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2021-09-19

All about tones

 Back To Basics

Tones… we all know what they are in non-radio terms, but they pose questioning glances from many Basic course students. When we explain tones during the course. Referring to our hobby, tones may be:

  • PL, CTCSS or sub-audible tones;
  • A report of CW signal quality; or
  • A tone used by repeaters to mark the end of a transmission.

PL, CTCSS and sub-audible tones

Let’s look at a typical question:

B-2-1-5 What is a CTCSS tone?

A. A special signal used for radio control of model craft

B. A sub-audible tone that activates a receiver audio output when present

C. A tone used by repeaters to mark the end of a transmission

D. A special signal used for telemetry between amateur space stations and Earth stations

In telecommunications, Continuous Tone-Coded Squelch System or CTCSS is one type of in-band signaling that is used to reduce the annoyance of listening to other users on a shared two-way radio communications channel.  It is sometimes referred to as tone squelch. It does this by adding a low frequency audio tone to the voice. Where more than one group of users is on the same radio frequency. CTCSS circuitry mutes those users who are using a different CTCSS tone or no CTCSS.

All users with different CTCSS tones on the same channel are still transmitting on the identical radio frequency, and their transmissions interfere with each other; however; the interference is masked under most (but not all) conditions. The CTCSS feature also does not offer any security.

A receiver with just a carrier or noise squelch does not suppress any sufficiently strong signal; in CTCSS mode it unmutes only when the signal also carries the correct sub-audible audio tone. The tones are not actually below the range of human hearing, but are poorly reproduced by most communications-grade speakers and in any event are usually filtered out before being sent to the speaker or headphone.

A receiver equipped with a CTCSS decoder will not reproduce a signal unless it carries a given sub-audible tone in the background, for example a continuous 100 Hz tone.  To work with such receivers, a transmitter must be equipped with a CTCSS encoder  Standard tones are in the range of 67 to 254 Hz, below the normal speech frequencies of 300 to 3000 Hz. 

One example of the purpose for repeater tones is here in the Greater Vancouver area of SW Canada. We operate VE7RSC in Surrey on a repeater frequency of 147.36 MHz. About 65 miles south, on Camano Island in Washington State, W7PIG operates on the same repeater frequency pair. Without tones, under ideal propagation, we hear their repeater and they hear ours, in most instances it is poor copy and distorted, so it is classed as interference. By using a different tone on each repeater, only stations on our frequency with our sub-audible tone programmed open up our repeater. The repeater will not respond if no tone, or the incorrect tone is detected. The same situation occurs on Camano Island and that repeater uses a different tone as its ‘key’.

Bear in mind that if both repeaters are in use there is still activity on one frequency by both users. Therefore the disadvantage of using CTCSS in shared frequencies is that users cannot hear transmissions from other groups. They may erroneously assume that the frequency is idle and then transmit at the same time as another user, thus interfering with the other group's transmissions. In our example, the distance is sufficient that there is little objectionable co-use and it is much more tolerable than not using tones.

Tones are not only used on repeaters. Many newer transceivers allow the user to program in a sub-audible tone when you wish to only hear simplex transmissions from other users in your group. Such use may be during an event or an outdoors recreational activity.

CTCSS is an analog system. A later Digital-Coded Squelch (DCS) system was developed by Motorola under the trademarked name Digital Private Line (PL).

Many radios also have a feature typically labelled ‘Tone Squelch’. That is similar to a repeater CTCSS tone but you can program it into your transceiver receive. When enabled, and the transmitting radio sends that sub-audible tone with the audio, your receive is unmuted only when that tone is received with an incoming signal. This feature may be handy if you are with a group of Amateurs and only wish to hear the conversation when one of the group is transmitting.


Therefore, the correct answer to the question in B-2-1-5 What is a CTCSS tone? is

B. A sub-audible tone that activates a receiver audio output when present

Next…

DTMF Tones

Dual-tone multi-frequency signaling (DTMF) is a telecommunication signaling system using the voice-frequency band over telephone lines between telephone equipment and other communications devices and switching centers. DTMF was first developed in the Bell System in the United States, and became known under the trademark Touch-Tone for use in push-button telephones supplied to telephone customers, starting in 1963. DTMF is standardized as ITU-T Recommendation Q.23.

In Amateur Radio, DTMF is enabled with a keypad on the transceiver or microphone. DTMF uses a mixture of two pure tone (pure sine wave) sounds, a set of eight audio frequencies transmitted in pairs to represent 16 signals, represented by the ten digits, the letters A to D, and the symbols # and *. As the signals are audible tones in the voice frequency range, they can be transmitted and heard through repeaters and amplifiers, and over radio and microwave links.


DTMF is commonly used to turn on a link via radio, such as may be needed to contact a station on IRLP or EchoLink. It was also heavily used before cellular phones became common, as hams could dial telephone calls via their radio using a ‘phone patch’ on a repeater. Some repeaters and clubs still offer this service.

Tones and signal reports

B-2-6-2 What does "RST" mean in a signal report?

A. Readability, signal speed, tempo

B. Readability, signal strength, tone

C. Recovery, signal strength, tempo

D. Recovery, signal speed, tone

"RST", A short way to describe signal reception (Readability: 1 to 5, Signal Strength: 1 to 9, Tone Quality (for Morse): 1 to 9).  For example, "11" unreadable, barely perceptible. "33" difficult to read, weak signal. "45" readable, fairly good. "57" perfectly readable, moderately strong.

The ‘T’ in RST is only used for CW (Morse code) reports and is a, indication by the receiver of the quality of the received tone.

Therefore, the correct answer to the question in B-2-6-2 What does "RST" mean in a signal report? is:

B. Readability, signal strength, tone

And finally…

Repeater courtesy tone

There are no questions in the Canadian Basic Amateur Radio exam question bank about courtesy tones nut the term is listed as an incorrect answer. Regardless, you should be aware of its meaning.

Most repeaters have a courtesy tone just before the transmitter stops transmitting. This is typically a ‘bee-boop’ sound.

The ones that do not will have a squelch tail that will transmit for a second or so after the input carrier or tone drops.

After the courtesy tone or carrier drops, if there is no courtesy tone, you should wait a second or two before keying up the mic. This provides space for others to break in if needed.

The courtesy tone is merely an audible indication that the repeater has finished transmitting and another station may start.

Kerchunking

While we’re on the subject, let’s also mention ‘kerchunking.

This is  one of the most annoying things for a repeater operator and people that listen to the repeater a lot.

Just in case you do not what Kerchunking is… Kerchunking is when you press the PTT and then let off without any speaking.

Some people will kerchunk the repeater but never talk. If you kerchunk the repeater to get it to wake up and ID before starting a new net or QSO that is fine because you follow up the kerchunk with your callsign and start a net or QSO.

Some people think that kerchunking the repeater is a way to test your radio but it really is not a valid test, as you have passed no audio.

In Canada, the rules state that you must ID at the beginning and end of a conversation and at least every 30 minutes (10 minutes in the United States) if your conversation lasts that long. Just a Kerchunk (or many) does not meet the regulations

Bottom line, do not kerchunk the repeater and not ID.

The ‘Alligator’

“The alligator bit you” is a term you may hear when on the air.

This is a slang term for the timer function of a repeater controller that limits the length of time the transmitter will remain keyed without a pause.   Typically the timer is set between 3 and 5 minutes. 

It is a protection device to prevent the repeater from overheating when transmitting. Aside from so-called “Long-winded operators”, I have seen instances where repeater users have accidentally sat on their mics and transmitted for some time without realizing it (when you are transmitting you do not hear other users or the repeater because your receiver is muted). If the time-out timer did not exists the repeater power amplifier would overheat causing an expensive repair.

Such times are not unique to repeaters. There is a very good chance that the transceiver you own also has protective circuitry to limit transmitting time.

~ John VE7TI

'Back To Basics' is a regular column in our newsletter, available at https://ve7sar.blogspot.ca


 

2021-09-16

The Annual SARC Fox Hunt

 Despite COVID, another successful event

Saturday, August was the date for this year’s annual SARC ‘Fox’ Hunt. As usual the venue was in South Surrey’s Crescent Park, a large venue with both forested trails and fields suitable for a picnic. The weather cooperated wonderfully providing mild temperatures and blue skies after a couple of days of much needed rain.

The briefing started at 9am, once five 80m foxes had been hidden throughout the park. A beacon had been activated allowing the competitors, many of them first timers, to practice their ARDF skills.



At 10am the foxes automatically activated as programmed and the hunt was on.

This year there were approximately 25 hunters with a welcome complement of ‘Junior’ hunters joining the Novice and Advanced groups, and yes, the receivers are easy enough to use even for a 5-year old.

The first finisher returned after an amazing 22 minutes, impressive given the amount of territory that had to be covered.



What followed was a barbecue expertly prepared by Brenda James with assistance of Heather Brodie and Anitha and Anil Cherian… Thank you.

We also thank fox placers Jeremy VE7TMY, Jan VA7VJ and Thomas VE7TXL. Special thanks to Chief planner Anton VE7SSD, who once again provided a smooth running and fun family event.

~ John VE7TI

A video of a SARC Fox Hunt: https://youtu.be/DMEKWOyaAnc

 

2021-09-13

RAC Canadian Award to SARC member

 

Thank You Fred !

The Canadian Amateur Radio Hall of Fame (CARHOF) is administered by an independent Board of Trustees, one per province, appointed by the Directors of Radio Amateurs of Canada.

Fred Orsetti, VE7IO, has served on the Hall of Fame Board of Trustees for 12 years as the representative from British Columbia and has recently decided to step down from this position.

The Board sincerely thanks Fred for his dedicated service and contribution to the Hall of Fame and Amateur Radio in Canada.


Fred was recently presented with a RAC Certificate of Appreciation signed by President Glenn McDonnell, VE3XRA.

Due to the rigid COVID public health restrictions in place the professionally printed Certificate had to be sent by mail to Fred but we look forward to being able to do in-person presentations once again.

The Board of Trustees wishes Fred continued success in his many endeavours.


~ RAC

 

2021-08-31

The September - October 2021 Communicator

 

108 Pages Of Projects, News, Views and Reviews

Ready for the start of a new Ham year. The September-October Communicator 'eZine' is now available for viewing or download at https://bit.ly/SARC21SepOct

Read in over 130 countries now, we bring you 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 view or download it as a .PDF file from:  


https://bit.ly/SARC21SepOct


Previous Communicator issues are at https://ve7sar.blogspot.com/search/label/The%20Communicator

As always, thank you to our contributors, and your feedback is always welcome. 

The deadline for the next edition is October 21st.

If you have news or events from your club or photos, stories, projects or other items of interest from BC or elsewhere, please email them to communicator@ve7sar.net

Keep visiting our site for regular updates and news: https://ve7sar.blogspot.ca    

73,

John VE7TI

'The Communicator' Editor



2021-07-01

The July - August 2021 Communicator

 

110 Pages Of Projects, News, Views and Reviews... 

We're back! The July - August Communicator 'eZine' is now available for viewing or download at bit.ly/SARC21Jul-Aug 

Read in over 130 countries now, we bring you 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 view or download it as a .PDF file from:  



bit.ly/SARC21Jul-Aug

Previous Communicator issues are at https://ve7sar.blogspot.com/search/label/The%20Communicator

As always, thank you to our contributors, and your feedback is always welcome. 

The deadline for the next edition is August 21st.

If you have news or events from your club or photos, stories, projects or other items of interest from BC or elsewhere, please email them to communicator@ve7sar.net

Keep visiting our site for regular updates and news: https://ve7sar.blogspot.ca    

73,

John VE7TI

'The Communicator' Editor


2021-05-13

A Vector Network Analyzer


Once only a lab instrument, today the prices are affordable for most hams.

The great thing about amateur construction projects is that it provides opportunities to learn about new things.  I was curious about a device called a VNA (Vector Network Analyzer) after Les Tocko VA7OM showed me his home-built VNA which he was using to tune up the triplexer, diplexer and bandpass filters currently under construction.   Here is what I learned from a Tektronix website.

Vector Network Analyzers are used to test component specifications and verify design simulations to make sure systems and their components work properly together.

From mobile phone networks, to Wi-Fi networks, to computer networks and the to the cloud, all of the most common technological networks of today were made possible using the Vector Network Analyzer that was first invented over 60 years ago.

R&D engineers and manufacturing test engineers commonly use VNAs at various stages of product development. Component designers need to verify the performance of their components such as amplifiers, filters, antennas, cables, mixers, etc.

Above: The NanoVNA, a very affordable instrument
Below: It can be connected via USB to your smart device or computer for
a larger screen and many additional functions



How does a VNA work?

A Vector Network Analyzer contains both a source, used to generate a known stimulus signal, and a set of receivers, used to determine changes to this stimulus caused by the device-under-test or DUT.

The stimulus signal is injected into the DUT and the Vector Network Analyzer measures both the signal that's reflected from the input side, as well as the signal that passes through to the output side of the DUT. The Vector Network Analyzer receivers measure the resulting signals and compare them to the known stimulus signal. The measured results are then processed by either an internal or external PC and sent to a display.


VNAs perform two types of measurements – transmission and reflection. Transmission measurements pass the Vector Network Analyzer stimulus signal through the device under test, which is then measured by the Vector Network Analyzer receivers on the other side.

Examples of transmission measurements include gain, insertion loss/ phase, electrical length/delay and group delay. Reflection measurements measure the part of the VNA stimulus signal that is incident upon the DUT, but does not pass through it. Instead, the reflection measurement measures the signal that travels back towards the source due to reflections.

It sounds like every serious amateur experimenter should own one of these devices.  While most of the available devices are expensive lab quality instruments usable at microwave frequencies, many are affordable and suitable for amateur use at HF. 

Next month, we will feature an article describing Les VA7OM’s VNA and reflection bridge, and how he used them to tune up the triplexer, diplexer and bandpass filters. 

~ John VA7XB

   19-04


NOTE: We are currently offering a series on the practical use of the Nano VNA for Amateurs. See the 2021 Communicator issues on this blog.



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