[BC] Audio "proofs"

[Mike Callaghan]

FWIW,  shortly after KIIS installed a new Nautel and a Catlink STL, I decided to do an audio proof
just to regale in the beautiful readings I'd get.   I was at the transmitter with the H/P 330 and
an associate was doing the studio end.   The mono SNR was - 30 db.  The stereo SNR was - 30 db.
L/R separation was - 30 db.  Finally, we took the processor/stereo gen out of the line, and the SNR
became 71 db.   That was the problem.  A few weeks later tho owner of the outfit making the
processor visited, and I commented about the lousy performance.  He didn't believe me.
So we put the station on the backup processor, and connected the culprit to the mod monitor.
30 db., 30 db., 30 db.  "THis is impossible",, I was told.   The phone gets dialed. Words get
exchanged.    We get an apology... "It turns out the front end of that processor uses a wideband
compressor meant for sports remotes.  It's really noisy.  There's a switch inside you can use to
turn it on or off.   You should turn it off for a proof.".   I asked if it was on when the units shipped.
The answer was yes.  We agreed that NO ONE does audio measurements anymore.
With today's programming, why bother ??

On 11/18/2010 10:20 AM, Harold Hallikainen wrote:

>>One huge issue is spurious emission stability under various tune, load and
>>power levels.  FM PA can exhibit strange issues a they run into different
>>operating points and loads.  Its almost a re-cert. in field.  By the way
>>when some one says proof are they saying RF spuri vs. the old audio proof?
>> Can't see any specs. today for an audio proof.

>>Warren Shulz
>>WLS CGO

>True, there are no specifications for audio anymore. I don't even see a
>specification for preemphasis other than the graph at
>http://www.hallikainen.org/FCC/FccRules/2009/73/333/section.pdf . Of
>course, there used to be specifications for frequency response, THD,
>noise, stereo separation, and stereo crosstalk (L+R to L-R and the
>reverse). The FCC decided that market pressures would pressure stations to
>have good audio. However, without a basic standard such as preemphasis,
>there is no "bright line perfection" to shoot for.

>On the term "proof", I believe the old audio measurements were indeed
>called "proof of performance" measurements. The new RF tests are
>"equipment performance measurements" (see
>http://www.hallikainen.com/FccRules/2011/73/1590/ ).

>Harold