signal strength requirement to decode

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shores

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hi
i've tried sdr# to dsdplus, i've tried unitrunker and sdrtrunk, none will decode my local fleetnet motorola p25 phase 1.

i have my rtl-sdr powered and warmed up, i've found the offset of 55ppm and put that in, so that the signal strength what i do receive is right on the right frequency of a local known tower.

i've tried both the little antennas with mcx connectors, and i've used mcx to F type connector to a run of rg-11 heavy, shielded coax right up to a simple dipole in my attic.

wondering what signal strength is a ballpark minimum to be able to decode.
sdrtrunk says idle, and unitrunker says running but never sees anything.

offset configured, frequencies in, mode, etc.
just never get any data let alone voice to listen to.

thoughts?
 

I_am_Alpha1

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What system? Open UniTrunker and set it to the control channel frequency...try zero offset. It should popup a window with the system information if set correctly. The signal meter is in the upper left corner. I was just doing this yesterday to check a tower by me using the cheap antenna that came with mine. I just googled SDR radio with UniTrunker and the info is there--but it did say to input an offset which didn't work until I set it back to zero.
 

Voyager

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Is DSD+ showing any decode at all? Are you using a virtual cable? (hopefully VB Cable)
 

shores

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Is DSD+ showing any decode at all? Are you using a virtual cable? (hopefully VB Cable)

Yes using the free vbcable dsdplus never decodes anything
And I've tried ppm as 0 as well
Its an 820t2 done from nooelec
 

KE5MC

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shores,

While RF signal strength is important which is the frontend of a series of connections the audio level into DSD+ is too. There is a window in DSD+ you can bring up that looks like an oscilloscope trace. When I am decoding the signal in that window the signal is about 80% of the height of the window. Audio out of SDR# is set to the high end and all noise/blanking functions turned off.

Mike
 

Voyager

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And is SDR# directed to output to the virtual cable? (via the audio settings or via the DSD plugin?)
 

shores

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Are you telling DSD+ to listen to the virtual cable?

Yes to telling dsd to use vbcable and yes to setting output to be vbcable on sdr#
Though I tried unitrunker too
I figured maybe I had poor signal but my hp436 works fine using same simple dipole and cable run
So that's why I figured maybe offset was bad but its warmed up and bang on at 55ppm and also tried 0 by default
 

Voyager

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Are you using the DSD plugin? Can you post some pics of the SDR# info (audio settings) and that of DSD when it starts?

Also remember that you want DSD set for virtual cable OUTPUT as the input to DSD and the output of DSD set to the speakers.
 

shores

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Are you using the DSD plugin? Can you post some pics of the SDR# info (audio settings) and that of DSD when it starts?

Also remember that you want DSD set for virtual cable OUTPUT as the input to DSD and the output of DSD set to the speakers.
I'll take some screen caps tonight or tomorrow of sdr sharp and dsd and unitrunker as well

I'm using the owen sound fleetnet tower for testing
 

shores

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I'll take some screen caps tonight or tomorrow of sdr sharp and dsd and unitrunker as well

I'm using the owen sound fleetnet tower for testing

looks like it is mostly a signal issue
if i use a local nxdn frequency/trunking system, i can lock on with dsd+ (did have to change default recording device in windows back to vb-cable).

it detects the system type but shows ERR when following control channel
it is encrypted but i would have thought you'd see talk groups just not able to listen to anything.

i have an SNR of about 75dB on that local station with good signal.
i can't muster more than 25dB SNR on the local fleetnet tower even with a dipole in the attic and shielded rg-11 cable to the 820T2 dongle.

i might have to go fully external or a different antenna to try and bring in the tower as i am right in between 2 sites
oddly enough however the 436hp and the bct8 both lock on to fleetnet for digital and analog respectively
 

slicerwizard

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(did have to change default recording device in windows back to vb-cable).
No, you're supposed to tell DSD+ what device to listen to.


it detects the system type but shows ERR when following control channel
it is encrypted but i would have thought you'd see talk groups just not able to listen to anything.

i have an SNR of about 75dB on that local station with good signal.
i can't muster more than 25dB SNR on the local fleetnet tower even with a dipole in the attic and shielded rg-11 cable to the 820T2 dongle.

i might have to go fully external or a different antenna to try and bring in the tower as i am right in between 2 sites
oddly enough however the 436hp and the bct8 both lock on to fleetnet for digital and analog respectively
No, SNR is more than high enough. You're doing something wrong somewhere. How about some screen shots?
 

shores

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No, you're supposed to tell DSD+ what device to listen to.


No, SNR is more than high enough. You're doing something wrong somewhere. How about some screen shots?
Will get some today for you
What's the minimum snr for decent reception?
I have to really crank gain to get the snr of 25 on fleetnet tower

The how to for dsd I read said to set default recording ti vbcable but I guess I could manually set dsd to the vbcable
 

shores

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i've got decoding on nxdn working ok, and good signal strength on sdr#.
right now i've got hardly any signal on the dipole in the rafters for anything farther than about 20km away, so i'm not picking up much including any fleetnet which is odd, unless it is due to weather
i at least had some decent signal before.

here's screencaptures of good signal for saugeen shores police, encrypted nxdn, and dsd decoding from the CC.

then here's 142.650 and 143.100 for owen sound tower, one of the closer ones, and not seeing anything right on, even though i can tune accurately to things very close.

just not a reliable signal to decode? need to go higher or change out antenna maybe?

i was doing a tafl search and nothing comes up for 143.0250, so not sure what that might be in the last photo,
 

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KE5MC

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shores,

Snipping Tool is included in Windows7 Home Premium on my system. Very nice for the quick grab and show. Attached is an example of Dallas PD channel on a very cheap MFJ dual band mini-mag mount sitting on a shelf. I'm not sure of tower location, but somewhere in the 15-20 mile range.
 
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shores

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shores,

Snipping Tool is included in Windows7 Home Premium on my system. Very nice for the quick grab and show. Attached is an example of Dallas PD channel on a very cheap MFJ dual band mini-mag mount sitting on a shelf. I'm not sure of tower location, but somewhere in the 15-20 mile range.

yes i know how to use the clipboard and snipping, when i saved them i used paint, and they were full screen.
i've never seen any webpage before that made them so much smaller, i think it is resizing on upload as they are a few hundred k and easily viewable in paint and windows picture preview.

odd.
i'll redo them later tonight or tomorrow.

basically it shows good signal and decoding on the local nxdn about 10km away, but i am not getting anything right on the expected freq for fleetnet/motorola p25 phase 1 tower about 30km away.

a few spikes and some solid transmissions coming on frequencies near them but about .2mhz off, so probably not the right ones, since the ppm is accurate on very near systems.
 

slicerwizard

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yes i know how to use the clipboard and snipping, when i saved them i used paint, and they were full screen.
i've never seen any webpage before that made them so much smaller, i think it is resizing on upload as they are a few hundred k and easily viewable in paint and windows picture preview.
They look like you have the image properties in Paint set to a rather large size.


Paint / File / Properties / set width and height to 50 / OK, then paste from the clipboard.
 
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