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Re: [IRCA] All-Digital AM Co-Channel Lab Test Results Unveiled
Russ,
At least in the Seattle area all-HD tests, the interference was much
greater.
One would expect the opposite, since the hash would be in the center of the
main frequency, but the hash was maybe two or three times more intense than
in the hybrid mode.
Thus, 1360 in Tacoma was mixed with noticeable HD hash during the KRKO
tests, although none is heard normally.
The area's 1400 is a much weaker station, and it stood no chance against the
HD onslaught.
Incidentally, I'm not local to KRKO. It's a strong signal which can be heard
in HD during the day, but not a full-quieting local.
Same for 1520, which is in Snohomish County (I'm in King County.)
Based on the tests I've heard, the hash from a completely local HD station
would be so noisy in analog that it could persuade analog AM listeners to
turn it off rather than even look around for other stations on the dial.
If the AM band were a mix of HD-only and analog signals, it would be almost
like having a bunch of vacuum cleaners running, each taking up a total of
60kHz.
I think that's the most graphic way I can explain what it sounded like in
analog.
But even in an all-HD situation, power would likely need to drop
considerably to keep HD-only stations from interfering with each other.
I can't see how all-HD signals would work compatibly in either a mixed or
total HD mode.
It was that bad.
--
Rick
-----Original Message-----
From: IRCA [mailto:irca-bounces@xxxxxxxxxxxxxxxx] On Behalf Of Russ Edmunds
Sent: Friday, April 22, 2016 1:51 PM
To: Mailing list for the International Radio Club of America
<irca@xxxxxxxxxxxxxxxx>
Subject: Re: [IRCA] All-Digital AM Co-Channel Lab Test Results Unveiled
Bottom line, this is, after all, the NAB, and their mantra is "More, more
more stations". I would expect their rsults to understate the potential
issues.
That said, a straight up digital signal would occupy the center of the main
channel - where today's analog signal is. And the digital signal should
occupy less bandwidth by itself and a typical analog signal. The IBOC hybrid
mode has the analog signal at center and the two hybrid digital signals on
either side. Thus the combined IBOC signal occupies substantially more
bandwidth than a single digital signal. That's why Chuck said ( or one
reason why ) it wasn't comparable. But that also doesn't predict much else.
Russ Edmunds
15 mi NW Phila
Grid FN20id
<wb2bjh@xxxxxxxxx>
AM: Modified Sony ICF2010's (2) barefoot w/whip
FM: Yamaha T-80 & T-85, each w/ Conrad RDS Decoder; Onkyo T-450RDS; Tecsun
PL-310 ( 2); modified Sony ICF2010 w/APS9B @ 15'; Grundig G8 w/whip;
modified Sony ICF2010 w/whip
On Fri, Apr 22, 2016 at 12:15 PM, Nick Hall-Patch <nhp@xxxxxxxx> wrote:
> It's quite easy to correlate Chuck. Just add ignorance and stir. I
> don't believe they actually said anything much about the digital
> signal, so assumption of all digital IBOC can reasonably be added to
> that mix. (other details about demodulation of the analog signal are
> also missing)
>
> Audio examples would be nice, and might help to convince the doubters.
>
>
> http://www.radiomagonline.com/deep-dig/0005/broadcast-engineering-conf
> erence-radio-technology-forum-sessions/37600
> offers descriptions of the conference sessions, but I haven't been
> able to quickly track down any more detailed results than what Dennis
linked to.
>
> http://diymedia.net/old/stuff/AM_IBOC_Test.pdf has a nice graphic on
> the first page which I assume is what Chuck is alluding to in terms of the
> difference between present IBOC and all-digital IBOC. Is that the case
> Chuck? If so, perhaps you could suggest a listening test that could
> be done with today's systems (thereby saving me the trouble of doing it
> incorrectly)? Those secondary OFDM subcarriers already sound pretty
nasty
> on KRKO's signal this morning, and they would be stronger in the
> digital only version.
>
> best wishes,
>
> Nick
>
>
>
>
>
>
> At 05:03 22-04-16, you wrote:
>
>> ...
>>
>> I don't see how you can correlate hybrid IBOC to all digital IBOC.
>> What you hear with KRKO/KAST is different from what you will hear
>> with all digital as the power spectrum and subcarrier levels are
>> vastly different.
>>
>> Chuck
>> ________________________________________
>> From: IRCA <irca-bounces@xxxxxxxxxxxxxxxx> on behalf of Nick
>> Hall-Patch < nhp@xxxxxxxx>
>> Sent: Friday, April 22, 2016 4:51 AM
>> To: Mailing list for the International Radio Club of America
>> Subject: Re: [IRCA] All-Digital AM Co-Channel Lab Test Results
>> Unveiled
>>
>> I presume "D/U" abbreviation in this piece refers to "desired /
>> undesired"?
>>
>> I wonder if someone recorded audio from those tests, rather than just
>> tossing dB's around? I have a recording of KAST-1370 from this
>> morning that says otherwise, with KRKO-1380 IBOC sidebands about 25dB
>> down and....welll, KAST is readable, but I wouldn't say it's lacking
>> interference. The noise becomes really dominant if KAST is less
>> than ~15dB above the IBOC level.
>>
>> best wishes,
>>
>> Nick
>>
>>
>>
>>
>> At 21:05 21-04-16, you wrote:
>> >http://www.radioworld.com/article/all-digital-am-co-channel-lab-tes
>> t-results-unveiled/278670
>> >
>> >Sent from my iPad
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