The inverted L was originally conceived as a transmitting antenna and was
cut to a resonant length. It is still quite popular particularly on the
lower frequencies. As a receiving antenna, few people try for resonance as
they are usually after broad band operation.
"starman" wrote in message
...
I doubt if most people try to make their inverted-L resonant for a
particular frequency. However in many cases it does turn out to be
resonant (like a longwire) at some frequency, particularly at the high
end of the HF spectrum where it's one or more wavelengths long.


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In article ,
"CW" wrote:

"Telamon" wrote in
message
...

Depends on how you connect it to the radio. With just a single
vertical lead-in then yes but use a coax grounded in some way then
no.

Feedline type has nothing to do with it. The classic inverted L was
connected with a single wire feedline. Coax feed is often used now
but not always. I, and many others, have run inverted Ls
(transmitting) right off the back of the radio.

If a coax cable is the vertical section then there is no vertical part
to the antenna so the answer is no. If it is a single wire then the
lead-in is part of the antenna and will radiate similar to the
horizontal section.

Another thing to consider is that the vertical portion should be a
significant portion of the antenna to qualify as an inverted L. An
antenna that is 15 feet high and 150 feet long the vertical portion
is only 10% of the total pickup area. I would consider that to be a
horizontal random/long wire.

There is a bit of truth to that. It is generally excepted that an
inverted L is most efficient when the verticle portion is as long as
possible.

I went looking for a definition and could not find one specifically. The
closest I could find resembled a Marconi type where the vertical and
horizontal sections were 1/8 wavelength each or 50%.

--
Telamon
Ventura, California

= = = (WShoots1)
= = = wrote in message ...
"Random wire" is the correct term, unless it is, as noted, a truly long wire,
something like 500 feet.

Bill, K5BY


Bill - K5BY,

I Will Repeat Myself: Most people think of the term "Longwire
Antenna" as they apply to the low frequencies especially the AM/MW/BCB
where a One Wavelength Antenna would be Bottom 540kHz = 1860Ft; Middle
1120kHz = 900Ft;
Top 1700kHz = 590Ft.

BUT, by 'definition' a "Longwire Antenna" is a "Longwire Antenna" when
its length is equal to One Wavelength (or more) at a given frequency.

EXAMPLES: One Wavelength "Longwire" Antennas for the following SW
Bands
49M Band = 165Ft
41M Band = 137Ft
31M Band = 104Ft
25M Band = 85Ft
22M Band = 73Ft
19M Band = 65Ft
16M Band = 57Ft
- - - All of which are less than 500Ft or more.

It then follows that the same "Longwire Antenna" would be Two
Wavelengths, a Half Wavelength, and a Quarter Wavelength at other
frequencies.

However, at all other frequencies this "Longwire Antenna" is simply a
'random' wire antenna.

iane ~ RHF
..
..

Hello CW,

YES, for a Classic "Longwire" Antenna, sizing is about the 'length' of
the Horizontal Wire.

BUT - The subject here is an Inverted "L" Antenna that would NOT be a
'random wire antenna'.

So the first consideration would be maintaining the Shape (aspect
radio) of the Inverted "L" Antenna.

Then the second consideration would be sizing the Inverted "L" Antenna
to be resonte at a given frequency (SW Band) for some one who had a
specific interest in that band.

One simple method would have been to suggest making the total length
of the Inverted "L" Antenna one wavelength for that band:
EXAMPLES: Total Length equals Vertical plus Horizonal Sections
49M Band = 165Ft Total
41M Band = 137Ft Total
31M Band = 104Ft Total
25M Band = 85Ft Total
22M Band = 73Ft Total
19M Band = 65Ft Total
16M Band = 57Ft Total

A better method would have been to suggest making the TOP Section of
the Inverted "L" Antenna One Wavelength and the END Section of the
Inverted "L" Antenna a Half Wavelength. Thereby maintaining the
Inverted "L" Antennas Aspect Radio of 2H:1V (Shape Factor).
NOTE: This better method is what I choose to describe in my prior
post.

EXAMPLES: "L" Section Lengths for Horizontal and Vertical.
49M Band = 165Ft Horizontal & 83Ft Vertical
41M Band = 137Ft Horizontal & 68Ft Vertical
31M Band = 104Ft Horizontal & 52Ft Vertical
25M Band = 85Ft Horizontal & 42Ft Vertical
22M Band = 73Ft Horizontal & 37Ft Vertical
19M Band = 65Ft Horizontal & 33Ft Vertical
16M Band = 57Ft Horizontal & 28Ft Vertical


iane ~ RHF
..
..
= = = "CW"
= = = wrote in message . net...
Better look up long wire. Verticle length has nothing to do with it.
"RHF" wrote in message
om...


If, by 'design' for a specific band of frequencies an Inverted "L"
Antenna has the Horizontal Top Section equal to One Wavelength and a
Vertical End Section equal to One Half Wavelength; then it would be
considered a Longwire Antenna for that Band.

StarMan,

That is True.

IIRC: Many of the 'original' HAM Transmitting Inverted "L" Antennas
were Quarter Wavelength Antennas with 1/8 Vertical and 1/8 Horizontal
for dual polarization of the signal in-theory (near and far
propagation ?).

The 'evolution' of the Inverted "L" Antenna application to an
'available space concept' for a SWL Receiving "Only" Antenna;
generally has the Top/Horizontal Section about twice as long as the
End/Vertical Section.

NOTE: Reversing the "L" and having the End Section feed point at the
far end of the antenna with a buried Coax Cable running directly under
it (acting as a Counterpoise) makes for a better (lower noise)
receiving antenna.


iane ~ RHF
..
..
= = = starman
= = = wrote in message ...
RHF wrote:

Telamon,

"the vertical portion should be a significant portion of the antenna
to qualify as an inverted L. An antenna"

TRUE - Look at the Letter "L" and you will see that an Inverted "L"
Antenna will have an END (Vertical) to TOP (Horizontal) 'aspect ratio'
between 1:1.5 (2:3) and 1:2; but beyond 1:4 it is really not an "L"
any more.

The vertical section of the inverted-L is also important for receiving
certain kinds of signals (propagation related) that the horizontal
section is less sensitive to.


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In article ,
Telamon wrote:
In article , starman
[snip]

Are all inverted-L's, random wires?

Depends on how you connect it to the radio. With just a single vertical
lead-in then yes but use a coax grounded in some way then no. Another
thing to consider is that the vertical portion should be a significant
portion of the antenna to qualify as an inverted L. An antenna that is
15 feet high and 150 feet long the vertical portion is only 10% of the
total pickup area. I would consider that to be a horizontal random/long
wire.

--
Telamon
Ventura, California

Nothing about antenna theory seems to ever be simple. The antenna you
describe, above about 15MHz, will have a horizontal pattern quite
different from a 150 foot horizontal wire. The horizontal wire will have
a horizontal pattern like the petals of a warped daisy flower, with many
lobes separated by deep nulls, some more than 40dB 'deep'. That
vertical section of the above-described inverted-L will do quite a bit to
fill in those nulls.

Also, the inverted-L is simple to ground. Electromagnetic theory does not
require such a ground, but your friendly local Electrical Code does.

Not saying you're wrong, Telamon; below 10 MHz, you're basically right.
Just saying that we SW & scanner types work with wavelengths from about
one mile down to about a foot, and it's hard to find rules or principles
that apply uniformly across the whole range.
--

R F Wieland Newark, DE 19711-5323 USA 39.68N 75.74W
Icom R75 Heathkit GR-81 Inverted-L in the attic
Reply to wieland at me dot udel dot edu

RFW,

What would be your evaluation of these three
SWL (Receive Only) Inverted "L" Antennas:

* 49M Band Half Wavelength Inverted "L" Antenna
Vertical 27.6 Feet and Horizontal 55.1 Feet with a Total of 82.7 Feet
- - - V = 1/6WL & H = 1/3WL

* 49M Band Three Quarter (3/4) Wavelength Inverted "L" Antenna
Vertical 41.4 Feet and Horizontal 82.7 Feet with a Total of 124.1 Feet
- - - V = 1/4WL & H = 1/2WL

* 49M Band Full Wavelength Inverted "L" Antenna
Vertical 55.1 Feet and Horizontal 110.3 Feet with a Total of 165.4 Feet
- - - V = 1/3WL & H = 2/3WL


iwtk ~ RHF
..
..
= = =
= = = (Robert F Wieland) wrote in message ...
In article ,
Telamon wrote:
In article , starman
[snip]

Are all inverted-L's, random wires?

Depends on how you connect it to the radio. With just a single vertical
lead-in then yes but use a coax grounded in some way then no. Another
thing to consider is that the vertical portion should be a significant
portion of the antenna to qualify as an inverted L. An antenna that is
15 feet high and 150 feet long the vertical portion is only 10% of the
total pickup area. I would consider that to be a horizontal random/long
wire.

--
Telamon
Ventura, California

Nothing about antenna theory seems to ever be simple. The antenna you
describe, above about 15MHz, will have a horizontal pattern quite
different from a 150 foot horizontal wire. The horizontal wire will have
a horizontal pattern like the petals of a warped daisy flower, with many
lobes separated by deep nulls, some more than 40dB 'deep'. That
vertical section of the above-described inverted-L will do quite a bit to
fill in those nulls.

Also, the inverted-L is simple to ground. Electromagnetic theory does not
require such a ground, but your friendly local Electrical Code does.

Not saying you're wrong, Telamon; below 10 MHz, you're basically right.
Just saying that we SW & scanner types work with wavelengths from about
one mile down to about a foot, and it's hard to find rules or principles
that apply uniformly across the whole range.