Thursday, August 25, 2016

Workbench: Screw Terminal Adapters and Lever-Nuts

Having collection of connectors with screw terminals or lever clamps is very useful.  In a pinch you could do a field-repair on a headset, a rig interface, or resurrect a broken power cord with just a pocket knife and a screwdriver.  Here are some of my favorites:

DC Barrel Connectors - these can be used to make a quick disconnect (in lieu of a switch) or an extension cord.  If you just want the plug to match an existing device, you'll have to measure the outer diameter and inner pin.  Most of the time the outer dimension is 5.5mm, and the inner pin is either 1.7mm, 2.1mm, or 2.5mm.

2.1 x 5.5mm paired DC Barrel Connectors

TRS "Phono" Connectors - these are really useful for building test cables or attaching a rig interface to the ADC port on an Arduino or ESP8266.  When you get to the mountain for a SOTA activation and realize your 5 year-old has yanked the end off your headphones, you'll want one of these.

1/8" (3.5mm) Tip-Ring-Sleeve "phono male" plug

1/8" (3.5mm) Tip-Ring-Sleeve "phono female" jack

For pocket tools, I prefer the Leatherman ES4 Squirt.  ( It's a ham's dream tool, with a wire stripping jaw, knife, scissors, file, and a screwdriver bit that works well on these screw terminal adapters.

Other interesting stuff....

Wago Lever-Nuts - these are really useful for quick repairs or experiments where you want to easily connect and disconnect wires.  You can use them to quickly add sections of wire for tuning dipole antennas.  Lift the lever, slide in a wire (or wires plural) and drop the lever - done.  Made a mistake?  Lift the lever, change, drop the lever.  They'll handle up to 400 VAC and 20 amps, so they can be used for household electrical repairs or rig power cords.  I keep a handful of these in my field bag, some my glove compartment, and a bunch on my bench.  I prefer the newer 221 Series because the lever is wider and easier to manipulate.

BNC Female w/ screw terminal - these are 75 ohm, designed for CCTV installs, but for receiver testing or low-power transmit they'll work OK.  Be aware that some adapters like this actually have baluns, which you don't want for RF testing.

RJ45 screw terminal plug - kinda bulky, but it's great for designing cables on a bench.  When I'm done and have a working design, I build a real cable using CAT6 and an RJ45 crimper or a punch-down terminal block.

Sunday, August 21, 2016

Repost: How to fix a Toyota Brake Light

Note: This is a repost/update from my old blog. 

Toyota Highlanders are well made cars - I bought a 2004 for my wife who later upgraded to a Sienna minivan, so I took the Highlander for myself.  It's at 130,000 miles and still going strong.  However, apparently they have a known problem where the brake lights on one side will intermittently stop working.  I've had people pull up next to me at stop lights and tell me I have a light out, then I get home to find the light is fine.

Then recently the light went out and stayed out.  I replaced the bulbs but they remained out.  Fuses were fine, my trusty Fluke 77 said voltage was getting to the assembly.  Posters in Toyota forums said that dealers are asking $40 - $140 for diagnostic, plus possibly $300 to replace a "circuit board"...?  Sounds like a scam to me.

I did some searching online and found reference to how the contacts on the bulb holder will get compressed and not make proper contact. (Kudos to Berto for the original post and Kujath for the photos.)  Kujath suggested using a flat-blade screwdriver to bend the contacts a bit, but I think a needle-nose pliers works better since you can control the amount of bending.  I did both bulb holders and the lights are working just fine. 

Monday, August 15, 2016

Use It or Lose It : Google makes a play for part of the 3.3 GHz amateur band

I've presented several times at Pacificon on the topic of spectrum auctions and the threat to amateur radio's allocations.  In my talk Ham Radio Must Die (So It Can Live) at Pacificon 2010, I specifically talked about the threat to the 3300 - 3500 MHz band.  The threat increased exponentially when the FCC converted the 3500 MHz band to the Citizen's Broadband Radio Service for use in heterogenous networks and densified mobile data systems, and now Google is asking the FCC for permission to test a wireless last-yard technology for delivering Google Fiber service in the upper half of the 3300 MHz band.

In my Pacificon talk I pointed out that the 3300 MHz band is almost never used, and the possible auction valuation to commercial users is very high.  If we presume a $2 per MHz-POP auction price (which is about what the AWS-3 commercial carrier spectrum went for) and a US population of 320 million, the value of the 3300 MHz band is $128 billion.  The AWS-3 auction, record-setting though it was, only raised $47 billion.  For a government $19 trillion in debt, $128 billion isn't much but it's a start.  Google could afford to buy that spectrum, and with the unprecedented access it enjoys due to the revolving door between itself and the White House, it has the political clout to make this happen.

There are just over 800,000 licensed amateur operators in the USA.  $128 billion puts the value of our 3300 MHz band at $160,000 PER OPERATOR.  For something we never use.  I'd be willing to say (and I'm being very charitable in this estimation) that 0.1% of all US operators make use of the 3300 MHz band.  That's $160 MILLION PER ACTIVE OPERATOR.

I'm not saying what Google's doing is right.  If you think it's wrong, file comments with the FCC.  I'm saying what they're doing is not surprising, and that I predicted this would happen six years ago.