FM radio puzzler
 

I'm in Mountain View, CA and trying to find station KSFH-FM, which is an
FCC-licensed Class "D" station. It is owner by a local school, and when I call
them they say they're on the air with programming. I am 1 mile from the campus
and can SEE the antenna. I tune to every channel from 88.1 to 107.9 MHz.
Nothing, except, of course, the other stations normally heard. I also try
holding my antenna sideway, vertical, every which way.
I call the FCC office in San Francisco and they say yes they're a legal
station, and they should reach at least 3 miles, so try again. Again nothing.
What is going on?

I think you should drive right up to the station, tune in on your car
radio, then drive home and see where and why the signal disappears. I
suspect your radio is being captured by a strong adjacent channel
transmitter.

Norm Lehfeldt

(Radioman390) wrotf:

I'm in Mountain View, CA and trying to find station KSFH-FM, which is an
FCC-licensed Class "D" station. It is owner by a local school, and when I call
them they say they're on the air with programming. I am 1 mile from the campus
and can SEE the antenna. I tune to every channel from 88.1 to 107.9 MHz.
Nothing, except, of course, the other stations normally heard. I also try
holding my antenna sideway, vertical, every which way.
I call the FCC office in San Francisco and they say yes they're a legal
station, and they should reach at least 3 miles, so try again. Again nothing.
What is going on?

Try URL:
http://www.radio-locator.com/cgi-bin/home

For Station Call Sign -- Type in KSFH

Sez they are at 87.9 MHz

KSFH-FM 87.9 MHz
Saint Francis High School
Mountain View, California
"Music Revolution"
Station Status Licensed Class D Non-Commercial FM Station
Area of Coverage View Coverage Map
Effective Radiated Power 10 Watts
Height above Avg. Terrain -75 meters (-245 feet)
Height above Ground Level 27 meters (89 feet)
Height above Sea Level 74 meters (243 feet)
Antenna Pattern Non-Directional
Transmitter Location 37° 22' 08" N, 122° 05' 02" W
License Granted October 09 2001
License Expires December 01 2005
Last FCC Update October 09 2001

Perhaps the map will help

--
Keyboard In The Wilderness


"Radioman390" wrote in message
...
I'm in Mountain View, CA and trying to find station KSFH-FM, which is an
FCC-licensed Class "D" station. It is owner by a local school, and when I
call
them they say they're on the air with programming. I am 1 mile from the
campus
and can SEE the antenna. I tune to every channel from 88.1 to 107.9 MHz.
Nothing, except, of course, the other stations normally heard. I also try
holding my antenna sideway, vertical, every which way.
I call the FCC office in San Francisco and they say yes they're a legal
station, and they should reach at least 3 miles, so try again. Again
nothing.
What is going on?

Also note the unusual frequency which is expalined at URL:
http://www.nationmaster.com/encyclopedia/FM-radio

Sez

FM radio channel assignments in the US
In the United States, frequency-modulated broadcasting stations operate in a
frequency band extending from 87.8 MHz to 108.0 MHz, for a total of 20.2
MHz. It is divided into 100 channels, each 0.2 MHz wide, designated "channel
200" through "channel 300." To receive a station, an FM receiver is tuned to
the center frequency of the station's channel. The lowest channel, channel
200, extends from 87.8 MHz to 88.0 MHz; thus its center frequency is 87.9
MHz. Channel 201 has a center frequency of 88.1 MHz, and so on, up to
channel 300, which extends from 107.8 to 108.0 MHz and has a center
frequency of 107.9 MHz.

--
Keyboard to you


"Keyboard In The Wilderness" wrote in message
news:xMI7d.41051$aW5.15438@fed1read07...
Try URL:
http://www.radio-locator.com/cgi-bin/home

For Station Call Sign -- Type in KSFH

Sez they are at 87.9 MHz

KSFH-FM 87.9 MHz
Saint Francis High School
Mountain View, California
"Music Revolution"
Station Status Licensed Class D Non-Commercial FM Station
Area of Coverage View Coverage Map
Effective Radiated Power 10 Watts
Height above Avg. Terrain -75 meters (-245 feet)
Height above Ground Level 27 meters (89 feet)
Height above Sea Level 74 meters (243 feet)
Antenna Pattern Non-Directional
Transmitter Location 37° 22' 08" N, 122° 05' 02" W
License Granted October 09 2001
License Expires December 01 2005
Last FCC Update October 09 2001

Perhaps the map will help

--
Keyboard In The Wilderness


"Radioman390" wrote in message
...
I'm in Mountain View, CA and trying to find station KSFH-FM, which is an
FCC-licensed Class "D" station. It is owner by a local school, and when
I
call
them they say they're on the air with programming. I am 1 mile from the
campus
and can SEE the antenna. I tune to every channel from 88.1 to 107.9 MHz.
Nothing, except, of course, the other stations normally heard. I also
try
holding my antenna sideway, vertical, every which way.
I call the FCC office in San Francisco and they say yes they're a legal
station, and they should reach at least 3 miles, so try again. Again
nothing.
What is going on?

Well, it was a trick question, but you got it right.

There was a potential second answer (maybe more) which has to do with the
phrasing I used which said I was one mile from the campus, and could see the
antenna. Well, maybe the antenna was far away (on a mountain top) and I was
out-of-range of the signal.

But my thinking in posing the mind-twister was that I didn't know the FCC had
actually granted three licenses for 87.9 (two translators and KSHR), and only
noticed while doing a search of the FCC database.

www.fcc.gov/mb
on the left side is a box marked "shortcuts"; scroll down to "FM query", and
then click on "start shortcut"

Ah OK a trick question no less

Turn about is fair play -- (but not too tricky)

On an AM radio -- one hears a station broadcasting on the tuned
frequency -- but also another station is heard that is broadcating on an
entirely different frequency !!!

Ignoring a strong adjacent channel station -- how is this possible ???

--
Keyboard mired in the political rants here (;-)


"Radioman390" wrote in message
...
Well, it was a trick question, but you got it right.

There was a potential second answer (maybe more) which has to do with the
phrasing I used which said I was one mile from the campus, and could see
the
antenna. Well, maybe the antenna was far away (on a mountain top) and I
was
out-of-range of the signal.

But my thinking in posing the mind-twister was that I didn't know the FCC
had
actually granted three licenses for 87.9 (two translators and KSHR), and
only
noticed while doing a search of the FCC database.

www.fcc.gov/mb
on the left side is a box marked "shortcuts"; scroll down to "FM query",
and
then click on "start shortcut"

Keyboard In The Wilderness schreef:

Ah OK a trick question no less

Turn about is fair play -- (but not too tricky)

On an AM radio -- one hears a station broadcasting on the tuned
frequency -- but also another station is heard that is broadcating on an
entirely different frequency !!!

Ignoring a strong adjacent channel station -- how is this possible ???

It is called mirror frequency interference.

When you receive say 540, your local oscilator produces 540 + 450 = 990
kHz. In the mixer 540 and 990 produces 990-540 = 450 (and 540+990, this
is almost fully rjected)
But suppose there is a strong signal on 1440 that is also coming into
your mixer you will find that this also produces the IF of 450 kHz,
since 1440 - 990 = 450.
So now you will hear the 540 and 1530 station; only good radio's have
proper antenna filters to reject the 1530 signal.


BTW: do US digitally controlled receivers have 87.9 ?
ruud

But

--
Keyboard mired in the political rants here (;-)

"Radioman390" wrote in message
...
Well, it was a trick question, but you got it right.

There was a potential second answer (maybe more) which has to do with the
phrasing I used which said I was one mile from the campus, and could see
the
antenna. Well, maybe the antenna was far away (on a mountain top) and I
was
out-of-range of the signal.

But my thinking in posing the mind-twister was that I didn't know the FCC
had
actually granted three licenses for 87.9 (two translators and KSHR), and
only
noticed while doing a search of the FCC database.

www.fcc.gov/mb
on the left side is a box marked "shortcuts"; scroll down to "FM query",
and
then click on "start shortcut"

Very good -- correct
Now try the other radio puzzlers.

--
Keyboard to you


"Ruud Poeze" wrote in message
...
Keyboard In The Wilderness schreef:

Ah OK a trick question no less

Turn about is fair play -- (but not too tricky)

On an AM radio -- one hears a station broadcasting on the tuned
frequency -- but also another station is heard that is broadcating on an
entirely different frequency !!!

Ignoring a strong adjacent channel station -- how is this possible ???

It is called mirror frequency interference.

When you receive say 540, your local oscilator produces 540 + 450 = 990
kHz. In the mixer 540 and 990 produces 990-540 = 450 (and 540+990, this
is almost fully rjected)
But suppose there is a strong signal on 1440 that is also coming into
your mixer you will find that this also produces the IF of 450 kHz,
since 1440 - 990 = 450.
So now you will hear the 540 and 1530 station; only good radio's have
proper antenna filters to reject the 1530 signal.


BTW: do US digitally controlled receivers have 87.9 ?
ruud

But

--
Keyboard mired in the political rants here (;-)

"Radioman390" wrote in message
...
Well, it was a trick question, but you got it right.

There was a potential second answer (maybe more) which has to do with
the
phrasing I used which said I was one mile from the campus, and could
see
the
antenna. Well, maybe the antenna was far away (on a mountain top) and
I
was
out-of-range of the signal.

But my thinking in posing the mind-twister was that I didn't know the
FCC
had
actually granted three licenses for 87.9 (two translators and KSHR),
and
only
noticed while doing a search of the FCC database.

www.fcc.gov/mb
on the left side is a box marked "shortcuts"; scroll down to "FM
query",
and
then click on "start shortcut"

Radio man asked if some digital FM radios cover 87.9 Mhz
Yep My Phillips boombox does


--
Keyboard to you


"Radioman390" wrote in message
...
Well, it was a trick question, but you got it right.

There was a potential second answer (maybe more) which has to do with the
phrasing I used which said I was one mile from the campus, and could see
the
antenna. Well, maybe the antenna was far away (on a mountain top) and I
was
out-of-range of the signal.

But my thinking in posing the mind-twister was that I didn't know the FCC
had
actually granted three licenses for 87.9 (two translators and KSHR), and
only
noticed while doing a search of the FCC database.

www.fcc.gov/mb
on the left side is a box marked "shortcuts"; scroll down to "FM query",
and
then click on "start shortcut"

On 03 Oct 2004 01:29:58 GMT, (Radioman390) wrote:

I'm in Mountain View, CA and trying to find station KSFH-FM, which is an
FCC-licensed Class "D" station. It is owner by a local school, and when I call
them they say they're on the air with programming. I am 1 mile from the campus
and can SEE the antenna. I tune to every channel from 88.1 to 107.9 MHz.

Their website http://www.ksfh.com says they-re on 87.9 FM.
What I get on that frequency, from farther up the peninsula, doesn't
sound like what I'd expect from a high school site. It also says they
have a live internet feed, whicg should make it easy to match up what
you're hearing ion the radio, but it's offline at the moment.

From (googled KSFH):
http://www.mv-voice.com/morgue/2001/2001_11_02.radio.html
"We can broadcast from and to anywhere with a phone line," he said.
Covering 90 percent of the South Bay region, KSFH 87.9 FM currently
operates at 10 watts giving them approximately a 15-mile transmission
radius from their campus. According to their Web site, in comparison,
most major commercial radio stations operate at about 5,000 watts.


That's a couple years old, but would explain why I don't hear
it.
Nothing, except, of course, the other stations normally heard. I also try
holding my antenna sideway, vertical, every which way.
I call the FCC office in San Francisco and they say yes they're a legal
station, and they should reach at least 3 miles, so try again. Again nothing.
What is going on?