|
Grex > Music2 > #182: Too much 'Kool 107' driving you nuts, too? Vent here. |  |
|
| Author |
Message |
other
|
|
Too much 'Kool 107' driving you nuts, too? Vent here.
| 
Feb 23 02:59 UTC 1999 |
I have reached a point of extreme frustration with the inability to receive
a clear signal from any radio station except 102.9 WIQB and 107.1 WQKL without
extensive manipulation and modification of the antenna of my bookshelf style
stereo unit.
I would like to lodge a formal complaint with the FCC, but I would like to
know how widespread this problem is first.
I live on South First, in central Ann Arbor, and I cannot listen to stations
on frequencies 88.7, 91.7, 93.9, 94.7, 95.5, 96.3, etc. due to interference
from the signal broadcast at 107.1. I live in a second floor apartment (i.e.
above ground).
As a side note, does anyone know of a simple and/or effective way to filter
out the signal on the 107.1 carrier? This is driving me bonkers.
|
| 37 responses total. |
steve
|
|
response 1 of 37:
|
Feb 23 03:11 UTC 1999 |
You could get what it called a notch filter, which dampens the signal
at 107.100 MHz but lets other frequencies through. It will dampen stations
right around there, too to 107.3 and 106.9 (if there are any there) are
likely to be washed out too.
However, that may not work at all for you. I believe the transmitter
is located ontop of Tower Plazza, and if so, you may be right in the
"lobe" of the transmitted signal, and your little radio may simply be
overloaded with signal, such that the 107.1 RF is strong enough to crawl
right into your radio.
Welcome to urban RF problems. *sigh*
Have you tried other radios?
|
senna
|
|
response 2 of 37:
|
Feb 23 03:21 UTC 1999 |
On the brief occasions I've been driving near your apartment, I've
gotten radio signals fine, Eric. My radio receiver at home, which is
connected to the large stereo system (we don't use it much) gets lousy
reception too. Except, we dont' have too many houses around.
|
hhsrat
|
|
response 3 of 37:
|
Feb 23 03:47 UTC 1999 |
ironic isn't it that 107.1 WQKL and 102.9 WIQB are both owned by the
same company (as is 1050 am WTKA)
|
n8nxf
|
|
response 4 of 37:
|
Feb 23 11:39 UTC 1999 |
I suspect that the problem may be with your receiver. Try something with
a decent front end like a GE Super Radio or Cambridge Soundworks Model 88.
I'm sure there are many others but I also know there are several radios
with very poorly designed tuners that are very very susceptible to RFI
and can barely tune a station in the best of conditions.
|
scott
|
|
response 5 of 37:
|
Feb 23 12:13 UTC 1999 |
... have a friend drop by with their radio before you buy, of course...
|
steve
|
|
response 6 of 37:
|
Feb 23 12:51 UTC 1999 |
What Klaus says is right. Most radios being sold are not very
well designed. The "front end" of a radio is that part which should
be able to differenciate signals. Unforunately, most don't do such
a good job.
|
danr
|
|
response 7 of 37:
|
Feb 23 13:20 UTC 1999 |
Have you contacted the stations? They may be able to help you. They would
certainly want to do that before fielding a complaint from the FCC.
|
bruin
|
|
response 8 of 37:
|
Feb 23 13:45 UTC 1999 |
I remember, when I lived on Ellsworth Road across from the "Old Meijer" store,
picking up WAAM (AM 1600) on my telephone/answering machine. Fortunately,
someone from Ameritech (them Michigan Bell--An Ameritech Company) placed a
filter on the line so I could not pick up any radio signals.
|
other
|
|
response 9 of 37:
|
Feb 23 19:08 UTC 1999 |
I phoned WUOM to ask if they had received any comments about it, and I was
put in touch with the chief engineer, whom I know through another
connection, and he suggested a filter of the type described above. I have
a JVC portable unit. I am not considering buying another radio. Here is
what the WUOM engineer had to say:
Regarding your call from this morning in which you stated that WUOM is wiped
out by WQKL on your radio:
It sounds like your experienceing "blanketing interference", which is what
can happen when a strong signal such as from a nearby transmitter
overpowers your receiver.
Though we have never been happy with the idea of WQKL (formerly WAMX)
having their transmitting antenna operating from the top of Tower Plaza, I
don't have any reason to think that they are operating outside of their
legal parameters.
Here's what the FCC Interference Handbook has to say about blanketing:
The second problem is called "blanketing." It occurs when electrical
or electronic devices are very close to the transmitter and where
the FM signal is very strong. Operators of new FM stations are
required to respond to all reasonable interference complaints in the
immediate vicinity of the station. If the station is more than a
year old or you live outside of the protected area, installation of
an FM broadcast band rejection filter at your TV and/or stereo
receiver antenna input leads, as well as use of a highly directional
antenna may reduce your problem. You may also wish to reposition the
location of your equipment to attempt to minimize or eliminate the
problem(s).
See
http://www.fcc.gov/Bureaus/Compliance/WWW/tvibook.html
for more about interference.
Because WQKL has been broadcasting from Tower Plaza for more than a year
they are no longer under any obligation to take care of listener complaints.
However they may wish to do so, if you give them a call.
What kind of radio do you have? Is there an external antenna? If so the
best bet is probably to install a tunable filter to reduce the strength of
the WQKL signal. Otherwise, if you have a
built-in telescoping whip antenna it might improve matters to shorten it.
|
janc
|
|
response 10 of 37:
|
Feb 23 19:22 UTC 1999 |
While I was living in College Station, and was desparate to get anything
other than the local boring radio stations, I bought an "antenna
amplifier" thing for my stereo. It plugs into the wall and has a little
knob you can twiddle to improve the reception of any particular station.
Moving it around sometimes helps too. I'm not completely convinced that
this thing is doing anything wonderful, and have no idea if such a
device would help Eric, but thought I would mention it.
|
other
|
|
response 11 of 37:
|
Feb 23 19:26 UTC 1999 |
i've seen versions of such an item in catalogs, usually a knob that fits in
the end of an antenna to boost signal reception indiscriminately.
|
steve
|
|
response 12 of 37:
|
Feb 23 19:36 UTC 1999 |
Most likely a preamp is *not* what you want in this situation. The
problem here is simply too much RF that is invading the front end of
the radio.
|
polygon
|
|
response 13 of 37:
|
Feb 23 21:00 UTC 1999 |
When I lived in the Flowerpot neighborhood in East Lansing, I could hear
WKAR-AM very clearly on my telephone. Eventually, I called up WKAR to let
them know about it, and they were effusively grateful that I had called.
Nevertheless, they were no help.
They told me that I should get rid of my cheap phone and get an AT&T phone
-- this was in the days when the pre-breakup phones were so much heavier
and better made than the flimsy ones available in stores).
I said: "This *is* an AT&T phone."
That silenced them, and they had nothing else to say.
|
scg
|
|
response 14 of 37:
|
Feb 24 00:10 UTC 1999 |
I haven't had this problem on my radio. I have found WQKL leaking through
on my TV on various channels. I like in a rather different part of town from
Eric, and when I've had that problem lately I've usually been able to turn
the antenna a bit and make it go away. A year ago, living in yet another
different part of town, I used to find WQKL coming in strongly enough on my
TV when I was watching channel 67 that it was hard to hear the sound from
channel 67 over it, and there didn't seem to be a way to make it go away.
That was really annoying.
|
johnnie
|
|
response 15 of 37:
|
Feb 24 00:42 UTC 1999 |
Perhaps a better way to go would be to call up a competing radio
station (one you'd like to listen to) and say "I love your station,
but the signal is pushed out by that darn oldies station. Any
suggestions?". That is, try to get info/help from someone who has
something to gain, rather than ask for help from someone who only
stands to lose.
|
russ
|
|
response 16 of 37:
|
Feb 24 04:31 UTC 1999 |
So THAT'S why both of my last 2 cars had trouble keeping WDET in tune
when driving downtown. The only other place I had anything like that
happen was on I-696 around Greenfield, in the tower forest.
This is a fairly common problem. An excessive signal going into
the receiver front end will force it into a non-linear region of
operation. This causes what is called "intermodulation distortion",
where different signals mix together. Generally, it means that
anything but the strongest signal is probably screwed up.
A notch filter isn't a bad idea, but there's another route to try:
an attenuator. Sometimes knocking all the signals down a ways will
get the receiver back into the linear operating region, and the
remaining signal at the desired frequency is still strong enough to
come in clearly. That's all you care about anyway. Lowering the
antenna, or pointing it directly toward or away from the source
of the blanketing signal, is another cheap technique. Problem is,
reflected signals get you from all angles.
A notch filter isn't that hard to make. There are two kinds of
notch filter, parallel-resonant and series-resonant. A parallel-resonant
filter looks like an open circuit at the notch frequency, and it's put
in series with the signal lead. A series-resonant filter looks like
a short circuit at the notch frequency, and it's put between the signal
lead and ground. You can probably fit a notch filter inside your JVC
box without much hassle. It is amazing how much empty space there is
inside radios.
The impedance of your whip antenna is probably 30 ohms or less, so
anything above about 10 ohms between the antenna and ground, or less
than 100 ohms in series, probably won't be very noticable. For a
series resonant trap, you might try something like a 1-5 pF trimmer
capacitor in series with a small coil, connected between the antenna
and ground. At 107.1 MHz, a 3 pF cap has an impedance of about 500
ohms. Put it in series with an inductor of about 1 microhenry and
you should be able to tune it onto the offender pretty easily. You
connect this between the antenna connection (inside your radio) and
the ground plane nearby on the circuit board. You tune it to 107.1
MHz, and the impedance of the capacitor and inductor are equal and
(in the ideal case) opposite; they cancel, making a short. At 106 MHz,
the impedance of the capacitor has increased by about 5 ohms, and the
impedance of the inductor has gone about 5 ohms in the opposite
direction. This gives you about 10 ohms from antenna to ground
instead of a dead short, and your signals should start coming in.
STeve, you've probably got ARRL handbooks handier than I do right now;
how many turns of 16 gauge wire at 1/4" diameter do you need to get
something between 0.7 and 1 microhenry? Does Rat Shack sell trimmers?
|
omni
|
|
response 17 of 37:
|
Feb 24 05:31 UTC 1999 |
They should sell trimmer pots.
|
other
|
|
response 18 of 37:
|
Feb 24 06:13 UTC 1999 |
i believe i've seen trimmer pots there. i'm not sure i'm sufficiently skilled
at electronics to translate the above into a solution, although i do
understand most of the language. what i'm lacking is the solid understanding
of the theory behind the list of components...
...and the time to do this...
|
flem
|
|
response 19 of 37:
|
Feb 24 06:20 UTC 1999 |
I love it when people talk about technology that I don't understand. It
sounds both profound and focused at the same time...
Don't mind me, I need to go to sleep.
|
danr
|
|
response 20 of 37:
|
Feb 24 13:27 UTC 1999 |
I like the idea of trying an attenuator before attempting to build a filter.
There much simpler, consisting of a couple of resistors. What kind of antenna
are you using, Eric?
|
krj
|
|
response 21 of 37:
|
Feb 24 14:19 UTC 1999 |
(( Winter Agora #182 <---> Music #182 ))
|
mcnally
|
|
response 22 of 37:
|
Feb 24 16:10 UTC 1999 |
What, waiting to time it just right so the item numbers match up?
|
krj
|
|
response 23 of 37:
|
Feb 24 20:20 UTC 1999 |
No, I messed up, the winter Agora number is wrong, sorry.
|
russ
|
|
response 24 of 37:
|
Feb 25 03:53 UTC 1999 |
Re #17: A tripper POT isn't useful for making a tuned circuit. You
need a trimmer capacitor, which is a rather different beast.
Re #18: You may not be, but the hams in this bunch probably are.
I can usually get things to work halfway if not better. If you're
willing to risk working on your radio, someone will probably volunteer
to calculate the numbers and do the soldering. I've already got some
numbers above. This doesn't require much theory, it's strictly cookbook.
You probably need one capacitor, some wire formed around a bolt,
some solder to connect it and a bit of hot glue to hold everything
down. Cost should be a buck or so. Time I can't help you with.
Re #20: A 20 dB attenuator should be easy. I'd try a 270 ohm resistor
between the antenna and the radio's (internal) antenna connection, and
a 27 ohm resistor from the antenna connection to ground. Both ought
to be off-the-shelf at Rat Shack.
Something that might be useful for experimentation: put the antenna
down, and try placing a sheet of something metallic (a cookie sheet or
aluminum foil) close to the radio to shield it. If you can get the
interference to go away while you still have the desired signal strong
enough to listen, an attenuator may be workable. If not, you need
something that's frequency-selective. That means a notch filter.
|