STARMAN,

"I've also noticed that the noise level is much higher when I
partially remove the antenna coax connector on the back of the
receiver, so that only the center pin is making contact."

1. With a Primary Grounding Point at the Antenna:

* If you have a separate Shack-Ground for your equipment
(radios etc) you 'may' NOT Notice this Higher Noise condition
when the 'outer-ring' of the PL-259 Plug is diconnected from the
back of the radio/tuner/switch.

* If you do NOT have a separate Shack-Ground for your
equipment (radios etc) you 'may' Notice a Higher Noise condition
when the 'outer-ring' of the PL-259 Plug is diconnected from the
back of the radio/tuner/switch.

2. A Primary Grounding Point outside and away from the house
offers many advantages for Noise Reduction and Safety.

3. A Secondary Grounding Point inside the house for the equipment
offers additional advantages for Noise Reduction and Safety.

4. This informational webpage presented by "Wellbrook Communications"
* LOW NOISE ANTENNA USING
* THE UNIVERSAL MAGNETIC BALUN
* PLUS THE ANTENNA FEEDER ISOLATOR
Universal Magnetic Balun is specifically designed to reduce noise,
especially mains borne, by isolating the feeder winding of the
Balun matching transformer from the antenna.
GoTo= http://www.wellbrook.uk.com/longwire.html
Take A Look At the Diagrams On This WebPage - They Tell It All !

5. Another Look at Noise Reducing Antenna Systems
- by Mark Connelly [WA1ION]
GoTo= http://members.aol.com/WA1ION/nrants.pdf
Here again WA1ION uses a 9:1 Matching Transformer between the
Antenna Element anf the Coax Lead-in-Line and a 'second' 1:1
Matching Transformer in the Shack between the Coax Lead-in-Line
and the receiver.

6. Grounding is KEY to Good Reception
- by John Doty
http://www.hard-core-dx.com/nordicdx...d/ground2.html
http://www.hard-core-dx.com/nordicdx...und/index.html

7. Impedance Matching Transformers for Receiving Antennas
at Medium and Lower Shortwave Frequencies
- by Bill Bowers, John Bryant and Nick Hall-Patch [VE7DXR]
GoTo= http://radiodx.com/spdxr/media/imt_doc1.doc

8. The Purpose for a Balun
- by John Doty
GoTo= http://www.hard-core-dx.com/nordicdx...ed/balun3.html
"The purpose of a balun is to block common mode waves (current
flowing in the same direction on both conductors of a transmission
line) and pass differential mode waves (current flowing in opposite
directions on the conductors)."

9. The "Grounding-Point" = Ground Rods and Ground Wires ETC.
GoTo= http://groups.yahoo.com/group/SWL-AM...na/message/425


iane ~ RHF
..
All are WELCOME at the "Antenna Ashram"
GoTo= http://groups.yahoo.com/group/SWL-AM...na/message/502
..
..
= = = starman
= = = wrote in message ...
Brian Denley wrote:

starman wrote:

I haven't found this to be so in my case. The coax shield on my low
noise inverted-L is grounded only at the bottom of the antenna's
single wire downlead, which is close to the ground. The coax runs
about 75-ft along the ground to the house, then up one story to the
receiver. There is no ground on the receiver end of the coax. The
noise from home applicances is almostly completely gone now with this
antenna configuration.


Starman:
My random wire coax feedline is also only grounded at one point (the center,
oddly enough) but the fact is that for the feedline to effectively not act
as part of the antenna, the shield must me grounded at BOTH ends. Is one
point better than nothing? Sure.

Like you, I live with it because I find it difficult to implement.

I came to the conclusion that the single ground at the far end of the
coax is 'effectively' preventing the shield from being a common mode
antenna because the noise level is much lower than before I built the
low noise 'Doty-L' antenna system. Another factor is that most of the
coax is laying on the ground. This also helps to reduce common mode
reception on the shield. There's about fifteen feet of coax above the
ground going up to the receiver on the second story. I've also noticed
that the noise level is much higher when I partially remove the antenna
coax connector on the back of the receiver, so that only the center pin
is making contact.