B&P radio communications

Has the B&P switched over to digital radio equipment?
I'm hearing what appears to be non-audio communications on 160.23 MHz, it started in the past month or so.

You are probably hearing the digital NXDN signal from the Toronto Area on 160.230. I am involved with the Broacastify rail feeds provided around the western NY area by ARS-NET.
When we installed the Erie to Buffalo feed ( https://www.broadcastify.com/listen/feed/37641) we had to immediately delete 160.23 B&P and 160.620 WNYPA due to the digital noise.
We attempted to live with slightly less severe interference on 161.52 CSX IG Dispatcher but had to abandon that also. The 160.620 also forced us to abandon plans to include the NYSW on our Finer Lakes Railway/Short Lines feed (https://www.broadcastify.com/listen/feed/36104) for the Geneva to Syracuse area.

With area rail operations being analog with carrier squelch there is no defense against digital interference from distant signals. The interference from the Toronto area may vary in intensity with weather conditions but atmospheric ducting is common over Lakes Erie and Ontario. With our wide area coverage from towers at unattended sites our only recourse is to delete affected frequencies from the feed.

We are able to include 160.230 in our Buffalo Area feed (https://www.broadcastify.com/listen/feed/37641) which is limited to local Buffalo coverage.

The probable sources of the interference are: 160.230 and 160.620 CN Concord - MacMillan Yard Operations
161.520 Metrolink GO16 Kitchener Line - Brampton RTC

This is something we are going to have to live with as rail communications switch to digital. The interference is not a major problem for the railroads with base stations located every few miles along the ROW to avoid problems with distant signals and the dispatchers use tone-up so they don't have to listen unless a unit is specifically calling them.

This signal is way too strong for Toronto. This is on a 'digital' receiver Uniden BCD996P2, but I don't have the NXDX option installed, just the more common P25.

The railroad technology of choice for digital is NXDN, and you'll likely see some carriers move there. If and when the railroads are forced to again narrowband their frequencies, you'll see wholesale moves.

Most newer railroad radios are already NXDN capable.

videobruce wrote: ↑Tue Oct 25, 2022 3:22 am This signal is way too strong for Toronto. This is on a 'digital' receiver Uniden BCD996P2, but I don't have the NXDX option installed, just the more common P25.

The signal is in the airwaves, so if it's on the frequency, your scanner will "hear" it. Having the "option installed" will have no bearing on whether your scanner receives the signal or not, just whether it decodes it.

Distance is the problem not the type of modulation.

Digital suffers from the "digital cliff." While analog signals fade to unintelligibility, digital reaches a point where there's not enough data to construct the audio.

The digital signal is nothing more than modulated audio on a carrier signal. Basically a modem.
If the receiver specifically knows that it should only be decoding the data, then you'd hear nothing if it can't decode the signal. If the receiver thinks it's supposed to receiving an analog audio signal, it'll play the audio, regardless whether it is voice or a digital modulated signal.

The digital cliff doesn't mean the data just stops though. It is still, in its most basic form, a modulated analog signal carrying the digital data and you'll still "hear" that data if you're listening to the audio with just carrier squelching. Which is what I suspect is happening even on the "digital" Uniden receiver. Since it isn't programmed to even attempt to decode the NXDN signal, it's treating the signal as an analog audio carrier and that's what you're hearing. And it's definitely possible for the signal to propagate across the lake under the right conditions.

The post from ctclark1 describes the situation perfectly. A receiver on the channel in normal analog NBFM mode in carrier squelch will hear the NXDN signal as a very loud pulsating noise and there is nothing you can do to eliminate it.

If railroads used coded squelch, the squelch circuit would at least prevent you from hearing the noise and maybe the desired analog signal could override it so it might be possible to still monitor local area railroad signals. But, with only carrier squelch mode, there is no way to eliminate it since the digital signal is still a "carrier". A special squelch circuit to recognize and mute digital signals but pass analog could be designed but it is not a normal radio feature. And, it would be of no value if the digital signal overrides the desired analog signals.

As soon as we installed the receiver at our Arkwright site we heard the 160.230 NXDN very strong and active quite frequently with the 160.620 not quite as active but it was obvious there was no way we could monitor those frequencies. The 161.520 was not as strong and infrequently active and we wanted to monitor the IG Dispatcher channel since this is primarily a CSX feed but it proved to be too annoying so we had to settle for just the CSX Road channels, the NG Dispatcher and the NS channels at that site.

clearblock wrote: ↑Mon Oct 24, 2022 8:13 pm This is something we are going to have to live with as rail communications switch to digital. The interference is not a major problem for the railroads with base stations located every few miles along the ROW to avoid problems with distant signals and the dispatchers use tone-up so they don't have to listen unless a unit is specifically calling them.

The dispatchers and trains use tone-up to converse with each other, but what about ground work comms between conductor and engineer having interference since they still use CSQ? As someone said, if it's on the airwaves, it's going to be heard. Ground work doesn't use tone-up for swtiching work, etc. On the railfan side, would dropping/jumping to the next frequency step maybe get rid of the noise and still catch your desired comms on bleed-over if you're close enough to the source?

The interference from distant NXDN is generally not strong enough to be a problem on crew portables or locomotive radios. For railfans, most scanners have an attenuator option that can be programmed on a per-channel basis to limit reception to strong, nearby signals. Tuning off- frequency would probably not be helpful and probably make things worse.