Set your calendars for December 11, 2017 as that is the kick off for the next <something> On The Air contest! Following the huge success of the National Parks on The Air contest from this past year, this new contest will include clubs from around the US which will operate from 16 NASA centers around the US. You can check out their web site for operational details. This looks like a really fun event. Check it out!
How about a new Field Day challenge? Welcome to Winter Field Day 2018, January 27-28, 2018. All you have to do is set up outside, in January, (If you want the points bonuses, and who doesn’t?) and make contacts that weekend. If you are so inclined, you may also operate from your cozy home shack, but what fun would that be? Check out the rules and points system here.
On Monday August 21st, from 1400-2200 UTC (6AM-3PM local time) there will be a total solar eclipse that will traverse the entire United States from Oregon to South Carlolina. It will cross 11 states at a speeds over 1,000 miles per hour.
A group called HamSCI is hosting the Solar Eclipse QSO Party. The pupose is to gather scientific data for Virginia Tech to study atmospheric propagation during the eclipse. If you are around on Monday, be sure to register your station, collect some QSO’s and turn in your logs.
The rules for the QSO Party can be found here. They are pretty basic. The exchange is the call sign, signal report, and your grid square number. You can find your grid square number here. As an example, most of Morgan Hill is either CM97ec or CM97ed. I would imagine they are hopping that people do something other than 59, like most do in a regular contest. This page has a good explination of the signal reporting system.
A couple of fun sites for the ecplise are a couple of simulators that will give you an idea what the eclipse will look like from your address or zip code.
One interesting aspect of the eclipse is that the sun rises and travels East to West, yet the eclipse crosses the US from West to East, entering the US at Oregon.
One last link is the American Astronomical Society page that has lists of safe and tested solar glasses that can be used to view the eclipse. There are unsafe glasses flooding the market. Do not mess with your peepers. If you do purchase some, make sure they are safe and from a reputable dealer.
Got this from the ARRL:
I am writing to you today because we are at a crossroad in our efforts to obtain passage of The Amateur Radio Parity Act.
Our legislative efforts scored a major victory in our campaign when The Amateur Radio Parity Act, S. 1534 now moves to the Senate, where we need every Senator to approve the bill. This is the companion Bill to H.R. 555, which passed in the House of Representatives in January.
You are one of over 730,000 licensed Amateur Radio Operators living in the United States. Many of you already live in deed-restricted communities, and that number grows daily.
NOW IS THE TIME FOR ALL HAMS TO GET INVOLVED IN THE PROCESS!
• If you want to have effective outdoor antennas but are not currently allowed to do so by your Home Owner’s Association, SEND THESE EMAILS TODAY!!
• If you already have outdoor antennas, but want to support your fellow hams, SEND THESE EMAILS TODAY!!
• If you want to preserve your ability to install effective outdoor antennas on property that you own, SEND THESE EMAILS TODAY!!
We need you to reach out to your Senators TODAY! Right away.
Help us in the effort. Please go to this linked website and follow the prompts:
Thank you to all that came out to support the MHARS, GVARC, SBCARA combined 2017 Field Day! We had a really great team that helped set up, feed, and operate this past weekend. This was the first year our group ran 24 hours for the event. We had several sleep on-site while others ran stations. The bands were very busy. 20 meters was a non-stop pile-up coast to coast. While we do this for fun, we still managed to wrack up over 300 contacts for the weekend. 20 metes was busy but 80 meters overnight was only slightly behind. Kudos to the overnight 80 meters team.
We ran 4A. Our station captains came well prepared with batteries and solar panels. Our antennas consisted of:
- 20 meter hex beam on 70 foot portable tower with rotator.
- 40 meter sloper off 50 foot crank up tower.
- 15 meter beam on push-up tower with rotator.
- 80 meter dipole between the 70 and 50 foot towers.
Some tallies for the weekend…
- 80 M – 107 contacts
- 40 M – 56 contacts
- 20 M – 115 contacts (+ about 30 CW contacts) for 135 total
- 15 M – 15 contacts
Arizona was the busiest state for us with 26 contacts.We covered over 60 sections.
We are already planning how we will improve for next year.
2017 Field Day is here! Join us on June 24-25 in Christmas Hill Park in Gilroy with members from GVARC, SBCARA, and the “We are not a club” club from Morgan Hill for 27 hours of Field Day. We will be operating 4A, with GOTA (Get On The Air).
If you would like to volunteer, please use the Field Day 2017 link and fill in the information for the shifts you would like to operate.
So… if you are new to amateur radio, or would like to find out more about it, stop by. Check out the map for the location in Christmas Hill Park…
The 27th Sea Otter Classic will be held on April 20-23, 2017. Help from amateur radio operators has been a vital resource for communication in the Fort Ord National Monument back country and the Gran Fondo (“Great Endurance”) Carmel Valley Route.
The Sea Otter Classic attracts over 9,000 athletes and over 70,000 spectators and is now universally regarded as the world’s premiere cycling festival. The areas where we assist have little or no cellular or repeater coverage. It is an excellent opportunity for demonstration and practice of emergency communications and help build readiness for a real disaster.
Continue reading “Looking for Amateur Radio Operators to help with the Sea Otter Classic”
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/
As some of you are aware, last year, AB 1785/CVC-23123.5 was passed which is a fairly broad ban of using any communications devices while driving. In years past, ham radio was specifically listed as an activity that was permitted. But in this latest version there is no such provision which puts radio use for S&R, event support, ARES deployments, and other uses of ham radio in jeopardy. There is a change.org petition to get clarification and to re-word the law to be less ambiguous, and to take the contributions of ham operators and other services into consideration. If you have not signed the petition, you should.
Check out Ham Radio Now’s episode 311 on the matter…
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:
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.
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.