close call can it capture APCO-25

[navalert]

I have a bcd396t and wonder if close call will also capture APCO-25 transmission near by? if it does , what does it indicate when it captures exactly?
I suspect it does not as lack of control channel data - does anything?

 

[mtindor]

It's going to detect a close call signal based upon that signal's strength over other surrounding signals. Once it discovers a very strong close signal, there is no reason why it wouldn't determine it was P25. As long as the mode is set to Auto or FM for close call, it's going to detect that FM sig whether it's P25 or not.

Mike

 

[Andrew]

It will pick up APCO-25. I have used my PRO-83 in close call mode at the airport and have captured the TSA radios, both the repeater and simplex. Of course the PRO-83 dosn't decode APCO-25 transmittions, so I couldn't understand anything. But I was suprised that it did capture that digital mode because it won't capture something like a Nextel signal.

 

[Chris-KH2PM]

Well, I'm surprised. I just tested this out using my 396 and an EF Johnson 5100 HT (PRC127 VHF). When I set the scanner to Close Call it will capture the frequency but won't decode the P25. Just the raw digital audio is what I hear. I would have thought the 396 CC would do it, but apparently not while in SEARCH mode or Close Call mode.
Yet, in the "Srch/CloCall Opt" setup on the 396, "Adjust P25 Level" is an option. I might have to tweak the settings in my 396 and test some more. I do have "data skip" turned off. I even tried my UHF 5100.

If I "quick save" a specific test frequency in the 396 and transmit P25 with the 5100, "P25" is displayed and the audio comes though fine. I have seen "ENC" displayed when encrypted comms are received as well.

*EDIT*

OK, I figured out it will work. I had CTCSS/DCS search enabled on the Search/CC options page. Turned it off and now it stops and passes P25 audio in CC.
It will display "P25" on the screen while receiving such audio, to answer the OP's question in post 1 above.

 

[slicerwizard]

I was suprised that it did capture that digital mode because it won't capture something like a Nextel signal.

Not surprising, since APCO25 is just an analog signal (it's really no different than a Motorola or EDACS control channel, which you expect to be able to hear with an analog scanner), while a Nextel iDEN signal is TDMA (which means that most of the time, it isn't there)

 

[Andrew]

Not surprising, since APCO25 is just an analog signal (it's really no different than a Motorola or EDACS control channel, which you expect to be able to hear with an analog scanner), while a Nextel iDEN signal is TDMA (which means that most of the time, it isn't there)

When you say "it isn't there", do you mean that its happening so fast it can't be locked on to?

 

[slicerwizard]

I mean that when you're yakking on the phone, your iDEN handset spends most of its time not transmitting.

With the older 6:1 timeslot arrangement, handsets would take 90 ms samples of your voice and transmit each one of them them in a much shorter 15 ms burst. Now they have improved that to 12:1.

It's one of the reasons that the battery lasts so long.

It's also why you can have a moving full duplex phone call - the handset has all those other timeslots to do other useful stuff, like receive the audio of the party you're talking to, and to sample the control channels of all of the current site's neighbours so a smooth handoff to the strongest neighbour can be done on a moment's notice.

And it's also why Close Call can't handle it - scanners don't like signals that aren't there 90% of the time.

 

[Andrew]

Thanks slicerwizard , that makes sense.