FM radio interference from planes

What did I say that was wrong [other than the typo you
should have been your]. The comment about FCC rules...they
do frown on transmitting or retransmitting the wrong
signals.

BTW, back in the 1974 period I gave a student a night dual
x-c from Tulsa to OKC and back one night. We picked up
several TV stations on the old AM radios in the C150 we were
flying. So bad radios, that do not have properly working
filters and signal rejection can do strange things.

We also had fun with CB radios in our cars back in the late
60's, parking outside a church or at the drive-in movie and
being able to have our comments come over the PA system.
Poor shielding let our 5 W CB radio get into their amp.

Some times you give criticism that isn't helpful. In my old
age, I do make misteaks [mistakes] and often brake rules
[break] because I sometimes remember the wrong bit of
information. And sometimes I'm right [correct] by accident.
mine..."| "Jim Macklin"
wrote in message
| news:AVTtg.67782$ZW3.26133@dukeread04...
| 104.1 FM is below the aircraft navigation and below the
| communication assigned frequencies. But there are
harmonic
| signals that you[r] cheap FM transmitter is not
screening out.
| Are you using a wired connection from the PC to the FM
| transmitter or a WiFi or other radio? Most likely
you're
| getting the interference in that way.
|
| You may be in violation of FCC rules.
|


--
The people think the Constitution protects their rights;
But government sees it as an obstacle to be overcome.
some support
http://www.usdoj.gov/olc/secondamendment2.htm
See http://www.fija.org/ more about your rights and duties.


"RST Engineering" wrote in message
...
| Macklin, I like you, you are a nice guy. But sometimes
you give advice that
| is way the hell out of your depth. Like this one.
|
|
|
| "Jim Macklin" wrote
in message
| news:AVTtg.67782$ZW3.26133@dukeread04...
| 104.1 FM is below the aircraft navigation and below the
| communication assigned frequencies. But there are
harmonic
| signals that you cheap FM transmitter is not screening
out.
| Are you using a wired connection from the PC to the FM
| transmitter or a WiFi or other radio? Most likely
you're
| getting the interference in that way.
|
| You may be in violation of FCC rules.
|
| Probably not, with a store-boughten transmitter. And
harmonics (which are
| integral multiples of a fundamental signal) probably have
little to do with
| it.
|
| Consider the most probable cause. An FM receiver at 104.1
has a local
| oscillator at 114.8 MHz to produce an IF of 10.7 MHz. Not
only will that
| beat with 104.1 on the low side of the LO, it will beat
with 125.5 on the
| high side. Most FM receivers have at least a +/- 50 kHz.
wide IF strip to
| allow the stereo subcarrier at 38 kHz. to come through, so
125.45, 125.5,
| and 125.55 will come through as well.
|
| The OP said that he doesn't get any interference when his
transmitter is
| off, so my best place to start looking is the front end of
the receiver,
| where the normal filtering of any decent FM receiver
should take care of the
| "image" problem. However, when a very strong signal (like
from a 100 mW
| legal transmitter) comes blowing into the front end of the
receiver from a
| few feet away, crossmod and intermod are NOT your friend,
and no designer in
| this world can make a brick wall filter that will take
care of it.
|
| Having said all that, the real problem is to keep whatever
small amount of
| aircraft band com energy is present at the front end from
getting into the
| receiver.
|
| And, before we start off on a wild goose chase, I'd advise
the OP to get a
| small handheld aircraft band transceiver or scanner and
see if the real
| transmitter is somewhere around 125.5 MHz.. It is always
good to be able to
| do a math calculation to see exactly what is getting into
what before
| spending a lot of time chasing your tail.
|
| For those who say "you can't hear AM on an FM receiver", I
say
| horsefeathers. It may be reduced in volume, it may be
distorted, but it
| will get through.
|
| Do the test, tell me what frequency from 118-136.975 MHz.
the aircraft is
| on, and we'll go from there.
|
| Jim
|
|

"Jim Macklin" wrote in message
news:CSVtg.68473$ZW3.64903@dukeread04...
What did I say that was wrong [other than the typo you
should have been your]. The comment about FCC rules...they
do frown on transmitting or retransmitting the wrong
signals.
*snip*
| Jim
|
|



He isn't transmitting anything on the wrong freq, he is receiving signals
that are originating from a freq outside the supposed range of the FM system
he bought.

That system he is using is undoubtedly a 'PART 15' device, with a label or
literature reading:

"This device complies with part 15 of the FCC Rules. Operation is subject
to the following two conditions: (1) This device may not cause harmful
interference, and (2) this device must accept any lnterference re-
ceived, including interference that may cause undesired operation."

So he can either live with it, find a HAM to build a filter, or take it back
and get something else.

"Jim Macklin" wrote in message
news:CSVtg.68473$ZW3.64903@dukeread04...
What did I say that was wrong [other than the typo you
should have been your]. The comment about FCC rules...they
do frown on transmitting or retransmitting the wrong
signals.

Forget it, Jim; the other Jim is exercising his depleted ego again.


"RST Engineering" wrote in message
...
| Macklin, I like you, you are a nice guy. But sometimes
you give advice that
| is way the hell out of your depth. Like this one.
|
|