dia,Height,ForceSides=0) { // based on nophead's polyholes
Sides = (ForceSides != 0) ? ForceSides : (ceil(Dia) + 2);
FixDia = Dia / cos(180/Sides);
cylinder(d=(FixDia + HoleWindage),h=Height,$fn=Sides);
}
//-----
// Blocky model of cable + splice + wire tap for subtraction
module Antenna() {
union() {
cube(Cable,center=true);
cube(Splice,center=true);
for (i=[-1,1])
translate([0,-Splice[1]/2,0])
cube([Splice[0]/2,Splice[1],2*Foam[2]],center=true);
}
}
// Outside shape of splice Block, less screw clearance
module SpliceBlock() {
difference() {
hull()
for (i=[-1,1], j=[-1,1])
translate([i*(BlockOA[0]/2 - CornerRadius),j*(BlockOA[1]/2 - CornerRadius),-BlockOA[2]/2])
cylinder(r=CornerRadius,h=BlockOA[2],$fn=4*8);
for (i = [0:NumScrews - 1], j=[-1,1])
translate([-BlockOA[0]/2 + ScrewOC[0]/2 + i*ScrewOC[0],j*ScrewOC[1]/2,-(BlockOA[2]/2 + Protrusion)])
PolyCyl(Screw[ID],BlockOA[2] + 2*Protrusion,6);
}
}
// Splice block less cable
module ShapedBlock() {
difference() {
SpliceBlock();
Antenna();
}
}
// Bottom
module BottomPlate() {
difference() {
ShapedBlock();
translate([0,0,BlockOA[2]/2])
cube(BlockOA + 2*[Protrusion,Protrusion,0],center=true);
Antenna(Splice);
for (i = [0:NumScrews - 1], j=[-1,1])
translate([-BlockOA[0]/2 + ScrewOC[0]/2 + i*ScrewOC[0],j*ScrewOC[1]/2,-(BlockOA[2]/2 + Protrusion)])
PolyCyl(Insert[OD],2*Insert[LENGTH],6);
for (i=[-1,1])
translate([i*((BlockOA[0] - Foam[0] + Protrusion)/2),0,(BlockOA[2]/2 - Cable[2]/2 - Foam[2])])
cube([Foam[0] + Protrusion,Foam[1],BlockOA[2]],center=true);
}
}
// Top
module TopPlate() {
difference() {
ShapedBlock();
translate([0,0,-BlockOA[2]/2])
cube(BlockOA + 2*[Protrusion,Protrusion,0],center=true);
Antenna(Splice);
for (i=[-1,1])
translate([i*((BlockOA[0] - Foam[0] + Protrusion)/2),0,-(BlockOA[2]/2 - Cable[2]/2 - Foam[2])])
cube([Foam[0] + Protrusion,Foam[1],BlockOA[2]],center=true);
rotate(90) {
translate([0,6,BlockOA[2]/2 - TextThick])
TextHack("KE4ZNU",8,0.0,1.15,TextThick + Protrusion);
translate([0,-6,BlockOA[2]/2 - TextThick])
TextHack("2016·12",6,0.0,1.20,TextThick + Protrusion);
}
}
}
module TextHack(Text="sample",Size=10,Offset=0.0,Space=1.0,Thick=ThreadThick) {
linear_extrude(height=Thick,convexity=10)
offset(r=Offset)
text(Text,font=":bold",size=Size,spacing=Space,halign="center",valign="center");
}
//----------
// Build them
if (Layout == "Antenna")
Antenna();
if (Layout == "SpliceBlock")
SpliceBlock();
if (Layout == "ShapedBlock")
ShapedBlock();
if (Layout == "Bottom")
BottomPlate();
if (Layout == "Top")
TopPlate();
if (Layout == "Text") {
translate([0,6,0])
TextHack("KE4ZNU",8,-TextFit,1.15,TextThick);
translate([0,-6,0])
TextHack("2016·12",6,-TextFit,1.20,TextThick);
}
if (Layout == "Show") {
translate([0,0,5])
TopPlate();
translate([0,0,-5])
BottomPlate();
color("Orange",0.2)
Antenna();
}
if (Layout == "Build") {
translate([0,-0.6*BlockOA[1],BlockOA[2]/2])
rotate([180,0,0])
TopPlate();
translate([0,0.6*BlockOA[1],BlockOA[2]/2])
BottomPlate();
}
view raw Loop Antenna Splice.scad hosted with ❤ by GitHub
Photography & Images

Red Oaks Mill Dam: Icy Water

Two recent walks showed the wintry side of the Mighty Wappinger Creek at Red Oaks Mill:

Red Oaks Mill Dam 2016-12-11
Red Oaks Mill Dam 2016-12-11

Plants growing on mid-stream rocks accumulate ice during a cold snap:

Red Oaks Mill Dam 2016-12-11 - ice on rocks 2
Red Oaks Mill Dam 2016-12-11 – ice on rocks 2

Even bare rocks sprout rims:

Red Oaks Mill Dam 2016-12-11 - ice on rocks 1
Red Oaks Mill Dam 2016-12-11 – ice on rocks 1

A week later, half a foot of snow added highlights:

Red Oaks Mill Dam 2016-12-18
Red Oaks Mill Dam 2016-12-18

Warmer air over the snow and ice filled the valley with low-lying fog:

Red Oaks Mill Dam 2016-12-18 - upstream fog
Red Oaks Mill Dam 2016-12-18 – upstream fog

Although it’s not quite as pastoral, a touch of pictorial graffiti recently appeared under the bridge carrying Rt 376 over the creek:

Red Oaks Mill Dam 2016-12-18 - graffiti
Red Oaks Mill Dam 2016-12-18 – graffiti

The “No war just smoke” tag suggests someone with a fundamental misunderstanding of life, somewhat along the lines of those absurd “Coexist” bumper stickers.

Anyhow, a happy holiday to one & all…