Joerg wrote:

Michael A. Terrell wrote:
Joerg wrote:
Michael A. Terrell wrote:
Joerg wrote:
amdx wrote:
"Joerg" wrote in message
...
amdx wrote:
"Richard Clark" wrote in message
...
On Fri, 19 Mar 2010 15:22:42 -0500, "amdx" wrote:

So I installed the antenna on the outside of the boat and the radio
inside,
now one station I listen to is weak, but if I unplug the antenna and
let the
center pin touch ground of the connector on the radio it comes in
great.
Just curious why it is working this way.
Hi Mike,

You moved the antenna.

Most loss of signal as you describe comes from not being a weak
signal, but the mixture of signals that combine negatively at some
spot due to multiple reflections. When you replaced the line cord as
antenna for this better implementation, you also found that "sour (not
sweet) spot." This can occur for any frequency with the equal
likelihood of reflections combining negatively. Move your antenna a
quarter wave and see what happens.

Your description of your having an aluminum boat almost guarantees a
multitude of RF-bright reflections. At short wavelengths, this also
guarantees many, many regions that will exhibit destructive (as well
as constructive) combinations of those reflections.

Put your antenna as far away from the superstructure or hull as
possible. This will reduce the reflection path differences.

BTW, the mod did cure the computer hash.
Mike
FM has what is called a "full quieting" effect. It would suggest that
your first signal levels were just barely above the level of full
quiet (and perhaps not even that good).

73's
Richard Clark, KB7QHC
Richard, after I read your letter I did a little better checking and
found
my signal is not weak it is to strong, I'm getting interference from
other frequencies.
Also I get stations on the wrong frequency.
I went out and collapsed the antenna to minimum about 1/3 of what it
was and
my problem station is perfect and the other station I listen to is still
good. The local
NPR station isn't good though. But I can download the podcast of Science
Friday :-)
Thanks, Mike
The usual, lousy FM tuner. They don't make'em like they used to. It's the
same with television sets, one large signal and they fall off the rocker.

If you have a radio with a signal strength meter you could notch out a
strong station. But that only works it it's just one and far away from the
NPR frequency. The only other options are to get a better radio, a
directional antenna, or just live with it and use the podcast.

--
Regards, Joerg
This morning I got on the boat and the signal that was improved to good by
shortening the antenna is now bad. 94.5 has interference from 101.1.
Oh well!
You really need a better quality radio and with radios and a lot of
other stuff older = better :-)

I mean, considering what the boat must have cost ...

Or a tuned trap to reduce the signal from that one station.

Well, that's what I suggested above, notch = trap :-)

But it's tough and can be impossible if there are useful weaker stations
near the one you want to muffle. In Europe they had a pager service
right at the lower end of the FM band. Whichever committee signed off on
that one should be dunked into a moat for gross incompetence, until they
either learn or quit their career. Anyhow, the inevitable happened, and
despite being a school kid I predicted that: A barrage of complaints by
FM listeners. In Germany they pay a radio tax so that makes them sort of
constituents with rights. Long story short the governement had to
furnish rather expensive notch filters to anyone who complained.


So you move the trap slightly to one side. A good trap can be narrow
enough to only affect one or two channels if it is built with the right
components, but it isn't cheap. ...
^^^^^^^^^^^^^^^^^^

Bingo!

... Glass piston capacitors and glass
inductors are temperature stable and have a very high 'Q'.


I just hope someone was read the riot act for making that frequency
allocation. I mean, that allocation was really borderline daft ;-)


You think that's bad? Some idiot sold two way radios to a school
system, and put them on a frequency reserved for ambulance service.
Every time the base tried to contact one of their ambulances, the damn
school bus drivers would start yelling at them to 'Get off OUR
channel". The so called frequency coordinator for the area refused to
do anything about his screw up for allowing them to be licensed on that
frequency.


--
Lead free solder is Belgium's version of 'Hold my beer and watch this!'