International Marconi Day - This Saturday

A 24-hour Amateur Radio Event

Amateur radios, point-to-point contacts, high-frequency transfers, a mysterious yet attractive prize for the most connected stations… All of this sounds like the beginning of a quirky B-movie. In reality, it is the essence of International Marconi Day, a 24-hour amateur radio event which celebrates the career of Italian wireless communications pioneer Guglielmo Marconi. 

Fitting with ‘The Rest Of The Story’ featured in the April 2018 Communicator, the event is held annually on the Saturday closest to to Marconi's birthday on 25 April 1874.  This year the contest runs on Saturday April 21st, operating hours are 0000 UTC to 2400 UTC (5pm Pacific time).

To commemorate the Nobel laureate’s achievements, fans use HF radio to make direct point-to-point contact between stations, relying on the same technology Marconi developed and utilized in his time. Although nowadays the Internet is the medium of choice for global communications, the idea behind International Marconi Day is to keep the spirit of invention alive. The event also provides an exciting throwback to the days when a connected planet Earth was but a bold dream and only a few exceptional people, such as Marconi, saw the value in it.

The organizers issue a very nice certificate for contacting 15 of 60 or more stations at significant sites around the globe related to Marconi's work.


At the time of writing, there are over sixty stations registered for the event. The full list, throughout Europe and North America is available at http://gx4crc.com/imd-stations/ 

Full details of the award and participating stations are available on the website gx4crc.com

World Amateur Radio Day

The following information is courtesy of the

International Amateur Radio Union

Every April 18, Radio Amateurs worldwide take to the airwaves in celebration of World Amateur Radio Day (WARD). It was on that day in 1925 that the International Amateur Radio Union (IARU) was formed in Paris. Amateur Radio experimenters were the first to discover that the short wave spectrum — far from being a wasteland — could support worldwide propagation. In the rush to use these shorter wavelengths, Amateur Radio was “in grave danger of being pushed aside,” the IARU’s history has noted. Amateur Radio pioneers met in Paris in 1925 and created the IARU to support Amateur Radio worldwide.

Just two years later, at the International Radiotelegraph Conference, Amateur Radio gained the allocations still recognized today — 160, 80, 40, 20, and 10 metres. Since its founding, the IARU has worked tirelessly to defend and expand the frequency allocations for Amateur Radio. Thanks to the support of enlightened administrations in every part of the globe, Radio Amateurs are now able to experiment and communicate in frequency bands strategically located throughout the radio spectrum. From the 25 countries that formed the IARU in 1925, the IARU has grown to include 160 member-societies in three regions. IARU Region 1 includes Europe, Africa, the Middle East, and Northern Asia. Region 2 covers the Americas, and Region 3 is comprised of Australia, New Zealand, the Pacific island nations, and most of Asia. The International Telecommunication Union (ITU) has recognized the IARU as representing the interests of Amateur Radio.

Today, Amateur Radio is more popular than ever, with over 3,000,000 licensed operators!

World Amateur Radio Day is the day when IARU Member-Societies can show our capabilities to the public and enjoy global friendship with other Amateurs worldwide.

IARU has provided a poster for World Amateur Radio Day. Any club may download it and use it to promote WARD in their area. The poster comes in two sizes: 61cm x 91cm and a small (A4) flyer.

Groups should promote their WARD activity on social media by using the hash tag #WorldAmateurRadioDay on Twitter and Facebook. The IARU will list all WARD activities on the webpage. To have your WARD activity listed, send an email to IARU Secretary David Sumner, K1ZZ.

April 18 is the day for all of Amateur Radio to celebrate and tell the world about the science we can help teach, the community service we can provide and the fun we have.

We hope you will join in the fun and education that is World Amateur Radio Day!

For more information and to download a poster please visit the World Amateur Radio Day webpage at http://www.iaru.org/world-amateur-radio-day.html

Source: The International Amateur Radio Union


Alan Griffin
RAC MarCom Director

Construct A $10 Dummy Load

A Communicator Reprise... October 2011

"I made this here dummy load and can’t figure out why I’m getting a 25:1 SWR!!”  “Got such great deal on this 100 watt 51 ohm resistor off of eBay and though it would make a great dummy load for the HF rig,” he beamed as handed me the homebrew project.  Did a nice job putting it into an aluminum project box, with both a UHF [SO-239] and a BNC connector...  

But of course the first giveaway was the aluminum encased resistor, the second was that it was 100watts in a relatively small package… When we hooked it up to the MiniVNA, and saw how it reacted to a sweep from 1 to 180 MHz., I could see then that it wasn’t your garden variety resistor, it was a wire-wound resistor – usually encased in an aluminum heatsink and a fraction of the size of a carbon composite resistor.  And boys and girls, what do we know about something that’s wound like a coil – an inductor?  Yessiree Bob… it’s an inductor. With enough wire to act like a proper load somewhere in the lower AM broadcast band.  So the closer to 1 KHz or DC, the better the SWR. So when he put 14.100 MHz into it, no wonder he measured 25:1!!  Of course the eBay seller didn’t say it was wire-wound and if you hadn’t seen one before, it just looked like a nice bright and shiny deal at $5.65.So, we chucked that experiment in the cylindrical file and proceeded to make him an inexpensive dummy load.

[Note: 3” discs would have been better in retrospect]

Here is what you need.  A paint can... you can buy new [and empty] for $1.36 at the local paint store.  A single hole SO-239 [$1], a piece of solid copper wire, two 2½” copper discs [in the photo] one has the drilling pattern already glued onto it and, twenty  5-Watt 1000 ohm carbon resistors.  Ceramic will do too… about $8 landed. 

The discs I cut from a piece of thin PCB, the resistors from eBay after I verified with the seller that they were not wire wound.  
After drilling the 22 holes in the discs and soldering all 20 resistors into place, one disc becomes the braid or shield side, the ground of the SO-239 and the piece of bare copper wire #10 or #12 bare copper goes from the centre pin on the connector to the disc on the bottom [of the photo].

The resistors were 5 watts, so 20 times 5 = 100 watts.
It gets hot enough in 30 seconds that you would not
be able to hold onto it for long.

What you have when finished  is 1000 divided by 20 or 50 ohms. But these are 5% resistors, and I didn’t ask for 20 hand measured resistors, so of course they were not all 1000 ohms or higher. All it takes is one to be 5% low and it brings the whole array down below 50 ohms. This one here measured 49.6 ohms. 


Close enough for its purpose.  Yes, this does present a small degree of capacitance and inductance – the discs do that, but it’s not enough to cause a problem.  

Hooked up to the MiniVNA and it was rather decent!  Not for 6 meters or higher, this was definitely a 1.8 to 30 MHz dummy load for under $10 in parts and about 2 hours of labour.  













The SWR didn’t change when put in the can with 1 litre of pure mineral oil from the drug store.  You could have used it as a dry load, but the oil makes it usable for minutes, rather than seconds and the paint can does reduce the RF radiated by roughly 60db.




As we can see from the sweep below, from 1.8 to 30 Mhz. the Impedance [green line] is pretty darn close to the 50 ohm reference line all across the entire HF band. The SWR 1.02:1 at 160 metres and about 1.26:1 at 30 MHz.  OK, not a perfect dummy load, but it costs less than $20, you can make it all at home and it does the job of giving your transceiver a non-radiating load for testing. The fancier commercial ones have LCR circuits incorporated in the array to compensate for the inductance and capacitance of the device – in other words, they doctor the load to get that perfect 1:1 across the band.

You can see  above, from 50 to 55MHZ, the SWR is about 1.3:1 across the six meter band, 
so it could be used if you needed to.  But by the time you get to the 2 meter band, it’s above 1.6:1 and not a good load. Thus commercial products tend to get more expensive at higher frequencies because you have to make them differently with higher tolerances, higher or more precise engineering and a few more parts to null out any inductive or capacitive reactance.

Next, the sweep below, from 1 MHz. to 180 MHz. is actually a good representation of most HF Cantennas, MFJ and other ‘non-VHF’ dummy loads.  The green line represents the impedance of the load.  From 1 to 21 Mhz. it’s pretty good at staying near 50 ohms and with an SWR of less than 1.1:1. But as you can see by the time it climbs out of the 30 Mhz section, the impedance drops and the SWR climbs, so by the time it reached 180Mhz., the limit of my MiniVNA,  it’s almost 2:1 with an impedance closer to 30 than 50 ohms.

This is mainly due to the construction of the dummy load, the 5% resistors soldered between two copper discs act somewhat like a capacitor, with the inductive reactance of lead lengths and 1¼ inches of #12 wire from the centre pin of the SO-239 and the lower disc, going through the centre of the discs, which must have some inductive quality. So not a perfectly symmetrical or resonant device, but as you have seen perfectly “HAM” in nature and quite adequate for the few times you need to test at full power without annoying others on the air.

The April 2018 Communicator Newsletter

Here is the latest Communicator 

In this edition you will find over 40 pages of Amateur Radio News from the South West corner of Canada and elsewhere.

We'll share several projects, tips and how-to's. You can download it directly from https://goo.gl/N15c1b .

If you print The Communicator, set your printer to ‘fit to page’

As usual, there are many hot links in the articles to websites as supporting material.

The last Communicator made it to 4 continents. As always, thank you to our contributors, and your feedback is always welcome. My deadline for the May edition is April 20th. If you have news, photos or projects from your Vancouver area club, events or other items of interest please email them to the communicator@ve7sar.net

GNUradio: Build Your Own Receiver

A bit of time and reading and you can enter this fascinating facet of the hobby (no license needed)

GNU Radio is a free & open-source software development toolkit that provides signal processing blocks to implement software radios. It can be used with readily-available low-cost external RF hardware to create software-defined radios, or without hardware in a simulation-like environment. It is widely used in hobbyist, academic and commercial environments to support both wireless communications research and real-world radio systems.

If you've never touched GNU Radio before, these pages will get you started with a running installation of GNU Radio and will show you how to take your first steps with this software radio tool.

The recommended way to get started with GNU Radio is to read the Guided Tutorials.

SARC members received a very interesting hands-on introduction in the fall of 2017. It was presented by Kevin VE7ZD. Here is a PDF of the slides.

A simple FM receiver in GNU

A Simple Field Strength Meter

A Communicator Reprise...

Summer 2011

A field strength meter is an instrument that measures the electric field strength emanating from a transmitter. A field strength meter is actually a simple receiver. After a tuner circuit, the signal is detected and fed to a micro-ammeter or, in this circuit, a digital voltmeter (DVM).

Anyone use a field strength (FS) meter anymore?  It’s kind-of like a radiometer for RF energy.  Remember the radiometer?  It’s those little black and white squares that spin inside a glass ball when light shines at it; the brighter [or hotter] the light, the faster it spins. Cool “instrument” from the 1870’s.

Well a field strength meter is sort of like that, in that in its heyday, it was used by Hams and CB’ers to measure the transmitted signal strength of any antenna - from a distance usually  1, 3, or 30 metres or whatever measured distance you had.  As long as the meter was “calibrated”, one could set up the antenna, mount a FS meter X number of feet or metres away, pump 1, 5, 10 or 100 watts out of it and measure the “strength” of the RF field at that measured distance.  It was simple, you could tune for maximum meter deflection, usually meant your SWR was at its lowest. An OK tool if you didn’t have a sophisticated watt meter or new-fangled SWR bridge.

Today, it can be used by the Ham antenna experimenter to measure the gain of the antenna – in RF volts or Db or whatever scale you had labeled on your meter, even S-units.  A sensitive FS meter can pick up low power bugs, or any source of RF energy – guess what those ghost hunters use?   More useful if you spent big dollars and put a tuned circuit, attenuators or a pre-amp in the circuit, and of course lots of LEDs.

But of course, good RF meters are expensive and somewhat hard to find, not many at the swap meets these days… and they are usually combined with other types of measuring devices, watt or SWR meters, thus more money than the typical cheap Ham wants to dish out.

Solution, make your own!!  OMG! What a concept!  A simple FS meter is the simplest thing to make and is good enough to see if the antenna under test is radiating more power than your old ground plane, old mobile vertical or just radiating at all in a particular direction or in all directions.

Here is what you need:

1. A digital voltmeter with a DC millivolt scale – every Ham should have a few in their shack.
2. A Germanium diode, just about any one, as long as it’s Germanium, like 1N34, 1N270, 1N914 or 1N100. The best one, a non-North American standard. The super-sensitive OA91 from down under or Europe/UK  – Great for your crystal radio project too.
3. A 3.3MΩ 1% resistor, 1/8 or ¼ watt.
4. A 100 picofarad capacitor
5. And a hand-made inductor [L₁] of 7 turns on a ¼ inch coil form with a ferrite slug (some experimentation required to cover the North American FM Band) 24 to 28 AWG lacquered wire.
6. Some miscellaneous parts like an antenna or antenna connection, a tiny box to put it all in, and some jacks that your DVM leads will insert into.

Using a digital meter, as opposed to an analogue meter has a few advantages in this circuit.

First, the impedance of a DVM is very high, around 10MΩ per volt on most meters.  This will not shunt or load down the tank circuit.  Second, compared to an analogue meter, very slight differences in signal strength can me more easily observed.  An third, a digital meter will have better linearity responding well to both weak and stronger signals.

All you want to see is the numbers, the higher the number, the more signal strength.  Just remember a few basic rules.  Keep the distance and power out the same for all your experiments, and turn off all your APRS trackers and digipeaters as they will want to add their 2-cents worth to your measurements.

If you have it in a hand-held configuration, you can “see” lobes, minimum and maximum RF fields as you walk around your test antenna. Oh, and then put a set of crystal ear plugs in place of your DVM and you might just hear the nearest AM broadcast station… well, until they all go digital.

Enjoy!

The original article appeared in the Communicator - Summer 2011 edition

Field Day 2015 Video

Our Field Day 2015 video was missing from our YouTube channel. Here it is:

https://youtu.be/EURKvTUv31A