DPL, PL, etc.

NBW791 · #1 (**permalink**) 10-28-2005, 01:22 PM

I've been a bit of a scanner junkie since I was about 13 years old, back for much of the trunking stuff came around, and always considered myself pretty savvy on the things. The TrunkTrackers are a little more confusing to me, but I can somewhat figure them out.

My question is about these DPL and PL codes (such as 183.5, 213.5, etc.).

#1 - What do the initials stand for?
#2 - What are they?
#3 - What good do they do me to have them programmed in my scanner?
#4 - Does it make much difference in my scanning ability to NOT have them?

Thanks for any help.....

-Nick-

Kirk · #2 (**permalink**) 10-28-2005, 01:31 PM

Quote:

Originally Posted by NBW791

I've been a bit of a scanner junkie since I was about 13 years old, back for much of the trunking stuff came around, and always considered myself pretty savvy on the things. The TrunkTrackers are a little more confusing to me, but I can somewhat figure them out.

My question is about these DPL and PL codes (such as 183.5, 213.5, etc.).

#1 - What do the initials stand for?
#2 - What are they?
#3 - What good do they do me to have them programmed in my scanner?
#4 - Does it make much difference in my scanning ability to NOT have them?

Thanks for any help.....

-Nick-

Private Line and Digital Private Line.

They're also known by their generic names of CTCSS (Continuous Tone Coded Squelch System) and DCS (Digital Code System). They're used to eliminate unwanted reception of signals.

The good they do you depends... If there are two agencies on the same frequency with different PLs or DPLs, you can use the decode feature on your scanner to enable you to listen to one or the other. If you get interference on one of the channels when running in open mode, adding PL receive can help eliminate it.

Does it make much difference? Again, depends. Where I live, it's not a big deal. In some areas, it can be a huge deal.

antfreq · #3 (**permalink**) 10-28-2005, 05:32 PM

Info right here on this very site.

http://radioreference.com/wiki/index.php/DCS

http://radioreference.com/wiki/index.php/CTCSS

Voyager · #4 (**permalink**) 10-29-2005, 12:44 AM

Quote:

Originally Posted by Kirk

Private Line and Digital Private Line.

They're also known by their generic names of CTCSS (Continuous Tone Coded Squelch System) and DCS (Digital Code System).

Actually, the generic term for DPL is CDCSS (Continuous Digital Coded Squelch System)
Many people shorten it to DCS. You could do the same for CTCSS, too (TCS).

Here is a list of just about any acronym you want to know that is radio related:
http://www.npstc.org/documents/Guide...px(VersII).pdf

Joe M.

kb2vxa · #5 (**permalink**) 10-30-2005, 12:44 PM

One thing you guys forgot is the Motorola PL coding system. Each refers to a tone frequency, eg. 3B, 4A, etc. You just may find them listed this way in certain circumstances, an old list (I had one around somewhere but...) would be helpful for such encounters.

Voyager · #6 (**permalink**) 10-30-2005, 05:35 PM

Quote:

Originally Posted by kb2vxa

One thing you guys forgot is the Motorola PL coding system. Each refers to a tone frequency, eg. 3B, 4A, etc. You just may find them listed this way in certain circumstances, an old list (I had one around somewhere but...) would be helpful for such encounters.

Actually, those are the EIA codes for the tones, not Motorola codes, although Motorola does use the EIA designations.

http://www.com-spec.com/atncht.htm

Joe M.

Exsmokey · #7 (**permalink**) 10-30-2005, 06:19 PM

Another use of CTCSS and CDCSS is to distinquish what repeater is being used. On many radio systems on the 150 and 450 bands with several repeaters in different locations the tone used to select the repeater (input tone) is also transmitted on the output frequency. You can program each repeater into a different channel and give it an alphanumeric tag which displays the name of the repeater or electronic site it is at. In rural counties you can then lock out some of the repeaters which have traffic for areas you might not be interested in listening to. Using a scanner with a good tone scanning feature (my BC-780 performs poorly on tone scanning) you can also program in the output frequency of the repeaters on a system, use the analog or digital squelch mode, leave the tone blank, and then just watch what tone frequency is displayed to determine what repeater is being used. You soon begin to recognize different repeaters by what tone frequency is displayed just as you recognize different agencies by the radio frequency displayed.

On many radio systems only one common tone is transmitted on the output frequency and the tone capability for the radio in this case is not important unless you have interference. When I travel to metro areas monitoring mobile I find a great deal of interference which can be filtered out by using the CTCSS as a filter. You just have to know what the proper CTCSS or CDCSS frequency is. I haven't taken a non CTCSS capable scanner into a metro area in almost 15 years and can't figure out how anyone in those areas get along without it. If you have a good outside antenna, mobile or fixed base, CTCSS seems absolutely necessary. If you are just using a rubber duckie non-mobile it probably doesn't make too much difference in reducing interference unless you are close, but not too close, to a source of RF (radio frequency) energy.

As much as some folks like to listen to skip on VHF low band, I don't like too unless I chose to. As the CHP is a very desirable frequency to listen to and they are on 39 and 42 MHz, I find a tone squelch scanner necessary. There are fewer and fewer low band radio systems as time goes on so "tone guarding" may not be important in some areas.

If you are a ham and don't know what tone is used to access a repeater once you have located one by searching, you then program the repeater's input frequency with the tone scan on to determine what tone to program with the repeater's in and out frequencies. Yes, you have to be within the range of radio transmitting to the repeater and often have to wait for someone to do so but this is easier on batteries than transmitting on each tone until you key up the repeater.

If you scan some businesses you will find that frequency sharing is very common and different businesses have different tones so that they don't have to always listen to the traffic of other businesses on the same frequency. I have a number of businesses I scan all the time (tow trucks, service companies you have called, and similar) and I don't want to listen to all the businesses on those frequencies.

When climbing peaks in the mountains I sometimes scan FRS and GMRS frequencies as you can sometimes hear people talking about weather and trail conditions to others who have stayed in camp or with the vehicle. I scan for the tones and if I want to talk with FRS/GMRS users, I just program in their tone into my FRS/GMRS capable radio and call them. Since manufacturers of those radios advertise their products using the term "privacy codes", many react with much surprise when I tell them I was listening in and would like to ask them for additional information. By the way I have a GMRS license in addition to my ham license.

Based on all of the above I would not purchase any scanner unless it had tone squelch capability and a good tone scan feature.