DTV Engineering Question

This one really has me stumped. Hope someone can explain or offer advice.

I have two televisions located in 2 of my 3 bedrooms. One is a newer model with a built-in ATSC tuner.
The other is an old-school CRT set hooked to an ATSC converter box.

One of my local stations, WPNT-22, has the following channel lineup.

22.1 - WPNT main channel
22.2 - American Sports Network
22.3 - COMET
22.4 - Get TV

For some odd reason ASN on 22.2 was the latest addition. Prior to that they were running
22.1, 22.3 and 22.4, with the .2 signal unoccupied.

The old school CRT set with the converter is able to tune all 4 subchannels with no problem.
My newer set with the integrated ATSC tuner however does not recognize 22.2. It flips right
past it as I thumb through the channels. If I direct tune 22.2 it says "no signal" (which is absurd,
as all the others are there, so I KNOW it has to be there). I have tried rescanning but to no avail.
It refuses to recognize one of the 4 subchannels, which are easily received in another room a few
steps away.

Any ideas?

Thanks. I did that and it did not seem to help. Really strange as all 4 programs are coming from the same tower
on the same RF channel.

FreddyE1977 said:

This one really has me stumped. Hope someone can explain or offer advice.

I have two televisions located in 2 of my 3 bedrooms. One is a newer model with a built-in ATSC tuner.
The other is an old-school CRT set hooked to an ATSC converter box.

One of my local stations, WPNT-22, has the following channel lineup.

22.1 - WPNT main channel
22.2 - American Sports Network
22.3 - COMET
22.4 - Get TV

For some odd reason ASN on 22.2 was the latest addition. Prior to that they were running
22.1, 22.3 and 22.4, with the .2 signal unoccupied.

The old school CRT set with the converter is able to tune all 4 subchannels with no problem.
My newer set with the integrated ATSC tuner however does not recognize 22.2. It flips right
past it as I thumb through the channels. If I direct tune 22.2 it says "no signal" (which is absurd,
as all the others are there, so I KNOW it has to be there). I have tried rescanning but to no avail.
It refuses to recognize one of the 4 subchannels, which are easily received in another room a few
steps away.

Any ideas?

Click to expand...

Check my reply to intermittent DTV receptions issues in the Engineering Tech Tips board. http://www.radiodiscussions.com/showthread.php?694390-Disappearing-HD-Channels

Make sure your coax and RF splitters meet the criteria.

ahhh......THAT explains it!

I was using an RF amp I have had since 1987! (bought it from a store where I sold VHS machines at the time!).
My other set is hooked direct to the rabbit ears, and that's the one where I have no issue. I presume the old
amp is just as bad as an old splitter. Will buy a new one and give it a try.

Still strange that 22.2 is the ONLY channel out of everything OTA locally that is a problem.

I seriously doubt that you have an RF problem if the TV can decode three of the four video services without issue. Those four video services are encoded separately and the M-PEG II "streams" out of each of the four encoders are then fed into a multiplexer to be mashed together into a single transport stream to be output as TS over IP, ASI or (god forbid these days) a SMPTE 310 signal that's fed into the exciter. All four services are on the same transport stream into the transmitter. If one of the services can be decoded from that single recovered transport stream then ALL should be available and the receiver just isn't looking for the correct PID info for the missing service(s). (There's an exception or two to that. For example I know of at least one "station" with two separate transmitter sites some distance apart. Services xx-1 through xx-6 are transmitted from their one transmitter site and services xx-7 through xx-12 are transmitted from their other transmitter site.)

But I digress . . . first check to see if the "tuning" indicator on the set is showing good signal strength, just to be sure. If it is then completely delete the channel of interest on the set and then do a re-scan. (It seems that in order to shorten the scan time some ATSC receivers will only check to see if a channel that's already in memory is still detectable and then blow by it assuming that nothing has changed.) That should work but if it doesn't try deleting all the channels before doing a re-scan.

Good luck, and post back with your results, please.

I've seen this happen before. If the bit errors are high during the scan, sometimes the receiver will ignore assignment of the ancillary channel in spite of finding the .1 or even a .2. As BigRed mentioned, most times rescanning will find the channel, but the reliability of the entire isolated stream/signal is probably on the ragged edge anyway.