= = = Richard Clark wrote in message
= = = . ..
On 13 Nov 2004 20:41:52 -0800, (RHF) wrote:

JK, RC and CM,

I want to Thank Each of You for your replies to this question.

Note: I am only talking about a SWL "Receive Only" Antenna here.

Hi OM,

As were the answers (with possibly one exception).

I suspect that may be one reason that this Far-End Loaded AM/MW
Coil may work is the fact that the RF Systems EMF Antenna is
'only' Sixteen Feet (16') Long; and the Two Inch to Three Inch
(2"-3") Ferrite Rod at the End of the Wire Antenna Element does
have some 'measurable effect' on improving the AM/MW Frequency
Band performance of such a short Antenna.
- Relative Size may be the Controlling Factor for this 'unique'
small Antenna

? ? Would this 'trick' work with a Larger {Longer} SWL Antenna ? ?

Let's approach this from the usual perspective. Many SWLrs posting
here already have the ferrite antenna in their receiver and come here
for a boost in signals. The fact that it is so easily accomplished by
the addition of that same 16 feet of random wire tossed across the
living room rug would suggest just how much contribution is found in
the ferrite antenna.

My target receivers are my Kenwood R-5000, Icom IC-R75, and
Grundig Satellit 800 M. Note with the Grundig Satellit 800 M
when the SO-239 is switch on to use the External Antenna the
'internal' AM/MW Ferrite Rod Antenna is disconnected.


Let's put some numbers to it. With the ferrite antenna a DX station
comes in S3, replace it with the wire and it climbs to S7. So, if we
start with just the wire antenna with the same signal at S7, and
adding the ferrite to pump up da volume to S7+ would this be worth $95
to you? What if by simply adding 6" more wire to the 16 feet gave you
that same +?


Not worried about the cost since this would be a 'home-brewed'
Antenna with parts I already have.

Looking to add a little more signal to the AM/MW Band area for
improved Weak Signal DXing from the Inverted "L" Antennas.

As a product, it is incredibly cheesy to boot. Look at that clunky
pl259 at the end of rg174. C'mon now, are we talking about your
granddad's RCA Victor this sucker is going to plug into? That and the
lead-in is only 16 feet in its own right? How much profit would be
lost to give you a decent length of wire and lead-in?

My more specific point of interest would be in whether using a
Ferrite Rod with the Wire Antenna Element Wrapped as a AM/MW
Coil around it would have some meaningful effect on a Horizontal
Random Wire Antenna that was 75-100 Feet long.
- For a Horizontal Random Wire Antenna ?WHY? 'place' the
Ferrite Rod at the Far-End of the Wire Antenna Element ?
- Why not 'place' the Ferrite Rod near the Feed-Point-End ?
- Why not 'place' the Ferrite Rod near the Middle ?
- Why not 'place' the Ferrite Rod near the slightly Off-Center
38%/62% like a Windom ?

This at least suggests a more practicable study. Loading coils don't
do very much without some form of capacitance above them to draw the
current. Putting a coil at the top is a fruitless exercise. It may
offer to "tune" but it sure won't sing.

73's
Richard Clark, KB7QHC

RC,

I have the two Inverted "L" Antennas and about a dozen 10mm X 200mm
Ferrite Rods to play with. So for me it is a matter of De-Rigging
the Antennas; winding the Antennna Wire on the Ferrite Rod; and
Re-Rigging the Antennas.

Doing a dry run with an extra piece of Antenna Wire; I can get
about Nine Turns per Inch; which would be 63 Turns uniformally
wrapped evenly over 90% of the Ferrite Rod.

So my 'focus' is on a "Low Noise' Inverted "L" Antenna that is
100 Feet long. Placing the Ferrite Rod at the "Top" of the
Vertical Leg where the Antenna Wire Element transitions from
Vertical to Horizontal. Rig the Antenna Wire Element with 33
Feet Up to the Ferrite Rod AM/MW Ferrite Coil and then have 67
Feet Out to the Far-End. Would this possibly work any better
then having the Ferrite Rod and Coil at the Far-End ? and Why ?

In my 'imagination' for the AM/MW Broadcast Band; the Vertical
Up-Leg would act like an Omni-Directional "Tuned" Vertical Antenna
(since the Ferrite Rod would be Vertical); with the Horizontal
Out-Arm of the Antenna acting like a Top Hat for the Vertical.
Then at the Shortwave Frequencies the 'effects' of the Ferrite
Rod would become less and the Antenna would simply act as a
normal SWL'ers Inverted "L" Antenna.

Now here is another thought; would having the Ferrite Rod with the
Antenna Wire wrapped around it at the Far-End of the Horizontal
Antenna Element cause the AM/MW Broadcast Band reception to be
Directional 'Off-the-Sides' of the Inverted "L" Antenna ? ? ?


in search of some ideas and answers ~ RHF
..
..

RHF,
Since you already have the items needed, why not give it a try?
The most you would loose would be the time/effort to 'de-rig' your
other antenna.
'Doc

PS - Without looking at the site mentioned, I tend to agree
with Richard. Sounds a lot like 'snake oil'. Which ain't
'bad', if you're selling 'snake oil'...

On 14 Nov 2004 06:42:51 -0800, (RHF) wrote:
So my 'focus' is on a "Low Noise' Inverted "L" Antenna that is
100 Feet long. Placing the Ferrite Rod at the "Top" of the
Vertical Leg where the Antenna Wire Element transitions from
Vertical to Horizontal. Rig the Antenna Wire Element with 33
Feet Up to the Ferrite Rod AM/MW Ferrite Coil and then have 67
Feet Out to the Far-End. Would this possibly work any better
then having the Ferrite Rod and Coil at the Far-End ? and Why ?

Hi OM,

If you want to resonate it at ONE frequency (the supposed reason for
having that lump at the end) then you would need an inductive
reactance of
1000 Ohms at the feedpoint to render the antenna a resistive 6 Ohms
and a poor average gain of -8.7dB;
or
1000 Ohms at 3' up to render the antenna a resistive 7 Ohms and a poor
average gain of -8.5dB;
or
1300 Ohms at 16' up - 7.8 Ohm Antenna @ -8.7dB;
or
1400 Ohms at the top - 9 Ohm Antenna @ -9dB;
or
1900 Ohms 16' out the horizontal leg - 11 Ohm Antenna @ -9.6dB;
or
2600 Ohms 32' out - 12.5 Ohm Antenna @ -10 dB;
or
5800 Ohms 48' out - 14.6 Ohm Antenna @ -10.5dB;
or
10200 Ohms 58' out - 15.4 Ohm Antenna @ -10.6dB;
or
56500 Ohms 64' out - 15.2 Ohm Antenna @ -10.6dB.

You should note the progression of increased inductance required to
tune this antenna to 1MHz (ymmv). At any other frequency and bingo,
all bets are off. You should also note there is only a 2dB spread
(AVC would quickly put that to rest). Also, the numbers above presume
you performed the chore of laying out 16 X 33' radials.

Let's compare that to the advertised antenna
9200 Ohms at the bottom - 32.5 Ohm Antenna @ -26.8dB;
or
13700 Ohms at 8' up - 35 Ohm Antenna @ -22dB;
or
108750 Ohms at 15' up - 39.6 Ohm Antenna @ -19.9dB.

This presumes the single lead-in laying along the ground (where most
of this Antenna Ohmage resides.

This, further, would put your antenna roughly 10dB ahead (sans
loading, and using a simple tuner) of the $95 spread. I hope you
notice the parenthetic statement of a tuner - it does the same thing
as these loads, and you get to tune to more than one frequency.

I will leave it up to you to determine how many wraps around how many
rods would give you 110000 Ohms inductive reactance at 1MHz.

In my 'imagination' for the AM/MW Broadcast Band; the Vertical
Up-Leg would act like an Omni-Directional "Tuned" Vertical Antenna
(since the Ferrite Rod would be Vertical); with the Horizontal
Out-Arm of the Antenna acting like a Top Hat for the Vertical.
Then at the Shortwave Frequencies the 'effects' of the Ferrite
Rod would become less and the Antenna would simply act as a
normal SWL'ers Inverted "L" Antenna.

Well, let's just test that hypothesis with the load at the top.

What you get is fairly well tuned at 10MHz (SWR 1.7) with omni
coverage in both horizontal and vertical. For other bands, of course,
a tuner would be useful.

Now here is another thought; would having the Ferrite Rod with the
Antenna Wire wrapped around it at the Far-End of the Horizontal
Antenna Element cause the AM/MW Broadcast Band reception to be
Directional 'Off-the-Sides' of the Inverted "L" Antenna ? ? ?

NO. For short antennas and low horizontals, there is almost no
directionality. What you are attempting to do is to capture the
quality of small loops (which are what the ferrites are) of being
directional. The signal from the parasitic wire (what is not part of
the small ferrite) is going to fill in the nulls and deluge its poorer
sensitivity as well. You can of course test this answer by finding a
way to answer my question inferred above about how many wraps and how
many rods to achieve 110000 Ohms inductive reactance.

73's
Richard Clark, KB7QHC

On 14 Nov 2004 06:42:51 -0800, (RHF) wrote:

So my 'focus' is on a "Low Noise' Inverted "L" Antenna that is
100 Feet long. Placing the Ferrite Rod at the "Top" of the
Vertical Leg where the Antenna Wire Element transitions from
Vertical to Horizontal. Rig the Antenna Wire Element with 33
Feet Up to the Ferrite Rod AM/MW Ferrite Coil and then have 67
Feet Out to the Far-End. Would this possibly work any better
then having the Ferrite Rod and Coil at the Far-End ? and Why ?

Generally, adding non-radiating reactance to an antenna decreases
broadband efficiency, although it may increase efficiency over narrow bands.

-jpd

In article ,
John Doty wrote:

On 14 Nov 2004 06:42:51 -0800, (RHF) wrote:

So my 'focus' is on a "Low Noise' Inverted "L" Antenna that is
100 Feet long. Placing the Ferrite Rod at the "Top" of the
Vertical Leg where the Antenna Wire Element transitions from
Vertical to Horizontal. Rig the Antenna Wire Element with 33
Feet Up to the Ferrite Rod AM/MW Ferrite Coil and then have 67
Feet Out to the Far-End. Would this possibly work any better
then having the Ferrite Rod and Coil at the Far-End ? and Why ?

Generally, adding non-radiating reactance to an antenna decreases
broadband efficiency, although it may increase efficiency over narrow bands.

Good point.

--
Telamon
Ventura, California

RC,

Thank You for Crunching the Numbers for Me.

~ RHF
..
..
= = = Richard Clark wrote in message
= = = . ..
On 14 Nov 2004 06:42:51 -0800, (RHF) wrote:
So my 'focus' is on a "Low Noise' Inverted "L" Antenna that is
100 Feet long. Placing the Ferrite Rod at the "Top" of the
Vertical Leg where the Antenna Wire Element transitions from
Vertical to Horizontal. Rig the Antenna Wire Element with 33
Feet Up to the Ferrite Rod AM/MW Ferrite Coil and then have 67
Feet Out to the Far-End. Would this possibly work any better
then having the Ferrite Rod and Coil at the Far-End ? and Why ?

Hi OM,

If you want to resonate it at ONE frequency (the supposed reason for
having that lump at the end) then you would need an inductive
reactance of
1000 Ohms at the feedpoint to render the antenna a resistive 6 Ohms
and a poor average gain of -8.7dB;
or
1000 Ohms at 3' up to render the antenna a resistive 7 Ohms and a poor
average gain of -8.5dB;
or
1300 Ohms at 16' up - 7.8 Ohm Antenna @ -8.7dB;
or
1400 Ohms at the top - 9 Ohm Antenna @ -9dB;
or
1900 Ohms 16' out the horizontal leg - 11 Ohm Antenna @ -9.6dB;
or
2600 Ohms 32' out - 12.5 Ohm Antenna @ -10 dB;
or
5800 Ohms 48' out - 14.6 Ohm Antenna @ -10.5dB;
or
10200 Ohms 58' out - 15.4 Ohm Antenna @ -10.6dB;
or
56500 Ohms 64' out - 15.2 Ohm Antenna @ -10.6dB.

You should note the progression of increased inductance required to
tune this antenna to 1MHz (ymmv). At any other frequency and bingo,
all bets are off. You should also note there is only a 2dB spread
(AVC would quickly put that to rest). Also, the numbers above presume
you performed the chore of laying out 16 X 33' radials.

Let's compare that to the advertised antenna
9200 Ohms at the bottom - 32.5 Ohm Antenna @ -26.8dB;
or
13700 Ohms at 8' up - 35 Ohm Antenna @ -22dB;
or
108750 Ohms at 15' up - 39.6 Ohm Antenna @ -19.9dB.

This presumes the single lead-in laying along the ground (where most
of this Antenna Ohmage resides.

This, further, would put your antenna roughly 10dB ahead (sans
loading, and using a simple tuner) of the $95 spread. I hope you
notice the parenthetic statement of a tuner - it does the same thing
as these loads, and you get to tune to more than one frequency.

I will leave it up to you to determine how many wraps around how many
rods would give you 110000 Ohms inductive reactance at 1MHz.

In my 'imagination' for the AM/MW Broadcast Band; the Vertical
Up-Leg would act like an Omni-Directional "Tuned" Vertical Antenna
(since the Ferrite Rod would be Vertical); with the Horizontal
Out-Arm of the Antenna acting like a Top Hat for the Vertical.
Then at the Shortwave Frequencies the 'effects' of the Ferrite
Rod would become less and the Antenna would simply act as a
normal SWL'ers Inverted "L" Antenna.

Well, let's just test that hypothesis with the load at the top.

What you get is fairly well tuned at 10MHz (SWR 1.7) with omni
coverage in both horizontal and vertical. For other bands, of course,
a tuner would be useful.

Now here is another thought; would having the Ferrite Rod with the
Antenna Wire wrapped around it at the Far-End of the Horizontal
Antenna Element cause the AM/MW Broadcast Band reception to be
Directional 'Off-the-Sides' of the Inverted "L" Antenna ? ? ?

NO. For short antennas and low horizontals, there is almost no
directionality. What you are attempting to do is to capture the
quality of small loops (which are what the ferrites are) of being
directional. The signal from the parasitic wire (what is not part of
the small ferrite) is going to fill in the nulls and deluge its poorer
sensitivity as well. You can of course test this answer by finding a
way to answer my question inferred above about how many wraps and how
many rods to achieve 110000 Ohms inductive reactance.

73's
Richard Clark, KB7QHC