Weird Radio

[Tophtoh]

Last night I heard traffic on 868.9875. It was not from a TRS because it has a PL of 250.3. It was garbeled when the units tramitted almost sounding like they were steping on each other but they weren't. Then the repeater dropped, they talked somemore I haven't heard anything since. 250.3 is the highest PL I have ever seen used. Who would use that high of one? Is 868.9875 a PS freq? Thanks

 

[N_Jay]

Last night I heard traffic on 868.9875. It was not from a TRS because it has a PL of 250.3. It was garbeled when the units tramitted almost sounding like they were steping on each other but they weren't. Then the repeater dropped, they talked somemore I haven't heard anything since. 250.3 is the highest PL I have ever seen used. Who would use that high of one? Is 868.9875 a PS freq? Thanks

Could have been IM

 

[Tophtoh]

What's IM?

 

[K2KOH]

Intermod...

 

[N_Jay]

What's IM?

Intermodulation.

Two or more signans can mix together either in the front end of your radio, or in an amplifier somewhere (Porrly designed pre-amp, or evenm a transmitter's PA).
Th eresulting signal can/will contain the sum and difference of the frequencies, plus the harmonics of the sums, pluse the sums of the harmonics.

E.G.

150 MHz + 160 MHz = 310 MHz, 10 MHz, 600 Mhz, 630 MHz, 290 MHz, 330 MHz, and lots of more mixes.

 

[Tophtoh]

I see, but isn't 250.3 a high PL? I've never seen anyone use it, how about anyone else?

 

[Voyager]

I see, but isn't 250.3 a high PL? I've never seen anyone use it, how about anyone else?

It's the highest standard tone there is, but it is a standard one. The only higher CTCSS is 254.1, but it's not a standard EIA-recognized tone.

Joe M.

 

[N_Jay]

I see, but isn't 250.3 a high PL? I've never seen anyone use it, how about anyone else?

You sure its a PL, and not just part of one of the mixing signals?

 

[Tophtoh]

It's a PL, decoded it too. Is it possible for someone to use that tone?

 

[Voyager]

It's a PL, decoded it too. Is it possible for someone to use that tone?

That would be true for a mix, too. If one signal has PL and the other doesn't, the mix would decode fine.

Tones that high are in use on several repeaters in my area. I think 254.1 is one a couple, too.

Joe M.

 

[Tophtoh]

Are they public safety repeaters? And for the Conv. Apco 25 freq's... what is a NAC tone?

 

[Voyager]

Are they public safety repeaters? And for the Conv. Apco 25 freq's... what is a NAC tone?

I think one is a PS repeater. The NAC is the digital equivallent of CTCSS/CDCSS (PL/DPL).

Network Access Code is what it stands for.

Joe M.

 

[N_Jay]

Are they public safety repeaters? And for the Conv. Apco 25 freq's... what is a NAC tone?

I think one is a PS repeater. The NAC is the digital equivallent of CTCSS/CDCSS (PL/DPL).

Network Access Code is what it stands for.

Joe M.

ANd teh NAC is not a tone, as it is bits in the P25 data stream.

It is quite a bit different than PL or DPL.

 

[Voyager]

Are they public safety repeaters? And for the Conv. Apco 25 freq's... what is a NAC tone?

I think one is a PS repeater. The NAC is the digital equivallent of CTCSS/CDCSS (PL/DPL).

Network Access Code is what it stands for.

Joe M.

ANd teh NAC is not a tone, as it is bits in the P25 data stream.

It is quite a bit different than PL or DPL.

Right - that's why I said it is the digital equivallent. It performs the same function for digital signals that CTCSS/CDCSS performs for analog.

Joe M.

 

[Tophtoh]

Then if you have a conv. APCO freq say 460.475, could you program that and listen on the pro-96? And could you make it mute like PL tones? and what state & county do you live in voyager?

 

[scanfan03]

Then if you have a conv. APCO freq say 460.475, could you program that and listen on the pro-96? And could you make it mute like PL tones?

No, the Pro-96 will not accept NAC codes.

 

[Tophtoh]

so can you listen to apco conv or no?

 

[scanfan03]

so can you listen to apco conv or no?

You can, but it doesn't support the NAC codes. You will here every person on that frequency.

 

[Voyager]

so can you listen to apco conv or no?

You can, but it doesn't support the NAC codes. You will here every person on that frequency.

It would be like listening to a frequency without CTCSS/CDCSS. You would hear every transmission. If you had several groups all using P25 on the same frequency, they could each have a NAC programmed in their radios and not hear each other. With the PRO-96, you could not select which group to hear and would hear them all - just like programming a frequency as carrier squelch where you would hear everyone.

Of course, this assumes those users are not using encryption. You would still hear the signal, but would not be able to understand the decoded audio.

The NAC would be nice to add to scanners - especially if you have several P25 users on the same frequency.

And PA, USA.

Joe M.