Basic Antenna Question

Steve B.

unread,

Jul 24, 2004, 8:21:56 PM7/24/04

to

Hello Everyone,

Here is a basic question, but hopefully not too basic:

What would be the best outdoor antenna for SWL performance?

Ok, I know that is a loaded question, so here are some parameters I'm
interested in:

1. Something as omnidirectional as possible, as I am somewhat limited
in space for orienting an antenna in any specific direction.

2. Obviously, something with as high a signal to noise ratio as
possible.

3. Something that will cover the entire HF range equally well (also
MW, if possible) rather than one that is tuned to only the broadcast
bands.

4. Something that is reasonably small, as I have many obtructions
(trees, etc) in my yard to deal with.

5. Something that will not break the bank.

Does such an animal exist, or is this the Holy Grail of SWL'ing that
nobody has found yet?

I'm currently using an Alpha Delta sloper that is pointed to the west,
but I'm more interested in receiving stations to the east...
unfortunately, west is the only way I can point it right now. As for
a receiver, I'm using a Drake SW-2. I'd like the best antenna
possible for this setup. I'm open to all possibilities, including
active antennas... or even a simple long wire if that is the best
solution.

Thank you in advance for all replies!

Steve

Jack Painter

unread,

Jul 24, 2004, 9:21:05 PM7/24/04

to

"Steve B." <m...@here.com> wrote

> 1. Something as omnidirectional as possible, as I am somewhat limited
> in space for orienting an antenna in any specific direction.
>
> 2. Obviously, something with as high a signal to noise ratio as
> possible.
>
> 3. Something that will cover the entire HF range equally well (also
> MW, if possible) rather than one that is tuned to only the broadcast
> bands.
>
> 4. Something that is reasonably small, as I have many obtructions
> (trees, etc) in my yard to deal with.
>
> 5. Something that will not break the bank.
>
> Does such an animal exist, or is this the Holy Grail of SWL'ing that
> nobody has found yet?
>
> I'm currently using an Alpha Delta sloper that is pointed to the west,
> but I'm more interested in receiving stations to the east...
> unfortunately, west is the only way I can point it right now. As for
> a receiver, I'm using a Drake SW-2. I'd like the best antenna
> possible for this setup. I'm open to all possibilities, including
> active antennas... or even a simple long wire if that is the best
> solution.

Hi Steve,

How tall are those trees all around you? Consider slinging a random length
wire up over a tall branch of one of the trees - get at least a 60 degree
angle and you will be omni-diectional. For random wires I use I.C.E.
(Industrial Communications Engineering) matching transformers at the
ground-rod/feedpoint. They have 4 different impedance connections for your
particular wire length/height above ground and do a real nice job. Bury the
RG-8X feedline from feedpoint to your home and shield-ground the coax at
another ground-rod right outside your shack for lowest noise. The ICE
Beverage matching transformer is about $40, two eight foot ground rods at
$12ea and unless you feel real lucky, an ICE coax lightning arrestor at $45
should have you going.

Jack Painter
Virginia Beach VA

Howard

unread,

Jul 24, 2004, 9:24:17 PM7/24/04

to

I have the short version of that sloper (40 feet, one ISO-RES coil)
and have had pretty good 'omni' coverage and mine is also 'pointing
west' like yours. Have not had the opportunity to "A-B" it to same
antenna in different direction; however, given that that it never
exceeds even one wavelength in length I wouldn't expect much
directivity. caveat ......... given my sufficiently dangerous
knowledge of antennas

Howard

Stuart Lent

unread,

Jul 25, 2004, 2:07:04 PM7/25/04

to

What you have described in your parameter list is called a tilted
terminated folded dipole (T2FD). You can buy them from RF Systems or B&W
but they are not inexpensive around $200-$300. There are several design
sites on the Internet to build your own. they have a low VSWR, less than
2:1 over the band. No tuner needed. They are less prone to picking up
man made noise. Check it out.

Richard Clark

unread,

Jul 25, 2004, 4:14:04 PM7/25/04

to

On Sun, 25 Jul 2004 00:21:56 GMT, Steve B. <m...@here.com> wrote:

>What would be the best outdoor antenna for SWL performance?

A wire one.

>Ok, I know that is a loaded question, so here are some parameters I'm
>interested in:
>
>1. Something as omnidirectional as possible, as I am somewhat limited
>in space for orienting an antenna in any specific direction.

This describes an antenna with a vertical polarization. There is an
alternative one that appears to be a horizontal loop. More on that
below.

>2. Obviously, something with as high a signal to noise ratio as
>possible.

Self contradicting with the goal for omni-directionality.

>3. Something that will cover the entire HF range equally well (also
>MW, if possible) rather than one that is tuned to only the broadcast
>bands.

A piece of wire slung out the window will do that reasonably well.

>4. Something that is reasonably small, as I have many obtructions
>(trees, etc) in my yard to deal with.

Use the tree as Jack points out - what choice do you have? It hardly
matters anyway for receivers.

>5. Something that will not break the bank.

500 foot spools of AWG 14 wire typically sell for less than $20. Use
$2 worth of wire and put the rest of your bankroll into a tuner.

>Does such an animal exist, or is this the Holy Grail of SWL'ing that
>nobody has found yet?

No. Listen to your radio, and read the headlines for the announcement
of the discovery of the Grail.

>I'm currently using an Alpha Delta sloper that is pointed to the west,
>but I'm more interested in receiving stations to the east...
>unfortunately, west is the only way I can point it right now. As for
>a receiver, I'm using a Drake SW-2. I'd like the best antenna
>possible for this setup. I'm open to all possibilities, including
>active antennas... or even a simple long wire if that is the best
>solution.

Hi Steve,

Your antenna is already a good one. The orientation of the slope adds
some sensitivity in preferred directions (and in all likelihood to
many directions you wouldn't expect), but that does not make it deaf
to the non-preferred directions. A sloper has a significant vertical
polarization that is enough to listen in any direction - some better
than others. However, given the range of SW frequencies,
directionality is not always preserved across them all.

There is an old adage about antennas: more wire higher up.

More wire catches more signal, it is arguable that this is better
however especially in comparison to the labor of effort to get more
wire up. On the other hand, higher moves you away from local sources
of noise (if you use a coax that is snubbed at the antenna connection
with a choke).

Higher up in this sense generally suggests a dipole, which then being
high and balanced (again, only if it has that choke) offers less noise
because it listens to less air space - it is directional as well as
isolated. This is fine if you listen in that direction, but this
contradicts your requirement above - hence the conflict of
requirements again. As an alternative; if you have the real estate
and the determination you can build an omni horizontal antenna. It
looks like a loop, but it is open on the side (or corner) that is
opposite the connection point. This requires four corners supported
which is the difficulty.

Designs beyond what you have bring an added level of complexity that
may not offer much more performance - you never know really unless you
try. You could replace the sloper with a top loaded vertical (add
radials to its base, at ground level or slightly buried). Top loading
would involve a horizontal wire to which the vertical is connected
either at the center (like a T) or at the end (Like an L). The effect
of this additional wire is to create the impression (to the
performance) that your vertical is taller than it is (but not so much
as by the length of that horizontal wire, but significantly). The top
loaded wire need not be flat and horizontal - nature rarely offers
such choices and no wire hangs flat anyway. However, the ends should
not drop more than 2/3rds the highest point or you may as well work
with a vertical loop.

There are several designs along that line but this is long enough as
it is.

73's
Richard Clark, KB7QHC

RHF

unread,

Jul 27, 2004, 6:15:18 AM7/27/04

to

SB,

Your Alpha Delta Sloper is a good SWL Antenna and 'if' you
have set it up as they recommend. You may not be able to build
or buy an SWL Antenna that will give you significantly improved
overall performance then it.

For a single Receive ONLY Shortwave Listeners (SWL) Antenna,
one that is Omni-Directional generally works better then one
that is intended to be directional.

* The SWL Version of the Inverted "L" Antenna works well as
an Omni-Directional Antenna. The SWL Inverted "L" Antenna
usually has a Vertical 'Leg' that is 1/3 to 1/2 the Length of
the Length of Horizontal 'Arm'. Plus the SWL Inverted "L"
Antenna usually is lower to the Ground. This closeness to the
Surface of the Ground results in the SWL Inverted "L" Antenna
being a form of "Near Vertical Incident Skywave" {NVIS} Antenna.
NVIS=> http://www.qsl.net/k5eph/nvis.htm

* These SWL Versions of the Inverted "L" Antennas can be any
size because they are in-fact simply Random Wire Antennas that
are designed to fit the available space.
http://groups.yahoo.com/group/Shortwave-SWL-Antenna/message/54

If you want a 'Set of Numbers' to Build their SWL Inverted "L"
Antenna here are a few 'Sets of Numbers' to consider for your
available space:
- 10Ft High Vertical 'Leg' with a 20-30Ft Horizontal Arm
having a Total Lenght of 30-40 Feet. Also: 20x40-60 & 30x60-90
- 15Ft High Vertical 'Leg' with a 30-45Ft Horizontal Arm
having a Total Lenght of 45-60 Feet.
- 25Ft High Vertical 'Leg' with a 50-75Ft Horizontal Arm
having a Total Lenght of 75-100 Feet.
- 35Ft High Vertical 'Leg' with a 70-105Ft Horizontal Arm
having a Total Lenght of 105-140 Feet.

Since you have trees to work with as supports for your Antenna
Wire Element. Consider using Insulated Stranded Wire for the
Antenna Element and routing it up into and through the trees
to make your Inverted "L" Antenna.

iane ~ RHF
.
Some Say: On A Clear Day You Can See Forever.
http://groups.yahoo.com/group/Shortwave-SWL-Antenna/message/502
I BELIEVE: On A Clear Night...
You Can Hear Forever and Beyond, The Beyond !
.
.
= = = Steve B. <m...@here.com> wrote in message
= = = news:<hlu5g0lve02vdvndn...@4ax.com>...