Tuesday, February 20, 2018

I Think This Is My Favorite 2018 Olympics Story

This is the story of Elizabeth Swaney, a 33-year old American skier who by studying what it takes to qualify, persistence, dedication, and setting goals for herself, is skiing for Hungary in the 2018 Winter Olympics still underway in Korea. 

By all accounts, Elizabeth is a mediocre skier, but that didn't stop her dreams of making the Olympics.  She learned what she had to do to make it and did everything she needed to do.
Swaney's half-pipe run on Monday involved one quasi-trick, no air, and a last-place finish. She frequently did not clear the top of the half-pipe. She qualified for the Olympics by leveraging her grandparents' Hungarian birth to attend International Ski Federation World Cup events, where she regularly finished among the top 30 skiers because fewer than 30 skiers showed up to compete.
One commentator I heard said that, unlike the stars of her sport, she'd show up at small events.  Some of them were so small, they didn't have 30 skiers.  That guaranteed she'd finish in the top 30. 
International Ski Federation judge Steele Spence told The Denver Post, "She would compete in [events] consistently over the last couple years and sometimes girls would crash so she would not end up dead last."
The Guardian puts it this way:
A Harvard graduate who once ran against Arnold Schwarzenegger in the race to be California governor, Swaney only started skiing at 25 and has been driven ever since in her quest to compete at an Olympics. After raising funds through online donations to help fuel her Olympic ambitions, Swaney managed to qualify for Pyeongchang due to the sheer volume of competitions she attended.
OK, so she's not a great skier.  So what?  It doesn't appear that "great skier" was her goal.  Her goal was being there - at the Olympics, in the athlete's village, living the life of an Olympian.  She made her goal through persistence and hard work.  I just can't find fault with that.  Lots of athletes compete for countries other than where they live and train - you see it all the time.  She's Hungarian by their laws, she qualified by rules everyone acknowledges are the rules. 


Liz Swaney photo from Instagram

Back in 2014,  US Navy Admiral William H. McRaven, gave a commencement speech to the University of Texas at Austin.  It has become a speech that was talked about a lot then and still bears paying attention, or watching the video.  It's called the 10 Life Lessons From Seal Training.  I think number 10 describes Liz Swaney perfectly. 
10. If you want to change the world, don’t ever, ever ring the bell.
“In SEAL training there is a bell. A brass bell that hangs in the center of the compound for all the students to see. All you have to do to quit – is ring the bell. Ring the bell and you no longer have to wake up at 5 o’clock. Ring the bell and you no longer have to do the freezing cold swims. Ring the bell and you no longer have to do the runs, the obstacle course, the PT – and you no longer have to endure the hardships of training. Just ring the bell. If you want to change the world, don’t ever, ever ring the bell.”
Reword that somewhat to "If you want to achieve your goals, don't ever, ever quit".  She set a clear goal, figured out how to get from nowhere near the goal to achieving it, and never, ever, quit.  In an Olympics mostly filled with celebrity Trump Derangement Syndrome, fawning over the North Korean Propaganda Minister, defining "not medaling while gay" as winning everything, I think I like Liz Swaney best of all.



Monday, February 19, 2018

Parkland

I haven't said anything about the Marjory Stoneman Douglas High School shooting last week down in Parkland.  I know the area and was in Parkland about a month ago (drove through it); it's about 7 or 8 miles from where my brother lives and along the route we used to drive from his place to my mom's house.  A couple miles closer to where I lived in the late 70s/early 80s.  Not that it's particularly relevant. 

To begin with, if you want to see a truly epic fisking of "we're coming to take your guns", see Raconteur Report's perspective, but there are lots of others people talking about this.  If anything, I see the result of a Feinstein-like, "turn them all in, America" as being worse (for them) than he says.  And, as McThag said for so many of us, I'm sick to death of being blamed for things I had nothing to do with.

The media and the Evil party (pardon my redundancy) are without exception saying we need to do something ("ban all the things!") and have completely steadfastly avoided mentioning anything that might actually work.

In intervening days, I've heard a few of the kids from school sounding very rational - as a counterpoint to the political demonstrations where the Useful Idiots staged a die in.  What's that awful smell?  Is it the DNC?  George Soros?  Michael Bloomberg?  What's the difference? 

With surprising regularity, comedians "get it" far more than their serious counterparts (exceptions for certain so-much-smarter-than-us late night comedians).  Saturday nights at 10 PM, Fox News channel runs the Greg Gutfeld show.  It's a time I frequently find myself sitting in the living room finishing up an hour of guitar practice, so I frequently end up watching. 

Greg's regular panel of commentators includes former professional wrestler Tyrus, who has also been a teacher and a personal bodyguard (to Snoop Dog).  He actually had a pretty good summary of what will work and I'm going to paraphrase madly.  He started by saying that just as 9/11 changed air travel forever, we need to change schools forever.  First, schools need access control.  One of the kids I heard said the killer walked onto campus from a nearby field (it tends to be woodsy in Parkland) and then into a doorway to a stairwell on school property.  That's where he started the attacks.  Nothing to block just walking into the building.  No locks, no searches, no "scanning in" with a card, no combination locks, nothing.  Why is that banks have access control, along with every other institution you can name, but not every school?   

Let's leave out the TSA grope and Perv-o-scan, though, and maybe just scan backpacks.  

Second, much like the air marshals on planes and arming pilots, we need to empower any teachers who are already concealed carriers and get them more training.  We're not talking about arming teachers, just helping those who have the ability to be better.  Guys like Coach Feis, who was a CCW carrier, but forbidden to have his gun at work, and so died because of that.   Polk County Sheriff Grady Judd made news over the weekend for saying he's going to train any teacher that wants it.  They call it their Sentinel Program and it was adopted by Southeastern University in Lakeland, Florida last year.  And my favorite part:
He acknowledged that some would not agree with his plan. However, he also noted that those who criticize have not offered alternatives, saying: “OK, Einstein, you got a better idea?”
Third, the media has to stop giving these horrible losers wall-to-wall news coverage.  They want their picture everywhere.  They thrive on being notorious for carrying out the worst shooting evah.  That's one of the reasons they do this.   Yeah, it's big news, but for cripe's sake, could you not show his picture every 5 seconds, like not show it at all?  And don't mention the guy's name.  He wants fame, not anonymity. 

Every other place that has things we value is protected by armed guards.  One "resource officer" isn't enough for a school the size of Stoneman Douglas - or anything much bigger than a one room schoolhouse.  Tyrus threw around the number that he understands approximately 435,000 veterans of the current wars are unemployed.  Many, if not all, are well trained in the use of firearms and would be easy to integrate into the school community.  Help the vets and help protect the kids in one move.

Frankly, while the talk about more screening for mental illness has some sense to it, it also raises my hackles about 4th amendment problems.  I was working on a long piece on this, but this guy on WRSA covers a lot of it.  As always, who decides and on what grounds?  What test?  Is there actual due process?  Do you get committed because a neighbor who's pissed off about your house/yard/car/dog/kids calls you in to the sheriff?  When the the Broward County sheriff's office is saying that people should call them when their neighbor comes back from the gun range instead of the grocery store (23:30 to 24:00 in that video), is that the kind of thing that gets you locked up for mental issues? 

It's hard to sum this up, but let's try this:  there are things we can do that will work, and then there's meaningless gun control blather.  All we're hearing in most of the media is things that we know won't work.  We need to try to push the discussion in the right direction. Give the PTB a little clue by four. 




Sunday, February 18, 2018

Blogiversary Time

It's time to announce that it's my:
OK, technically, my blogiversary is Wednesday because the first post I ever did was Sunday, February 21st, and Wednesday is the 21st.  On the other hand, I've traditionally posted about it on a Sunday because all across most of my reading list, Sunday is relatively quiet day.  On the other, other hand, I don't think I would have guessed that I'd be here posting pretty much daily for eight years back on that February Sunday so any day is a good day to notice. 

I didn't even do a blogiversary post last year.  I forgot.

Blogger tells me there were 1817 discrete pageviews yesterday, and most days I get a count in the range of 1500 to 1600.  I don't look every day or even every week, so I'm sure I miss a lot.  There could be days over 2000.
Pageviews all time history:         2,873,175
Total posts  (including this one):         2710
Most popular post of all time: A Little More About .308 vs 7.62x51 with 16,810 views
Most popular page of all time:  My AR-15 From an 80% Lower with 17,969 views
Thanks for stopping by.  My aim, as I regularly say, is to be a full service blog, so you never quite can tell what you're going to find next time, whether it's a picture of Alice Cooper and Colonel Sanders, or a discussion about antennas.  To make it worth every cent you pay to visit. 


Saturday, February 17, 2018

Introducing the Next Project

The book I ordered is in and I've started ordering the metals I don't have for the next project.


As is so often the case, the metal I ordered ended up being a fraction of the shipping.  The metal was about $18 and the shipping $30.  On one piece in particular is an extreme example, 3-1/2" diameter aluminum to turn down to 3-3/8", and about an inch thick.  The smallest piece I could find at Online Metals was a "random length" piece of bar, just guaranteed to be between 10 and 12" long, for $65.  Then I found this seller on eBay that would sell a 1" thick slice for $5 and $7 for shipping.  Even though the shipping is still more than the metal, it was nice to get it for $12 instead of $65 plus shipping. 

Frankly, Online Metals has gone from my "Go To guys" to "I'm not so sure about this" because of the shipping.  Again, the shipping was $30 for no more than (being generous) 4 pounds of metal that fits in a box that's 12 x 6 x 6".  The Postal Service tells me they'll ship it across country as 2 day priority mail "Regional Flat Rate Box A" at $10.18. They made it worse in my eyes by shipping the three pieces of metal in three boxes from three different warehouses with three different delivery dates.  Yes, I realize that the labor to gather the metals and put them in a box costs them something and they need to cover that cost, and I realize that the way the shipping industry works, they'll get different rates depending on a whole gaggle of factors. 

Griping aside, I have enough on hand to get started.  I also expect I'm going to go through this a few more times before I'm done.


Friday, February 16, 2018

A Little Look at the Heavy Lift Landscape

The launch of the SpaceX Falcon Heavy 10 days ago created a lot buzz online with dozens of people posting their own video captures of the Tesla Roadster in space.  Even conservative commentator Bill Whittle's channel did a half hour Right Angle show through the launch, marveling "this really happened!"

This week, ARS Technica presents some numbers to think about in a piece called, "The Falcon Heavy is an absurdly low-cost heavy lift rocket".  They compare the costs of the Delta IV Heavy, NASA's Space Launch System, and the Falcon Heavy.

For the baseline, SpaceX prices the Falcon Heavy rocket, with reusable side boosters, at $90 million.  For a fully expendable variant of the rocket, which is required for payloads and orbits that are so challenging that the boosters can't be recovered, the price is $150 million.  That includes a calculated maximum of 64 tons to low-Earth orbit.  The Heavy has not been DOD-certified yet, but SpaceX says its rocket can handle all known Department of Defense reference missions.
Only the Delta IV Heavy rocket, manufactured by the United Launch Alliance, also has this capability today. It is more expensive, but how much more is a matter of some debate. On Twitter this week, the chief executive of the Colorado-based rocket company, Tory Bruno, said the Delta IV Heavy costs about $350 million per flight. This figure, however, is strikingly lower than what Bruno cited during a congressional hearing in 2015, when he asserted that, "A Delta IV, depending on the configuration, costs between $400 and $600 million dollars."

Moreover, the costs referenced above by Bruno exclude a "launch capability contract" worth about $1 billion annually, which the US government pays exclusively to United Launch Alliance. Based upon current law, this contract payment will phase out in 2019 (for Atlas rockets) and 2020 (for Delta rockets), which should increase the costs allocated to each mission. Finally, in 2019, United Launch Alliance will make the last flight of a Delta IV Medium rocket. Once this variant is retired, all of the Delta's fixed costs will fall on the Heavy variant. This will push the per-flight cost above $600 million, and perhaps considerably higher, in the early 2020s.  [Bold added - SiG]
Bottom line, according to ARS, the DOD may have to pay half a billion dollars more for a single launch of certain military satellites on the Delta IV Heavy versus the Falcon Heavy.  The Delta IV Heavy has a longer track record than the Falcon Heavy, eight successful missions.  With the kinds of missions the DOD launches, they might think the more expensive rocket is a better investment for their Billion dollar payloads.  One wonders how long that might last.

The wildcard is NASA's Space Launch System, which will out lift even the Falcon Heavy.  It is, however, still in development.  The SLS is an impressive system, and a family of boosters (pdf warning) the smaller one of which has more liftoff thrust and payload than a Saturn V. 
However, these improvements come at a very, very steep price. Consider just a single data point: NASA annually spends about $2.6 billion to develop the SLS rocket and ground launch systems for the massive rocket at Kennedy Space Center. The SLS rocket was originally supposed to launch in 2017, but now the maiden flight of the SLS booster has slipped to 2020. That is understandable; most large aerospace rockets experience delays. However, the cost of a three-year delay is $7.8 billion.

For the sake of argument, consider the costs of this three-year delay against the lift capability NASA could have bought by purchasing Falcon Heavy rockets from SpaceX in 2018, 2019, and 2020. That $7.8 billion equates to 86 launches of the reusable Falcon Heavy or 52 of the expendable version. This provides up to 3,000 tons of lift—the equivalent of eight International Space Stations or one heck of a Moon base. Obviously NASA does not need that many launches, but it could buy several Falcon Heavy rockets a year and have the funds to build meaningful payloads to launch on them. [Bold added - SiG]
ARS states that in practical terms, NASA has paid nothing for the development of the Falcon Heavy rocket. In fact, by leasing its unused Launch Complex-39A to SpaceX for Falcon launches, the space agency has said it saves about $1 million in annual maintenance costs on the historical launch complex.  The numbers leave a former NASA deputy administrator saying:
"The question is really, why would the government continue to spend billions of dollars a year of taxpayer money for a rocket that will be unnecessary and obsolete?" Lori Garver, a deputy administrator of NASA from 2009 to 2013, told Ars. "If the US continues this travesty, it will siphon off even more funds NASA could otherwise use for science missions, transfer vehicles, or landers that actually get us somewhere."
Without a doubt, the successful test of the Falcon Heavy lobbed a metaphorical hand grenade into the launch business.  Even the Director General of the European Space Agency said they'd better start developing "disruptive ideas" to counter competitive pressure in the aerospace industry.  

There's no mention of the Blue Origin New Glenn booster, and no explanations, so while I know it's going to be big, perhaps they haven't released data to compare to the other vehicles.  



Thursday, February 15, 2018

A Little Interlude

After 3 hours in the dentist's chair, and the area being a lot more sore since the local anesthetic wore off, it's a good night for a short, light posting. 
Don't know where I got this; it was in the file I keep for nights like this.  If it's yours, I'll gladly credit you.


Wednesday, February 14, 2018

Science Photo of the Year

Look closely at the center of this photo:
There's a small dot visible in the apparatus, between the two turned-metal rods that taper down to tiny pins and the the two trapezoidal features that come down from the top and up from the bottom.  That bright spot is one single strontium atom, fluorescing in ultra violet light. 

The Engineering and Physical Science Research Council of the UK, EPSRC, has named this the photo of the year for 2017.  The description begins:
An image of a single positively-charged strontium atom, held near motionless by electric fields, has won the overall prize in a national science photography competition, organised by the Engineering and Physical Sciences Research Council (EPSRC).

‘Single Atom in an Ion Trap’, by David Nadlinger, from the University of Oxford, shows the atom held by the fields emanating from the metal electrodes surrounding it. The distance between the small needle tips is about two millimetres.

When illuminated by a laser of the right blue-violet colour the atom absorbs and re-emits light particles sufficiently quickly for an ordinary camera to capture it in a long exposure photograph. The winning picture was taken through a window of the ultra-high vacuum chamber that houses the ion trap.
Note that it said the distance between those two metal pins was about 2mm.  A quick lookup shows the atomic radius of a strontium ion to be around 220 picometer; so since that's about one 9 millionth of the gap, how is it that we see it?  I believe (but they don't say) that the atom itself is too small to see but the fluorescence is too bright to not be captured - much like star light at night to your eyes (on an angular basis, the star is far too small to see).  
David Nadlinger, explained how the photograph came about: “The idea of being able to see a single atom with the naked eye had struck me as a wonderfully direct and visceral bridge between the miniscule quantum world and our macroscopic reality. A back-of-the-envelope calculation showed the numbers to be on my side, and when I set off to the lab with camera and tripods one quiet Sunday afternoon, I was rewarded with this particular picture of a small, pale blue dot.”
My guess is his calculations involved the amount of light the atom would be re-emitting.

If you haven't seen individual atoms, they've been imaged regularly for since about 1981 with non-optical methods.  IBM famously spelled out their initials by dragging individual Xenon atoms into place to form the letters on a nickel crystal in 1989.  We could go into pages about what "seeing an atom" means, but that's probably better left for another time.



Tuesday, February 13, 2018

Interesting Play Day at the Range

I've written here many times over years about reloading and, since last summer, about my Ruger Precision Rifle in 6.5 Creedmoor that I got on a good sale last July (and even through another six months of sales in the gunny world, still a good price though not the very best).  Naturally, those two should go together, and the idea of doing precise handloads for the RPR has been at the front of my mind.  I bought dies for my RCBS Rock Chucker before I even had the rifle and have added some Berger "Elite Hunter" bullets in the 140 grain size the rifle seems to like.  The hardest component to acquire has been what seems to be the consensus choice for best powder, Hodgdon H4350.

NRA's Shooting Illustrated did a story on the 6.5 Creedmoor and keeps using the analogy of the "Perfect Storm".  On powders, they say,
... consider Hodgdon’s H4350 propellant. ... In the early days of production, Hornady, which makes reloading tools and components as well as ammo, published recommended hand-load data on the boxes of factory ammo using H4350 powder. Millions of shooters discovered that it worked so well, their search for the perfect handload started and ended right there.

In a normal handloading world, that would be a footnote in the cartridge introduction for future reloading manuals. In this perfect storm, it means there is a world-wide, multi-year shortage of H4350. Hodgdon is making and shipping more of the stuff than ever, but this huge popularity has caused the demand to far outstrip supply. It’s gone on for years and shows no signs of abatement. I have never seen anything like this and neither has Chris Hodgdon. He tells me that the company breaks records every month for the amount of H4350 shipped and still can’t meet demand, all because of the 6.5 Creedmoor. One cartridge, used almost exclusively for one purpose, is driving the H4350 market to unheard of heights. That is something the shooting world has never seen before.
I can verify that I've been looking for H4350 on every "Powder Sale" to cross my email since July and have yet to see in stock anywhere.  To date, I've had my best results with 140 gn Hornady ELD-M rounds, and I think it was one that talked about reloading with H4350 (I swear I recall seeing that on one of the first boxes I bought).  Chris Hodgdon goes on to recommend another powder his company makes:
Chris Hodgdon recommends using Enduron IMR4451. He told me, “It’s relatively the same burning speed as H4350. Enduron is temperature insensitive like H4350, plus it has copper-fouling-reducer technology.” 
IMR4451 seems to be more available, but ordering powders and working up loads is Research and Development, and other powders might be worth looking at.  Reloader 17, and the newer RL16 may be better (according to what "they say").  IMR4350 is another to investigate.  The only two rifle powders I have on hand are Hodgdon Varget and H4895.  Neither is recommended - but might produce serviceable reloads.

One of the things people recommend, and one that has come up around here a few times, is to use a chronograph.  A week ago last Saturday was my birthday, and I finally decided to treat myself to one, the MagnetoSpeed Sporter.  Today, I thought it was a good day to try it out at range.  Since I don't know anything about it, nor did I particularly trust it to work "first time, every time", I brought my AR and two boxes of factory 55 grain FMJBT PMC ammo, along with my Savage Scout rifle and a box of Winchester 7.61x52 147 grain.

Unlike most chronographs, the MagnetoSpeed design straps to your barrel, and instead of detecting the bullet by optical means, senses it with a magnetic field.  The Sporter model differs from the "big brother " V3 model by including fewer options for attaching to the gun, so I suspect it isn't as versatile for things like pistol reloads, but that's lower priority to me.   Besides, I think that stuff may be available - or copyable if you know someone with a machine shop. 


The advantages over the typical chronograph are substantial: no tripods to carry and set up, no wires between the tripod and shooting bench, no susceptibility to light and passing cloud shadows, no need to have the range go "cold" if the wind blows the tripod and chrony over.  The disadvantage is that the weight on the end of the barrel is going to mess up its harmonics and affect your point of impact.  It seems that might make the load development process a bit more iterative.  Develop a given speed and then test that speed without the Sporter hanging from the barrel.

The ultimate solution to that is probably something like Lab Radar, which has all of the same advantages as this, but doesn't hang from the barrel and change the point of impact.  At over 3x the price, a Lab Radar is not in the cards for me for the foreseeable future.  

One of the attractions of the MagnetoSpeed system is that they have a small accessory to allow you to download the captured session to your Android or iPhone device, and a free app in Google Play or iTunes store.  The app makes looking through the data you've taken easier than clicking through it on the control box that the sensor plugs into, and can then email the date to you as a Comma Separated Variables (.csv) file to load into your favorite spreadsheet program.  For example, here's the spreadsheet from the box of Winchester 308 I shot. 
Synced on: 2018-02-13 12:14:06

Series 2018-02-13_12_14_06 Shots: 18
Notes Winchester 147grn Mil Spec .308

Min 2787  Max 2861
Avg 2819  S-D 19.2
ES 74 





Shot Speed

1 2826 ft/s
2 2825 ft/s
3 2818 ft/s
4 2839 ft/s
5 2795 ft/s
6 2832 ft/s
7 2861 ft/s
8 2815 ft/s
9 2809 ft/s
10 2797 ft/s
11 2817 ft/s
12 2829 ft/s
13 2844 ft/s
14 2830 ft/s
15 2823 ft/s
16 2808 ft/s
17 2787 ft/s
18 2793 ft/s
---- ---- ---- ----
The ES value is Extreme Spread, or (Max - Min); S-D is the standard deviation of the series.

I feel pretty comfortable with the MagnetoSpeed now, after the first trip.  It gave me a couple of absurd values across two boxes of .223 - real WTF? values that you throw out when you see them.  In my case, it had one round at 4419 fps and the other at 3960.  If you care about the analysis and stats, you can do those in your spreadsheet.  I did.  It seems like the way to approach this might be to load eight of each weight of powder; four for the chronograph and four for a group.  Or three each with two spares. 

Now if I could only get my hands on a pound or two of H4350...



Monday, February 12, 2018

Rand Paul Was Right

Rand Paul famously shut down the government briefly in the early hours of the morning on Friday to make a point.  This prompted washed-up, old singer Better Midler to tweet, "where's Rand Paul's neighbor when we need him?" in apparent yearning for the days when his neighbor assaulted him for no apparent reason.  Senator Paul was quoted as saying,
“I don’t advocate for shutting the government down, but neither do I advocate for keeping it open and borrowing $1 million a minute. In fact, the statistics this year are closer to $2 million a minute,” Paul claimed. “This is a government that is horribly broken.”
He's right.  In fact $1 million a minute is too optimistic.  The official number from the Federal Reserve Bank of St. Louis (FRED) is that in 2017 the US ran a budget deficit of $666 billion.  The conversion is easy, and if you count every minute of the year (all 525,600 of them), that gives a spending rate of $1.27 Million per minute.  The budget plan is projecting a deficit of $800 billion in FY '18.  That's $1.52 Million per minute.  The Committee for a Responsible Federal Budget (CRFB), an independent think tank, projects that the deficit for FY '19 will balloon to $1.2 trillion in FY 2019, or $2.3 million per minute. 

Data from FRED, projections from CRFB, posted at the Daily Caller's Fact Check.

Long time readers will know that I'm a deficit hawk and believe this is eventually has to stop; a classic example of "things that can't go on forever, won't go on forever".  The amount of borrowing has to eventually hit a stop.  The world isn't infinite, and neither is money that's worth anything. 

These, though, are unprecedented times.  First and foremost is that while the market appears to have firm foundations for the first time in a long time; to borrow a line from Tom Aspray in Forbes:
Therefore, those who look at the market from a fundamental standpoint  have trouble turning bearish right now, since the only fundamental concern is rising rates, while earnings and the economy are strong.
Simply, in a week the major indices retreated back in time two months to the second week of December.   The companies that were reporting earnings were reporting good, solid earnings and there's no reason to think they're less valuable than they were two weeks prior.  There's simply no reason to dump those stocks.  Unless the concern is looking forward into the year and wondering if the Fed is going to raise interest rates more than originally slated.  Very simply, money chases yield and if bond yields go up, that would tend to move money out of the stock markets and into bonds. 

Why would the Fed raise interest rates?  That's their response to too much inflation and the Fed seems institutionally unable to separate its own currency manipulations from inflation or recession.  For the last decade they've been telling us inflation is under 2% as we've paid more for smaller packages and watched what appears to be 8 to 10% inflation every year (Shadowstats, in 1980 terms, bottom graph).  None of that bothered them, but increases in wages have them ringing the klaxons and preparing for disaster.

Trump is the first president I can think of who has specifically stated he wants to raise wages for the middle class and there's evidence it's happening.  Rising wages are something that Janet Yellen and Ben Bernanke before her always talked about as if it was the apocalypse.  One of the main aims of the Fed seemed to have been to keep wages from rising - and they seem to have been effective at doing it. 

The point is, though, Rand Paul was right.  The country is borrowing more than a million dollars a minute, and that can't go on.  It might not crash this year, or next year, but it will sooner or later and it's better to try to land a crippled aircraft than wait until its really desperately awful trouble.  The answer, as it has always been, has to be to stop kicking the can down the road, and start cutting spending and working toward balanced budgets.  Which requires being adults, and very, very few in Washington have shown that tendency - as the president's proposed $1-1/2 Trillion dollar infrastructure plan shows.



Sunday, February 11, 2018

The Explosive 3D Printing Industry

That doesn't refer to the industry undergoing explosive growth, it refers to the 3D printing of explosives.  Machine Design covers the story with input from Los Alamos National Labs (pdf warning). 

Whether for movie special effects, planned demolition, or as weapons, it should go without saying that explosives are serious business.  To borrow a phrase from shooting, the two worst sounds in the world are silence when it's supposed to go BOOM and BOOM when it's supposed to be silent.  Despite centuries of work with explosives and the modern use of high speed cameras and computers, there still is much to learn about how explosives work on the shortest time scales 
TNT is susceptible to unplanned detonation. This led the team at Los Alamos to develop insensitive high explosives (IHE). These explosives can be hit with a hammer, dropped, or thrown into a fire and not detonate. This might ruin some Hollywood movies, but it might also ruin a timed detonation.

Making an explosive more difficult to detonate when there’s an accident also makes it more difficult to detonate intentionally. Explosives such as TNT’s behavior are largely controlled through hot spots. Introducing inclusions, such as air bubbles, into TNT will trap air inside, causing it to compress and rapidly heat up. The uneven flow into and around these bubbles results in points of intense heat called hot spots. These hot spots largely control the energy necessary to initiate detonation in TNT and other high explosives.

This is where 3D printing is disrupting explosives. With the ability to control material, and voids, Mueller’s [LANL's] team looks to control the release of energy through a sophisticated arrangement of hot spots.
Switching to LANL's explanation for a few words:
During detonation, a chemical reaction zone (CRZ) races immediately behind the supersonic shock wave; the shock-compressed voids in the CRZ generate hot spots and in turn initiate the chemical burn reaction. Because a shock front will move through different materials at different speeds, the type, size, and distribution of hot spots (collectively referred to as the hot-spot profile) can change the size and speed of the CRZ as it travels through the material—this affects the strength of the subsequent blast.
If you've ever seen a cross section  of a 3D print, they have varying amounts of porous space in them. This is primarily for strength and prints made for higher stresses are more solid, but porous space in the explosive mix can help researchers learn about how the explosion forms and propagates.

(A look at the inside of an object as it's being printed shows the support structure - International Science Times)

It's also allowing them to experiment with new materials and create new explosives.

A couple of thousand miles away in Indiana, Purdue university researchers are using inkjet-type 3D printing to experiment with their explosive blends.
“It is really just an assembly of commercial-off-the-shelf technologies,” says Jeffrey Rhoads, professor of mechanical engineering and principal investigator on the project. “The key is formulating the proper ‘ink’ and then integrating these components in a way that allows for appropriate mixing, precise printed geometries, etc.

“Our solution is to combine two components as we’re printing them. We can have a fuel and an oxidizer in two separate suspensions, which are largely inert. Then with this custom inkjet printer, we can deposit the two in a specific overlapping pattern, combining them on a substrate to form nanothermite.”
Allison Murray, a Ph.D. candidate in Mechanical Engineering, built the custom inkjet printer.  The feed is a tube that can be electrically constricted to control droplet size while the table moves under the print head.  She says, “The stage can move with a 0.1 micron precision, which is basically a thousandth the width of a human hair.” 

Still, they're working with thermite material, which is still exploding, once the proper stimulus is applied.  3ders.org says the newly developed 3D printer works by depositing both a fuel and an oxidizer (two largely inert colloidal suspensions of nanoaluminum and nanocopper (II) oxide in dimethylformamide with polyvinylpyrrolidone) in an overlapping pattern, combining them on a substrate to form nanothermite, a metastable intermolecular composite with small particle size.
The resulting nanothermite reacts just as quickly and powerfully as thermites applied in traditional ways.  “It burns at 2,500 Kelvin [over 4,000 degrees Fahrenheit],” said Murray, “It generates a lot of thrust, a lot of heat, and makes a nice loud shockwave!”
The link to Purdue includes a high speed camera video of a couple of demonstrations, and it's always slightly hypnotic to watch high speed photography of things exploding, even if they're small explosions inside a lab.

Purdue's aim is to make handling small explosives, like the air bag detonators in cars, safer to handle and more reliable.  The military, though is looking at ways to make bigger explosives safer and more reliable for everyone handling them.  Much bigger explosives.
“In order to maintain the U.S. nuclear deterrent at a level appropriate for the 21st century, technicians in the Pantex Additive Manufacturing Program have spent the past five years evaluating and implementing dozens of applications for additive manufacturing.

“The team works with a Connex 500 for polymer-based designs and uses an SML 280 for metals. Components that once took weeks or even months to machine can now be made in mere days. The fruit of the team’s labor is evident across the 16,000-acre facility in the hundreds of fixtures now being used. In 2014, the Additive Manufacturing team received an esteemed Defense Programs Award of Excellence for its work.”
...
In addition, the ability to print complex shapes lets users take advantage of topographical optimization, meaning material is only added where needed. This would be expensive, time-consuming, and in some cases, impossible with traditional processes. In a life extension program for the B61-12, which is a nuclear weapon, topographical optimization is able to make a new fixture that saves cost, weight, and time, while increasing strength.
(LANL photo)

I find this interesting because of the spillover into new fields that follows the introduction of a new technology.  As the Purdue article said, “Energetic materials is a fairly understood field, and so is additive manufacturing.”  Taking advantage of the additive manufacturing techniques to produce exactly the characteristics of  an explosive that are wanted for study is neat combination of the two.




Saturday, February 10, 2018

Really Cool Model V-12 Engine

If you thought the supercharged V10 we talked about in September was cool; modeler mayhugh1 did a quarter scale V12 Merlin engine, based on some castings he was able to acquire.  The castings are gorgeous and the engine improved them.



The Merlin was the engine used in Brtain's famed WWII Spitfire fighters and then adopted into the US' P-51 Mustang.

Full build thread here. It's 84 pages, following the build from February of 2015 through November of '17, and this start up video is on page 80, dated August 28 of '17.

As for my next project, it's not that cool, but it's a step along the way.  I'm building a fire eater engine from the book The Shop Wisdom of Philip Duclos.  No castings will be involved, just pieces of metal bar stock.  There are a few videos of them in action; here's a short one.

These are known as atmospheric engines, vacuum engines, flame eaters, flame lickers, and I'm sure there are names I don't know.  I like to call them external combustion engines because of the little alcohol lamp outside the cylinder that powers them.  To start it, we flip the flywheel, and as the piston starts to move out of the cylinder, the engine sucks in the flame.  Expanding hot air helps push the piston away and a flap covers the input port keeping air from rushing in.  The air in the cylinder rapidly cools as it pushes the piston out and after the flywheel finishes that half rotation, the atmospheric pressure outside the cylinder forces the piston back toward the top of the cylinder (the reason they're called atmospheric engines), when the flap opens and allows the flame to be sucked in again.

Some of the videos feature someone trying to get the engine to run reliably for a couple of minutes, and I can imagine the inventors thinking, "if only we could get that combustion inside the engine, maybe we could get it to run more reliably.  Some kind of internal combustion..."  One of the model makers' websites says the first patent on one of these engines was granted to a Henry Wood in 1758.  That predates the Otto engine by a hundred years, which is generally called the first four stroke, internal combustion engine.


Friday, February 9, 2018

Time for Our Annual Pilgrimage to Orlando

Orlando is best known as home to Walt Disney World, Sea World, Universal Studios and a few other theme parks, but no mice, killer whales, or movie characters were involved.  Today was our annual visit to the Orlando Hamcation, which we have been doing without missing a year since 1982.  The Hamcation's website says that they are now the number two hamfest in the country, behind the Dayton Hamvention.  "Dayton" is now Dayton in name only; the hamfest moved to Xenia, Ohio last year when the city of Dayton closed the convention center/arena where it had been held, and Hamvention won't be in Dayton for the foreseeable future.  


(A view across the north hall, one of three halls full of displays, in 2017 - Orlando Hamcation photo)

As we did last year for the first time, we decided to attend on Friday this year.  The major hamfests seem to be selling themselves more as vacations than for locals, so if one is taking time off from work to travel hundreds of miles to a ham radio convention, taking the extra day to go on Friday vs. Saturday isn't a big deal, and Sundays have been marginal at best at hamfests for as far back as I can recall.  The most crowded days are going to remain Saturdays.  Going on Friday, we got excellent parking, crowds are much easier to live with, and the whole experience is just better.

What was familiar was: essentially everything.  There was the usual collection of old radios, some in use for over half a century, along with radios from every decade since then.  If anything, a larger number of dealers were selling the various brands of Chinese VHF/HF handie talkies like Baofeng, Wouxun and others.  That said, there were some new radios on display and I stopped for literature at a few place. 

Speaking as a guy who spends a lot of time running a barbecue smoker, the folks who do the barbecue there put up a fine lunch.  $8 for a stuffed brisket or pulled pork sandwich is really in line with what you pay in a sit-down restaurant, and it's good barbecue. 

There were predictably more drones for sale.  What was missing was that there didn't appear to be any big product announcements going on.  I saw fewer Arduino project kits although they remain well-supported, and given that I've probably seen a dozen web-based projects that made a CNC-driven laser wood burner out of a DVD drive LED, I expected to see something like that.  Nope.  Likewise, not a single 3D printer. 

The weather was good; while it peaked out at around 80 maybe 82, the skies held enough clouds to keep the sun from beating down too much while not giving any rain.  The only things I picked up were some accessories for the station, especially while testing things: coaxial connector adapters and some test cables. 


Thursday, February 8, 2018

A Little Machine Shop Steam Engine Puzzle

I've done some experiments with my little "steam" wobbler engine over the course of the last week.  I tried it with three different flywheels.  As always, there's a story behind this, but first, if you're so inclined, here's a four minute video that shows the experiments.


The video is a combination of three separate videos.  The first video is the solid one in that's mounted on the motor in the still photo thumbnail you should be seeing.  That flywheel is actually a remake of the first flywheel, which is the one on the left with the six half-inch holes in it, and I posted when I drilled the holes using my rotary table.  That flywheel was on the engine in the video I posted in that link at the top.  The brass (bronze?) wheel is smaller than the others, 2" diameter instead of 2-1/2".  The weights of the solid aluminum flywheel and that one are within 6 grams of each other, but the important mechanical property is the moment of inertia, and I haven't calculated that. 

What's the bottom line?  As of the moment, I like the looks of the lightweighted aluminum best, and the solid aluminum one the least, but the solid aluminum wheel is on the engine for now.  It wobbles more (visible in the first video) and despite that it runs best down to the lowest pressures (12 or 15 PSI). 

The engine is "touchy", the tightness of the flywheel is critical.  Right now, there's about .010 gap between the upright and the flywheel and it runs well.  If I adjust that gap so that there's virtually none, the engine won't run. 
In this view, it looks like they're solidly against each other, and the same with the crank wheel on the other side.  If they're that close, I can't get it to run. 

Comments invited, of course.


Wednesday, February 7, 2018

A Little More Antennas 101 - Part 3

One of the conclusions I had last time was:
  • All antennas have a radiation pattern and a gain. 
They have a gain compared to something.  If you think about it, the conclusion is that antennas can be chosen for the purpose you want.  For example, there's a lot of talk in the gunny community about NVIS antennas.  NVIS is "Near Vertical Incidence Skywave", an extremely long-winded way of saying, "for local communications", and it's done in High Frequency (shortwave) bands that are usually thought of as being for long distance, while VHF/UHF is thought of as being for the local communications.  Low angles of radiation reach the ionosphere farther away than waves at higher angles or those going straight up.  If the atmosphere is dense enough, the vertical waves reflect more or less straight down, allowing communications in shorter distances than antennas radiating at low angles while the low radiation angle waves end up much farther away.  NVIS is great for getting over hills or mountains without needing directional antennas on both ends and a repeater on the mountaintop.  How do we make one?  Simply put a horizontal dipole close to the ground.

This is a plot of a computer simulation of a 7 MHz (40m) half wave dipole.  The simulation on the left is with the antenna 66' above the ground, a half wavelength.  You can see the radiation peaks are about 35 degrees above the ground.  The simulation on the right is with the antenna 1 foot above the ground and you can see the main radiation is straight up.  Instant NVIS.  Just put your antenna on the ground (or close to it - I can't tell the plots apart with the antenna 6' up).  The software, as you can read in the upper right, is the free demo version of EZNEC.  The demo version is perfectly adequate for even a few dipoles or monopoles, and is free.  Antenna modeling is a whole 'nother world that could take days to go over.


The thing is, this doesn't have to be a separate antenna, if you can raise and lower an existing dipole you can make any dipole into an NVIS antenna.  Raise and lower one with pulleys on poles?

All simulations like this are never going to be right if you have your antenna in the midst of trees, or surrounded by things like a metal roof - which is a perfect ground at frequencies where the antenna is around half the dimension (length or width) of the roof.  Fun fact: guys who study the effects of things close to the antenna say living trees are more like a person in the field than lumber.  Trees are full of water, more like people than lumber, which is dried.   

Pattern distortion is an especially big concern for vehicle-mounted antennas.  Trunk mounted antennas are very popular for mobile operating.  The roof is a better mounting spot (if you can get in your garage!).  Lots of money has been spent on simulating and measuring antenna patterns on vehicles by militaries and governments all over the world.  You may think you're getting a wonderful, clean, little doughnut pattern like theory says, but when you put it on your car, if the base of the antenna isn't several wavelengths away from metal, you probably get a lumpy, bumpy pattern with all sorts of weaker and stronger points in it.



Field from a rod antenna on the roof of a car; advertising post by EMCoS  Warmer colors (red, orange...) denote stronger fields, cool colors (green to blue) denote weaker fields.  This is actually pretty good, but the antenna is on the roof.

Finally, should you be concerned about SWR - Standing Wave Ratio (pdf warning)?  I'm of the opinion that hams worry too much about this but I also know most solid state radios reduce their output power to protect themselves from the reflected power and some shut down at lower reflected powers than others.  I have a radio with a builtin antenna tuner, and I have an external antenna tuner;  I use them without hesitation.  If my radio is happy, I'm happy.  It's true that the best place for a tuner is at the antenna, but I don't personally have the budget of an aircraft developer, all of whom build in an antenna tuner at the bottom of all their HF antennas as part of the aircraft design.  The main disadvantage of an SWR that's "too high" is that power is lost in the antenna's feed cable.

When the impedance isn't matched, some of the power delivered to the antenna reflects back to the transmitter.  Let's say 5% as a rough number.  That 5% gets back to the antenna nanoseconds later and gets reflected toward the antenna; again, let's say 5%.  That means almost all (95%) of the 5% gets added to the transmitter's signal and goes back to the antenna.  This repeats.  There's a technique called a lattice diagram that illustrates this, but the conclusion is that the only power that doesn't make it out of the antenna is the power lost in the cable.  Good quality, low-loss cable is worth it. 

Antennas can be mind-bogglingly hard to measure in the field, because of the way they interact with the everything.  Antenna design is a perfect example of the inflexibility of the laws of physics.  There's over a hundred years worth of experience with them to learn some lessons from. 


Tuesday, February 6, 2018

Hat Tip to SpaceX

SpaceX's flagship Falcon Heavy apparently had a fully successful test flight today, boosting Elon Musk's own Tesla Roadster into orbit and recovering both of the strap-on Falcon 9 boosters.  As I'm writing this, a successful recovery of the central Falcon 9 first stage is not confirmed.  It's pretty common for the turbulence of the landing to cause loss of the signal, but that has typically come right back.  If an antenna was damaged, that would make it difficult to know.  The drone ship "Of Course I Still Love You" is unmanned during a landing, but a crew boards it later to secure the booster.  I don't know the protocol for how long they wait before doing that. 

The two side boosters of the first stage have flown before. One launched the Thaicom 8 communications satellite in May 2016, and the other lofted a Dragon cargo ship to the ISS for NASA in July 2016, according to SpaceX.  

View from the VAB of launch complex 39A.
The view from my backyard.
The Falcon heavy is the most powerful rocket to launch from the US since the Apollo Saturn V days.  SpaceX says
When Falcon Heavy lifts off, it will be the most powerful operational rocket in the world by a factor of two. With the ability to lift into orbit nearly 64 metric tons (141,000 lb)--a mass greater than a 737 jetliner loaded with passengers, crew, luggage and fuel.

Falcon Heavy's first stage is composed of three Falcon 9 nine-engine cores whose 27 Merlin engines together generate more than 5 million pounds of thrust at liftoff, equal to approximately eighteen 747 aircraft. Only the Saturn V moon rocket, last flown in 1973, delivered more payload to orbit.
At this time, SpaceX has said the upper stage has performed two of its three scheduled burns with the last scheduled around 5 hours after the last burn, or around 9:30 EST tonight.

EDIT 2/6/18, 1921 ESTFrom Spaceflight Now: "Speaking to reporters at the Kennedy Space Center, Elon Musk says the Falcon Heavy's center core did not survive its descent to SpaceX's drone ship in the Atlantic Ocean."

Hopefully, more later.


Monday, February 5, 2018

The Las Vegas Shooting And the Ammo Seller Arrest

It took me a while to tease out of this story what I think is going on.  The news story is summarized on Ammoland's website.  Their article pretty much echoes what little I saw on the national news.
Authorities have charged Douglas Haig, 55, of Mesa Arizona with selling “armor-piercing ammunition” to Las Vegas killer Stephen Paddock according to court documents acquired by the Associated Press. Haig works full time as an aerospace engineer and part-time as a manufacturer of reloaded ammunition.
The story said the local police recovered tracer rounds from Paddock's room, and traced them back to Haig by fingerprint.
According to the court documents police also found unfired armor-piercing rounds within the hotel room. Law enforcement was able to lift a fingerprint off one of the armor-piercing cartridges. Douglas Haig matched that print and was named a person of interest in the case after law enforcement found his name, and address on a box that was in Paddock's possession.
...
Haig and his lawyer, Marc Victor, held a press conference on Friday claiming that Haig was innocent. According to Haig, he met a well-dressed Paddock at a gun show in Phoenix, Arizona. He stated Paddock wanted to more [SIC] tracer rounds than he had on hand at the show, so Paddock called him a few days later to set up a sell of 720 tracer rounds at Haig's house.
....
Haig further claims that Paddock did not use his ammunition in the attack because he only sold him tracer rounds.
David Codrea links to the actual court document.  There is one charge.
Conspiracy to Manufacture and Sell Armor-Piercing Ammunition
(18 U.S.C. 371, 922(a)(7),(a)(8) and 924(a)(1)(D))
So the headlines typically shout he was arrested for manufacturing armor piercing rounds and never mention tracers.  I don't have to tell this audience that when the terms "armor piercing" and "tracers" are used, "one of these things is not like the other".  The police are saying he manufactured the armor-piercing rounds and got one of Haig's fingerprints off one, but Haig claims he never sold Paddock anything except tracer rounds.  The court filing says they were .308 rounds "metallurgically classified as armor piercing incendiary" by some definition.  Does that mean Haig considered them tracers but the FBI lab said they were armor piercing, too? 

The headlines also scream he was manufacturing armor piercing rounds without a license.  As far as I can tell, there is no special license for manufacturing armor piercing ammunition, or even tracers, just a general prohibition against manufacturing armor piercing ammo (for which there are too many definitions) unless it's for sale to the US government or export (18 U.S. Code § 922 A 7).  There's a general requirement to be licensed if manufacturing ammunition and reselling it.  It seems likely that Haig had what the IRS calls a hobby business, which is one that isn't the owner's livelihood, and that some people keep so they can successfully get reimbursed for the expenses of their hobby.  (I've known several people over the years that sold things they made to help pay for their hobbies).  All the sources say Haig is an "aerospace engineer" with the reload business on the side.  The ATF website shows the following:
Is a person who reloads ammunition required to be licensed as a manufacturer?

Yes, if the person engages in the business of selling or distributing reloads for the purpose of livelihood and profit.

No, if the person reloads only for personal use.
There's a long gap between selling for profit and selling for the purpose of one's livelihood.  This is a gray area: let's say someone shoots your reloads and likes them, so they offer to buy the components and give you a few bucks to do the work.  It's hard to argue that's making a profit.  How many people have arrangements with neighbors along the lines of "if you cut my lawn for me or shovel my driveway I'll give you a few bucks".  It's not livelihood, but if the BATFE wants to argue it's for profit, they have the infinite checkbook of the federal government.

I suspect Haig is in the gap between recovering the cost of his hobby and truly making it his livelihood and they're getting ready to hang him so that they can say "we got someone".

Douglas Haig

Of course, if any of you know more or better, the floor is yours!


Sunday, February 4, 2018

A Little More Antennas 101 - Part 2

Yesterday, I mentioned that non-resonant antennas are used all the time and that they can be made to accept power better with devices called manual or automatic antenna tuners that transform the impedance of the antenna to the preferred value.  The ratio of the transmitter's designed load impedance to the antenna's impedance gives us something called the standing wave ratio.  There are a few ways to think of SWR, but I find it best to think of it as an impedance ratio, and the antenna tuner as an impedance transformer. 

You'll find that most transmitters are designed to operate with a transmission line system of 50 ohms, and it's a circuit law that the best power transfer occurs when the transmitter, cable and antenna are all matched to that 50 ohms.  The antenna tuner can transform the impedance the transmitter sees at the end of the cable to something closer to 50 ohms so that full power can be transferred.

Antennas convert the power that's delivered to the terminals into electromagnetic waves; they also convert electromagnetic waves that strike the antenna into (much smaller) received powers.  They don't do this equally in all directions and there are two concepts to introduce here that so intertwined, they're almost one and the same.  The standard dipole antenna has a pattern that looks like a squished sphere; the radiated signal is weaker straight up and straight down than it is toward the horizon.  The pattern is shaped sort of like a doughnut.  This illustration, from an old Byte magazine article, shows it well. 
The wire is vertical in the top illustration (red), so the pattern is strongest broadside to the wire and at right angles to the direction the wire runs.   The bottom left is looking at the end of the wire, sticking into and out of the screen.  This pattern is with the antenna alone in the universe (or not within a few wavelengths of anything else).  The pattern will be distorted in your yard or any real place, unless you have it very high and far away from other things. 

I want to call your attention to the blue numbers on the bottom.  It says the dipole has gain of 2.17 dB, that is, it's 1.65 times stronger than the reference.  (It doesn't say dBi but that's pretty much the published gain of a dipole compared to a perfect isotropic antenna, radiating equally in a sphere.)  I talked about this concept in the article on radio charging batteries.  The dipole only has gain compared to one of these imaginary, isotropic radiators.  The radiation pattern of a quarter wave vertical is very similar, except that in the side view (bottom right) it cuts off at zero degrees elevation because that's the reflecting ground plane under the vertical.   Ideally (perfect reflecting ground), it has maximum gain toward the horizon.   The gain of the quarter wave monopole depends on how big that perfect reflecting ground under the antenna is, and can actually exceed the dipole gain. 

Antenna gain always works to create gain by forcing signal from some directions into another.  It's the same way as you can squeeze a balloon and force more air in one place by making the part you're squeezing smaller.  In the case of the dipole over the isotropic radiator, the signal that would go straight up or down is pushed out around the perimeter.  It has less gain than the isotropic radiator along the up/down axis (bottom right) and more around the edges of the doughnut.  Imagine having a spherical balloon and you squeeze it vertically, making it smaller top to bottom; it will get larger in diameter. 

A commonly used antenna takes several half wave dipoles and by spacing them properly, along with making them slightly longer or slightly shorter, produces gain in one direction.  This is called a Yagi array (more properly a Yagi-Uda array) named for the researcher(s) who developed this almost 100 years ago (1926). 
(source)
Notice that the biggest part of the pattern, the front lobe, goes past 10 to perhaps 15 or 16 dB.  Compared to what?  Gain is always a comparison between two things, so with nothing noted in the drawing we just don't know, but as I said in that battery-charging article, it's probably dBi because it produces bigger numbers than dB compared to a dipole and bigger numbers sound better. 

Let's say that's 15 dB gain, which in linear terms is 31.6 times.  If I put 100 watts into the antenna, how much power is in that lobe?  If I put 100 watts into the antenna, it puts 100 watts into that lobe.  (Yes, that was a trick question)  That gain of 31.6 times only means that compared to an isotropic radiator the signal is 31.6 times stronger.  An antenna can't add power, adding power requires power.  All the antenna can do is squeeze signal from other directions and force it to the front.  Notice that there are lobes on the back of the antenna and all of them are weaker than -10 dB; 1/10 of the power is in the strong points off the back of the antenna.  That's the power that got pushed into the main, 15 dB-gain lobe.

Think about those battery charging systems again; they might like to generate pencil-point sharp radiation patterns, but if they're radiating power levels that are safe, all they can do is minimize the power in unwanted directions.  They can't increase the power delivered to the thing being charged with any antenna tricks.  

Quick summary:
  • Antennas work best when the radio wave mechanically fits the antenna. 
  • The mechanical size of the wave gets smaller as the frequency goes up.
  • That often leads to having different antennas for every band you're interested in.
  • Antennas can be used on bands other than the ones that fit perfectly with antenna impedance matching circuits, called tuners or transmatches.
  • Receivers can be designed to work better with more casual antennas than transmitters.
  • All antennas have a radiation pattern, and a gain.  The most common reference antennas are a dipole or a theoretical isotropic (equal in all directions) antenna. 
  • Gain comes from squeezing signal out of some directions into the preferred direction.
  • Antenna gain doesn't amplify signals.  They're just stronger at a receiver than a signal from the reference antenna.
Example of an antenna that's 3/2 (three halves) wavelength long, center fed.  The pink traces show the current peaks in the center, nulls at 1/4 wave (just between the first two nulls is a 1/2 wave dipole) and then repeat an additional half wave on each side.  This is the popular G5RV antenna.  This shows that antennas that are an odd number of quarter wavelengths on a side still fit the signal well.  They also produce impedances near the desired 50 ohms.  The drawback is that as the antenna gets longer, the radiation pattern changes to something less like a doughnut.  The pattern turns into lobes along the wire getting closer to the wire as the wire gets longer. 


Saturday, February 3, 2018

A Little Antennas 101 - Part 1

The topic comes up in many places, but my motivations for this post are mostly my own talks about my receive only antenna and the examination of the radio frequency battery charging system, along with an article in the trade magazine Microwaves and RF, "Reversing 25 Years of Antenna Degradation".  Most of us carry a cellphone.  In the article, the author states that over that 25 year interval we've thrown away 90% of the transmit power from the phones as the antennas have become a progressively worse compromise in the cellphone networks. 

How can that be?  Another way of looking at it is that the networks we connect to have improved so dramatically, that they’ve been able to deal with phone designers screwing up the performance of the handset antenna without much backlash from consumers. 

Antennas can be difficult to wrap our heads around because they're both electrical and mechanical.  The basis of this (in my opinion) is that radio waves have physical size, and the size of the antenna has to match the size of the radio waves it's going to handle.  That's a concept that most people simply don't have until they take a class to get a ham radio license, or start looking into building an antenna.  Until that time, either they never saw the radio had an antenna (most AM/FM radios have an internal antenna the user never sees) or antenna was just a short piece of wire sticking out of the radio. 

Every frequency of radio has a specific wavelength, and they always follow the relationship that frequency times wavelength is the speed of light, or c=f*l.  

Now an antenna doesn't have to be a wavelength long; in fact they fit the antenna best when the antenna is one half wavelength long, fed at the center.  This is going to blow some of your minds, but the current and voltage distribute like this on a half wave long, center-fed antenna, with each side 1/4 wave long.  Let's call the voltage positive on the top side (left) and negative on the bottom (right); so current is positive above the line, too.

The "why??" is pretty simple.  Remember that power is voltage time current, so if the power is constant, the product can stay the same while the current and voltage can both vary from zero to their maximum along the wires.  The current is minimum at the ends because the current has nowhere to go.  Electrons can't go past the end of the wire.  The voltage is maximum at the ends because the current stops; since I*V is constant and I is getting very small, the voltage gets very big. 

Note that the picture is a snapshot of a very short period in time.  The voltage is continually changing polarity, end to end, at the frequency of the wave, and so is the current, but the current and voltage being out of phase with each other as pictured (one max while the other is min) doesn't change.  There's a good animation in the wikipedia.

By the way: if you want to build a dipole, two quarter wave long wires fed in the middle, a century of experience says to cut the wire to 468/f, where f is the frequency in MHz and it gives you the answer in feet.  Antennas interact a lot with their environment, so it's not uncommon to have to tweak those dimensions to get the best antenna, but this ordinarily gets you close enough to start. 

Remember how I said that "the size of the antenna has to match the size of the radio waves it's going to handle"?  There's some slack in that statement because as you move the frequency away, it can still "mostly fit".  This is what's called the bandwidth of the antenna.  This drawing shows the wave fitting on the antenna because the peak of current is a half wave.  If the frequency gets too far away, the current would go below zero and every cycle would look a little different because the position of where it crosses zero would move around. 

In reality, non-resonant antennas are used regularly.  Just as Power is voltage times current and constant, let me drag a concept back from AC circuits: impedance.  Impedance is an AC resistance which includes the effects of resistance and reactance.  Just like DC resistance is defined as Voltage divided by Current (V/I), impedance is V/I with AC measures.  Antennas have a defined impedance, like any AC circuit, and you can make an antenna's impedance look better with tuning circuits.  Manual and automated tuners are commonplace.  They allow you to make a non-resonant antenna more useful. 

The half wave dipole is a standard antenna in a few senses.  They are used as an element in other antennas, and their performance by themselves is a standard of comparison.  The other standard antenna is 1/2 of a half wave dipole, a quarter wave monopole, usually called a quarter wave vertical because half the antenna is replaced with it's "reflection" in a mirror-like ground that it's mounted vertically over.  The current and voltage waves look exactly like the half wave dipole. 
Everyone is familiar with these antennas and common versions of them: the small rubber-coated springs used on handheld radios ("rubber ducky"), car AM/FM radio antennas, CB whip antennas, even AM radio broadcast antennas, are all versions of quarter wave verticals.  Since the length of a half wave dipole is 486/f, the length of the quarter wave is half that or 234/f.  A CB whip, for example, should be 234/27.5 MHz, or 8-1/2 feet long.  It's very common to see "base-loaded" CB antennas that are substantially shorter than that.  Base-loading is a way of transforming the impedance of the shorter antenna up to the impedance "desired" by the transmitter.  As a rough rule to go by, antennas shorter than about 1/8 wave (117/f, or 4-1/4 feet in the case of the CB whip) are harder to base load and less efficient than longer antennas. 

In particular, cell phones went from having very obvious, external, quarter wave whip style antennas to internally mounted or otherwise hidden antennas, like these:
This is where the loss of 90% of the transmitter power comes from. 

Tomorrow - deeper into the weeds.