San Francisco Public Safety going Digital June 2021

[rustyhodge]

Side question: if you're not using encryption, what is the point of using digital?
SFFD has been very active on the new digital system today. Several times I've heard the dispatcher complain about how "the new radios are muffling" and such.

 

[scannerboy02]

Side question: if you're not using encryption, what is the point of using digital?
SFFD has been very active on the new digital system today. Several times I've heard the dispatcher complain about how "the new radios are muffling" and such.

The simple answer, the manufacturer's are no longer supporting the products. Also digital has a lot of "under the hood" benefits that analog does not.

 

[mcjones2013]

The audio issues will be addressed as more users come into the system. In Sacramento, we had the benefit of some smaller agencies/departments using the system for a couple years prior to the bulk of agencies transitioning, so they were able to address any issues that arose.

 

[nokoa3116]

I think P25 became the standard for public safety many years ago. It has certain other capabilities also that analog do not. Easier radio ids sent, audio sounds clearer further. Priority features, better emergency and man down features. Some fire accountability features. Of course secured encryption. The trunked systems offer more efficient usage of radio frequencies allowing a department to have many talkgroups while not having a dedicated frequency that just sits silence most of the time. Also the trunked P25 systems becoming a standard allows for better mutual aid and interoperability with system wide coverage. In San Mateo County every city has its own analog radio system, while driving through them you will lose reception very quickly from 1 city to another. Because of that San Mateo County has special channel for pursuits, and special incidents, those channels work in the whole county and a bit out of it. The main goal in Santa Clara County was for interoperability, so departments can work together and assist each other. Departments can go on pursuit and still have access to radios even when leaving the county and say going into the East Bay from the South Bay. I have seen some radio usage guides from San Jose PD and they can use mutual aid channels on EBRCS and some other adjacent systems also. Some departments used to be VHF and some UHF and at the time they weren't able to directly talk to one another.

P25 voice is more difficult to understand sometimes versus analog voice. It was also seen to not be as reliable with multiple instances for Sunnyvale DPS having an outage, or some issues compromising public safety. Some fire departments across the country still use analog for just their tactical or command channels, so they can have reliable, and understandable communications. For the most part I like P25, you don't have static sounding transmissions, you see who is talking, the trunked systems cover larger areas, and it's all in one.

 

[gmclam]

Side question: if you're not using encryption, what is the point of using digital?

The audio is not audio any more, it is digital data. That data can be more easily transported and stored. I think issues will be worked out over time. Afterall, we're in the early stages of this transition.

 

[rustyhodge]

P25 voice is more difficult to understand sometimes versus analog voice.

That is really the only problem I have with the P25 systems. The CODEC technology seems ancient. They need the high quality voice CODECs used in modern VOIP and cell phones rather that 15-20 year old CODECs they're using now.

 

[rustyhodge]

I logged a bit of traffic on TGs 926, 954 and 956 (but didn't have recordings so didn't hear the traffic just logged it). They don't seem to match up with anything (trying the multiply by 16 to get comparable old tg id)

I'm not logging anything on the SFPD channels.

Top TGs for 2021-09-15 so far today:


57 DPW 3SSR
58 WPCOM
59 ANIMAL
61 REC A4
65 DTIS 1104
90 DPW 1CONTROL
94 SFFD DISP
112 SFLIB1
133 S EVENT 2
265 SFFD A10
346 SFFD A1
438 SFFD A2
448 SFFD A3
527 DPW 2BSES
975 SFFD EMS4

Yesterday's traffic:
Top TGs for 2021-09-14:

55 SFLIB3
59 SFFD A7
61 SFFD A11
72 SFFD A14
79 SFFD DISP
97 EVENT 2
98 S EVENT 2
133 SFLIB1
327 REC A4
500 DPW 2BSES
806 SFFD A1
969 SFFD EMS4
1105 SFFD A2
1166 SFFD A3


Top Radio IDs

285 RID 329
335 RID 332
410 RID 336
459 RID 337

(These were all logged with the p25rx)

 

[footage]

I logged a bit of traffic on TGs 926, 954 and 956 (but didn't have recordings so didn't hear the traffic just logged it). They don't seem to match up with anything (trying the multiply by 16 to get comparable old tg id)

I'm not logging anything on the SFPD channels.

Top TGs for 2021-09-15 so far today:


57 DPW 3SSR
58 WPCOM
59 ANIMAL
61 REC A4
65 DTIS 1104
90 DPW 1CONTROL
94 SFFD DISP
112 SFLIB1
133 S EVENT 2
265 SFFD A10
346 SFFD A1
438 SFFD A2
448 SFFD A3
527 DPW 2BSES
975 SFFD EMS4

Yesterday's traffic:
Top TGs for 2021-09-14:

55 SFLIB3
59 SFFD A7
61 SFFD A11
72 SFFD A14
79 SFFD DISP
97 EVENT 2
98 S EVENT 2
133 SFLIB1
327 REC A4
500 DPW 2BSES
806 SFFD A1
969 SFFD EMS4
1105 SFFD A2
1166 SFFD A3


Top Radio IDs

285 RID 329
335 RID 332
410 RID 336
459 RID 337

(These were all logged with the p25rx)

@rustyhodge Could you explain where you're getting these TG numbers from? They don't line up with what I see coming from the P25RX or anywhere else. Thanks.

 

[rustyhodge]

@rustyhodge Could you explain where you're getting these TG numbers from? They don't line up with what I see coming from the P25RX or anywhere else. Thanks.

Sorry, forgot to indicate, the first # is the hits on that TG. I just included the known talkgroups per the RR database. I'll edit the post to include the header on the table.

 

[footage]

Oh, stupid of me. Thanks! That's great data.

 

[rustyhodge]

Here's the bash script I'm using to summarize that data, so it would work on Mac or Linux (or Cygwin on Windows)

#!/bin/bash

datecode=`date +"%Y-%m-%d"`

echo "Date: $datecode"

#Modify this to be the path do your p25rx data file, with the date text removed
#/Users/rusty = your home directory
#0xXXXXXXXX is your p25rx's serial number
base="/Users/rusty/p25rx/0xXXXXXXXX/p25rx_recmeta_"

target="$base$datecode.txt"

echo "Top TGs for $datecode so far:"
cut -f3 -d',' $target | sort | uniq -c | sort -n | tail -15
echo
echo "Top Radio IDs"
echo "Hits  Talgroup Name"
echo "-------------------"
cut -f8 -d',' $target | sort | uniq -c | sort -n | tail -6

echo

echo "Unknowns:"
echo "Hits   TGID"
echo "-----------"
grep unknown $target  | cut -f2 -d',' | sort | uniq -c | sort -n | tail -15

 

[Mike_G_D]

That is really the only problem I have with the P25 systems. The CODEC technology seems ancient. They need the high quality voice CODECs used in modern VOIP and cell phones rather that 15-20 year old CODECs they're using now.

It's not just the codec, it's the available channel bandwidth that comes into play. Narrowband LMR systems need to compress everything into 12.5 kHz RF channels widths, 6.25 kHz RF channel widths, and now even 3.125 kHz channel widths. Cellphone systems don't have the same restrictions.

And consumer cell phones are designed to work in relative high level RF areas (the systems are designed to "saturate" the area with fairly high RF levels) so the receivers don't need to be super sensitive, unlike LMR systems wherein the levels can very often be just above the noise floor.

Plus, the emphasis in digital LMR audio is in voice readability under extreme conditions - lots of noise and fading, etc. You want the words understood as a last resort at the expense of fidelity.

That said, P25, and most other modern LMR digital modes, use AMBE vocoders. IMBE was the precurser and the original P25 vocoder. AMBE is backward compatible with IMBE. Frankly, it amazes me how well they work with voice in such narrow bandwidths.

I still think you may be hearing noty yet fully configured or "fine tuned" system issues (including the one brought up that you may be hearing hybrid patched analog-to-digital and/or vice-versa audio).

I am pretty picky about digital audio in LMR cases and remember the early IMBE stuff and how "bad" it sounded to my analog FM trained ears. But I have noticed how much better it has gotten since, even just using consumer scanner receivers. The DSP code keeps getting improved as does the hardware.

The system I monitor in San Diego County is a mix of P1 and P2 on a fully digital countywide trunked system. Using the P25RX, as you do, I am frankly little short of stunned at how well it now sounds! As close to analog +/- 5kHz deviation (now called "wideband") FM as I have ever heard it sound! With the possible exception of the school bus folks who, I believe, probably get the lower tier equipment (though they are obviously P2 sooo...??) and seem to be the least radio-savvy in terms of how to speak when using the radio (I swear, they seem to be ALWAYS yelling including even the dispatchers!).

Anyway, point is, I think given some more time for adjustment, build out, testing, re-adjustment, etc., your area system may drastically improve. Time will tell.

Also, on the P25RX, don't forget you can play with the channel band filters a bit - that may allow you to improve things a little.

-Mike

 

[officer_415]

There's a bunch of encrypted talkgroups in the 14xx range, anyone know what they are?

 

[footage]

Unencrypted SFPD TGs showing up this morning for the first time:: 803, 805, 811.

 

[footage]

But the unencrypted SFPD TGs I referred to are absent this morning.

 

[Eng74]

I was in the City for a little while today. I had to avoid the SFFD automated dispatch. The pre alert is just way too loud.

 

[footage]

I was in the City for a little while today. I had to avoid the SFFD automated dispatch. The pre alert is just way too loud.

I've got to figure out how to suppress them on the G4. Has anyone done that?

 

[Eng74]

I think the only thing you could do is it program the talk group.

 

[rustyhodge]

Just an update. Still not hearing any SFPD in the clear, but lots of SFFD/EMS activity on both dispatch and TAC channels.

 

[KD6JEK]

Yeah, the automated dispatch uses long DTMF tones at the beginning.



I've been using a BCD325P2 and it works fine. There's been limited PD activity on the system, and mostly encrypted lately.

I’m debating on getting the BCD325P2. How does it work on simulcast? Are you out and about and able to pick up the broadcasts clearly? Otherwise it’s going to be an SDS-100, but that’s twice as much and I’m not sure how much I want to shell out if PD is going to be mostly encrypted.