KABC and KSPN are now Digital

[SuperRadioFan]

Anyone notice? I believe they started yesterday broadcasting in digital with the now-infamous digital hash on 700 and 720 AM as well as on 780 and 800 AM. On an analog radio all the AM stations that are digital sound somewhat more muddy and that's not a good thing. 2 questions for engineers, etc. 1) Why do these stations turn off their digital signal at sunset?2) If they ever expand their digital broadcasting to 24 hours/day, what effect if any will it have on night time reception in outlying areas such as where I live in South Orange County IF and/or when I buy a digital receiver? IOW KSPN's signal is interfered with a lot by one or two Spanish Language stations after sunset --- Would I receive a lot cleaner, clearer signal on a digital receiver with little or no interference from a co-channel station (still broadcasting in analog I presume)?BTW I notice 830 AM has had their digital signal turned off for a while. Does that have anything to do with their new owner, Arte Moreno of the Angels?

 

[oldiesradiousa]

Do am digital stations have hd 2 and hd 3 channels like fm?

 

[w9wi]

1) Why do these stations turn off their digital signal at sunset?

'Cause the FCC says so(grin). Seriously, under the interim IBOC rules digital operation by AM stations is only permitted during the day. Rumor has it that a proceeding to "permenantize" the IBOC rules will be considered "any day now" and when it's approved, nighttime IBOC by AMs will be allowed.

2) If they ever expand their digital broadcasting to 24 hours/day, what effect if any will it have on night time reception in outlying areas such as where I live in South Orange County IF and/or when I buy a digital receiver? IOW KSPN's signal is interfered with a lot by one or two Spanish Language stations after sunset --- Would I receive a lot cleaner, clearer signal on a digital receiver with little or no interference from a co-channel station (still broadcasting in analog I presume)?

Either it'll sound great or you won't get it at all.....In my experience the AM HD signal is pretty fragile, doesn't deal well with interference. If you're hearing interference on KSPN's analog signal right now, I doubt a HD radio will be able to decode their digital signal. Except..... that the IBOC signal is *not* transmitted on the same frequency as the analog. It's transmitted in the two frequencies on either side. (in KSPN's case, the upper halves of the 690 and 720 channels and the lower halves of the 700 and 730 channels) It's *those* channels -- not 710 -- that have to be reasonably clear of interference for HD to work. I *think* you only need one side -- if 720 and 730 are reasonably clear it might work even if XETRA is wrecking 690 -- but not 100% certain.

 

[spark gap]

No HD2 or HD3 on AM. Not enough bandwidth. As for sunset/sunrise the problem is, as stated above, the interference on the adjacent channel. At night AM travels farther than in the day. What is unknown; how much will the sideband hash from HD negatively affect adjacent channel stations in their primary service area?Never mind all the areas in between. To get an idea what it might sound like at night on the AM band if all the stations were allowed to keep HD on....travel up to 1240, 1400, or 1490 at night...listen to the noise.