Astro Spectra Distorted Audio

fire-medic8104 · Post by **fire-medic8104** » Wed Jan 17, 2007 10:12 pm

I am trying to listen to a APCO25 digital system and this is the first time I have messed with digital systems. I can hear the units fine, but there are times they sound like mechanical voices and the voice is garbled. I am thinking I have the NAC codes set right since I hear them.

The system is for Texas DPS and they share the same channels, but the NAC codes are different so I can't set it to digital squelch like I have read on a previous post since I would hear other units I don't want to listen to.

Anyone got any suggestions of fixing it or know what I am doing wrong? I am pretty sure it is a programming problem, since I have never messed with this.

My coventional channels I have programmed sound fine and transmit and recieve just fine.

Josh · Post by **Josh** » Thu Jan 18, 2007 6:47 am

I don't know why you need the NAC codes for... just set it up in Digital Carrier Squelch and it'll works just fine.

If things sound garbled, it could still be many things including weak signal, which does happen and wouldn't be your fault anyhow, unless the operations are simplex, when a better set up would be advised.

Depending on how new their conventional system is, you may want to change the channel bandwidth to 12.5Khz, or set the modulation to CPQSK (as opposed to standard IMBE, or WIDE), whatever you can do to match their radios, the better- with exception to NAC codes, because from a monitoring standpoint, as you've stated, they're unnecessary.

-Josh

txshooter · Post by **txshooter** » Thu Jan 18, 2007 10:00 am

Josh wrote:I don't know why you need the NAC codes for... just set it up in Digital Carrier Squelch and it'll works just fine.

If things sound garbled, it could still be many things including weak signal, which does happen and wouldn't be your fault anyhow, unless the operations are simplex, when a better set up would be advised.

Depending on how new their conventional system is, you may want to change the channel bandwidth to 12.5Khz, or set the modulation to CPQSK (as opposed to standard IMBE, or WIDE), whatever you can do to match their radios, the better- with exception to NAC codes, because from a monitoring standpoint, as you've stated, they're unnecessary.

-Josh

From a monitoring standpoint with this system ut is very necessary to use the NAC codes. Most of this system is full duplex, non-repeated. There are only a couple of frequencies Statewide. Different areas use different NAC codes. If you do not program the correct NAC codes from a monitoring stanpoint you would begin hearing transmissions from many different areas and have a difficult time,

As far as the audio problems you are having, it can be several things. First, I would check the firmware on you radio. The older the firmware, the more different you audio may sound. Kind of sounds like troopers in a barrel?

That is probably the issue you are having here. In. addition to a weak signal which can also cause some of what you are describing, have you considered intermod? Just guessing from some of our previous discussions.

fire-medic8104 · Post by **fire-medic8104** » Thu Jan 18, 2007 10:04 am

I only have 5 thank you

I think it is a programming issue because one of my friends has a XTS and it does the same thing. I'm on a mobile, he's on a portable at the same spot and we are hearing the same thing.

It does sound like they are in a barrel or a robotic voice. Sometimes it is choppy.

I have experimented with the different types of settings. I guess my best bet would be to get with one of the troopers since I used to work with them dispatching and see if they will let me read one of their units and get my settings identical to theirs.

jmr061 · Post by **jmr061** » Thu Jan 18, 2007 10:59 am

What is the host/dsp of your units?

Jason

fire-medic8104 · Post by **fire-medic8104** » Thu Jan 18, 2007 1:33 pm

11.10.00 / 8.02.06

txshooter · Post by **txshooter** » Thu Jan 18, 2007 2:09 pm

fire-medic8104 wrote:It does sound like they are in a barrel or a robotic voice. Sometimes it is choppy.

The Trooper in a Barrel Sound you are experiencing is more of a sound effect of the digital modulation that is being used. It is simply different than the Analog transmission you are used to. The robotic sound you describe is the effect of going from a analog signal to the New Improved Digital Signal they are now using. One of the issues with this as well may be that DPS has had these radios for sometime...i.e. older HOST/DSP in their radios. When they made the switch receantly it was a simple reporgramming of units that had been in vehicles for quite sometime. They started putting Astro Spectra's in the troopers vehiclesback many years ago. I know some of them were in vehicles as early as 2000. This could also be a issue. It may not be an issue with how you are recieving the audio as much as it is with the audio being transmitted.

fire-medic8104 · Post by **fire-medic8104** » Thu Jan 18, 2007 2:11 pm

So that is just the way it will sound until the complete the transition? Or is that for good? I was just trying to make sure it wasn't my end of the deal. Thanks for the info.

txshooter · Post by **txshooter** » Thu Jan 18, 2007 2:26 pm

fire-medic8104 wrote:So that is just the way it will sound until the complete the transition? Or is that for good? I was just trying to make sure it wasn't my end of the deal. Thanks for the info.

This will last way past the so called transition. The so called transition in the Houston Area is complete. This will remain about the same until the firmware is upgraded in the Units. This will be a many year process and knowing what I knwo about DPS, it most likely will no be done until units are replaced and new units come into the field from Austin. Hopefully firmware will be upgraded in the radios then, but there is not guaruntee. Remember, a lot of troopers were still using Bendix Kings as portables until this recent transition. This should give you a clue as to how old some of the equipment is and how long upgrades will actually take to get completed.

motorola_otaku · Post by **motorola_otaku** » Mon Jan 22, 2007 7:50 am

I'm gonna venture a guess and say that what he's hearing is packet loss coming from either two stations keying at the same time on the same frequency, or splatter from an analog station.

fire-medic8104 · Post by **fire-medic8104** » Mon Jan 22, 2007 1:32 pm

That is possible. I talked to one of the troopers and they are getting the same thing at times. Texas City (30 miles south) was supposed to be on a different freq. They were interfering with one of the fire departments down there and had to change to the one I am monitoring, but different NAC code.

I am sure if I went to digital squelch I would probably not get it near as bad, but then I would hear everything down there also.

I guess I will just have to live with it.

motorola_otaku · Post by **motorola_otaku** » Mon Jan 22, 2007 2:01 pm

Even with your radio set to Digital CSQ, you're still going to get packet loss and garbled audio since the radio has no way of knowing which signal it's supposed to be synching with.

Texas City was on 159.2175, but moved back to 159.2100 because of the Friendswood VFD interference issue. I guess DPS Houston and Beaumont are on .2100 as well? I've been without a mobile install for awhile so I haven't really been keeping up.

fire-medic8104 · Post by **fire-medic8104** » Mon Jan 22, 2007 3:24 pm

I couldn't remember which VFD it was. Yes Beaumont and Houston are on .2100 also

Astro Spectra Distorted Audio

Astro Spectra Distorted Audio

Re: Astro Spectra Distorted Audio

Re: Astro Spectra Distorted Audio

Trooper in a Barrel Sound

Trooper in a Barrel Continued