• Effective immediately we will be deleting, without notice, any negative threads or posts that deal with the use of encryption and streaming of scanner audio.

    We've noticed a huge increase in rants and negative posts that revolve around agencies going to encryption due to the broadcasting of scanner audio on the internet. It's now worn out and continues to be the same recycled rants. These rants hijack the threads and derail the conversation. They no longer have a place anywhere on this forum other than in the designated threads in the Rants forum in the Tavern.

    If you violate these guidelines your post will be deleted without notice and an infraction will be issued. We are not against discussion of this issue. You just need to do it in the right place. For example:
    https://forums.radioreference.com/rants/224104-official-thread-live-audio-feeds-scanners-wait-encryption.html

question

Status
Not open for further replies.

pinellasfirefighter

Completely Banned for the Greater Good
Banned
Joined
Jun 28, 2006
Messages
438
Location
seminole fl
when is see a frequency to enter in and after the frequency there is 156.7 p.l. what is this?
i`m not familiar with conventional.
 

kb5udf

Member
Joined
Apr 7, 2004
Messages
505
Location
Louisiana
What is P.L.

The term 'pl' comes from "private line" a form of squelch control, I believe
was developed by GE. Most speakers used to reproduce audio on two-way
radios are unable to reproduce bass frequencies, ie 300hz and below.
Taking advantage of this, clever engineers decided to transmit low frequency tones
along with the speech audio in the radio, as a way to control interference.

For example, if you have a radio in conventional mode, runningon 'carrier squelch'
any old electronic noise might set it off. For example, I find gas stations
very 'noisy' in the VHF hi spectrum. But if the repeater I am monitoring is set
to unmute the squelch only if it receives the right PL tone, then I won't hear the noise.

Another application is to allow multiple user groups to share the same frequency,
and not hear each other if they don't want to, by using different tones.

PS on some radios, if you hook them up to a suitably large speaker, you will hear the PL tone as a humming in the background.

Jean B.
 

pinellasfirefighter

Completely Banned for the Greater Good
Banned
Joined
Jun 28, 2006
Messages
438
Location
seminole fl
ok thank you guys.. wasnt sure what it was. i entered the channel but got no signal it was for my skywarn spotter group meeting.
 

hotdjdave

K9DJW - Senior Member
Database Admin
Joined
May 10, 2005
Messages
1,711
Location
"The Valley" (SFV), Los Angeles, CA
Note, if you are trying to tune into the freqeuncy without putting in the CTCSS (PL, CG) or DCS (DPL, DCG), you will still be able to hear the transmissions. What the CTCSS and DCS does it filter out other users on the same frequency that are not using the same CTCSS or DCS for those users that have the CTCSS/DCS decode enabled.

The CTCSS or DCS does serve another function as well. The CTCSS or DCS acts kind of like a password to turn on a repeater. The mobile (or base) radio transmits on a frequency using a particular CTCSS or DCS tone/code. The repeater will not repeat the broadcast unless the transmission contains the proper CTCSS or DCS tone/code. This keeps unwanted traffic from accessing the repeater. There are also other technologies employed to do this as well.


Squelch: CTCSS stands for Continuous Tone-Coded Squelch System and DCS stands for Digital-Coded Squelch.


pinellasfirefighter said:
when is see a frequency to enter in and after the frequency there is 156.7 p.l. what is this?
The numbers 156.7 is actually a frequency; it is a subaudible tone of the frequency 156.7 Hz.


kb5udf said:
PS on some radios, if you hook them up to a suitably large speaker, you will hear the PL tone as a humming in the background.
This is true. I have done this and have heard the various CTCSS tones. A good set of headphones works, too.
 
Last edited:
Status
Not open for further replies.
Top