P25 Proximity for input frequencies

[VA4JOE]

Hi there again,

Just wondering if anyone knows how close in proximity someone has to be to the transmitting radio to acquire hits on the P25 system input frequency?

 

[VA4JOE]

Reason being, I am getting hits at my home 1/2 mile north of WInkler linked to one particular talkgroup in the 40000 range...

 

[nd5y]

How far you can hear mobile and hand held radios depends on the quality of your receiver and antenna, how high your antenna is, how high the transmitting station's antenna is, the terrain in between and other factors. P25 has nothing to do with it.

 

[wtp]

i get handhelds in the thousands of feet and cars about 1/2 to 1 mile.
it does depend on what is in between.
P25 or analog it was the same.
the old analog was in the 800 and the new P25 is in the 700 range.
back of set antennas and still using the same scanners.
i listen to the input a lot do to simulcast problems, but i always wanted to know what was happening in the neighborhood.

 

[boatbod]

The modulation on the input side of a P25 system is different from the output side. You may find that only some of the sdr softwares are capable of decoding it.

 

[FKimble]

The modulation on the input side of a P25 system is different from the output side.

Hmmm, this would indicate that P25 radios could not talk in simplex radio to radio! Did you mean frequency?

Frank

 

[wgbecks]

The modulation on the input side of a P25 system is different from the output side.

Hmmm, this would indicate that P25 radios could not talk in simplex radio to radio! Did you mean frequency?

Frank

Obviously, inbound and outbound frequencies are different. You have to define the type of P25 transmissions that you're talking about.
For example, on a Phase 2 P25 TRS, the subscriber unit transmits using H-CPM on the Inbound side while the Outbound side transmits
using H-DQPSK.

 

[FKimble]

Well , I learned something new. So the radio's can receive two different type signals!

Frank

 

[wgbecks]

So the radio's can receive two different type signals!Frank

Essentially correct. Subscriber Units (SU's) are capable of receiving FDMA C4FM and CQPSK for Conventional P25 and Phase 1 TRS,
and then TDMA H-DQPSK for Phase 2 TRS. However, they are not capable of receiving the H-CPM that is transmitted by the SU toward
the infrastructure side during Phase 2 transmissions.

 

[VA4JOE]

The modulation on the input side of a P25 system is different from the output side. You may find that only some of the sdr softwares are capable of decoding it.

I listen for the little burst transmissions that show the radio is active nearby on the input frequency using GQRX, then hop over to op25 to see which talkgroup ID is active.