Control frequencies, RWC Simulcast C vs Maricopa County P25

[sonnikaz]

A bit of background: Initially owned a BCD436HP - I couldn't receive Chandler and a few other RWC services - so I bought an SDS100. This solved my "simulcast hell" issue. The SDS100 indicates that I'm receiving on Simulcast C, but I'll admit I may need to look at the actual frequencies a bit more.

I also started looking into SDR (RTL SDR, SDR#) a bit recently. I was able to get DSD+ Fastlane working on Maricopa County P25 (including Phase II) - but apparently not on RWC. As shown below, I'm seeing indications of a control frequency for Maricopa County (P25) - but not for Simulcast C.

I can "shotgun" frequencies on RWC and get audio, but without the control frequencies - it's a matter of getting lucky or not.

So, I'm wondering which one of the two scenarios I'm seeing here:

• RTL SDS is subject to Simulcast noise (assuming this is the case due to low cost).
• My understanding of control frequencies in simulcast system like RWC is massively out of whack.

I'd appreciate anyone's thoughts here.


Maricopa County P25 / Phase II - control frequency


RWC, Chandler Silmulcast C - control frequency

 

[cfsimmont]

The control channels for Simulcast C are below, you only need the Primary (Red) and alternate (blue) frequencies, the rest are just voice channels and the control channel will automatically go to them as needed. I can't help you with the SDR, as I messed around with one for a bit but gave up on it after I bought the SDS. Where are you located? Location is going to play a big part in what you are able to receive. I have been able to pick up Simulcast C on US60 out in Gold Canyon (past Apache Junction) and as far south as Florence, but your location and antenna will affect what you are able to receive.

 

[sonnikaz]

Thanks - I don't think it's location, I'm just a few miles off center of the red circle (well within range) - from the map - the SDS100 runs fine at the same location. I'm thinking SDR limitations (not as good as the Uniden technology).

 

[cfsimmont]

Ok my misunderstanding, I thought you were having difficulty receiving Simulcast C on your SDS. With the SDR's antenna plays a major role as well, but I'm sure someone that is more familiar with them will chime in and be able to help more.

 

[cellphone]

Check your gain (range) settings, and make sure it is high enough. Also check your antenna and connections. You might consider a better antenna. The antennas included with the cheap SDRs are pretty bad.

Below is using a $33 Nooelec NESDR Smart v4 SDR ($25 when I purchased it).

The current control channel freq for Simulcast C is 770.10625 (not 772.3625 which is what you show in your screenshot). The control channel rotates, and can be any of the 4 control channel freqs listed in the DB, but it is almost always 770.10625 or 772.10625. I am inside the circle for Simulcast C, and am receiving -47dB. As you can see, I am also pulling in many adjacent signals.



Similar to your situation, I am on the edge of the circle for Mesa TRWC Simulcast (853.350 control channel), but still receive it at -70dB with my external antenna.


Also keep in mind the range circles on radio reference are estimated coverage. They do not take into account terrain, and don't represent true coverage.

Regarding Simulcast reception with the cheap SDRs, they do very well. The cheap SDR hardware is likely not much different than what Uniden uses in the SDS radios. The power of SDRs is with software. SDRTrunk for Windows works very well for P25 simulcast, or OP25 for Linux works better. Both require a lot of configuration to get them set up right (Uniden did that for you with the SDS100 which is why it works so well). There are countless sites and YouTube videos for setting up SDRs online, so have fun! SDRs are the future of radio!

 

[sonnikaz]

Check your gain (range) settings, and make sure it is high enough. Also check your antenna and connections. You might consider a better antenna. The antennas included with the cheap SDRs are pretty bad.

Below is using a $33 Nooelec NESDR Smart v4 SDR ($25 when I purchased it).

The current control channel freq for Simulcast C is 770.10625 (not 772.3625 which is what you show in your screenshot). The control channel rotates, and can be any of the 4 control channel freqs listed in the DB, but it is almost always 770.10625 or 772.10625. I am inside the circle for Simulcast C, and am receiving -47dB. As you can see, I am also pulling in many adjacent signals.

Thanks. It was either my ignorance that the control channel rotates, or the antenna. Since I just started messing with SDR this past week or so, I was kind of hasty in my setup, and it seems like there wasn't a great selection of antennas out there. I did receive a Nooelec M6 RaTLSnake v2 which seems to be helping. When I just went to fire it back up at 772.3625 as the control, it was working right away.

I guess my eyes go straight for red, and didn't stop to look at the red/blue notation in the database. I had probably seen this before, but forgot about it.

Thanks all for everyone's help.