Inverted-L Antenna And Close Proximity Coax ?
 

Hello:

Planning on putting up an outside Inverted-L antenna.
Listening only.

Looks like I will be stringing the vertical section along the
house side (an inch or two off of the wood on some kind of standoffs) to the
top, where it
will begin the horiz. section to a nearby tree.

At the bottom of the vertical section, a foot or so off of the ground, I
plan on burying a long length of copper
tubing for a ground, and probably an ICE lightning protector (to the same
ground point).

A Balun and a start of the coax run to the receiver also starts at this
bottom point.

Question:
The easiest way by far for me to get the coax to the receiver is to run it
up from the Balun to my second floor where the receiver is.

If I run it upwards "right alongside" (or even tied to) the active vertical
section of the antenna, will I have any problems ?
Remember, this would be coax, and I do receiving only.

Guess I'm worried about if the grounded shield of the coax presents some
kind of ground element right next to the active element ?

Thanks,
Bob

Inverted-L Antenna And Close Proximity Coax ?
 

On Wed, 11 Jan 2006 07:40:52 -0500, "Robert11"
wrote:
The easiest way by far for me to get the coax to the receiver is to run it
up from the Balun to my second floor where the receiver is.

If I run it upwards "right alongside" (or even tied to) the active vertical
section of the antenna, will I have any problems ?
Remember, this would be coax, and I do receiving only.

Guess I'm worried about if the grounded shield of the coax presents some
kind of ground element right next to the active element ?

Hi Bob,

There is no inherent advantage in the inverted L except it being a top
loaded vertical with some horizontal polarization properties (being
unbalanced and all). You can save yourself some bewilderment by
driving the bottom directly into ground and simply connecting your
coax right at your second floor window with the coax shield connecting
to the wire going down, and the coax center to the wire going up and
to the tree. When lightning suggests itself, unconnect the coax from
your receiver and drop the coax out the window.

You will never notice the proximity of the wood siding, but you may
notice the proximity of house wiring that is in that wall. That
wiring may be carrying house noise (like a computer's monitor's hash).
However, that is best left for future investigation instead of
paralyzing you now.

Also, build an antenna tuner, or buy a very cheap, no-meter 3-knob Ham
tuner (less than $30). When you get into better antennas, you get
into overdrive possibilities from nearby AM stations (and I bet there
are a bajillion there in Mass). This is called "desensing" when those
stations (even when you are not tuned to them) overpower your radio
and drive the AGC so high, that you cannot hear weaker DX in the SW
bands.

73's
Richard Clark, KB7QHC

From OP: Ratio For Legs ? Inverted-L Antenna And Close Proximity Coax ?
 

Hi,

Much thanks for info.

BTW: For general shortwave listening, is there a generally accepted
"optimum" for the length ratio between the horiz
and vert. legs ? Is the ratio freq. dependent ?

Thanks,
Bob

---------------
"Richard Clark" wrote in message
...
On Wed, 11 Jan 2006 07:40:52 -0500, "Robert11"
wrote:
The easiest way by far for me to get the coax to the receiver is to run it
up from the Balun to my second floor where the receiver is.

If I run it upwards "right alongside" (or even tied to) the active
vertical
section of the antenna, will I have any problems ?
Remember, this would be coax, and I do receiving only.

Guess I'm worried about if the grounded shield of the coax presents some
kind of ground element right next to the active element ?

Hi Bob,

There is no inherent advantage in the inverted L except it being a top
loaded vertical with some horizontal polarization properties (being
unbalanced and all). You can save yourself some bewilderment by
driving the bottom directly into ground and simply connecting your
coax right at your second floor window with the coax shield connecting
to the wire going down, and the coax center to the wire going up and
to the tree. When lightning suggests itself, unconnect the coax from
your receiver and drop the coax out the window.

You will never notice the proximity of the wood siding, but you may
notice the proximity of house wiring that is in that wall. That
wiring may be carrying house noise (like a computer's monitor's hash).
However, that is best left for future investigation instead of
paralyzing you now.

Also, build an antenna tuner, or buy a very cheap, no-meter 3-knob Ham
tuner (less than $30). When you get into better antennas, you get
into overdrive possibilities from nearby AM stations (and I bet there
are a bajillion there in Mass). This is called "desensing" when those
stations (even when you are not tuned to them) overpower your radio
and drive the AGC so high, that you cannot hear weaker DX in the SW
bands.

73's
Richard Clark, KB7QHC

From OP: Ratio For Legs ? Inverted-L Antenna And Close Proximity Coax ?
 

On Wed, 11 Jan 2006 19:18:01 -0500, "Robert11"
wrote:

BTW: For general shortwave listening, is there a generally accepted
"optimum" for the length ratio between the horiz
and vert. legs ? Is the ratio freq. dependent ?

Hi Bob,

If there's any its on the order of 1:3. However, there's no point
going there with any high expectations - or even low expectations.
Going from a whip, or internal antenna to the external antenna you
have your mind set on is a leap in improvement. The next leap of
improvement will require $500 to a grand to set up a tower - and then
start thinking about the antenna on it. All steps between leaps are
small steps indeed.

You might try looking into phased arrays, but you should really
concentrate on making one good antenna and noting your baseline in
performance. On marker is how much noise do you live in? SWL varies
considerably through the bands, through the day/night, through the
seasons, and through the sun spot cycle. You have to consider that
what you may be trying to hear just isn't hearable because of those
same variables, much less an antenna.

73's
Richard Clark, KB7QHC