Putting a Ferrite Rod at the Far-End of a Random Wire Antenna ?
 

FO&A,

Here is my Question: Is there any sense in putting a Ferrite Rod
at the Far-End of a Random Wire Antenna with the Wire from the
End of the Wire Antenna Element 'wrapped' around it in a
"Tuned Coil" to improve the AM/MW Band Reception ?

* Any 'theory' behind why this Idea might Work ?

* Does this Idea actually Work ?

* Or is this Idea just so much Antenna 'hype' and Sales Marketing

I am Asking these Questions is because of what I have read about
the RF Systems "EMF" Electro-Magnetic-Field Passive Wire Antenna
http://www.universal-radio.com/catalog/sw_ant/0743.html

In "John Wagner's Shortwave Tips & Tricks" he writes:
http://www.dxing.com/tips.htm
"The EMF antenna has two 35mm film canister looking objects
connected to it. The canister on the Far-End is actually an
excellent "Tuned Ferrite Rod" designed for MW (Medium Wave)
and really helps any receiver without a built in MW Antenna
Rod. Canister two (in middle) is a Balun that helps SW
reception very much."


i want to know ~ RHF
..
..

I took a look at the antenna you're describing...

"RHF" wrote in message
om...
* Any 'theory' behind why this Idea might Work ?

My thought would be that, at MW frequencies, the 'wire' part of the antenna
is pretty much 'lumped' (no significant phase change along its length), so
you have a standard ferrite rod antenna that you're hooking up via a long
piece of hookup wire. That's a reasonable enough antenna.

As you approach HF, the 'wire' part of the antenna starts to become active
and the two signals combine.

Still, this is very much a 'hands waving' explanation; hopefully someone
else will have a more solid response.

* Does this Idea actually Work ?
* Or is this Idea just so much Antenna 'hype' and Sales Marketing

I imagine it works as well as either antenna alone (the ferrite rods or the
long wire) would, and the real question is... do the two together produce
any significant additional gain? I suspect not (much), but even if so,
sometimes a wideband standard gain antenna is more desirable than a higher
gain single bander.

---Joel

On 13 Nov 2004 09:24:08 -0800, (RHF) wrote:
* Any 'theory' behind why this Idea might Work ?

Hi OM,

The age old theory that a sucker is born every minute.

* Does this Idea actually Work ?

For the guy you are handing $95 to, it does.

* Or is this Idea just so much Antenna 'hype' and Sales Marketing

AW! You already knew the answers.

I am Asking these Questions is because of what I have read about
the RF Systems "EMF" Electro-Magnetic-Field Passive Wire Antenna
http://www.universal-radio.com/catalog/sw_ant/0743.html

For $95, who would be tempted to clip off that sucker at the end and
discover it didn't amount to a hill of beans? Self-fulfilling
illusion of value perception.

In "John Wagner's Shortwave Tips & Tricks" he writes:
http://www.dxing.com/tips.htm
"The EMF antenna has two 35mm film canister looking objects
connected to it. The canister on the Far-End is actually an
excellent "Tuned Ferrite Rod" designed for MW (Medium Wave)
and really helps any receiver without a built in MW Antenna
Rod. Canister two (in middle) is a Balun that helps SW
reception very much."

Are we to believe John cracked his wallet open to then crack open the
film canisters? As far as guesses goes, this is as good as any; but
given the techno-drivel that populates the rest of the page, the going
doesn't go very far at all.

i want to know ~ RHF

Ah, but that would cost you $95. You would have to first discover
what "designed for MW (Medium Wave)" actually means. Given the
manufacturer explicitly states nothing in that regard (devoting most
of the coverage to a BalUn) and calls it a "magnetic module."

Consider, if it is "designed for MW (Medium Wave)" then it is neither
designed for LW nor SW, and yet the ad clearly states "covering 100
kHz to 30 MHz." Such contradictions are a clear warning with red
lights and flags waving. If it is designed for "covering 100 kHz to
30 MHz," then the doo-hicky at the end is probably more useful as a
monkey-fist for tossing it up into a tree.

73's
Richard Clark, KB7QHC

RHF wrote:
* Any 'theory' behind why this Idea might Work ?

Anything that will increase the current in the wire below top-loading
is a good idea.

* Does this Idea actually Work ?

I don't know the answer. A ferrite inductor will increase the magnitude
of inductance over an air-core coil and top-loading will increase the
current in the wire part of the antenna. It's an interesting idea
assuming that antennas are reciprocal for transmitting and receiving.
--
73, Cecil, W5DXP

In article ,
RHF wrote:
FO&A,

Here is my Question: Is there any sense in putting a Ferrite Rod
at the Far-End of a Random Wire Antenna with the Wire from the
End of the Wire Antenna Element 'wrapped' around it in a
"Tuned Coil" to improve the AM/MW Band Reception ?

* Any 'theory' behind why this Idea might Work ?

* Does this Idea actually Work ?

* Or is this Idea just so much Antenna 'hype' and Sales Marketing

I'll pick door number 3, Monty.

If the far end of the antenna were grounded there might be some pickup
at the self resonant frequency of the ferrite coil, and it would be
a good DC ground at the far end that might reduce some noise.

If it's not grounded, it's just a convenient weight to toss it into
the trees, because there's no loop in the circuit for any current to be
coupled into, and a small isolated ferrite coil isn't going to produce
a voltage differential to ground that could couple through capacitance.

Mark Zenier Washington State resident

In article ,
"Joel Kolstad" wrote:

I took a look at the antenna you're describing...

"RHF" wrote in message
om...
* Any 'theory' behind why this Idea might Work ?

My thought would be that, at MW frequencies, the 'wire' part of the antenna
is pretty much 'lumped' (no significant phase change along its length), so
you have a standard ferrite rod antenna that you're hooking up via a long
piece of hookup wire. That's a reasonable enough antenna.

As you approach HF, the 'wire' part of the antenna starts to become active
and the two signals combine.

Still, this is very much a 'hands waving' explanation; hopefully someone
else will have a more solid response.

* Does this Idea actually Work ?
* Or is this Idea just so much Antenna 'hype' and Sales Marketing

I imagine it works as well as either antenna alone (the ferrite rods or the
long wire) would, and the real question is... do the two together produce
any significant additional gain? I suspect not (much), but even if so,
sometimes a wideband standard gain antenna is more desirable than a higher
gain single bander.

Work is not a very well defined word. The antenna will work in that it
will pick up some signal and deliver it to the radio. I think you mean
to ask how well compared to another antenna.

I pretty much agree with what Joel wrote but add the following
explanation. Any time you add some type of coil to a wire you are
electrically increasing the electrical length over the physical length
of the wire. The coil on the end will cause the wire part of the antenna
to resonate at a lower frequency. This is generally not a good or
effective way to make a sensitive antenna but it will "work."

Generally a wire antenna will pick up a significant amount of signal
energy at frequencies above its electrical length and perform much worse
below its resonate frequency so basically this looks like a attempt to
get a rather short piece of wire (16 feet) to "work" down to a frequency
far below its resonant physical length.

The BALAN coil depending on design could be a good thing in that it will
cause the high impedance of the wire to be closer on average to the
impedance of the coax cable part of the antenna and the radios input.

--
Telamon
Ventura, California

This should have no effect on reception.

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.

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 ? ?

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 ?

What about a "Low Noise' Inverted "L" Antenna that is 45-100 Feet
long. For an Inverted "L" Antenna ?WHY? not 'place' the Ferrite
Rod at the "Top" of the Vertical Leg where the Antenna Wire Element
transitions from Vertical to Horizontal ?
- 15 Feet Up Ferrite Rod AM/MW Ferrite Coil and 30 Feet Out.
- 20 Feet Up Ferrite Rod AM/MW Ferrite Coil and 40 Feet Out.
- 25 Feet Up Ferrite Rod AM/MW Ferrite Coil and 50 Feet Out.
- 33 Feet Up Ferrite Rod AM/MW Ferrite Coil and 67 Feet Out.
Or again here would having the Ferrite Rod and Coil at the
Far-End work some 'magic' trick ? and Why ?

in search of some ideas and answers ~ RHF
..
..
= = = (RHF) wrote in message
= = = . com...
FO&A,

Here is my Question: Is there any sense in putting a Ferrite Rod
at the Far-End of a Random Wire Antenna with the Wire from the
End of the Wire Antenna Element 'wrapped' around it in a
"Tuned Coil" to improve the AM/MW Band Reception ?

* Any 'theory' behind why this Idea might Work ?

* Does this Idea actually Work ?

* Or is this Idea just so much Antenna 'hype' and Sales Marketing

I am Asking these Questions is because of what I have read about
the RF Systems "EMF" Electro-Magnetic-Field Passive Wire Antenna
http://www.universal-radio.com/catalog/sw_ant/0743.html

In "John Wagner's Shortwave Tips & Tricks" he writes:
http://www.dxing.com/tips.htm
"The EMF antenna has two 35mm film canister looking objects
connected to it. The canister on the Far-End is actually an
excellent "Tuned Ferrite Rod" designed for MW (Medium Wave)
and really helps any receiver without a built in MW Antenna
Rod. Canister two (in middle) is a Balun that helps SW
reception very much."


i want to know ~ RHF
.
.

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.

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 +?

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

= = = 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 wrote:
JK, RC and CM,
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.

Yes, I was assuming you had a short antenna and wanted to load
it. The reason for loading a short antenna is to increase its
electrical length closer to resonance and the benefits are much
more pronounced for transmitted signals. Most modern HF receivers
have enough gain to make up for a less than optimum antenna.

Loading a long wire antenna doesn't make much sense.
--
73, Cecil, W5DXP

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'...

(RHF) wrote in message . com...
FO&A,

Here is my Question: Is there any sense in putting a Ferrite Rod
at the Far-End of a Random Wire Antenna with the Wire from the
End of the Wire Antenna Element 'wrapped' around it in a
"Tuned Coil" to improve the AM/MW Band Reception ?

* Any 'theory' behind why this Idea might Work ?

* Does this Idea actually Work ?

* Or is this Idea just so much Antenna 'hype' and Sales Marketing

I am Asking these Questions is because of what I have read about
the RF Systems "EMF" Electro-Magnetic-Field Passive Wire Antenna
http://www.universal-radio.com/catalog/sw_ant/0743.html

In "John Wagner's Shortwave Tips & Tricks" he writes:
http://www.dxing.com/tips.htm
"The EMF antenna has two 35mm film canister looking objects
connected to it. The canister on the Far-End is actually an
excellent "Tuned Ferrite Rod" designed for MW (Medium Wave)
and really helps any receiver without a built in MW Antenna
Rod. Canister two (in middle) is a Balun that helps SW
reception very much."


i want to know ~ RHF
.
.

Back in 1965, when I was 14, I tried many variations on
"Long Wire" antennas. Given my parents back yard was about 60'
wide and 120'long, it is clear that they weren't really "long" at
any freqeuncy below 30MHz.
My uncle gave me some variable caps, Air-dux and two large,3/4"X16"
ferrite rods. I tried wrapping wire around the ferrite and, except
for short, 10' wire antennas, with the rod between the antenna and the
receiver the rod made no differnce. None. And nothing worked as well
as my "standard" 96' wire antenna. I did make some dipoles cut for WWV
on 10 and 15MHZ and they were slightly better in receiving WWVH then
the 96' wire antenna. They made no difference on WWV.
I was able to build a match box with Air-dux and the caps and that
really
helped. The radio was a Zenith SW that died that fall. The LO coil
developed a short between the primary and secondary and Dad could not
find a replacement part. So, for a late birthday present my mom and
dad
bought me a Heathkit GR64. It was a gaint step in that it had a
"S-meter".
I even tried a antenna reciever matching transformer suggested by an
article in Radio-Electronics. Which did not work. It consisted of two
air coupled windings sheilded in a soup can. I wish I had known about
transformer deisign that John Doty came up with. Dad also bought me a
ARRL handbook and I started to understand that antennas where not
complete magic.
Just 99%!
Save your maoney and just put up the longest wire you can, be carefull
to
keep it well away from noise sources. John Doty's suggestions for a
"low
noise" antenna are a good palce to start. Works very well and it is
very cheap.
Terry

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

Terry wrote:
Is there any sense in putting a Ferrite Rod at the Far End of a Random
Wire Antenna with the End of the Wire Antenna Element "wrapped around
it" in a tuned coil to improve AM/MW Band reception?"

Frequency selectivity improves signal to noise ratio. Antenna tuning
reduces the possibility of receiver input overload. A naturally resonant
length for the medium-wave band will be more than 150 feet, so a coil is
likely needed to resonate a random length of wire.

Placing a coil at the far end of an antenna increases the current below
the coil which makes it more effective. Such an antenna was patented in
1909. A copy of the diagram which was filed on August 10, 1909 by Simon
Eisenstein of Kiev, Russia appears in Fig 9-24 on page 9-17 of the 1994
edition of ON4UN`s "Low-Band-Band DXing". Circuit to the open-end of the
loading coil is completed by a capacitive hat beyond the coil.

The ferrite rod increases the coil core permeability. This allows fewer
turns for a given inductance. A higher Q results in a more efficient
tuned circuit. Multiple methods may be used to resonate an antenna
circuit. Eisenstein used a coil and a capacitive hat for top loading. It
still may not be enough, and can be augmented with other reactances
located elsewhere.

Best regards, Richard Harrison, KB5WZI

If the rod does anything at all, it increases the effective length of
the antenna. You can accomplish the same thing by physically increasing
the wire length. And all that will do is to increase the amount of
signal -- and noise -- entering your receiver. Once you have enough
signal and noise to overcome your receiver's internal noise, there's no
advantage of any further increase, since there's no improvement in the
signal to noise ratio. Try disconnecting your antenna from your radio.
If the noise level drops when you do, you've got adequate signal
strength from the antenna, and lengthening it -- either physically or
with some kind of loading -- won't help you hear signals.

The explanation of the properties of the antenna at the distributor's
web site is wholly hype and sales marketing. It's a mismash of misused
technical terms, which means nothing and and is quite apparently
intended to mislead a potential customer and present the antenna as
having wonderful properties which it doesn't in fact have. I'd avoid
buying it for that reason if for none other.

Roy Lewallen, W7EL

RHF wrote:

FO&A,

Here is my Question: Is there any sense in putting a Ferrite Rod
at the Far-End of a Random Wire Antenna with the Wire from the
End of the Wire Antenna Element 'wrapped' around it in a
"Tuned Coil" to improve the AM/MW Band Reception ?

* Any 'theory' behind why this Idea might Work ?

* Does this Idea actually Work ?

* Or is this Idea just so much Antenna 'hype' and Sales Marketing

I am Asking these Questions is because of what I have read about
the RF Systems "EMF" Electro-Magnetic-Field Passive Wire Antenna
http://www.universal-radio.com/catalog/sw_ant/0743.html

In "John Wagner's Shortwave Tips & Tricks" he writes:
http://www.dxing.com/tips.htm
"The EMF antenna has two 35mm film canister looking objects
connected to it. The canister on the Far-End is actually an
excellent "Tuned Ferrite Rod" designed for MW (Medium Wave)
and really helps any receiver without a built in MW Antenna
Rod. Canister two (in middle) is a Balun that helps SW
reception very much."


i want to know ~ RHF
.
.

Richard Clark wrote:
"For short antennas and low horizontals, there is almost no
directionality."

True, assuming the the low horizontal ian`t a Beverage or similar wave
antenna.

Ferrite loopsticks have broadside to the axis of te rod sensitivity as
compared to air-core loops which are sensitive in the plane of the loop.

Daytime MW propagation is via the groundwave which is confined to
vertical polarization beyond the line of sight distance.

An L-antenna is using its horizontal portion as a capacitive hat for its
vertical portion which is the real antenna during the daytime hours.

Best regards, Richard Harrison, KB5WZI

= = = Cecil Moore wrote in message
= = = ...
RHF wrote:
JK, RC and CM,
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.

Yes, I was assuming you had a short antenna and wanted to load
it. The reason for loading a short antenna is to increase its
electrical length closer to resonance and the benefits are much
more pronounced for transmitted signals. Most modern HF receivers
have enough gain to make up for a less than optimum antenna.

Loading a long wire antenna doesn't make much sense.


CM,

A 100 Foot long Inverted "L" Antenna is not a Long Wire for the
AM/MW Broadcast Band with coverage for 530 kHz to 1700 kHz

* One Wave Length for 530 kHz is 1896 Feet; and 100 Feet at
530 kHz would only be 0.053 WL.

* One Wave Length for 1700 kHz is 591 Feet; and 100 Feet at
1700 kHz would be 0.169 WL.

Like most people I do not have 600 to 1900 feet of space to
string up a true "Long Wire" {One Wave Length} Antenna for
the AM/MW Broadcast Band. So this is why I am 'questioning'
the use of Ferrite Rod Antenna with a Coil as an integral part
of a 100 Foot long Inverted "L" Antenna.

still searching for answers ~ RHF
..
..

You don't need a long wire for listening. One a fairly small fraction of
a wavelength is probably adequate. If the noise level drops when you
disconnect the antenna, it's long enough, and making it longer or adding
gadgets to it won't help a bit.

A number of the people posting on this thread are thinking of the
requirements for an efficient antenna. Efficiency is important when
transmitting, but of almost no importance for receiving. The antenna
just has to be efficient enough to deliver more atmospheric noise than
you have internal receiver noise. Any more makes no improvement.

Roy Lewallen, W7EL

RHF wrote:

A 100 Foot long Inverted "L" Antenna is not a Long Wire for the
AM/MW Broadcast Band with coverage for 530 kHz to 1700 kHz

* One Wave Length for 530 kHz is 1896 Feet; and 100 Feet at
530 kHz would only be 0.053 WL.

* One Wave Length for 1700 kHz is 591 Feet; and 100 Feet at
1700 kHz would be 0.169 WL.

Like most people I do not have 600 to 1900 feet of space to
string up a true "Long Wire" {One Wave Length} Antenna for
the AM/MW Broadcast Band. So this is why I am 'questioning'
the use of Ferrite Rod Antenna with a Coil as an integral part
of a 100 Foot long Inverted "L" Antenna.

still searching for answers ~ RHF
.
.

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

(RHF) wrote in
om:

FO&A,

Here is my Question: Is there any sense in putting a Ferrite Rod
at the Far-End of a Random Wire Antenna with the Wire from the
End of the Wire Antenna Element 'wrapped' around it in a
"Tuned Coil" to improve the AM/MW Band Reception ?

* Any 'theory' behind why this Idea might Work ?

* Does this Idea actually Work ?

* Or is this Idea just so much Antenna 'hype' and Sales Marketing

I am Asking these Questions is because of what I have read about
the RF Systems "EMF" Electro-Magnetic-Field Passive Wire Antenna
http://www.universal-radio.com/catalog/sw_ant/0743.html

In "John Wagner's Shortwave Tips & Tricks" he writes:
http://www.dxing.com/tips.htm
"The EMF antenna has two 35mm film canister looking objects
connected to it. The canister on the Far-End is actually an
excellent "Tuned Ferrite Rod" designed for MW (Medium Wave)
and really helps any receiver without a built in MW Antenna
Rod. Canister two (in middle) is a Balun that helps SW
reception very much."


i want to know ~ RHF
.
.

I have a 20 foot straight wire in my garage, that works better for MW
DXing than the ferrite rods in any radio I have, due to the fact that it
is much further from any noise sources in the house. I imagine the 16
foot wire being sold there would pick up some MW, but I doubt that
adding the ferrite bar at the end helps one bit.

"Roy Lewallen" wrote
Once you have enough signal and noise to overcome
your receiver's internal noise, there's no advantage of any
further increase, since there's no improvement in the
signal to noise ratio.
__________________

Pardon the thread drift, but making the receive antenna directional can
improve system SNR by reducing the total noise voltage delivered to the
receiver input, as a ratio of the desired signal.

RF

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

Thank You One and All for your Replies.

Well I have the two Inverted "L" Antennas and the proof would
be in the Doing by de-rigging one and wrapping the Antenna Wire
around a Ferrite Core; so that the Coil will be at the Top of
Vertical Up-Leg. Then doing some Side-by-Side Testing of the
two Antennas.

NOTE: Taking a second look at the RF Systems "EMF" Antenna.
The more I get the impression that it is susposed to be Rigged
as a Vertical using the Coax Cable as a Counterpoise or may be
as an Inverted "L" with the Coax Cable as the Vertical Up-Leg
and the Antenna as the Horizontal Out-Arm.

once again thank you very much one and all ~ RHF
..
..
= = = Conan Ford wrote in message
= = = .159...
(RHF) wrote in
om:

FO&A,

Here is my Question: Is there any sense in putting a Ferrite Rod
at the Far-End of a Random Wire Antenna with the Wire from the
End of the Wire Antenna Element 'wrapped' around it in a
"Tuned Coil" to improve the AM/MW Band Reception ?

* Any 'theory' behind why this Idea might Work ?

* Does this Idea actually Work ?

* Or is this Idea just so much Antenna 'hype' and Sales Marketing

I am Asking these Questions is because of what I have read about
the RF Systems "EMF" Electro-Magnetic-Field Passive Wire Antenna
http://www.universal-radio.com/catalog/sw_ant/0743.html

In "John Wagner's Shortwave Tips & Tricks" he writes:
http://www.dxing.com/tips.htm
"The EMF antenna has two 35mm film canister looking objects
connected to it. The canister on the Far-End is actually an
excellent "Tuned Ferrite Rod" designed for MW (Medium Wave)
and really helps any receiver without a built in MW Antenna
Rod. Canister two (in middle) is a Balun that helps SW
reception very much."


i want to know ~ RHF
.
.

I have a 20 foot straight wire in my garage, that works better for MW
DXing than the ferrite rods in any radio I have, due to the fact that it
is much further from any noise sources in the house. I imagine the 16
foot wire being sold there would pick up some MW, but I doubt that
adding the ferrite bar at the end helps one bit.

Yes. My response was intentionally simplified. Making a directional
antenna is often not a viable option for an SWL, because they typically
operate over a wide frequency range, and want to receive signals from
many directions. This pretty much limits them to something like a
rotatable log periodic antenna. Wire antennas can be made directional,
but typically only in fixed or a small number of directions, and with
directional patterns that change with frequency. Within the range of
discussion, then, I don't believe it's realistic to attempt a
directional antenna. The advertised antenna certainly doesn't produce
any advantage in this regard.

Roy Lewallen, W7EL

Richard Fry wrote:
"Roy Lewallen" wrote

Once you have enough signal and noise to overcome
your receiver's internal noise, there's no advantage of any
further increase, since there's no improvement in the
signal to noise ratio.

__________________

Pardon the thread drift, but making the receive antenna directional can
improve system SNR by reducing the total noise voltage delivered to the
receiver input, as a ratio of the desired signal.

RF