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
.
.