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

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.

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

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.

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

It's a mystery. I don't think it can be that though because it happens most
when WFAN is strong, whereas a local signal would show up more at some point
in its fading. Also a series of 120 Hz lines + harmonics show up on an audio spectrum
around the carrier when it's detuned in SSB by a kHz or so.

I have the feeling that they don't use straight AM transmitters anymore; something like
SSB transmitters with carrier reinserted, fed into a broadband final. The high power part
doesn't care what feeds it. Bandwidth limiting is done at audio frequencies, for instance.

Well I can't experiment again until WFAN is again audible, sometime tonight.

I can distinguish directionally very easily (I have an 8-element MW phased array) but
have been unable to do anything but null away WFAN, winding up with weak Cuban stations
rather than a surviving hum signal.
--
Ron Hardin


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

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

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.

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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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!
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