Some kind of digital transmissions

[nay27uk]

Does any one know what the digital transmissions in the UK CB band are in Leicester? they seem sporadic with the majority of it happening on channel 23 but sometimes with smaller signals cropping up on channel 15, channel 25 and a few other channels around 23 after the main transmission on 23, it almost looks like some sort of trunking system on the SDR.
Definitely some form of digital mode.
Anyone got any ideas?

[Admiral]

If it's an eight quid SDR dongle then probably an image from VHF breaking through where it wouldn't normally.

[JollyRoger]

If this is what your hearing CLICK HERE then it will be packet 1200 baud or APRS on channel 23

[nay27uk]

Nope not that JollyRodger. I will try and get a recording of it.

Admiral it is a cheap 100 kHz to 2 gHz chinese SDR so about £30 but yeah I was also thinking the same but the signals are far to strong.

I will try and get a recording.

[nay27uk]

OK the main transmission seems to have moved to channel 26 today.

Some pictures bellow of what it looks like.

The first picture is the main big transmission then the second picture is the ones that come in after the main transmission.

I do have some recordings of it in NFM and DSB both the best for sound quality, Where can I upload then so the link plays them?

FIRST

1.jpg

SECOND

2.jpg

[nay27uk]

OK some Audio Files

Narrow FM

DSB

[delboyonline]

Data transmissions are legal on several cept channels and are normally heard when propagation is running.

I don't think it ever took off in the UK but i know is popular in Germany.


"Some countries allow for packet or other digital modes on CB radio. Germany is one of them, specifically 26.565, 26.675, 26.685, 26.915, 26.925, 27.025, 27.035, 27.235, 27.245, and 27.405 MHz"

[26TM5890]

The Netherlands & Belgium;
01 Landelijk Repeater CBRN aanroep kanaal 26,965
02 26,975
03 26,985
04 Algemeen Oproepkanaal Duitsland 27,005
05 27,015
06 27,025
07 27,035
08 27,055
09 Noodoproep kanaal 27,065
10 27,075
11 Landelijk repeater WRLP aanroep kanaal 27,085
12 27,105
13 27,115
14 Algemeen oproepkanaal Nederland 27,125
15 Algemeen oproepkanaal België AM 27,135
16 27,155
17 27,165
18 Landelijke repeater WRLP ontvangst kanaal 27,175
19 Truckerskanaal 27,185
20 27,205
21 Algemeen oproepkanaal België FM 27,215
22 Kanaal voor Campers en korte mobiele verbindingen 27,225
23 27,255
24 Internationaal kanaal voor Packetradio 1k2 27,235
25 27,245
26 27,265
27 27,275
28 27,285
29 27,295
30 Internationaal kanaal voor SSTV 27,305
31 27,315
32 Kanaal voor kerkdiensten (voornamelijk vanuit Groot-Brittannië) 27,325
33 27,335
34 27,345
35 27,355
36 27,365
37 27,375
38 LSB Amerikaanse CB-stations 27,385
39 Internationaal kanaal voor Packetradio 1k2 27,395
40 Landelijk Repeater CBRN ontvangst kanaal Internationaal kanaal voor Packetradio 1k2, 2k4 en 4k8 27,405

[normal]

Do you get the same thing somewhere around 151MHz ?

[dcwuk]

Sounds like pager breakthrough to me.

[Black_Pirate]

i agree with the pager break through....maybe your near a tower...! thats not packet that would be 245.....aprs mainly...you could get wspr or Ros on 365 but as conditions are flat you would be lucky very lucky...

[Admiral]

Here's the thing, when you hear that crap on the SDR with a cheap and very nasty upconverter in it, tune in a 'real' radio and have a listen, I bet it isn't there.

I don't want to patronise you if you are already familiar with how them things work, and I'm no expert, but the RTL2832U based dongles aren't designed to work from 0-24Mhz, so if you want to use it down there then you need an upconverter, they generally use 120Mhz ones these days, also a125Mhz and some 200Mhz, always try and avoid the older 100Mhz ones as they will give you the most breakthrough grief with the FM broadcast band, but they then trick the SDR chipset into thinking it's tuning a frequency it can do, so if you want to listen to Talksport on 1053Khz, or 1.053Mhz, the upconverter allows the chip to actually tune at 121.053Mhz and filter out the 120Mhz, sadly the upconverters in these are often a tiny chip and a few pieces of coiled copper and a lot of the stronger frequencies from the upconverter can slip past the filtering, so if you had a strong local signal on 121.053Mhz then you'd hear it coming in with Talksport. If your SDR goes from 0-3Ghz then it probably has one built in and you didn't know it was there. That probably made no sense, so have a Google for upconverter and read what someone who knows what they're talking about says.

[bozzy]

I would agree that it sounds like pager breakthrough.

In SDR, try turning down the RF gain to around 30db, if the signal totally disappears then it is pager breakthrough.

I have similar problems with pagers here especially around 137mhz and 450mhz, reducing the RF gain a tad totally removes it.

[robo70]

yep, pager. they are incredibly strong signals and very wide band, ive seen pager breakthrough signals all over the place .. you can decode them with PDW software, its mostly hospitals, ambulance etc. it makes for some grim reading .. eg " 62 year old female suspect cardiac arrest... 23 Lansdowne road Edinburgh eh138ugh " stuff like that.
the weird thing is, its from ALL over the country.. its not necessarily local.