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

DIY Bluetooth Powered Speakers

Bluetooth BoomBox

 

There are dozens of videos on YouTube showing how to build your own Bluetooth speakers or boom boxes.  A number of them have ready-made Bluetooth radios and audio amps in common.  These Bluetooth and audio amp modules are interesting because they are quite cheap (most under $20–see this one on Amazon as an example), fully built and tested, and easy to interface to.  You could probably build one of these without even knowing how to solder!  It’s a simple matter to fit one of these small BT/amp boards into a box with speakers you’d mount yourself, or even retrofitted into an old plastic-fantastic boom box you have laying around, or maybe purchase for next-to-nothing at a Goodwill store.  All you really need is the housing and the pair of speakers.  Everything else can go!

For those of you that are old enough, remember the little transmitters you could buy or build that output a fairly unstable signal somewhere on the 88 to 108 MHz FM broadcast band?  They were often called FM or wireless mikes.  Plug one in, and tune in to it on of your FM radios you happened to have around the house.  They worked sort-of OK, but were never very good, and the 9V battery usually went dead in a few hours’ use.  In the Bay Area, you also had lots of trouble finding a fairly open radio channel to use.  The whole system was, as the British say, kind of fiddly.  It was more of a science experiment than anything else..

With Bluetooth, it’s so much easier, and the sound is just light-years ahead of the old analog FM stuff!  Most of us carry smart phones with Bluetooth built into them already, so it’s almost trivial to play the music or podcasts on your phone through your car stereo system or an inexpensive set of Bluetooth tabletop speakers.  Most of the cheaper BT speakers don’t have such great sound, though.  They tend to be small and tinny-sounding, but that’s not Bluetooth’s fault.

Anyway, here are several links to folks that have built their own Bluetooth speaker systems.  Maybe they’ll inspire you to roll your own:

DIY Bluetooth Speaker

Overnight Sensation Bluetooth Speakers

DIY Bluetooth Speaker: Super Easy

DIY V5.0 Boombox, Bluetooth

DIY How to Make the Best Bluetooth Speaker EVER!

 

Here’s an under-$20 BT dongle that plugs in to any 3.5 mm jack, giving you instant Bluetooth audio for a home stereo system or maybe even a car stereo.  This is sold by Parts Express (good company–lots of speakers and speaker kits as well), but there are many similar and cheaper units on Amazon as well:

Add Bluetooth to amplifiers, receivers, car stereos, computers, iPod docks

 

New (cheap) Microphone for Yaesu and TYT TH-9800 Radios

MH-48 clone microphoneI found this inexpensive Chinese copy of the venerable Yaesu MH-48 mike on Amazon for $14.99.  At that price, even if the mike doesn’t sound as good as the original, you could open it up and pull out whatever replacement parts you need on your original mike, and throw the rest away!  Turns out that it actually sounds pretty good.  I bought one to try out on my TYT TH-9800 because I’m not too keen on the mike that ships with it.  Oh, it’s not horrible, but if you’re going to make a clone of a Yaesu radio, why not clone the mike as well?

That’s basically what this mike it–a true Chinese knockoff, right down to the “Yaesu Musen” small type and logo!  It pretty much feels like the MH-48 on your FT-1900, FT-2900, FT-8800, FT-8900 and etc.  The only difference I’ve found so far is that the PTT switch doesn’t have the nice tactile feel that the original does.  This one’s kinda squishy, but not horrible.

Anyway…if you’re going to try this out on your TYT radio, you’ll be disappointed to find that the PTT button doesn’t work.  Yaesu mikes run on 8 volts, and the TYT runs on 5v.  So, you have to open up the mike and parallel a 100 ohm resistor across another, then it works fine.

Click on the mike’s picture to go to its Amazon page.  For those with TYT radios that might want to try a “real” Yaesu mike, I’ve uploaded a pdf file containing the instructions for adding the resistor:

Yaesu MH-48 microphone with the TYT TH-9800