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

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