Interpretation of scan results

Reception, channel detection, network issues, CableCARD setup, etc.
Posts: 10
Joined: Thu Nov 02, 2017 3:22 pm

Interpretation of scan results

Postby jseaman » Sun Nov 12, 2017 8:10 pm

Just looking for a bit of explanation on the output produced from a tuner scan
An example:

SCANNING: 665000000 (us-bcast:46)
LOCK: 8vsb (ss=75 snq=74 seq=100)
TSID: 0x0001
SCANNING: 659000000 (us-bcast:45)
LOCK: 8vsb (ss=92 snq=89 seq=100)
TSID: 0x13D7
SCANNING: 653000000 (us-bcast:44)
LOCK: 8vsb (ss=100 snq=100 seq=100)
TSID: 0x20BB

I can decipher some of it - the 9 digit number is the frequency - the next number on the line is the channel of that freq.

Next line shows the type of modulation - this is followed by 3 numbers - first one is signal strength - next two are? And what scale does 0 to 100 represent on these values? Is knowing the values anything I can make use of in improving reception?

3rd line TSID ... What is it?

The following lines are the subchannels - showing the virtual channel number and whatever ID they go by. Any idea why the first group (channel 46) is showing 0 as the virtual channel and no station letters?

Posts: 477
Joined: Fri Mar 25, 2016 9:55 am

Re: Interpretation of scan results

Postby rpcameron » Sun Nov 12, 2017 9:03 pm

SCANNING: <frequency> (<chanmap>: <chan>)
LOCK: <mod> (ss=<ss> snq=<snq> seq=<seq>)
TSID: <tsid>
PROGRAM <prognum>: <prog>

frequency: Channel frequency (in hertz (Hz))
chanmap: Channel mapping standard
chan: Channel number according to <chanmap>
mod: Modulation
ss: Signal strength (as percentage)
snq: Signal-to-noise quality (as percentage)
seq: Symbol error quality (as percentage)
tsid: Transport stream ID (?)
prognum: Program number on channel
prog: Program name (often shown as <vchan> (or <chanmaj>.<chanmin>) <csign>)
vchan: Virtual Channel number
chanmaj: Major channel number
chanmin: Minor channel number
csign: Channel call sign

The reason your channel 46 is showing no programs is probably because your tuner cannot receive/decode any streams being broadcast on (UHF) channel 46.

Posts: 10530
Joined: Sun Oct 28, 2007 9:23 pm

Re: Interpretation of scan results

Postby jasonl » Mon Nov 13, 2017 4:10 pm

snq is signal quality, a measure of how clean the signal is. The lower the quality, the more of the error-correction data is required to decode the stream. Below 50% means that the signal cannot be fully reassembled. It's an average over time. seq is Symbol quality is a similar measure, but instantaneous rather than an average. snq the higher the better, and seq should always be 100.

TSID is the transport stream ID, which is a unique(ish) number assigned to the broadcast, intended to be used in allowing tuning equipment to identify which stations using the same virtual channel number are the same (e.g. translator stations) and which are different (e.g. different stations from different markets and you live in the right spot to pick up both). In practice, many low-power station operators don't bother to get their own allocation and default to 0 or 1.

Channel 46 is 0 because the station is not broadcasting PSIP data. The FCC requires that all stations broadcast PSIP data, but the equipment that does it is notoriously unreliable so it may be unavailable from time to time. Big stations tend to have automated monitors and notifications set up for outages like this, and other popular ones will at least get calls and emails when there's a problem. 46 is HSN so not so much on either.

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