Favorite Things–Part 2

OK, this time, more things and fewer words. Very unlike me, I know. Let’s declare a theme for most of these items–soldering. If that’s not interesting to you, I’ve saved you some reading! Do at least have a look at the office chair wheels towards the end of the list, though, if you have a wheeled chair in your shack or home office. There, more reading avoided if not!

  • Organizer boxes for small parts. I have lots of small electronic parts. For some, I use the slide-out drawer-type storage compartments that mount on a wall. And I have quite a few of these, but for certain items like small SMD surface-mount “chip” parts, I need smaller compartments that I can move around, and that do not spill the little parts if dropped or turned upside down. I bought a couple of these recently, and they fit the bill nicely. They won’t spill things, can be easily re-configured for larger or smaller compartments, and generally look to be good quality for the price, which is $10.99 each. By the way, they are the soft-feeling plastic, not the hard, brittle type. Since they are “just” plastic, I would avoid putting anything in them that could be damaged by static electricity.
  • If you do much soldering or building, or need to repair soldered pc boards on occasion, here is a very inexpensive hot-air soldering and rework station. Price is an unbeatable $75.99 for everything, including various sizes of hot air tips. If you’ve never used hot air for de-soldering an SMD part, you’re in for a treat. Hot air can also be used to solder, if you’re careful. Be sure to keep the temperature high, the air tip small, and the airflow low. You don’t want to blow other components out of place. Been there, done that. It’s not rocket science, though. Just be aware of that little issue. Doing SMD repairs with this gadget (along with the liquid flux mentioned next) will save your sanity.
  • If you’ve ever done any soldering, this may not be something you’ve had any experience with before. That’s because many people don’t understand the need for soldering flux, but I swear by this little bottle. It’s helped me do so many otherwise difficult (or semi-impossible) soldering jobs with SMD components. Without going into a chemistry lecture, let me simply say that it makes the parts you want to solder together more attractive to solder. It gets rid of the surface tension or oxide that sometimes causes the solder you’re applying to ball up or just drop off the part, rather than melting nicely to it. For SMD parts, I literally drown the little chips in this flux (you can drown them with a single drop), and they just magically adhere to whatever you’re trying to get them to stick to. It does this by its mildly-acidic nature, stripping oxide off of copper or tin pads or wires, and then keeping oxide-causing air away while you solder the parts. Another bit of goodness is that this is genuine Kester soldering flux. Kester has always been a big name in solder and soldering chemicals. This little 2 oz bottle is $13.18 with the usual free shipping, and it will likely last you the rest of your life, unless you do as much soldering as I do. I’m on my second bottle. Highly recommended for soldering even big parts together, and the little needle-like applicator helps you by doling it out at just a drop at a time. Many times you’ll only need one drop.
  • After you’ve soldered something, especially if you used flux, this next item is a nice-to-have near your soldering station. It’s an alcohol pump dispenser for $9.90. You grab a cotton swab or Q-Tip, tap the top of the dispenser with it, and a little bit of alcohol soaks it. You can then swab the solder joint or pc board to get rid of flux or just for general cleaning. This is almost mandatory to do if you are using high-impedance (and static-sensitive) devices, such as MOSFET’s, CMOS microprocessors, etc. The left-over flux can attract dirt and dust, and eventually form a low-resistance short between two points you didn’t intended to have shorted to each other. This scenario is most likely when you are working on a printed circuit board, rather than freehand soldering of, say, two wires together. At work, we have one of these pumps and some cotton-tipped sticks at each soldering station. Good stuff, and you avoid having a constant alcohol-ish smell in the lab.
  • Keeping with the soldering theme, you should clean the tip of your soldering iron often, ideally each time you solder a single joint or part. If that seems excessive or OCD to you, let me assure you that it’s not. As soon as you finish soldering a connection, the remaining solder or metal on the tip of your iron starts to oxidize. That layer of oxide will act as an insulator when you go to solder your next part, making it seem like your iron temperature has gone down, often significantly. It also makes it very hard to tin your tip with a little solder, which you should do before soldering a new connection. To keep oxidation of the tip from happening, many people, including me sometimes, use a wet sponge. Wiping the tip with a damp sponge helps keep the tip nice and shiny, but also wipes away any solder still remaining, and that isn’t always what you want. This next item solves the tip preparation problem by giving you a small, bottlecap-sized container of tin and ammonia for only $6.35. I hot-melt glued mine to my soldering iron holder, and I just rub the tip on it briefly before starting a new solder joint. It’s texture is hard, but just a bit of it melts on to your iron with each application. It cleans the tip of oxide, and adds back a little tin to “tin” your iron each time. As you probably know, solder is mostly made of tin, lead, and a little flux. At least, it used to be that solder was tin/lead. Now we have lead-free solder, which I can tell you from experience is mostly horrible stuff. It has a wetting (adhesion) problem. Thank goodness you can still buy the good ol’ 60/40 or 63/37 tin/lead solder. The link is for a one-pound roll of the best solder on the planet for just $27.28. A pound will last you a long time. Regarding the worldwide lead-free rules, it’s true that we have to use it in electronics manufacturing, yes, but not for hobby or lab use, thankfully. Wash your hands after a soldering session, though.

  • Speaking of soldering, there are other ways to hold things in place. In the past I’ve used the white foam double-stick tape for mounting various small objects, as I’m sure you probably have. I’ve always thought that there should be something better. Something with more grip. Something permanent. And then I noticed that our little WiFi modules were mounted to some TV chassis with this interesting black tape that really stuck them in place. They were definitely not going anywhere with this tape on them. Trust 3M to have developed Scotch VHB tape for this purpose. VHB stands for Very High Bond, I think. You can stick just about anything to just about anything else! Here is a 1 inch by 15 foot roll of it for $17.99. Very good stuff. It has some thickness to it like the white foam stuff. Just make sure you really want to stick something in place before you, well, stick it in place. Makes the white foam tape look sad and anemic.
  • You might find this next one a bit strange, considering the electronics theme we’re on, but let’s say that this might improve your soldering by giving you better mobility and keeping static electricity down a bit. I’m talking about replacing the little plastic casters on your wheeled office chair with these very useful replacement urethane wheels made for office chairs. They are $38.95 and worth it. They work way better on many carpets than those little hard plastic casters, and eliminate the need for those awful plastic carpet protectors. Here in the mountains of Utah, carpet protectors are HUGE static electricity generators. I can sit down on one, move a foot or roll the chair a bit, and draw a 1/4″ spark off of anything I touch. You can actually get anti-static carpet mats, but they cost 2X-3X or more. Anyway, these wheels roll way easier, don’t get fouled up in things as much, and have way less rolling resistance. They are made to fit the (almost) universal rod and lock ring found on most office chairs. And there are 5 of them, which I didn’t realize is a very common number of legs on wheeled office chairs. I popped out my old ones and put these in with no tools in under 5 minutes. Whee! Now I can really roll–I love them! The only downside, and it’s minor, is that they make the chair seat about 1″ taller. If you have your chair lowered all the way down like I do, that might be an issue. It actually is for me. I’m 6’1″ tall, but I’m about 6’7″ from the waist up (and I’m only a 31″ inseam–I think they call it being over-square or something). So I sit tall, so to speak. People in my office who occupy a conference room after me always know where Dave sat–their eyes are sometimes level with the tabletop! Anyway…try these on your next chair–you’ll be surprised.
  • Since my theme seems to be soldering-related, and I’ve just mentioned static electricity, here’s one that tries to help one by eliminating the other. It’s an 18 by 30 inch anti-static mat that is made specifically to withstand direct assaults by soldering irons and hot solder. It sells for $57.50. I have several of these, and they work quite well. They also give you a consistently-colored, flat surface to look for small SMD parts you might have just dropped. At my work, even though it’s in Northern California, we make extensive use of anti-static mats, wrist straps, and even anti-static floors, and chairs with little metal chains that droop down to make constant contact with the floor. Even if you don’t feel a jolt, static electricity can and does pass between you and anything you touch. I seem to recall that we have a threshold of feeling that’s somewhere around 5 thousand volts. Anything less may go unnoticed by people, and at the same time, blow out the junction on a MOSFET. We also practice the “touch me before you hand me the pc board” protocol to dissipate these lower-level jolts (much harder to do now with social distancing). Anyway, these are good mats. Remember to ground them to the screw on your AC wall plate or a similar electrical ground spot.

OK, so that’s it for now. I’ll try and add more soon. The young lady in the Prime van said to tell you hi, and that she misses her family.

Dave – K7DAA

A Few of My Favorite Things–Part 1

With apologies to Julie Andrews, I thought I’d share a few favorites that I’ve bought at least once on Amazon. Many are ham-related, but certainly not all. I buy stuff on Amazon fairly frequently, to the point where they now have a Prime van parked 24/7 in front of my house. Fairly frequently. I said that. We take food out to the driver occasionally and let her use the bathroom. We’re not uncivilized people.

I’m a fan of noise-cancelling headphones. I bought the very first wired model that Bose produced way back when. They have lots of competition today. Since last year, my new favs have been the wireless Sony WH1000XM3 Bluetooth headphones with built-in mike for Alexa or mobile-phoning. I got the silver model (hey, everybody does black!), and they are wonderful to wear. Excellent sound for all kinds of music, comfortable over-the-ear cushions, and very easy to use.

If you don’t like the over-the-ear style, then quit reading now, because I like them to cover my ears completely so all the conversations and jet-engine whooshing noises can be reduced to near-zero. I hate sticking earbuds directly into my ear canals (I think I ruined them with the wax pellets that they handed out when I flew in the USAF), and the “open” style of noise-cancelling headphones appear to me to be as useful as screen doors on a submarine.

I was going to say that this is not a ham-related item, but I’ve been experimenting with connecting them to my Elecraft K3s transceiver, and I have to say that I think they are a winner for short-wave listening. I use an external Bluetooth transmitter connected to one of the K3’s audio outputs, and I can walk around and listen, still fiddling with other things in my shack. If you buy a Bluetooth transmitter for ham use, make sure to get one that does the new low-latency audio, which the Sony supports very well. Cuts the normal BT audio delay down to less than 40 milliseconds.

The only real downside to them is that they are $350. As my dad might say, “You’ve really got to be madly in love with something to pay that kind of money!” Yeah, tell me about it. But I travel a lot, and these are the best for that activity, hands down. Just don’t ask me what the pilot told us.

But it turns out that I also want something cheaper that I can use in the wood shop, doing something dusty or messy, or just something to knock around without worrying about the cost of replacement. I found this pair of headphones that do just about everything the expensive Sony headphones can do, but at a super-low price!

And the winner is the Anker Soundcore headphones, and they are only $59.95 on Amazon. They are not perfect copies of the Sony, performance-wise, but they have a decent quality feel, and are certainly an excellent deal for the price. I’ve been very happy with them, and recommend them without reservation. Now I’ll list a few good and less-good points. Oh, you might call them reservations, I guess.

Pros:

  • Very good sound with very decent bass (one of my requirements). Capable to doing the official Bluetooth HD mode for hi-res audio, like the Sony.
  • About as comfortable as the Sony and look just about like them, with decent fit and finish
  • Easy-to-use controls
  • They’ve screen printed a big “L” and “R” on the inside of the left and right earcups, respectively. A nice touch for us reading-glasses-for-everything-smallish types.
  • Built-in rechargeable lithium battery like Sony, with long listening time (claim is 40 hours and I have no reason to doubt this). Uses a micro-USB charging jack. The Sony uses a USB3 connector.
  • Has a built-in mike so you can use them with a mobile phone, again just like the Sony model.
  • Can be paired with more than one thing at a time. You can only use one audio stream at a time, of course, but you can have them paired with, say, your computer and your mobile phone. If you have Windows on your computer, be aware that Windows will occasionally try and “steal” the connection back, but this is a stupid, freaking, idiotic, %&@#*!($% Windows shortcoming, not the fault of either pair of headphones. Everyone else on the planet has figured out how to make their operating system work reasonably well with Bluetooth except Microsoft! This from the people who are still trying to destroy your computer with stupid, freaking, idiotic, poorly-tested updates to Windows 10 in 2020! What? Oh, OK, I’ll wipe my brow and sit down again. Sorry, they just really hack me off, as the British like to say.

Cons:

  • The Sony can do a new type of low-latency Bluetooth streaming that I mentioned earlier, which you’ll only care about if you watch TV or play fast-action games with the headphones on. This Anker model is missing that feature. You may never notice it, though.
  • With the ANC (active noise cancelling) turned on, the Anker will occasionally emit a loud “POP” from both earpieces if you are chewing crunchy food (yes, I’m not kidding!), or you sneeze or cough loudly. This is a minor annoyance, but still annoying. Maybe it’s just a quirk in the pair I own, but you’ve been warned.
  • Lacks the Sony fun touch-surface controls that allow you to turn the volume up and down, pause, answer the phone, etc. You can still do all these things, but the Anker uses little discrete buttons or rocker switches rather than the iPhone-like touch surface of the Sony. Not a deal-breaker by any means, and if you remind yourself you’ve got an extra $300 in your pocket, you’ll definitely never miss the feature.

OK, so there you go. I’ve saved you some dough, got to rag on Microsoft again, and I’ll add some more favorites as time permits.

73 and good listening,

Dave – K7DAA

Attack of the $100 DMR Hotspots!

The Chinese have now successfully copied the DV Mega digital radio board (also called the MMDVM) that had been the key to many of the $200-300 hotspots many hams have been using to get on DMR. I put mine together last year by buying a DV Mega 70cm board and mating it with a Raspberry Pi 3. It’s worked like a champ, but I spent about $200 for the two boards, then added a $100 case and power supply that has allowed it to run on the cylindrical 18650 Lithium cells. All together, I spent about $330.

Now you can buy a tiny hotspot that does everything mine does (except the batteries), and now including a neat little color display, for $105 on Amazon or eBay. I decided to buy the one on Amazon and check it out. Here is a link to the one I now have:

https://www.amazon.com/gp/product/B07BTS738L/

It comes with a 3 foot USB to USB mini cable that is used to power it up.  The only thing you have to do to get it started is to copy a small file that has your Wi-Fi network name and password to the micro SD memory card that comes with the hotspot.  This allows you to reboot it and then edit the details in a web page that hooks it up to the right BrandMeister server and has you name, DMR ID, and a few other things.  You should order a micro SD-to-USB adapter if your laptop doesn’t already have an SD slot.  That’s only another $8 or so.

The software that runs on this hotspot is called Pi-Star, and is a collaborative effort between a guy in Shenzhen, China, and a U.S. ham, so you likely won’t encounter much of that inscrutable Chinglish verbiage that often plagues Chinese radio buyers.

I’m very impressed with both the Pi-Star software/firmware, and the tiny size of this neat little unit.  Running on the standard USB 5 volts, you can grab it and plug it into your computer, your phone charger, or maybe even a USB port in your late-model car.  It takes about 2 minutes to boot up (watch the display for a clue), then you’re good to go…maybe.  Did I forget to mention that you must carry around a Wi-Fi to cellular phone modem?  You can enter the names of several Wi-Fi networks, and the Pi-Star software will switch to whatever it finds.  Many people don’t realize that they have free or low-cost ($25/mo) Wi-Fi cellular modems in their smartphones.  This little guy will work with any of them, as long as it’s using the 2.4 GHz band.  Sorry no 5 Gig.

Anyway, you can’t beat the price, and I can tell you that mine works as well as my $300+ unit.

 

 

Get on 40 meters SSB voice for $59

http://www.hfsigs.com
The BitX40 “you finish it” kit for $59

On tonight’s net, I mentioned that you can get on 40 meters for under $60, and without the need to be a virtuoso on the soldering iron or know tons about radios.  Say hello to the BitX40, an almost completely-finished 7 watt transceiver.  All you need to do is supply a box or case of some sort to put it in, a battery, and an antenna.  Everything else is already there for you.  To finish it, you solder on wires to a few controls, the battery (or 12 volt power supply), the antenna connector, and you’re ready to get on the air.

The BitX series of radios have an interesting back story.  A ham in India named Ashhar Farhan, VU2ESE, was concerned about how low the number of hams there were in his country, as well as other third-world countries.  After pondering this issue for a bit, he decided that one of the greatest problems a prospective ham faced was the high cost of even used ham equipment there.  He set out to make a 20 meter voice transceiver that used less than $20 in materials.  Thus was born the BitX20 about 10 years ago.  He cut costs in some very innovative ways.  For example, instead of the relatively-expensive ferrite toroids that are often used in radios, he substituted fiber or metal washers and wound his coils on them instead.  He decided to limit the power output to less than 10 watts so that a very common power MOSFET transistor could be used.  He also designed a novel main VFO tuning system made from a plastic drinking straw and a coil of wire.  I have one of these original (slightly improved) kits.

About 6 months ago, Ashar decided to try and help employ women in India to make a radio that might sell in higher quantities if he made it easier to build, but still supplied a quality product.  He created the BitX40, and founded a new small business to support it.  This is what I have in a my hands today, and I have to say that it is a very high-quality product, and he’s made it very easy to complete.

Gone is the drinking straw VFO, replaced by a very cool “Radiuino” board.  It is a very hackable Arduino that drives a 2-line LCD display and a DDS chip that outputs a highly-accurate, clean RF signal.  This one item alone increases the “fun factor” quite a bit, and helps contribute to a feeling that you are using a high-quality product that you yourself completed and mounted in your own custom housing.  Mount the display face and knobs to a plastic or metal ammo can and throw in a small battery pack, or put it in a cigar box (do they still have those?), or make your own custom wood enclosure.  It’s all up to you.

I suggest you give this cutie a try.  It’s not very intimidating, you’ll be very pleased with the results, and you’ll be helping some folks in India become more self-supporting.  You can find his website and ordering info here:  http://www.hfsigs.com/

 

 

A Few Items from Tonight’s Tech Net

On tonight’s tech net, the main items of discussion centered around coax, antennas, power supplies and batteries.  All things that we as hams have to deal with.  Due to the length of my explanations here, I’m going to skip batteries for now, and just throw down a few thousand words about coax and antennas:

Coax

Coaxial cables come in many different types and sizes.  One question was why are there so many different sizes of coax?  Without getting deeply into the mud, I suggest that there are broadly two main reasons:  loss and power handling capabilities.  Let’s talk about power first, since it’s pretty straightforward.  The more power a coaxial cable needs to handle, the bigger it must be.  Part of that is like battery cables, the center and outer shield have to be beefy enough to handle the power.  Another part is that the more power going through a coax cable, the higher the voltage difference is between the center conductor and the shield.  Just like with high-voltage transmission lines, as the voltages get up into the thousands, the two parts of the coax must be moved further and further apart to keep them from arcing over.  I have seen coax in use at a 50,000 watt TV station that is larger in diameter than my arm (and I’ve been working out!).

Regarding loss, the general rule is that the smaller the diameter of the coax, the greater the loss is going to be.  Also the higher the frequency we’re using, the greater the loss is going to be. In the Wi-Fi consumer electronis industry, we routinely use 50 ohm coax cable smaller than the lead in a pencil because of the need to be able to snake the cable in and around very tight spots.  We accept the fact that the loss of this cable in the 2.4 and 5.0 Gigahertz WiFi bands is substantial but, due to the short lengths we usually use, it’s acceptable.

Below is a quick list of coax cables you are likely to meet as a ham.  There are hundreds of types, so this is a very pared-down, ham-friendly list.  RG-174 is often used by QRP (low power) operators, because it is small and light, and easily carried in a back pack or go kit.  RG-214 and RG-8 are a bit over 1/2 inch in diameter, and like LMR-400, are your best bet for carrying VHF and UHF signals for 50+ feet without too much loss.  In fact, please use LMR-400 rather than either RG-8 or RG-214 for VHF+.  RG-214 has a double shield, and is quite expensive, but good for use in repeater cabinets.  RG-8 and its cousins are good for 2-30 MHz use, and is much cheaper also.  Note that these thick cables can also withstand 5,000 volts, and RG-6 (75 ohm cable TV) is only good for 350 volts.

So why did we settle on 50 ohms for most coax?  Actually, 72 ohms is best for least receiving loss of very small signals, and that’s why the cable TV industry like it.  It turns out that 50 ohms was calculated back in the 1930’s (and re-calculated many times) to show that it was the best impedance for transferring power.  For receiving, 72 ohms is still best (and some hams use 72-75 ohms for that reason), but 50 is a good compromise.  It also turns out to be a happy value, close to the natural impedances of certain types of monopole and dipole antennas.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Antennas

Taking the simple example of a steel wire antenna poking up from the center of a car’s roof, if it’s about 19 inches long, we can say that this is a quarter-wave antenna in the 2 meter ham band.  It radiates (and also picks up when receiving) signals from directions generally best represented by imagining throwing a big, inflatable doughnut over it, like the ring-toss game.  The pattern favors the horizon in all directions out from the car, with some pickup also from maybe 30 degrees above and below the horizon, as this drawing shows:

This 1/4-wave antenna has a slight gain (meaning you get more power or received signal than you put into it!) compared to an isotropic antenna.  Isotropic is a theoretical pattern described by a beach ball–it both transmits and receives well in all directions.  Our 1/4 antenna gets about 1.2 dB (abbreviation for decibels, which relate in logarithms of the powers of 10, so 3 dB is a doubling or halving of power) more gain at the horizons only compared to an isotropic antenna, because we squished that beach ball with giant hands down in the middles, top and bottom.  It’s all the same amount of energy that we started with, but we’ve squirted a larger amount of it in a direction that’s more useful to us!

Speaking of squishing a beach ball, now let’s squish it down in the middle even more by changing the antenna to a 1/2-wave type.  A half-wave antenna simply squirts even more energy at the horizons (so the signal goes further across a city, for instance), and even less up or down.  We also lose more of that fat, doughnut shape, and it starts to look a bit more like a frisbee, but (and here’s the big deal) more of it squirts out towards the horizons, which are the useful directions we really want our signal to go.  Here is an image showing “Unity”, or about like a 1/4-wave antenna, then two more antennas that have 3 and 5 decibels of gain over a dipole (that’s the little “d” after the “dB”, it’s the thing we are referencing ourselves to).

 

That’s all antenna gain is–we refocus the energy from that theoretical beach ball in directions we care the most about.  A beam antenna becomes more like the reflector on a flashlight.  Held in the open, a flashlight bulb somewhat weakly puts light out in all directions.  However, that same bulb, now placed in a flashlight with the reflector right behind it, can really put out a strong beam, but only in one direction.  Dish antennas are very close to flashlight reflectors, and accomplish pretty much the same task: they reflect back any energy in a single (well, mostly) direction, causing increased signal in that direction.

So, broadly speaking, gain-type antennas create this wonderful gain because they redirect the antenna’s energy in the directions we care most about.  Make sure you walk away from this little tutorial with one important thing in your head:  Gain antennas don’t create any new energy.  If they did, the Law of Conservation of Energy would be violated, and would probably get quite upset about being violated in such a rude way.  No new energy, simply the same amount aimed where we would like it to be most effective.  The universe maintains its balance.  No dark matter was harmed in the making of this movie.

Aha, so “gain” is actually a misnomer, isn’t it?  There is nothing gained in one place that isn’t also equally lost in some other,  thus maintaining nature’s balance.  Maybe instead of calling them “gain” antennas, we should start a campaign to call them “redirecting” antennas.  Well, maybe it would catch on…

As a final thought, we can make gain antennas either by making them a certain length, or by stacking multiple antennas, or by brute-force reflectors (like a dish).  It turns out that certain lengths of antennas have more gain than others.  A half-wave has 1.2 dB more gain than a 1/4-wave.  A 5/8-wave wire has 3 dB more gain than a 1/4-wave wire.  Stacking several 1/2-wave antennas has more gain than them all!  The only “trick” to getting all this gain is that you have to make each new length or added antenna happy by matching it to the exact impedance of the rest of the antenna system, and that can get tricky, because it will rarely be 50 ohms. Not super-difficult, just tricky.  The reason everyone likes a 1/4-wave antenna is because,given a decent ground plane to work with (the car’s roof, in this case), it happens to come out to a nice, round 50 ohms characteristic impedance.  That means we can connect any old 50 ohm coax, and we’re done!

What if we want the gain and directionality of the 1/2-wave antenna?  OK, here’s a new challenge:  The 1/2-wave antenna, at its two ends, are thousands of ohms in impedance, instead of just 50 ohms (but you can find 50 ohms in the middle of that 1/2 wave antenna–makes sense?).  Darn, now what?  Well, we have to create a (hopefully simple and small) matching network to transform 50 ohms to several thousand, and connect it up to our half-wave antenna.  The trick (and the reason I get paid for this!) is to lose as little energy as possible, and make it for cheap and simple.  I can tell you that the matching network will probably involve an inductor (small coil of wire) that has a tap on it about 1/4-1/2 turn up from the bottom), and a capacitor to resonate with the coil near the design frequency.  Depending on how big and lossy those parts are, we could easily lose most of the gain.  You won the battle, but lost the war, so to speak.  (RF engineers’ joke:  What do you get if you end up with a poorly-designed matching network?  Answer:  New antenna company on eBay with offshore mailing address!)

OK, haha, thanks.  So adding a bunch of 1/2-wave, 5/8-wave, or even 3/4-wave antennas together will give you more and more gain, offset by whatever losses you have in your matching networks (and there’s always some energy lost).  A vertical stack of these antennas to make one high-gain, 20 foot-tall antenna of maybe 9-12 dB is called a collinear array.  All the while, that pattern you see above gets flattened more and more out towards the horizon.  Is there a practical limit to the size of a collinear antenna?  Yep, eventually, the losses in your matching networks at each junction of new antenna elements will add up to give you diminishing returns.  You will have less and less of the original energy available down at the antenna connector.  The array also becomes more and more mechanically unstable until finally someone shouts “Jenga!”  Again, you’re welcome.

Super PowerGate: Part of a Ham’s Home UPS

During our tech net tonight, I couldn’t remember the name or model number of the piece of gear that allows me to have my own uninterruptible power supply (or UPS) to keep all my ham gear running, especially when the lights go off.  So here it is:  The West Mountan Radio PG-40S PowerGate.

Along with a decent-sized deep cycle 12 volt battery (1 or more in parallel) and a 13.8 volt power supply, the PG-40S ties them together to give you uninterrupted power, and also keeps your battery charged, ready for action.  It can provide up to 10 amps charging current to the battery when the power comes back on.  It can handle up to 40 amps, or the equivalent of two fully-equipped HF 100 watt transceivers, or as many as four 50 watt-type VHF/UHF mobile radios.

I’ve had mine for years, and can say I wouldn’t have it any other way.  It’s silent, and the status LEDs on top tell you at a glance what is going on.  The connectors on top are Anderson PowerPoles, pretty much the standard 12 volt connectors in use by all of us these days.  Available at our local HRO stores or mail order.  Price is about $140.  Not cheap, but I can’t live without mine!  We also have this same unit in operation at the WB6ZVW repeater (442.500 MHz, + 5 MHz, 100 Hz PL) on Crystal Peak to handle its battery backup needs.  This one item kept us running without fail during last summer’s big Loma Prieta fire.

Items covered in our 1/4/17 Tech Net

In this week’s first-of-the-month Tech Net, we covered quite a wide range of Q’s and A’s, as well as some new and old laws on the books.

The first of those laws is the new California restriction on distracted driving and cell phone use that does not exempt holding an amateur radio mike or walkie talkie in your hand.  Nobody knows yet how this is going to play out, or if any hams are going to end up being pulled over.  Here is the paragraph taken from State Assembly Bill AB-1785 that defines what a “restricted device” is:

(f) For the purposes of this section, “electronic wireless communications device” includes, but is not limited to, a broadband personal communication device, a specialized mobile radio device, a handheld device or laptop computer with mobile data access, a pager, or a two-way messaging device.

I guess we would be caught under the “specialized mobile radio device”, but the wording, and even the definitions they provided, are so vague that I could probably be pulled over for talking into a corn dog.  And yes, they did exempt anyone operating as an emergency services person.

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Along this the above new law is a requirement that the restricted device be mounted to the dashboard.  One of our members reminded us of another law that is in effect that does not allow you to mount anything in the center of the dash, or on the low-center part of the windshield.  You must mount your GPS, phone, or whatever in either the right or left corner of the dash only.  The idea being that anything mounted in the center will obstruct your vision.

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Sugru is a neat, new product that just might find a use around your home or garage.  See it here:  http://www.sugru.com  It is a flexible, heat- and cold-resistant, grippy and moldable polymer that can do some pretty cool things.  After you mold it to the shape that you want, it remains flexible.  Easiest thing to do is to have a look on their website at the pictures and also videos that show some good ideas.  Aaron, W6TDR, brought it up and mentioned that he’s used it.  I have several sample kits of it, but I haven’t actually used it yet.  I also got a fun kit from them that includes some button magnets.  Oh boy!

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We talked briefly about using silicone grease (not silicon!) in RF connectors to displace water and to keep corrosion off of connector pins.  I am also reminded that I used a small tube of silicone grease on several rubber o-rings that I recently installed inside of my new water softener.  Avoid using silicone grease in very high-power RF, since you’ll get carbon tracking and flash-over, but for amateur power levels, that’s probably not a concern.  It is apparently OK to wipe silicone grease on the mating surfaces of RF connectors, and they will be protected from corrosion and presumably will wipe away from the points at which direct metal-to-metal contact needs to be made.  Remember that we are talking about SILICONE the polymer, not SILICON the soft metal that bursts into flames when exposed to a little moisture.  People constantly confuse the two in everyday speech.  Even those that should know better.  If you are ever having trouble remembering which is which, please refer to the “Rule of Two Valleys”:

1. SF Bay Area and Tech Capitol of the World:  Silicon Valley

2. Hollywood, full of “enhanced” actresses:  Silicone Valley

You’re welcome.

See here for further info:

https://www.w8ji.com/dielectric_grease_vs_conductive_grease.htm

http://lists.contesting.com/_towertalk/1998-09/msg00477.html

Dow Corning High-Vacuum Silicone grease comes highly recommended by some 2-way radio pros.  I have my own tube of it that will probably last me a lifetime.  Here is an Amazon link to it:  http://amzn.to/2hZEHAw

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A question was asked about whether DStar is becoming more or less popular, especially when DMR seems to be coming on strong.

My take (my opinion only, of course) is that DStar is declining in popularity, but truly DMR is experiencing explosive growth right now.  Some comparisons:

Even though DStar and DMR use the same analog-to-digital codecs, DMR’s has FEC (forward error correction) built into it, and there is much less “R2-D2” voice garbling than DStar when signal strengths get low.  In fact, because of FEC, DMR seems to get about 10-15% better range than even analog FM can do.  The only downside is that you’ll have to get your ear used to hearing band-limited, digitized audio.  This is the case for either DMR or DStar, BTW.

DStar is supported by one ham manufacturer, Icom, and has never caught on with any others.

DMR is a world-wide standard driven by the need to serve the professional 2-way radio crowd, so even though it didn’t hit the market until 2007, all sorts of radios and infrastructure are available for it now, driving down costs to $100 or so for an entry-level radio.  With DStar, I’ve always been annoyed by the “DStar tax” I would have to pay if I bought an Icom radio.

The best part of DMR for me is the wonderful volunteers that have set up several world-wide networks and charged exactly zero for the rest of us to join in.  There are tons of hams to talk to at any hour of the day.

The only downside to both DStar and DMR is that they have a bit of a learning curve as a barrier to getting started.  You can’t just buy a radio and put it on the air 10 minutes later.  That’s where a knowledgeable ham friend who has been down that road already can be invaluable in getting you started.  Now, that said, let me offer some quick steps to help you at least get to the front door of the house:

  1.  Go to http://www.dmr-marc.net/ and click on “Register ID” in the upper right-hand corner.  You will be registering for a user ID, not a repeater.  On the bottom of the next page, click “User registration” and follow the prompts where they will validate you, making sure you have an active amateur radio call.  Within a day or two, you will get an email from them with your new 7-digit DMR ID number.  You will later program this into your DMR radio.  Note that you can also go back to this website later to see what you or your friends’ DMR ID’s are, or to find the name of the person whose only info that came up was his DMR ID. Here is a direct link to the database search page:  https://www.dmr-marc.net/cgi-bin/trbo-database/
  2. Buy a DMR radio.  Most of us locally have started with the TYT MD-380, and it’s just over $100.  If you have a TYT, you’re much more likely to find help with any questions you might have.  Most of us bought them on Amazon, such as this link:  http://amzn.to/2j199am
  3. Install the MD-380 programming software on your PC (available here as a download after you sign up for their very good newsletter).
  4. Get one of us to email you a codeplug that you can program into your radio, and then you’re good to go!  We can also explain what a codeplug is, and how you can change it to suit your own needs.

Thoughts and Links to a Few Things Discussed on Our Tech Net Tonight

PL on your receiver, or CTCSS:

We all know that you need to transmit a PL tone to unlock a repeater.  That’s how we keep repeaters from keying up unnecessarily.  In the old days, when there weren’t many around, we didn’t use PL at all.  Today, with ham repeater channel pairs all used up in all metro areas, it becomes necessary to place repeaters on the same frequency, and as far apart as geographically as possible, but then separate them further by requiring each to use a different PL tone for access.  That way we get better frequency reuse, where we can place them somewhat closer together, and users can make sure they only bring up their own system, and not the other ham group’s repeater.

On our own receivers, though, there has never been such a rule that we use PL.  The official term for PL on your receiver is CTCSS, which stands for Continuous Tone Coded Squelch System.  It basically means that, when set to this mode, you won’t hear anything from your receiver’s speaker until it hears a specific subaudible PL tone to open it up.

By the way, you would be correct to say that, while your own radio might not need to use it, when seen from the perspective of the repeater, it indeed uses CTCSS on its own receiver before your voice gets repeated.

OK, so besides not hearing other people on your repeater’s channel that might be far away, what other use does CTCSS have.  There are a number of them, but I’m only going to mention one other that you may care about.  If you are walking or driving around, and hearing occasional beeps, squawks, or blasts of white noise from your radio, using CTCSS will prevent random junk from coming out of your speaker.

As an example, in my house, my cable modem emits a digital harmonic that just happens to fall right on 147.33 MHz, the frequency of our two meter repeater.  I can’t monitor that frequency for very long without CTCSS, because the receiver is always opened by the digital noise.  With CTCSS, it’s blissfully quiet until someone keys up the repeater, which transmits a PL tone to my receiver, opening up the speaker.

As a parting note, beware that there are still quite a few ham repeaters that don’t transmit PL.  You’ll just have to check on a case-by-case basis.  To save you a little bit of time, I can assure you that all of the K7DAA, GVARC, and SBCARA repeaters do transmit PL.  On the two K7DAA repeaters, I also perform one other, very minor trick:  I turn off the PL transmit tone about 1-2 seconds before the repeater transmitter drops.  This gives your receiver time to notice that the PL tone is gone, and it again mutes the speaker before the usual squelch crash when the repeater’s transmitter drops off the air.  Nothing is perfect, though.  You’ll still hear a crash after an ID or other very short transmissions, but not during regular conversations.

 

DMR (Digital Mobile Radio):

I’ve bought two of the TYT MD-380 UHF DMR radios for $100 or so on Amazon (a click opens an Amazon search window–multiple vendors)

Hytera is a well-respected name in the DMR two-way radio industry.  They are now marketing to hams through Gigaparts

Hotspots:  Even though most of us in the South County and Hollister areas can use the W6YYY DMR repeater on Crystal Peak, it’s very nice to have your own little DMR system at home or portable in the car.  At present, the two most popular ways to do this are:

  1.  Buy the SharkRF Openspot, a relatively new all-in-one product with no DIY skills needed:  SharkRF website here
  2.  Buy the DVMega board, plug it into either a Raspberry Pi, an Arduino, or a BlueDV board (if you use Android), and add software

By the time you are done, any of the above will end up costing you about $200-300, just so you know.  The Shark has the least number of fiddly things you’ll have to do to get it running, but the ham that sells them gets backed up often, so you’ll spend a week or three in back-order status (not a big deal, though).

The BlueDV is a neat unit that you can control with your Android device, but as an Apple guy, I didn’t find that as attractive.

If you do Arduino, make sure you buy the Arduino Due (Due is Italian for Two).  Not just any Arduino will work.

If you go the route I did, with the Raspberry Pi, be sure and get the Pi 3 like I did.  It is faster than the others, and has built-in WiFi.  All of the choices in #2 use the DVMega radio board.  Note that you can buy either a single- or dual-band board.  There is about $40 difference.  I bought the cheaper UHF-only model, since almost all of the DMR activity is on UHF around here.  I also mentioned the DHAP, which is the 3D-printed case that my hotspot rides around in.  It’s perfectly OK to put a DVMega/Pi combo in one of the taller cases designed for the Rasberry Pi (and only $12 or so), but I wanted something more integrated that also included space for batteries.  That’s how I ended up with the Hardened Power Systems DHAP case.  It’s $99, but includes a dual-mode power supply, and space for four 3.7 volt Li-Ion batteries for easy portable use.  I had to wait about 3 weeks for delivery, by the way.  And yes, I got the bright yellow one!

So far, I’m the only one in the area with a DMR Hotspot, but Dan, KJ6LXX says he might go for a Shark, so feel free to ask him for opinions.  If you try to duplicate what I did, I can certainly help you with it.  Since we’re in the very early days of DMR radio, not a huge amount of “…For Dummies” guides are available yet, so don’t feel shy about asking lots of questions, or for help getting something going.

Mel, KK6MES, and Steve, W6MNL, are the two folks whose brains I’ve been able to pick regarding the DMR world, so feel free to hit them up with questions if/when you hear them on the repeater.

As was also mentioned tonight, the listing of DMR radio manufacturers roughly by cost and features as of today:

  1. Motorola–top of the line, expensive, but used gear on eBay.  Watch out for $300+ programming software you must have!
  2. Hytera–like Motorola, the only two that can do roaming across multiple ham repeaters.  Just began marketing to hams.  See Gigaparts above.
  3. Connect Systems, or CSI–very ham-friendly people, very solid gear, American company.
  4. Kenwood–surprise!  Let’s see what Kenwood brings to the market in DMR.  Note the link to VA3XPR.net, a good source of DMR news
  5. TYT or Tytera–I know, they’re Chinese, but several of us really like their MD-380 radio.  UHF-only, excellent tx and rx audio, easy to use.
  6. All the other Chinese vendors, only because I don’t know their product personally.  Wouxon and Alinco also have ham DMR stuff.

As a parting thought, before I buy or build any of the above, I usually have a look at various reviews and comments on all these items on YouTube.

Ham Radio 360 Podcast features local hams

George, KJ6VU, has a great podcast and accompanying web page with some interesting gear and DIY projects going on. They are presently doing a group build of a 1-30 MHz antenna analyzer based on the Arduino platform. Have a look and/or listen at www.hamradio360.com

 

I mentioned this on tonight’s tech net at 9 PM.  While you are perusing that website, have a look around at a few other very interesting things.  For instance, see George’s presentation from this year’s Dayton Hamvention, where he introduced the very handy portable end-fed antennas from his new company called PackTenna.

 

The presentation does a very good job of showing you how to wind some simple baluns (actually they are un-un’s) to get your 50 ohm feedline matched to the very high impedances of either a resonant, end-fed dipole, or a random-length end-fed antenna.  Or…you could buy one ready-made from PackTenna for $89.  If you go to www.packtenna.com and look around, be sure to read the QST magazine “test drive” of his antennas.  Highly recommended.

Amazon = Radio Shack + Frys + Halted + everyone else

This is probably old news for some of you, but if you miss having Radio Shack around, Amazon is the new Radio Shack, including all the other electronics parts stores rolled into one.

If you are a regular Amazon buyer, you’ve probably noticed that the Chinese “quick and dirty” module and parts suppliers that started out on eBay have all opened stores on Amazon now as well.  Being on Amazon generally means that they have to live up to a higher standard, if that kind of thing kept you from clicking the “Buy it Now!” button on eBay, but I’ve never gotten ripped off by any of them on eBay either.

Anyway, these guys offer just about anything imaginable for the Ham, DIY’er, or even an RF engineer like me.  I’m truly amazed at all the parts and pre-made modules you can buy from them.  If you have an Amazon Prime membership, which I highly recommend, you can buy just about anything and find it on your doorstep a day or two later, often without tax or shipping charges.

The prices are almost always way better than Radio Shack’s ever were.  Here’s just one example:  I needed to buy a 2.1 x 5.5 mm coaxial power plug–the type that you often see on the end of the “wall wart” power supplies.  Looking on Amazon, I had tons of choices, including whether or not I wanted some with wires already soldered on them and ready to go.  I finally chose these:

Coaxial power plugs with pigtails

So, for less than $.60 apiece, I got 10 plugs with wires already attached.  No tax charged, and free two-day shipping.  Can’t beat that!  Stock up for your next project!

 

Category: DIY