Wednesday, June 20, 2018

Morse Lives in Hollywood


Near Hollywood and Vine

Located in the center of Hollywood, near the intersection of Hollywood and Vine, stands a very recognizable landmark, a circular office building, the home of Capitol Records, 
It was built in 1956 and has the distinction of being the world’s first circular office building. The shape was chosen as it was more earthquake resistant and more efficient for heating and cooling.

Known as the ‘Sound Capitol of the World’, the building includes a sound-proofed chamber located 20 feet below ground designed by famed guitarist Les Paul. The first recordings made in the building were a series of instrumentals by Frank Sinatra titled “Frank Sinatra Conducts Tone Poems of Color”. Since then artists such as The Beatles, Beach Boys, Tina Turner, Steve Miller, Bonnie Raitt and others have recorded there.

Of interest to hams is the spire atop the building. It has a red light at the peak to comply with federal airline safety regulations. It blinks the word ‘Hollywood’ in Morse Code. In fact, the light’s initial activation on April 6,1956 was ceremoniously conducted by Leila Morse, granddaughter of Samuel Morse.

Only once in the building’s 50 year history was the message changed.  This occurred in 1992 when Capitol records celebrated 50 years in business. For the occasion the red light blinked ‘Capitol 50’ in Morse.

And while you're in that neighbourhood...


Disneyland - New Orleans Square: The telegraph office attached to the New Orleans Square Railroad Station replays a part of Walt Disney's Disneyland Opening Day Dedication in Morse code.

"TO ALL WHO COME TO DISNEYLAND, WELCOME. HERE AGE RELIVES FOND MEMORIES OF THE PAST, AND HERE YOUTH MAY SAVOR THE CHALLENGE AND PROMISE OF THE FUTURE."

Amateur radio operator George Eldridge helped restore the message in 1997. After taping the message, Eldridge discovered that it had been cut short. The telegram was improperly edited when Imagineers transferred the message from a continuously looping tape, to a digital recording. Thanks to Eldridge, the recording now plays the correct message.



Saturday, June 16, 2018

Multi-meters


A Communicator Reprise: February 2012


I’m sometimes surprised when a fellow ham asks a troubleshooting question and they have no knowledge of simple voltage, current or resistance measurement. When instructing the Basic course I used to spend a fair bit of time on series and parallel circuits and the means to make basic measurements, and there are several questions in the question bank that test these skills. I use my multi-meter several times a week, to check for a short, open circuit or even whether a dry cell battery requires replacement. This month we’ll look at the meters themselves… next month the basics of how to use them.
Multi-meters or multi-testers, also known as a VOM (Volt Ohm Meter) is an electronic measuring instrument that combines several measurement functions in one unit. They are inexpensive and very handy tools for measuring what is going on in a circuit and will offer Voltage, Current and Resistance ranges adequate for home use. Most new multi-meters are digital. Until recently, digital multi-meters were expensive, and some lab quality instruments still are, as much as $5,000. For as little as $10 you can purchase one on-line or on sale at Canadian Tire. The average home user can get by with a basic model. 

History

The first moving-pointer current-detecting device was the galvanometer in 1820. These were used to measure resistance and voltage by using a resistor bridge, and comparing the unknown quantity to a reference voltage or resistance. While useful in the lab, the devices were very slow and impractical in the field. These galvanometers were bulky and delicate. By adding a series or shunt resistor, more than one range of voltage or current could be measured with one movement.

Multi-meters were invented in the early 1920s as radio receivers and other vacuum tube electronic devices became more common. The invention of the first multi-meter is attributed to British Post Office engineer, Donald Macadie, who became dissatisfied with having to carry many separate instruments required for the maintenance of the telecommunications circuits. Macadie invented an instrument which could measure amperes, volts and ohms, so the multi-functional meter was then  named Avometer. The meter comprised a moving coil meter, voltage and precision resistors, and switches and sockets to select the range.
Any meter will load the circuit under test to some extent. For example, a microammeter with full-scale current of 50 microamps, the highest sensitivity commonly available, must draw at least 50 microamps from the circuit under test to deflect fully. This may load a high-impedance circuit so much as to affect the circuit, and thereby give a false low reading.

To eliminate loading, Vacuum Tube Voltmeters (VTVM) were used for voltage measurements in electronic circuits. The VTVM had a fixed input impedance of typically 1 megohm or more, usually through use of a vacuum tube input circuit, and thus did not significantly load the circuit being tested. Modern digital meters and some modern analog meters use electronic input circuitry to achieve high-input impedance—their voltage ranges are functionally equivalent to VTVMs. Before the introduction of digital electronic high-impedance analog transistor and field effect transistor (FETs), vacuum tubes were commonly used. 

How Does It Work?

An un-amplified analog multi-meter combines a meter movement, range resistors and switches. For an analog meter movement, DC voltage is measured with an internal series resistor connected between the meter movement and the circuit under test. If no resistors were used, the excessive voltage or current would quickly burn out the small wires that make up the meter coil. A set of switches allows greater resistance to be inserted for higher voltage ranges. As an example, a meter movement that required 1 milliamp for full scale deflection, with an internal resistance of 500 ohms, would, on a 10-volt range of the multi-meter, require 9,500 ohms of series resistance. Why? Remember Ohms Law, R = E / I or 10 volts divided by .001 amp which equals 10,000 ohms. The meter has an internal resistance of 500 ohms so we must add series resistance of 9,500 ohms to obtain a full scale reading. Now any voltage between 0 and 10 volts will produce some proportional deflection of the meter and this value can be read from the scale.  

For analog current ranges, low-resistance shunts are connected in parallel with the meter movement to divert most of the current around the coil. Again for the case of a hypothetical 1 mA, 500 ohm movement on a 1 Ampere range, the shunt resistance would be just over 0.5 ohms.

Moving coil instruments respond only to the average value of the current through them. To measure alternating current, a rectifier diode is inserted in the circuit so that the average value of current is non-zero. 

To measure resistance, a small dry cell within the instrument passes a current through the device under test and the meter coil. Since the current available depends on the state of charge of the dry cell, an analog multi-meter usually has an adjustment for the ohms scale to zero it, to compensate for the varying voltage of the meter battery. In the usual circuit found in analog multi-meters, the meter deflection is inversely proportional to the resistance; so full-scale is 0 ohms, and high resistance corresponds to smaller deflections. The ohms scale is compressed, so resolution is better at lower resistance values. Inexpensive analog meters may have only a single resistance scale, seriously restricting the range of precise measurements. 


Resolution of analog multi-meters is limited by the width of the scale pointer, parallax, vibration of the pointer, the accuracy of printing of scales, zero calibration, number of ranges, and errors due to non-horizontal use of the mechanical display. Accuracy of readings obtained is also often compromised by miscounting division markings, errors in mental arithmetic, parallax observation errors, and less than perfect eyesight. Mirrored scales and larger meter movements are used to improve resolution; two and a half to three digits equivalent resolution is usual and adequate for the limited precision needed for most measurements.

Analog meter movements are inherently much more fragile physically and electrically than digital meters. Many analog meters have been instantly broken by connecting to the wrong point in a circuit, or while on the wrong range, or by dropping onto the floor.
On the favourable side, Analog meters are able to display a changing reading in real time, whereas digital meters present such data in a manner that's either hard to follow or more often incomprehensible. Also a digital display can follow changes far more slowly than an analog movement, so often fails to show what's going on clearly. 
Analog meters are also useful in situations where its necessary to pay attention to something other than the meter, and the swing of the pointer can be seen without looking at it. This can happen when accessing awkward locations, or when working on cramped live circuitry.

Analog displays are also used to very roughly read currents well above the maximum rated current of the meter. For this, the probes are just touched to the circuit momentarily, and how fast the pointer speeds towards full-scale deflection is noted. This is often done when testing state of charge of dry batteries.
The ARRL handbook also says that analog multimeters, with no electronic circuitry, are less susceptible to radio frequency interference, important if working on radio gear.

Digital Meters

The first digital multi-meter was manufactured in 1955 by Non Linear Systems. Modern multi-meters are often digital due to their accuracy, durability and extra features. In a digital multi-meter the signal under test is converted to a voltage and an amplifier with electronically controlled gain preconditions the signal. A digital multi-meter displays the quantity measured as a number, which eliminates mechanical errors. Measurement enhancements available include:
Auto-ranging, which selects the correct range for the quantity under test so that the most significant digits are shown. For example, a four-digit multi-meter would automatically select an appropriate range to display 1.234 instead of 0.012, or overloading. Auto-ranging meters may include a facility to 'freeze' the meter to a particular range, because a measurement that causes frequent range changes is distracting to the user. Other factors being equal, an auto-ranging meter will have more circuitry than an equivalent, non-auto-ranging meter, and so will be more costly, but will be more convenient to use. An other reason to 'freeze' the range is that this somewhat avoids 'hunting' which is a situation where the meter continuously switches between two neighbouring ranges as when the instrument is in the low range, the value is too large but too small in the larger range.
Auto-polarity for direct-current readings, shows if the applied voltage is positive (agrees with meter lead labels) or negative (opposite polarity to meter leads).
Sample and hold, which will latch the most recent reading for examination after the instrument is removed from the circuit under test.

Current-limited tests for voltage drop across semiconductor junctions. While not a replacement for a transistor tester, this facilitates testing diodes and a variety of transistor types.

As you can see, not all meters are created equally and the choice depends upon your needs. For general home use however, a $10 digital multi-meter will accomplish most tasks with the least possibility of damage to the circuit or the meter.





Thursday, June 14, 2018

Community Involvement


Can we do more to preserve our hobby?



Amateur Radio has spectrum, a lot of it. We have frequencies from the low bands into the gigaHertz. The demands for commercial use are very great... and persistent. Frequency auctions often generate millions of dollars for government. 

I can't help but wonder if the current low use of some of our bands, particularly on VHF and 70cm will yield to pressure from commercial interests and be reduced to a smaller range of frequencies. There have been a number of articles written that wonder about the future of the hobby and our ability to draw in young Amateurs.

I believe that every Amateur has a responsibility to 'give back' to the community for the privilege of access to our spectrumI'm also a strong believer in exposing our hobby to the public - particularly the work Amateurs do in emergency response. Public demonstrations, science fairs, library and school visits have been well attended and receive favourable response locally.   'Spreading the word" will serve us well to gain public support when commercial interests come knocking.

~ John VE7TI 

Monday, June 11, 2018

Surrey Doors Open Observations


A peek behind our Operations and Training Centre Doors

This is a follow-up to post https://ve7sar.blogspot.com/2018/05/surrey-doors-open.html

This year 30 venues participated. Despite the prediction of rain, the skies cleared and we had a beautiful day. Opening was scheduled for 11am but our first visitor arrived at 10:20. The majority of our visitors arrived between 11am and 1pm and they not only seemed very interested in our demonstrations but complimented the volunteers and the role they play in the emergency program. From feedback, the hidden transmitter hunt was the most challenging, although the simulated contact and report emergency simulation was popular with kids who had not had any exposure to radio use. The most notable HF contact was with a commercial jetliner at 30,000 feet over Nebraska piloted by a ham. The adults were uniformly impressed by the technology Amateur Radio offers. I have no doubt that most, if not all, left with an appreciation of what Amateur Radio, and the OTC contribute to the City. Our exposure and feedback on social media was also uniformly positive. They included former Mayor Dianne Watts, a strong supporter of Amateur Radio.





We had one confirmed signup for the next Basic course, and a further three expressions of interest. The total for the day was 47 visitors.
My thanks to the following volunteers from SARC and SEPAR (most of whom wore two hats):

John VA7XB
Art VE7WAE
Robert VE7CZV
Don VA7GL
Pam VE7PFH
Michael VE7GMP
Robert VA7FMR
Jinty VA7JMR
Dixie VA7DIX
Lata VA7LVB
Kjeld VE7GP
David VA7DRS
Ron VE7VTA
Jeremy VE7TMY
Jason VA7IJT

Thank you all again!

John VE7TI
SDO Coordinator

Friday, June 1, 2018

The June 2018 Communicator Newsletter


Here is the latest Communicator 


In this edition you will find almost 50 pages of Amateur Radio News from the South West corner of Canada and elsewhere. You will find Amateur Radio related articles, profiles, news, tips and how-to's. You can download it as a .PDF file directly from https://goo.gl/KRxhn8



As always, thank you to our contributors, and your feedback is always welcome. This is the last Communicator until September, as we take our usual Summer break.  My deadline for the September edition is August 20th. If you have news or events from your Vancouver area club or photos, stories, projects or other items of interest from elsewhere, please email them to the communicator@ve7sar.net

Have a great Summer and keep visiting this site for regular updates and news.

73,
John VE7TI
Communicator Editor


Wednesday, May 30, 2018

A LED Replacement Light For Your Soldering Iron



A Communicator Reprise: January 2012





One of handiest tools for the Ham Shack workbench is a Weller soldering gun.   It’s a 100 and 140 watt gun in a good old Bakelite case. This year it’s celebrating its 40th year on the work bench.  The thing  has been dropped so many times, it’s a miracle the gun still works, but thanks to several tubes of 5-minute epoxy and some crazy glue, it’s still in fine working condition.


But recently the little incandescent pilot lamp/tip illuminator burnt out and I just couldn’t find the right replacement bulb… a 2.0 volt bulb with a focusing lens at the end, something you used to be able to find in a common flashlight… a common flashlight 40 years ago. So while hunting in my parts bin, I came across a white light LED and decided to update the old gun with a modern light source.

So I removed the bulb from it’s screw base, found the right current-limiting resistor for 20ma at 2 volts and proceeded to assemble my new LED spot light.
There are a few things to ponder… the gun supplies 2v AC, your LED is a diode, so it’s going to work on one half the cycle, which translates into less light output…
Also the junction breakdown voltage is rather low on a LED, so if one were to use  higher AC voltages, it would most likely “expire” rather quickly.  But it’s only 2 volts, so I wasn’t worried.  You could put a 1N4007 in series on the other lead to help the LED deal with reverse voltages, but only if you were working with higher than 6-9 VAC.

So to hold things in place, I potted the resistor in epoxy putty, which set in 3 minutes and then soldered the LED to it.  I only had a ½ watt resistor, larger than I needed but it fit nicely in the screw base.  So if I wanted a 20mA current draw, that would be R = E / I = 2/.02 = 100 ohms and I just happened to have a 100 ohm resistor in my parts cabinet.  P (in watts) = E x I = 2 x .02 = .04 watts or 40 mW of heat dissipation so a ½ watt resistor wasn’t necessary, but it was the only size I have in stock and size wasn’t an issue.


A few minutes later I had a modern light source in an antique tool… but would it work?  But of course… for ½ the cycles per second -- so the light from it wasn’t as bright as I was hoping, but good enough to shed a bit of illumination on what was being soldered and certainly adequate for a pilot light to verify the gun was on.   OK for younger eyes, but this old buzzard needs a few more candle power!  Why didn’t I put a tiny bridge rectifier on the power leads to feed the LED with better DC?  Cause it was only a 2 volt tap off the coil inside the gun.. and for every diode you insert, you lose 0.7 of a volt.   Why did I need this in the first place you ask?  Well the tips of my fingers and tongue hadn’t recovered from my earlier attempts to see if the soldering tip was getting hot!  





Sunday, May 27, 2018

Marine Mobile...



A Communicator Reprise: January 2012


Most countries' amateur radio licenses allow licensed operators to install and use radio transmission equipment while at sea. Such operation is known as maritime mobile amateur radio. In most cases the operator's call sign needs to be extended by adding the suffix '/MM' when transmitting at sea.

There are some special considerations when installing and using amateur radio transmitters and receivers afloat. These include power supply, RF ground, antenna design and EMC (Electromagnetic compatibility) with other electronic equipment aboard.

For MF and HF use, the most common antenna design is to add two RF insulators into the backstay of the mast and feed it from the transceiver using a sintered bronze ground plate, bolted to the outside of the hull, well under the waterline, as a ground. On metal hulled boats the ground plate can be dispensed with, and the whole hull used for this purpose. In this case, the thickness of any paint layer is entirely negligible at RF. On a yacht with twin backstays, if insulators are placed in both of them and they are fed from the masthead, they may be usable as an 'inverted vee' avoiding the need to feed the antenna against ground. Either format will require the use of an ATU (Antenna Tuning Unit) to achieve resonance for the HF frequency in use, as the physical length of the antenna will almost invariably be incorrect at the frequency of choice. A few twin-masted sailing vessels have the space to erect a "Tee" antenna or an inverted "L" between masts. These antenna configurations are more common on merchant ships.

For VHF and UHF operation, one option is to mount a small yagi antenna to a pole 1–2 m (3–6 ft) long and haul this to the masthead using a flag halyard. If the halyard is correctly knotted to the middle and bottom of the pole, it is easy enough to make the antenna project above the clutter at the masthead into clear air. The problem is in rotating it - it usually needs to be lowered and re-raised to alter the direction of its beam. For the safety of masthead fittings and lights it is better if these yagis are light in weight and made largely of, for example, plastic tubes supporting internal wire conductors. Operating in this way is best reserved for when in harbour or at anchor, to avoid interfering with the operation of the boat. Repeated loss of signal due to rolling and pitching would make it impractical for useful communication at sea anyway.

For FM operation on the 2m band, the masthead vertical whip that is normally installed for marine VHF operation will provide good omni-directional, vertically polarized signals. The frequency of operation around 145 MHz is close enough to the antenna's design frequency of 156 MHz that most amateur transceivers will not need an ATU and will not suffer unduly from a poor (high) SWR.


Grounding

For a single-ended HF antenna, a good electrical ground connection is essential. It is also necessary from the points of view of safety and EMC considerations on any radio transmitter installation on a boat or ship. As mentioned above, metal-hulled vessels have a natural advantage in that, especially at HF and lower frequencies, the hull can be considered to be in contact with the water, as the insulating properties of the paint layer against the water is a capacitance that presents very little electrical impedance to the RF currents. For fibreglass and wooden hulls and HF transmission, the usual solution is to attach a sintered bronze plate to the outside of the hull for RF ground. The construction of a sintered bronze plate is porous to water so that although the plate may be only a square foot or two and an inch thick, the actual surface area of metal in electrical contact with the water is very many times that.

Once a good connection to the sea water has been established, it is necessary to make a good RF connection from the transceiver and/or the ATU to the grounding system. While it might seem that a good, thick wire is all that is needed, for large RF currents it is usually recommended that copper grounding tape is used. This is not because thick wires will not be able to support the currents involved, but because it is more likely that RF currents will remain flowing along something that has a wide surface area without re-transmitting themselves along the way due to skin effect. The key pathway from the ATU of a single-ended antenna system to the ground plate, or the hull ground-point, should be as short and as straight as possible. This should be considered from the start when deciding where to mount the various components within the hull. There is not much that the installer can do about the losses in, and the efficiencies of, the transceiver, the ATU, the antenna or its feed, but extra effort put into the efficiency of the ground paths will pay much bigger dividends, in terms of radiated power and freedom from EMC problems later, than any other single aspect of the installation. The salty sea makes an exceptionally good ground plane, and effort put into achieving a good connection to it will be handsomely repaid.


Going on a cruise?

You will first need the permission of the cruise ship company itself to even have an Amateur Radio transmitter in your possession while on board (whether in use or not).  So your first step is to make sure you have written authorization to have your radio with you.
Next, besides the company itself you will need to have permission of the ship's captain in order to use the radio.  Do not assume you can simply throw up a vertical outside of your stateroom and operate!

Once you have authorization to operate ship board, you still have to worry about reciprocal operating privileges with the country where your ship is, including territorial waters.

Canadian and US licensees need no special permit or authorization other than their own Industry Canada or FCC license and they stay within Canadian, US or International waters.  When an FCC licensed amateur is operating an amateur rig aboard a US-registered vessel in international waters, he or she must follow Part 97 of the FCC rules, particularly Section 97.11. 

If the ship is of foreign registry, you must obtain a reciprocal operating authorization from the country of registry in addition to being in compliance with Section 97.11. When amateurs enter the territorial waters of a country, they fall under their communications jurisdiction. This means that they must obtain the required reciprocal operating authorization. There are three such authorizations: CEPT which applies to most European countries and certain overseas territories; IARP which applies to certain countries in the America's; Reciprocal Permit which is available from most countries, but application must be made to the country and a fee paid.

In Canada, these permits may be obtained from Radio Amateurs of Canada (RAC) for a modest fee.






CQ CQ CQ

Morse Lives in Hollywood

Near Hollywood and Vine Located in the center of Hollywood, near the intersection of Hollywood and Vine, stands a very recognizable landma...

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