In article ,
Ron Hardin wrote:

Since Thursday morning I've been hearing 120Hz hum on WFAN (NYC) 660,
does anybody else?

The R8B hears it except with DSB synch detection, so there's some
relation between I and Q channels that cancels the hum.

In article
Ron Hardin wrote:

It's still there at 4:30am EST. It's not audible at all if you're hearing
both sidebands but obvious in quiet phone call pauses (no music, not fan
noise). It's some difference between the upper sideband and lower sideband
that gets modulated by hum; so if you don't hear them equally the hum
starts to creep in, and at some point becomes noticeable. (So propagation
at night can make the hum come and go if you're hearing both sidebands, by
depressing one and raising the other.)

WFAN's transmitter is diplexed into a common antenna with WCBS's (880
kHz) transmitter. Part of the diplexing arrangement includes impedance
matching networks that are supposed to equalize the antenna load
impedance reflected towards the transmitter output over the sideband
bandwidth. I suppose they could be slightly out of adjustment, causing
asymmetrical sideband response. One side effect of asymmetrical response
would be the generation of AM-to-PM.

At the joint transmitter site are older Continental transmitters that
function as backup for the regular Harris DX50 transmitters. Maybe they
have one of the Conti's on occasionally?

Most of these high power transmitters run off of 480V 3-phase power.
Ripple frequency with a straight 3-phase rectifier would be 180 Hz, not
120 Hz. A popular supply arrangement is the 3-phase 6-pulse rectifier
which outputs a 360 Hz ripple frequency. 120 Hz ripple frequency would
most likely originate in either an audio or low level RF stage powered
from a conventional 2-phase rectifier.

I'll take another listen tonight.

Since Thursday morning I've been hearing 120Hz hum on WFAN (NYC) 660,
does anybody else?

I've been hearing a background hum on WFAN for a LONG time, but only
when listening in "forced" AM Stereo. When listening in mono, the hum
disappears.

Normally, AM Stereo receivers rely upon a 25 Hz "pilot tone" that is
transmitted by an AM Stereo station, which tells the receiver to
switch into stereo mode. However, unlike FM Stereo, this pilot tone
is NOT necessary to receive AM Stereo, so some receivers --
particularly from Sony -- operate in "forced" AM Stereo mode, which
receives _all_ AM signals in stereo mode, regardless if a 25 Hz pilot
tone is received or not.

Thus, with my Sony receiver, I can listen to WFAN (and other "mono"
stations) in "forced" AM Stereo mode, and in this mode, I hear the 120
Hz background hum. However, the hum is "out-of-phase", indicating that
it is being received in the L-R "stereo difference" component of the
signal. When the receiver is switched to mono, the L-R component is
not received, and WFAN's hum disappears.

I once asked WFAN's engineer about this hum, and they said WFAN was
not transmitting it, and that it was being caused by my reception
conditions, such as electrical interference. However, I hear this hum
from WFAN, and ONLY from WFAN, 24 hours a day, even when there's a
local power failure and thus no electrical interference can possibly
be generated!

WFAN _was_ an AM Stereo station until about two years ago, when they
reverted to mono. But, it IS possible that their C-Quam AM Stereo
exciter is still installed and operational, but merely is being fed
with mono audio and has its 25 Hz pilot tone generator switched off --
which, for all intensive purposes, means WFAN is transmitting a
conventional "mono" signal. However, if that AM Stereo exciter ITSELF
is the causing this 120 Hz hum, it could be introducing it into WFAN's
signal in the manner that I described -- only "forced" AM Stereo
listeners will be able to hear it, while mono listeners won't hear the
hum.

Also, listeners with sophisticated communications receivers may also
hear it in Independent Sideband (ISB) mode, which operates in a
similar manner to AM Stereo reception and can pick up the stereo
difference component transmitted by AM Stereo stations (although not
in a manner which provides correct left-to-right stereo separation in
the received audio). Thus, with this kind of receiver, you may also
be able to hear this mysterious "WFAN hum".

That's the most compelling argument I've seen to explain this...when Ron mentioned
that the modulation was in the Q channel, you had to know that it wasn't coming from
conventional amplitude modulation.

The only other explanation I can come up with, building on this one, is that this
transmitter's exciter has developed a phase-modulated hum. Keeping in mind that all
transmitters have exciters which operate from low voltage power supplies, and those
supplies are usually powered with single-phase 120 VAC, a 'lytic that went south
could possibly explain it without having to resort to an abandoned but still
connected stereo exciter. You wouldn't hear the hum, as already established, if you
were dead-on tuned, since the RF exciter's amplitude, even if it was affected by the
problem, is clipped by the next class C stage the RF path encounters, but you'd see
the sidebands in a spectrum analyzer, and you could hear all but the quietest of
these when you tuned through the center.

If I were the engineer in charge, I'd be embarrassed to have to admit the latter, but
probably even more embarassed to admit that maintenance on the rig was so bad that
this situation could occur. After all, it's detectable with a simple
tune-through...is this to say that the station's engineers NEVER tune into the
station? When I ran a transmitter plant, it was an expected job function to LISTEN
to the station for frequent quality checks, even if it wasn't the preferred format
for the engineer. And from WBRW says, this was mentioned to the CE a long time
ago....if he was doing his job, he'd have looked into it. I couild understand if
this was a 1kW daytimer, but this is a Class I Clear, after all. And what
quasi-natural interference, in anyone's experience, isn't amplitude modulated?

And they say that deregulation is good for broadcasting!
--
For direct replies, take out the contents between the hyphens. -Really!-


"WBRW" wrote in message
om...
Since Thursday morning I've been hearing 120Hz hum on WFAN (NYC) 660,
does anybody else?

I've been hearing a background hum on WFAN for a LONG time, but only
when listening in "forced" AM Stereo. When listening in mono, the hum
disappears.
[...]
I once asked WFAN's engineer about this hum, and they said WFAN was
not transmitting it, and that it was being caused by my reception
conditions, such as electrical interference. However, I hear this hum
from WFAN, and ONLY from WFAN, 24 hours a day, even when there's a
local power failure and thus no electrical interference can possibly
be generated!

WFAN _was_ an AM Stereo station until about two years ago, when they
reverted to mono. But, it IS possible that their C-Quam AM Stereo
exciter is still installed and operational, but merely is being fed
with mono audio and has its 25 Hz pilot tone generator switched off --
which, for all intensive purposes, means WFAN is transmitting a
conventional "mono" signal. However, if that AM Stereo exciter ITSELF
is the causing this 120 Hz hum, it could be introducing it into WFAN's
signal in the manner that I described -- only "forced" AM Stereo
listeners will be able to hear it, while mono listeners won't hear the
hum.
[...]

In article ,
Tim Brown wrote:

In article ,
Ron Hardin wrote:

Since Thursday morning I've been hearing 120Hz hum on WFAN (NYC) 660,
does anybody else?

The R8B hears it except with DSB synch detection, so there's some
relation between I and Q channels that cancels the hum.

In article
Ron Hardin wrote:

It's still there at 4:30am EST. It's not audible at all if you're
hearing
both sidebands but obvious in quiet phone call pauses (no music, not fan
noise). It's some difference between the upper sideband and lower
sideband
that gets modulated by hum; so if you don't hear them equally the hum
starts to creep in, and at some point becomes noticeable. (So propagation
at night can make the hum come and go if you're hearing both sidebands,
by
depressing one and raising the other.)

WFAN's transmitter is diplexed into a common antenna with WCBS's (880
kHz) transmitter. Part of the diplexing arrangement includes impedance
matching networks that are supposed to equalize the antenna load
impedance reflected towards the transmitter output over the sideband
bandwidth. I suppose they could be slightly out of adjustment, causing
asymmetrical sideband response. One side effect of asymmetrical response
would be the generation of AM-to-PM.

At the joint transmitter site are older Continental transmitters that
function as backup for the regular Harris DX50 transmitters. Maybe they
have one of the Conti's on occasionally?

Most of these high power transmitters run off of 480V 3-phase power.
Ripple frequency with a straight 3-phase rectifier would be 180 Hz, not
120 Hz. A popular supply arrangement is the 3-phase 6-pulse rectifier
which outputs a 360 Hz ripple frequency. 120 Hz ripple frequency would
most likely originate in either an audio or low level RF stage powered
from a conventional 2-phase rectifier.

I'll take another listen tonight.

Okay. I set the receiver to USB and tuned in WFAN this evening and can
now hear the "hum". The frequency sounds more like 125 Hz, not 120 Hz,
which is significant. Assuming that they still have their CQUAM exciter
patched into the transmitter, my guess is that we are hearing the 5th
and other odd harmonics of a 25 Hz stereo pilot square wave. This would
be phase modulating the carrier, which is why it is not audible when
receiving the station with a conventional envelope detector.

One way to deal with this would be to make a really clean recording of
some "hum" infested program material, burn it onto a CD-R, and mail the
CD and a -nicely- written letter to the corporate director of
engineering at Infinity. I'll wager you, it will get fixed really fast!

Tim Brown wrote:
I'll take another listen tonight.

Okay. I set the receiver to USB and tuned in WFAN this evening and can
now hear the "hum". The frequency sounds more like 125 Hz, not 120 Hz,
which is significant. Assuming that they still have their CQUAM exciter
patched into the transmitter, my guess is that we are hearing the 5th
and other odd harmonics of a 25 Hz stereo pilot square wave. This would
be phase modulating the carrier, which is why it is not audible when
receiving the station with a conventional envelope detector.

One way to deal with this would be to make a really clean recording of
some "hum" infested program material, burn it onto a CD-R, and mail the
CD and a -nicely- written letter to the corporate director of
engineering at Infinity. I'll wager you, it will get fixed really fast!

Here's some short .wav recordings from around 5am (apparently ``The Continent'' Carlin
does overnights on weekends, nice career arc; luckily he has a speaking style that
produces a lot of dead air)

http://rhhardin.home.mindspring.com/HUMUSB.WAV (31k) synch det USB (4:52am EST)
http://rhhardin.home.mindspring.com/HUMDSB.WAV (17k) synch det DSB (4:54am EST)
http://rhhardin.home.mindspring.com/HUMLSB.WAV (27k) synch det LSB (4:56am EST)
http://rhhardin.home.mindspring.com/HUMAM.WAV (28k) AM (4:59am EST)
http://rhhardin.home.mindspring.com/HUMAMU.WAV (27k) AM detuned to 662.400 (5:08am EST)

I see lines at 120 240 360 480 600 720 840 1080, the lines above 480 being faint,
with ``birding'' software that has a granularity of about 20Hz, but in particular
it doesn't seem to have any lines that would reflect a low frequency around 20 Hz.

These recordings all went through a Timewave 599zx DSP to get the AGC to jack up dead
air loudness. The lines are all visible in any program material but the ear doesn't
notice them when something else is there too, so much.
--
Ron Hardin


On the internet, nobody knows you're a jerk.

Tim Brown wrote:

WFAN's transmitter is diplexed into a common antenna with WCBS's (880
kHz) transmitter.

When did they start sharing the antenna? Was there ever a time when the
three major radio networks (NBC, CBS, ABC) in NYC each had there own
antenna?


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http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
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Sure. For one, WABC has "it's own" antenna at Lodi, New Jersey.

--

----------------------------------------------------------------------------
--
Don Forsling

"Iowa--Gateway to Those Big Rectangular States"
"starman" wrote in message
...
Tim Brown wrote:

WFAN's transmitter is diplexed into a common antenna with WCBS's (880
kHz) transmitter.

When did they start sharing the antenna? Was there ever a time when the
three major radio networks (NBC, CBS, ABC) in NYC each had there own
antenna?


-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

That's the most compelling argument I've seen to explain this...when Ron
mentioned that the modulation was in the Q channel, you had to know that
it wasn't coming from conventional amplitude modulation.

Here's my recording of the "WFAN hum", as received today on a
battery-powered Sony SRF-A100 receiver in wideband AM Stereo mode:

ftp://ftp.amstereoradio.com/uploads/wfan-hum.mp3

This was received in C-Quam-compatible mode, but switching to ISB
(Kahn) mode yielded no audible difference. A spectrum analysis of the
L-R component reveals it to be a 120 Hz hum with multiple harmonics
extending well above 1 kHz... so it's more of a "dirty" hum, akin to
that of an audio device with inadequate filtering of its DC power
supply.

I HAVE A HUM??
BERNIE....................................

Ruud Poeze wrote:

Ron Hardin schreef:

Tim Brown wrote:

In article ,
Ron Hardin wrote:

Since Thursday morning I've been hearing 120Hz hum on WFAN (NYC) 660,
does anybody else?

The R8B hears it except with DSB synch detection, so there's some
relation between I and Q channels that cancels the hum.

If I offtune 1 kHz and use CW, the 120Hz lines move up 1 kHz.

Other stations don't have it.

On the other hand I don't hear it on WFAN on other receivers, hence
this query. But I don't get a good WFAN signal on other receivers
either. The R8B is running on DC.

10:11 PM - I'm listening to them on my R-2368 receiver and hear
absolutely no hum at all (60, 120 or 180 Hz). Your receiver has a 50 kHz
IF frequency. You sure your not getting an image in there 50 kHz away
from 660 kHz (like WOR at 710 kHz)?

Tim Brown

It's still there at 4:30am EST. It's not audible at all if you're hearing both
sidebands but obvious in quiet phone call pauses (no music, not fan noise).

Either receive it SSB, or synch detect one sideband, or offtune until the signal
almost distorts on AM, and I think you'll hear the hum.

It's some difference between the upper sideband and lower sideband that gets
modulated by hum; so if you don't hear them equally the hum starts to creep in,
and at some point becomes noticeable. (So propagation at night can make the hum
come and go if you're hearing both sidebands, by depressing one and raising the
other.)

Is there some form of stereo that produces sideband differences? WFAN is famous
for ground loops in its audio and maybe they left one plugged in to the stereo
difference channel or something.
--
Ron Hardin


On the internet, nobody knows you're a jerk.

It is more likely that the hum is provided by an electronic device
generating a signal almost on 660 kHz.
Stereo is not sideband split, and an AM TX cab never produce a different
signal in one of its sideband: except for bandwidt.
ruud

Yeah, that's what my ears tell me, too....it's not a ground loop, in my
opinion...sounds just like the buzz I get when I plug a DC-powered radio into a
battery eliminator, before the eliminator's loosely-coupled transformer-powered DC
supply's come up to full filtering. The only other thing I could think it is (which
you've pretty much eliminated when you said you see it even in the midst of a power
failure (I assume that was in August?) is that I've seen it where the AC line can get
intermodulated somehow with a station, which is localized around only one station or
so. Even that, however, is amplitude modulation, so it's doublenixed as a possible
explanation.
--
For direct replies, take out the contents between the hyphens. -Really!-


"WBRW" wrote in message
om...
That's the most compelling argument I've seen to explain this...when Ron
mentioned that the modulation was in the Q channel, you had to know that
it wasn't coming from conventional amplitude modulation.

Here's my recording of the "WFAN hum", as received today on a
battery-powered Sony SRF-A100 receiver in wideband AM Stereo mode:

ftp://ftp.amstereoradio.com/uploads/wfan-hum.mp3

This was received in C-Quam-compatible mode, but switching to ISB
(Kahn) mode yielded no audible difference. A spectrum analysis of the
L-R component reveals it to be a 120 Hz hum with multiple harmonics
extending well above 1 kHz... so it's more of a "dirty" hum, akin to
that of an audio device with inadequate filtering of its DC power
supply.