"Harris" wrote in
. net:

Thanks very much for the lengthy response. I see that I have much to
learn about scanners and antennas.

Regards.

How are you determining what the signal strengths are? (I'm talking
about actual rf signal levels at the input to the scanner, NOT what
you're seeing on an "S" meter or hearing from the speaker.)

If your outdoor antenna were delivering more signal strenghth to your
scanner, your intermod would get worse, not better.

As I tried to explain, when the scanner is subjected to STRONG local
(unwanted) signals, the scanner will be de-sensitized. This will make
it difficult to hear weaker signals. If attenuation is placed between
the antenna and scanner, this "de-sensitization" effect will be
reduced, and weak signals will actually appear stronger. In other
words, less signal strength may actually improve reception in your
case.

Often folks try using pre-amps to improve reception, only to find that
the preamp degrades reception (especially with handhelds). This is
similar to what I described above. Sometimes, less is more!

There you go. Adding attenuation improved your reception. I'm
speculating that the attenuation (loss) in your feedline is having the
same effect.

RG-6 is much better than RG-58. However, 85 feet is a pretty long run.
All coax cables have higher loss as you go higher in frequency. If
your overload/intermod problems are indeed caused by nearby cell
sites, those 800 MHz signals will be attenuated more than signals at
lower frequencies. And your outdoor antenna is probably less effective
at 800 Mhz than at lower frequencies. So your antenna and feedline are
acting like a "low-pass" filter in that they attenuate the higher
frequencies. All of that is consistent with what you are hearing.


Art N2AH

Soliloquy . ..

^ |
^ \|/
^ +
^ /|\
^ |
^
^ My onmi-directional antenna looks like the above ...

^ If I were to attempt to place a reflector on this antenna,
^ it would, I trust, be electrically connected to the center
^ radials but insulated from the brackets? How would I
^ determine the size and spacing?

My comments were in response to your query on directionality and they are
probably not useful in your system. I am not an antenna expert, only an
amateur experimenter, and I have not seen any documentation on reflectors and
directors on anything except half-wave dipoles. Although, as I move around
town and examine TV antennas it appears to me that they are making some sort
of use of reflectors, directors, or both.

But the function of reflectors and directors, on the receive side, is to
increase the amount of the desired frequency reaching the antenna. They may
not be very useful if the intent is to scan a wide range of frequencies.

N2AH appears to have your answer.

Frank