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New User / Getting Started Forum The place for new users to discuss how to get started, and generally feel safe from the rest of the rabid technical community. If you just got your first scanner, this forum is for you.

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Old 06-18-2009, 7:20 AM
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Cool Frequencies & pl tones

This may sound like a stupid question to you veteran scanner hobbieists. However i am new to the scanning hobby.my question is, i am using freescan software to program my bc 346xt.the software optimizer is saying that i have duplicate frequencies programed.however these duplicate frequencies have different pl tones.can someone what this means and what i should do. Thanks so much.







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Old 06-18-2009, 4:10 PM
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Cool Frequencies

I am new to the scanning hobby, so please bare with me.my question is, how can i tell which frequencies are trunked and which frequencies are not.
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Old 06-19-2009, 11:18 PM
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Improperly posted to the Community Announcements and News forum so moved here.
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Old 06-19-2009, 11:22 PM
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Quote:
Originally Posted by mike6508 View Post
This may sound like a stupid question to you veteran scanner hobbieists. However i am new to the scanning hobby.my question is, i am using freescan software to program my bc 346xt.the software optimizer is saying that i have duplicate frequencies programed.however these duplicate frequencies have different pl tones.can someone what this means and what i should do. Thanks so much.

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I would certainly think that even if the PL tones are different, the same frequency is the same frequency. Have you tried putting it in another bank?
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Old 06-20-2009, 1:26 AM
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I would program them both, here in AZ highway patrol reuses many of the same frequencies just with different PL tones for different districts. I guess it's to save a little money on the frequencies that have to be licensed.
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Old 06-20-2009, 3:18 PM
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Quote:
Originally Posted by mike6508 View Post
.however these duplicate frequencies have different pl tones.can someone what this means and what i should do.
The best way to describe PL (aka "private line") is that a very low frequency audio tone is sent along with the transmission, and when you have that specific PL tone enabled on the channel you want to monitor, only transmissions with that tone will unsquelch the radio.

A good example are those FRS or "family radio" handhelds. Take one of those to a very busy park, beach or public event, and you will hear everyone that is on the same channel. This could get annoying really fast. If the FRS radio has PL capability, and you assign your group a PL of say "100 hz", then ONLY transmissions with that pl will unsquelch the radio. Helps to cut down on the annoyance factor of hearing unwanted traffic.

The use of PL can also help by keeping your speaker squelched when there is interference, as nothing in nature generates pl tones naturally. It won't reduce the interference, but just keep your receiver squelched until there is a transmission with the pl you programmed.

Note that pl is anything but "private" - that is a misnomer as all anyone has to do to monitor any frequency with pl is to just turn off the pl, or use a scanner that doesn't have it in the first place.

The overall affect with the use of PL is to enable groups of users to share the same frequency without annoying each other too much, but this pales in comparison to sharing a group of frequencies with trunking.

So if you have pl enabled on a channel, make sure it is the right one as listed in the database. If you don't know it, either turn it off completely, or perhaps use the scanner's pl-search feature to find it.

The big problem with self-assigned PL operations is that while it will keep the receiver squelched until a specific pl tone is heard, groups sharing the same channel on a different pl won't hear each other, and may unintentionally jam each other by trying to transmit at the same time. So the polite thing to do, especially with FRS radios, is to use an "unsquelch" button or "pl-disable" or something similar temporarily, to see if the channel is clear before transmitting.

For hilltop repeater systems where neighboring cities or counties might use the same channel, the use of different pl's can help keep the repeaters or receivers from activating on those weaker signals that are not really intended to use anything but the local repeater.

Last edited by hertzian; 06-20-2009 at 3:43 PM..
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Old 06-20-2009, 4:51 PM
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While FreeScan is correctly pointing out that you have duplicated frequencies, you may choose to have duplicates for a number of reasons. One reason is that the frequency is used by two or more users each with its own PL tone. In that case, you could leave the duplicates, but label them differently to indicate which agency you are hearing when that frequency comes up with that particular PL tone. For example,

City A Police 460.300 PL 123.7
City B Police 460.300 PL 100.0

Each person has their own view about whether to program PL tones into their scanner. My preference is to ignore the PL tones unless I find that I am hearing two users on the same frequency that I could sort out with the PL tones or unless I am getting interference from something that I can avoid hearing with the PL lockout. The PL lockout is the opposite of the normal PL. With normal PL you only hear the transmission if the PL on the signal matches what you have programmed. With PL lockout, you hear the transmission unless the PL matches what you have programmed. This can be useful for excluding a distant user that comes through on your radio when there is a band opening, for example.

Another reason that you might want to have the same frequency programmed more than once might be so that you will hear it regardless of which system you are scanning at the time. For example, there is generally a frequency that law enforcement agencies use to communicate with each other. You might want to have that frequency in the system for City A and also in the system for City B so that regardless of which one you are scanning you will hear those interagency transmissions.

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