Dallas PD

[Ambrose_Wolfinger]

This past week I was monitoring the DPD dispatch channels on 460 MHz in my car. When I was driving through downtown, I frequently heard digital bursts that sounded a lot like DMR. This is in addition to the analogue transmissions. I know DPD uses analog FM on these frequencies, so I'm not sure what the digital signals are.

Also, I noticed that Dallas PD also has channels on a city of Dallas 800 MHz trunked system. I'm not sure how this works. Is one is a simulcast of the other, or are the dispatch channels on 460 MHz different from the patrol deployment channels on 800 MHz?

 

[KevinC]

I would imagine your radio is being overloaded by strong signals in the downtown area.

 

[nd5y]

Digital was probably interference from something maybe from another user on 12.5 kHz adjacent channels. I don't think Dallas has any digital at all on the PD and FD UHF channels.

I haven't kept up to date but as far as I know dispatch and regular patrol is on UHF and everything else is on the trunked system(s). I don't know if the PD still uses the local government system. They may have moved to one of the P25 systems by now.

Dallas P25 / NCTCOG Trunking System, Dallas, Fort Worth Area, Texas

Dallas P25 / NCTCOG Trunking System Profile

www.radioreference.com

or site 3-002 on

North Texas Interoperable Radio Network (NTIRN) Trunking System, Various, Texas

North Texas Interoperable Radio Network (NTIRN) Trunking System Profile

www.radioreference.com

 

[hiegtx]

This past week I was monitoring the DPD dispatch channels on 460 MHz in my car. When I was driving through downtown, I frequently heard digital bursts that sounded a lot like DMR. This is in addition to the analogue transmissions. I know DPD uses analog FM on these frequencies, so I'm not sure what the digital signals are.

Also, I noticed that Dallas PD also has channels on a city of Dallas 800 MHz trunked system. I'm not sure how this works. Is one is a simulcast of the other, or are the dispatch channels on 460 MHz different from the patrol deployment channels on 800 MHz?

In Downtown Dallas, there are literally dozens of licensees on DMR that show a transmitter at the Bank of America tower (the 70 story green glass building at 901 Main St.)

Dallas PD, and DFR (Fire & EMS) both use Uhf for their dispatch & operations. There are a few PD related deployment talkgroups on the old local government system, along with a few special ops TGIDs as well. There are a couple of PD related talkgroups on the Dallas P25/NCTCOG system. The only channel consistently linked across the Uhf & trunked systems is DPD Ch 12, which is the default 'special events' channel, used for the State Fair, as well as any large gathering in the city.

 

[Gopher]

I used to be able to pick up DPD transmissions roughly 50 miles north of Dallas very well. After the July 7th sniper incident several years ago they don't seem to come in as strong anymore. Is it possible they have reduced power or is it something else?

 

[IAmSixNine]

I used to be able to pick up DPD transmissions roughly 50 miles north of Dallas very well. After the July 7th sniper incident several years ago they don't seem to come in as strong anymore. Is it possible they have reduced power or is it something else?

More likely due to it being an old system that is starting to show its age and have more and more issues. But also remember each DPD division has a transmitter in their back yard. SO if your north of dallas you will get DPD 5, 6 and 2 much better than 3,4 and 7. So when you say you used to be able to pick up DPD transmissions 50 miles north of Dallas it helps to be channel specific since the transmitter sites are in different places.
This only applies to the main dispatch channels. Channels like 8, 9, 10, 11 and 12 are city wide channels and based near down town dallas.

 

[tvengr]

Do you have the PL tones programmed?

 

[Gopher]

Do you have the PL tones programmed?

Probably not. I have them in an old Pro 404 handheld with a rubber ducky antenna so I may be a bit limited. It was the same on a Pro2021with an outside antenna.

 

[Ambrose_Wolfinger]

Do you have the PL tones programmed?

No I do not, but they aren't needed just for receiving

 

[Ambrose_Wolfinger]

After listening for a few days, I'm hearing digital signals even out in the suburbs. On some frequencies it sounds like DMR but on others it sounds like NXDN. I can't imagine any other agency being assigned the same frequencies as DPD and DFD but I could be wrong.

 

[KevinC]

After listening for a few days, I'm hearing digital signals even out in the suburbs. On some frequencies it sounds like DMR but on others it sounds like NXDN. I can't imagine any other agency being assigned the same frequencies as DPD and DFD but I could be wrong.

What radio are you using?

 

[Ambrose_Wolfinger]

Icom ID-5100

 

[Russell]

Some of the Southwest Regional Communications Center NXDN frequencies are real close to DPD. If you're not set to narrow band or your scanner is not being real selective you could be hearing these.

 

[Ambrose_Wolfinger]

So possibly intermod? Makes sense.

 

[hiegtx]

So possibly intermod? Makes sense.

It's not really intermod, as that is generally caused by the mixing of different frequencies. It's adjacent channel interference. When the SWRCC system first went into use several years ago, one of their frequencies caused issues with a frequency that Plano used for radio control of the irrigation (lawn sprinkler) systems used in Plano city parks.

In addition to SWRCC, the Lancaster NXDN system also have frequencies close to some Dallas PD & DFR channels.