PL and DCS Codes

[Marine_Cotporal]

Every major agency that is still on analog VHF or UHF will utilize PL or DCS codes on simplex and repeaters. Whether it be the Local police, EMS, Fire, School Board, Hospital, ect.

So my question is why isn’t it used on amateur radio more often. Almost every repeater I see will either have no tone in or out or just a tone in but no tone out. There are very few that will use both tones in or out. Why is that?

When I connect to a rare repeater that has a PL input of 100 and and a PL output of 127.3 for example, it comes in crystal. 100 percent. Why aren’t they used more often?

 

[rescuecomm]

Back in the early 1980's when I first got licensed, few amateur repeaters used PL (CTCSS) or DCS because the RF noise level was consistently low. Only a noise squelch was needed in most cases. In fact, my first 2 meter handheld (an Icom IC2-AT) had no built in encoder. With the coming of cellular phone systems and Nextel among other things, the receivers were deluged with noise that caused them to constantly key up and identify. Now in my operating area, only two repeaters run with out PL on the receivers. One of them might be running an oversize pass band filter cavity just to do so.

Bob

 

[nd5y]

So my question is why isn’t it used on amateur radio more often. Almost every repeater I see will either have no tone in or out or just a tone in but no tone out. There are very few that will use both tones in or out. Why is that?

Public safety and commercial users generally don't know much about radio and get distracted or upset when they hear something else on "their frequency"; interference, other local users on the same frequency or distant users during a band opening. This isn't the case as much in ham radio.

When I connect to a rare repeater that has a PL input of 100 and and a PL output of 127.3 for example, it comes in crystal. 100 percent. Why aren’t they used more often?

This makes absolutely no sense. If the signals are strong enough and the system on each end is designed, installed and maintained properly then everything should be crystal clear. CTCSS and DCS have absoultely nothing to do with how well you hear something.

It's impossible CTCSS or DCS to magically improve audio quality. It can actually do the opposite on radios like most Japanese amateur rigs that don't have high pass filtered receive audio to remove the tones when a good external speaker is used.

 

[W5GX]

CTCSS or DCS tones were, I've understood, created to give some privacy between two or more parties when other unrelated parties may use the same frequency.

That is kind of the antithesis to the "art" of amateur radio - to talk to others. It's handy for repeaters or when noise is unavoidable, but in general, I personally think it's a slight faux pas. But I wouldn't begrudge anybody for using it.

Just a preference.

 

[Marine_Cotporal]

I guess I should clarify that I am using a Baofeng. With those I get interference with non pl code repeater frequencies in certain areas but when listening to public safety frequencies with pl codes on both ends or when using simplex with PL codes on both ends, the interference and cracking is non existent.

 

[edweirdFL]

There are 2 reasons based on my experience with other amateurs in my area that tone out isn't used on a repeater.

1. They like to know when enhancement is causing distant signals not normally heard to be received. This prompts the VHF/UHF weak signal enthusiast to check for new contacts in the simplex portions of the bandplan.

2. There used to be a cost associated with tones, but now even though it is included on most modern repeaters, enabling it would cause headache and hand holding issues for folks who would suddenly report the repeater was off the air since either their old equipment doesn't support tone squelch and/or they don't know how to program that on their radios.

I'm not defending these reasons since there are web based tools for monitoring enhancement and one of the stated purposes of AR is to elevate the art of AR. Just telling it like it is.

 

[jim202]

In looking at the use of tone squelch on repeaters, you need to consider that there are only a limited number of frequencies available. This causes the re-use of the frequencies. The ham repeater coordinators are using a software program to have a distance between repeaters so they don't normally cause a problem with another repeater on the same frequency. In many cases, the repeaters may also use a tone squelch on the repeater output frequency so users can monitor only the repeater they are looking to use by having a selected tone squelch on their receiver.

I tend to use older commercial radio equipment for my ham use. Even the old radios had the ability to use tone squelch. As I tend to do a bunch of traveling around the country, my limitation is the channel limit in the radios I use. In some cases I need to have a software load for different parts of the regions I travel in. This lets me have the ability to program the needed tones and frequencies as I travel around.

There are very few of the new radios on the market today that do not have the ability to program the needed tone squelch on both transmit and receive.

Jim

 

[k6cpo]

CTCSS or DCS tones were, I've understood, created to give some privacy between two or more parties when other unrelated parties may use the same frequency.

That is kind of the antithesis to the "art" of amateur radio - to talk to others. It's handy for repeaters or when noise is unavoidable, but in general, I personally think it's a slight faux pas. But I wouldn't begrudge anybody for using it.

Just a preference.

Part of the reasoning behind CTCSS and DCS was to allow greater use of frequencies. It allowed a station in one area use the same frequency as a station in another area without each station hearing the other's traffic all the time. Each station was still required to break squelch before transmitting to make sure the frequency wasn't in use.

When I went to work for the police department at San Diego State University in 1972, there were 19 different campuses in the California State University System. Each of the 19 police departments used the same radio frequency, but each had a different PL (CTCSS) code. We didn't hear the traffic from the other campuses but still had to monitor the frequency before transmitting. In practice, we didn't do that often...

 

[mmckenna]

We didn't hear the traffic from the other campuses but still had to monitor the frequency before transmitting. In practice, we didn't do that often...

On modern commercial mobiles, the "Hang up Box Defeats PL" or "Off Hook" functions would switch the radio to carrier squelch when the mic was taken off the hanger.

As others have said, CTCSS, also referred to a PL (PrivateLine) by Motorola was intended to allow reuse of frequencies, or allow multiple users to share one frequency (community tone panel…)
Commercial users don't want to hear traffic that is not intended for them, so CTCSS/DCS is popular.

Amateur, on the other hand, usually want to hear everyone. CTCSS/DCS tones are not common on simplex. Most (not all) repeaters use a CTCSS on the input side to reduce co-channel interference from other repeaters. I've been on high mountain tops where it's easy to hear many amateur repeaters on the same frequency pair.

Amateurs could learn from the commercial side. Putting CTCSS/DCS tones on the OUTPUT of the repeater can have some benefit, also.


For my own personal use, I run a CTCSS tone on the simplex 2 meter frequency we utilize. That lets me leave a radio running 24x7 without having to hear all the traffic on the channel. Using the off hook function, it switches to carrier squelch when the mics comes off hook. I've got the mobiles set up the same way. Really handy as people set up IP nodes on simplex channels and let them run 24x7.

One of the reasons many of us use commercial radios on amateur frequencies is to make use of some of these features.

 

[Project25_MASTR]

Ha one of my pet peeves. You see a lot of toneless repeaters in many states. These are often older repeaters. The Texas VHF-FM society will no longer allow you to coordinate a CSQ repeater...has to have a tone on it. That being said, there is little to no imagination (well, some of it is due to the availability of reeds). For example, 70% of the coordinated VHF repeaters in Texas use one of 20 pairs and one of 5 tones.

Anyway, personally I really like seeing a tone on the output. However, I absolutely hate it when a repeater is transmitting tone and IDing. Just my personal preference...and yes, I use commercial radios with hang up features.

 

[Marine_Cotporal]

There seems to be some confusion. I’m not saying that CTCSS tones makes things clearer.

What I’m saying is that when locked on to a repeater that has an outgoing tone, my cheap Baofeng behaves normally just like any other radio and the squelch doesn’t open up to interference. When it is locked on to a repeater that doesn’t have outgoing tones, my cheap Baofeng opens up squelch to outside interference.

 

[n1das]

CTCSS:

A historical and technical overview of tone squelch (PL, CG, QC, CTCSS, etc.) systems.

DCS:

DPL / DCS Information

 

[mmckenna]

There seems to be some confusion. I’m not saying that CTCSS tones makes things clearer.

What I’m saying is that when locked on to a repeater that has an outgoing tone, my cheap Baofeng behaves normally just like any other radio and the squelch doesn’t open up to interference. When it is locked on to a repeater that doesn’t have outgoing tones, my cheap Baofeng opens up squelch to outside interference.

That's what a tone/digital squelch will do. It'll not pass audio until it hears that tone/digital squelch.
Your Baofeng opening squelch randomly when it's not using a tone sounds typical. They are not high tier radios and odd behavior seems to be more common than not. Not slamming your choice in radio, if it works for you, then great, but on the scale of two way radios, the CCR's are pretty darn close to the bottom of the barrel.

 

[kayn1n32008]

I refuse to load repeaters that DONOT transmit PL. Unfortunately when I travel in BC I am forced to use repeaters that do not transmit PL because many do not.

Can’t even go through a drive through with your volume up on a radio if you don’t have receive PL, due to the incredible noise most cheap electronics puke out these days.

 

[kayn1n32008]

If find many repeaters don’t transmit PL due to the ‘tradition’ of the repeater not transmitting PL. Stupid. Every repeater should transmit PL/DPL(preferred) due to the horrendous noise, and crappy front ends on modern(most) hammy radios.

 

[ElroyJetson]

The reason most amateur repeaters don't both encode and decode PL/DPL is simply because the operators of many of them are so concerned about their most senior hams not having upgraded their equipment in the last 50 years to "newfangled" technology, and don't want to exclude them from being able to use the repeater.

That seems to be exactly the case in my neck of the woods. And it's justified, because we have our share of advanced geriatric hams who literally haven't bought a new radio since the 70s and will have no part of such novel newfangle technologies as "transistors".

 

[ko6jw_2]

As the trustee of two repeaters that DO encode CTCSS, the convenience of older hams has nothing to do with it. If an operator chooses not to set up PL decode, it will not change their ability to hear the repeater. Interfering signals, noise and intermodulation are all present in any receiver and may desense the receiver PL or not. This is because the PL decode takes place in the audio section of the receiver. This is true from the cheapest radio to the most expensive. Better receivers are less susceptible to overloads, of course.

Another repeater that I'm involved with does not currently transmit PL. We've tried it both ways and we get less interference without it. This repeater is on a mountain top site with literally hundreds of transmitters. We use the usual duplexers and retuned another set of cavities as a band pass filter to prevent more interference to the receiver.

PL is transmitted continuously whereas DCS is a burst. This is a clear advantage. In the future we will convert all of our systems to DCS. The choice not to transmit PL is related to the use of continuous tones on the audio. This seemed to actually increase interference.

Our choices are based on sound engineering not stupidity. The convenience of an old lid is not my concern. The old operator who hasn't bought a new radio in 50 years is mostly a silent key now. I have two friends locally who are 80 and 90 respectively and they both have System Fusion radios. One of them operates on HF in digital modes. I'm an old guy too and I use all the latest modes.

One of our repeaters is System Fusion. It operates in the automatic mode with PL encoding on the analog side. No PL's in digital systems. Those that don't like hearing the digital "noise" need only set up PL decode and it will go away. However, the RF will still be present in the front end of their radio.

In our area we have an intermod based on a national weather service broadcast and a county fire department repeater. This interferes with another fire channel. Since both use the same transmitted PL, the intermod punches right through. PL is not foolproof. It is also very very old technology. I remember when commercial gear had reeds to encode and decode PL. It should be phased out in favor of DCS or digital modes.

 

[rescue161]

Years ago, our club repeaters (2) only used encode and transmitted CSQ. From time to time, ducting would allow hams in the area to hear distant repeaters on the same output as ours. There were a lot of complaints as one of the distant machines was using a rooster crowing as its courtesy tone. There were many complaints about how to get rid of the "c0ck-a-doodle-do," so I suggested that we add PL to the output of the repeater. It was like pulling teeth to get people to understand that just because the repeater is transmitting the tone does not mean that folks with older radios won't be able to use the repeater with their old radios. People still protested and got angry when we added the PL.

Same thing happens on my repeaters. All of them transmit a tone. One uses a split tone, DCS to access and PL on RX. I don't know how many times I have to tell people that you do not need to program in the RX tone if you don't want to or if your radio doesn't have that feature (split tones). All they need to do is TX the DCS. Leave it in CSQ for all I care, but the repeaters should always transmit the tone/code in this day and age of interference.

The change to the club repeaters was years ago and I still get complaints about the rooster crowing.

 

[mikewazowski]

All of my repeaters encode pl.

 

[nd5y]

PL is transmitted continuously whereas DCS is a burst.

Please explain.