Digitized TX's...Help please!

[jkbodden]

Recently, the Blount Co. TN LEO & EMS agencies switched to the new digital Tennessee Valley Corridor System. I programmed in all of the frequencies into my PRO 106 and left the Talk Groups as "wildcards". I can clearly receive about 60% of the TX's, about 10% are completely "digitized" that nobody can hear (including Comm Center and other units), however here's the main issue. The other 30% of the TX's appear to be "digitized" only on my radio (i.e. most of the time I can hear only one half of the conversation and the other half is in-audible.) These, to the best of my knowledge are not intentionally "scrambled", since most of these conversations are basic EMS TX's, etc.

Is there some sort of setting I need to change to fix this OR could it be the TX's are actually being transmitted by a repeater outside of my county (even though those TX's show full signal strength) Since this system basically runs thru the entire eastern TN corridor, if a mobile unit is closer to a repeater outside of the county, will the TX "utilize" the closer repeater and that's why it comes across digitized?

Thanks in advance!

Jeff

[rdale]

Check with the TN forum - it would be a reception issue most likely, and not any sort of setting in your scanner.

[OsloViking1975]

Important Note




Some talkgroups on this system are using Phase II TDMA modulation which cannot be monitored by any scanner.

http://wiki.radioreference.com/index...ct_25_Phase_II

[rdale]

I'm not sure he would hear anything in that case.

[KE5TLF]

Originally Posted by OsloViking1975

Some talkgroups on this system are using Phase II TDMA modulation which cannot be monitored by any scanner.

Which is a technically incorrect statement. Talkgroups don't control TDMA usage, radios do. Honestly it should say "Some transmissions on this system may be using...."

TDMA usage has no effect whatsoever on a 106.(or any scanner for that matter).

If it really is EMS then by law(HIPPA) they are required to not send patient's personal info "in the clear" so it could be encryption. The 106/197/500/600 do not skip encrypted traffic like the Unidens do. I have yet to hear one sided encryption on our 700MHz state system but I guess it is possible. I hear it every single day on conventional FED channels.

[rdale]

It's not encrypted or the RRDB would show an E.

[N8IAA]

Originally Posted by KE5TLF

TDMA usage has no effect whatsoever on a 106.(or any scanner for that matter).

Actually, it does. The current RS/GRE scanners, (106/197, 500/600) cannot decode Phase II TDMA. The 800, however, does decode X-2 TDMA.
This question probably would get a better answer in the Tennessee state forum.
Larry

[rdale]

It does not have an effect - you can't hear it. That was his point.

[loumaag]

Originally Posted by KE5TLF

Which is a technically incorrect statement. Talkgroups don't control TDMA usage, radios do. Honestly it should say "Some transmissions on this system may be using...."

TDMA usage has no effect whatsoever on a 106.(or any scanner for that matter).

If it really is EMS then by law(HIPPA) they are required to not send patient's personal info "in the clear" so it could be encryption. The 106/197/500/600 do not skip encrypted traffic like the Unidens do. I have yet to hear one sided encryption on our 700MHz state system but I guess it is possible. I hear it every single day on conventional FED channels.

The use of TDMA (either P2 or X2) on a talk group is set by the system admin. It is either allowed or not. The TG is either TDMA or FDMA or Dynamic. The radios do not determine that (except for the dynamic part) the controller determines that. Providing Dynamic is not involved, the statement that the TG is TDMA (P2 or X2) is correct. Providing Dynamic is involved (and paid for), if a FDMA radio affiliates then the TG changes to FDMA and all the radios on the TG change, if Dynamic is not paid for and a FDMA only radio attempts to affiliate with a TDMA talk group it is denied. So, bottom line, the statement as written is correct.

You are probably correct about the encryption. That is determined by each radio. I hear it all the time, one joker will have encryption enabled on a normally not encrypted TG so you can't hear him, but every one else is clear.

Originally Posted by rdale

It's not encrypted or the RRDB would show an E.

Your faith in us having the correct information in the DB is astounding. But as I just pointed out, we only mark them as encrypted "E" if the TG is normally encrypted; not if some joker flips it on his radio alone.

[KevinC]

Originally Posted by loumaag

The use of TDMA (either P2 or X2) on a talk group is set by the system admin. It is either allowed or not. The TG is either TDMA or FDMA or Dynamic. The radios do not determine that (except for the dynamic part) the controller determines that. Providing Dynamic is not involved, the statement that the TG is TDMA (P2 or X2) is correct. Providing Dynamic is involved (and paid for), if a FDMA radio affiliates then the TG changes to FDMA and all the radios on the TG change, if Dynamic is not paid for and a FDMA only radio attempts to affiliate with a TDMA talk group it is denied. So, bottom line, the statement as written is correct.

.

Correct, a TG is either FDMA only, TDMA only or DDM

[rdale]

Originally Posted by loumaag

But as I just pointed out, we only mark them as encrypted "E" if the TG is normally encrypted; not if some joker flips it on his radio alone.

Agreed - and if he is hearing 30% "scrambled" that seems like an excessively high number of jokers flipping their switches. Other explanations make more sense, aka reception.

[jkbodden]

Originally Posted by loumaag

The use of TDMA (either P2 or X2) on a talk group is set by the system admin. It is either allowed or not. The TG is either TDMA or FDMA or Dynamic. The radios do not determine that (except for the dynamic part) the controller determines that. Providing Dynamic is not involved, the statement that the TG is TDMA (P2 or X2) is correct. Providing Dynamic is involved (and paid for), if a FDMA radio affiliates then the TG changes to FDMA and all the radios on the TG change, if Dynamic is not paid for and a FDMA only radio attempts to affiliate with a TDMA talk group it is denied. So, bottom line, the statement as written is correct.

You are probably correct about the encryption. That is determined by each radio. I hear it all the time, one joker will have encryption enabled on a normally not encrypted TG so you can't hear him, but every one else is clear.

Your faith in us having the correct information in the DB is astounding. But as I just pointed out, we only mark them as encrypted "E" if the TG is normally encrypted; not if some joker flips it on his radio alone.

Lou,

Thanks for your input...not that I understood a word of it, but that's OK.

I have since "figured out" something that may allow someone like yourself to better answer my original question/problem.

Yes, I am still receiving "digitized" TX's, however it's usually only 1/2 of any conversation and about 30% of the time. There appears to be NO rhyme or reason to these digitized TX's (i.e., intentional scrambling), and I don't believe any of these are generated by the local "base comm center", only by the mobile units responding or a mobile unit talking to another mobile unit.

I happened to listen to a vehicle chase recently and most of the mobile units I could hear, however one or two (out of the 15 or so involved) were digitized.

That being said, here's what I have found out. While listening to another RR member's live feed, I didn't hear any digital TX's, but after paying closer attention, he also does receive the same digital TX's, however he has "squelched" those TX's on his radio. Do you know if the PRO-106 has the same capability? If not, can you recommend one that can squelch digital TX's? Could it be possible that, since this is a multi-county system, the digitized TX's are actually mobile units being closer to and using a repeater outside of my county, using a different frequency? The other reason I bring this up is because the local jail utilizes the same system and I don't believe I have ever heard any digitized TX's from the jail. I can always hear both sides clearly. Or, although I consistently show full signal strength on all TX's (including digitized) could it be a reception issue? Although we live in the E TN foothills, there are some mountains (although I have a direct line of site unobstructed view of one of the repeaters about 10 miles away).

Please accept my apologies for all of the questions.

Thanks in advance for any help you can provide.

Jeff

P.s. This may also help. I just heard a conversation where a Deputy with a mobile unit walked into a building. His TX's prior to walking in were fine, however once he was inside the store, the TX's started to partially "digitize". Maybe it's simply a reception issue on my end?

[wingmaker]

Seems like there using encryption at times. LOVE AND BLESSINGS

[loumaag]

Originally Posted by wingmaker

Seems like there using encryption at times. LOVE AND BLESSINGS

Yes, sounds like encryption to me also. I don't know anything about the PR0-106, I have a thing about RS stuff of late. In any case I don't know if it has any ability to quiet the encryption and encryption is a choice that some folks can make at the radio by turning it on or not.

[KevinC]

Originally Posted by loumaag

Yes, sounds like encryption to me also. I don't know anything about the PR0-106, I have a thing about RS stuff of late. In any case I don't know if it has any ability to quiet the encryption and encryption is a choice that some folks can make at the radio by turning it on or not.

No way to quiet encryption on the 106, you either L/O the TG or you hear the garbage.

[jkbodden]

Guys...thanks for your input, however I do not beleive these tx's are intentionally encrypted Here's why. I can listen to a "generic" EMS call, dispatching the call to the address, then listen to the EMS mobile unit responding to the call, digitized. I have listened to too many "non-stealth" type conversations, where one half of the conversation is "digitized" and the other half isn't, to think they are intentionally encrypted. After today, I'm simply leaning towards the "poor reception" thing from the mobile unit, although my scanner shows full signal strength during these "digitized" TX's.

[gewecke]

No one has mentioned the multi-path issue which causes many transmissions to become digitized to the listener when their antenna is not orientated correctly. The op may only need to reposition his antenna to understand the audio. Multi-path fools many listeners into assuming a call is encrypted when it may not be.

73,
n9zas

[rdale]

Originally Posted by gewecke

No one has mentioned the multi-path issue which causes many transmissions to become digitized to the listener when their antenna is not orientated correctly

Well, except the very first reply which mentioned reception issues

[gr8rcall]

As I'm sure the OP now knows, the PSR-800 can decode FULL P25 Phase II TDMA.
Just a little added info!