WNYC AM vs FM IBOC aircheck

[LinoNYC]

In another vain attempt to counter fiction with fact, I present an aircheck from WNYC's am & fm.

I chose this station because it is what I listen to, but more importantly, this show is live, local -no compressed net feeds or storage and it is a simulcast so direct comparison of AM vs FM is possible.

It starts with the FM iboc then switches to AM and after a buffering period to AM iboc then back to FM which buffers into iboc and finally returns to AM.

The radio is an Acurian set to "normal" Reception in NYC east side of Manhattan with the set showing three out of five "bars" of signal.

http://www.sendspace.com/file/dp20bm 23 mb WAV

OR

http://www.sendspace.com/file/m0nwr5 High Q MP3 @320k (5mb)

Lino

 

[Mike Walker]

Interestingly, I don't hear much noise when the AM is analog, before it switches to digital.

The FM OBVIOUSLY sounds better. It's not as over-compressed (I mean audio compression/limiting) as the AM, and there are obviously less data compression artifacts from low bitrate. The AM certainly sounds fine, but in addition to WAY TOO MUCH LOUDNESS (compared to the FM), there's a certain "roughness" to upper-mids and highs...a dead giveaway of low bitrate coding.

It's GOOD, but I am absolutely certain that, blindfolded, and minus the analog parts to give me an audible "heads-up" of what was coming, I could reliably tell the FM stream from the AM. I think most careful listeners could as well. Not an indictment of the AM system, only of overly aggressive compression/limiting, and more important of the very low bitrate.

Thanks for posting! More should do that!

 

[LinoNYC]

The AM certainly sounds fine, but in addition to WAY TOO MUCH LOUDNESS (compared to the FM), there's a certain "roughness" to upper-mids and highs...a dead giveaway of low bitrate coding.

Some background, WNYC-am has daytime power of 10K multiplexed from the stick of WMCA in NJ. Where I'am located it's signal is lower than WABC but, higher than WCBS-am which is 50k but slightly nulled toward me.

In making this aircheck I simple switched from AM-FM and did not compensate for the fact that the Acurian does seem to have an approx 4db average level from AM signals.
WNYC's AM is agressively compressed though this only becomes obvious when compared to their FM.

The "roughness" in AM-iboc is due to the fact that there isn't enough bandwidth for true digital above 4.5 khz and uses spectral replication for the "highs". I do find this slightly annoying but better preconditiong of the feed can ameliorate this problem. Current Am-iboc processing seems to suffer from the same desire 'impress with highs" that FM did some 35+ years ago.

You noted the absence of noise on the AM analog, it's important to note that AM-iboc does not perform well in a high noise environment (storms etc) on any but the strongest signals. This is a bit disappointing but not surprising given the nature of digital streams.

I gave an anecdotal account of this a few months ago:

http://www.radio-info.com/smf/index.php/topic,77530.0.html

lino

 

[JohnnyElectron]

You want to hear what decent AM radio sounds like?
Listen to this and salivate: http://www.fanfarefm.com/soundbites.html

NOW that's good sounding AM radio! I wish we were fighting for receiver standards (AMAX) like those samples meet, instead of HD-AM. Note: 80+ miles away from a 10KW station and 50+ miles away from a 50KW.

 

[Tom Wells]

I believe a well engineered AMAX should sound better than these clips.
I wonder just how truly it represents the high-end response of the radio.
I can say with certainly the old Delco AM CQUAMs had more high-end response than this shows.

I will record some AM high-fi long distance and local and post a file soon.
The stereo's nice but I'd rather have wideband and a 10 khz notch filter.

 

[Mike Walker]

I don't know what the frequency response of the Fanfare is (on AM), but I'm surprised to not hear any more high end than that. My SRF-A100 is MUCH brighter, and more "fm-like" on a well-engineered C-Quam station (getting rarer and rarer!) The old Carver TX-11a/TX-11b tuners also had far better high-end response than this. Still the low-end is good (on the fanfare), and the sound is quite pleasant. It's just that I've heard better, and on far cheaper tuners!