FO&A,

FYI [FA] - Ferrite Rod Loop Antenna
+ VLF Band Coverage: 150 kHz - 450 kHz
+ AM/MW Band Coverage: 500 kHz - 1750 kHz
- by eBay Seller 'wjdi' Dave Schneider
WJDI = http://www.wjdi.net/site1001.htm

eBay Auction Listing for this Ferrite Rod Loop Antenna
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=5739735132

These Ferrite Rod Loop Antennas appear to be 'hand-made'
with common parts; that are readily available in most areas
for electronic hobbyist.

TIP - The Design and Layout are worth taking a look at
for your own Ferrite Rod Loop Antenna Projects.

IMAGE - Loop Head Ferrite Rod with Coil
http://www.wjdi.net/400.jpg

IMAGE - Loop Base 3/4 View
http://www.wjdi.net/651.jpg

IMAGE - Loop Base Internal Circuitry
http://www.wjdi.net/652.jpg

IMAGE - Proto-Type 24 Inch Litz Wire Loop Antenna
http://www.wjdi.net/500.jpg


PLEASE NOTE: This is NOT My Auction and
I am NOT Affiliated with the eBay Seller.


iane ~ RHF
..
..

This is fascinating, and brings up some questions -

Is this coil double wrapped? I cannot quite tell from the photos.

On a ferrite rod assembly like this, the coil(s) wrap around only a
small portion of the rod. Noting this, will the rod still transfer
signal along its entire length? In other words, can a shorter rod be
used as effectively?

Is there any value to wrapping the coil(s) more widely spaced along the
length of the ferrite?

Thanks,
Bruce Jensen

bpnjensen wrote:

This is fascinating, and brings up some questions -

Is this coil double wrapped? I cannot quite tell from the photos.

On a ferrite rod assembly like this, the coil(s) wrap around only a
small portion of the rod. Noting this, will the rod still transfer
signal along its entire length? In other words, can a shorter rod be
used as effectively?

Is there any value to wrapping the coil(s) more widely spaced along the
length of the ferrite?

You might wish to direct your questions to Dave Schneider, wjdi AT hvc.rr.com

dxAce
Michigan
USA

BPNJ,

When back and checked the eBay Auction Listing.

The main Photo/Image shows Two (2) 'separate' "Individual" Ferrite
Rod Loop Antenna Heads (VLF & AM/MW) with one Base Unit.

AFAIK - The Coil is the Coil and for the same 'type' Ferrite Material
and Cross Sectional Area: The Coil will not vary too much in its size
and length for the same band of frequencies.
? Comments Please . . .

Most Ferrite Rod Antenna Coils that I have seen for AM/MW are Single
(One) Layer Wrapped: Most likely because for the at home builder
'doing-it-by-hand' this is the easiest method.
? Comments Please . . .

However - I have seen Coils that a
- Evenly "Spaced" over the 'full length' of the Ferrite Rod
- Single Coil = One Coil near one end of the Ferrite Rod
- Twin Coils = One Coil near each end of the Ferrite Rod
? Comments Please . . .

For the same 'type' Ferrite Material and Cross Sectional Area as the
Ferrite Rod gets Longer and Shorter the amount of RF EMF Energy
{Signal} gathering Increases or Decreases respectively.
? Comments Please . . .

The Ferrite Rod is used to gather and concentrate the RF EMF Energy
{Signal} and reduce the physical size of the Antenna Element for
an effective smaller antenna.
? Comments Please . . .

It is my understanding that for a given 'type' Ferrite Material with
a given Cross Sectional Area the Ferrite Rod can only be so long
before the Gains are overcome by the minuses of using a longer
Ferrite Rod. At some point as the Ferrite Rod gets longer; then
the Cross Sectional Area has to Increase too. The result is a
Longer and Thicker Ferrite Rod and these are Costly Items that
usually do not warrant the cost based on any potential or actual
improvement Signal Handling.
? Comments Please . . .

iane ~ RHF
..
..

In article .com,
"bpnjensen" wrote:

This is fascinating, and brings up some questions -

Is this coil double wrapped? I cannot quite tell from the photos.

On a ferrite rod assembly like this, the coil(s) wrap around only a
small portion of the rod. Noting this, will the rod still transfer
signal along its entire length? In other words, can a shorter rod be
used as effectively?

Is there any value to wrapping the coil(s) more widely spaced along the
length of the ferrite?

The core is material that has a higher permeability to magnetic lines of
force than the air it is in so yes the signal will pass through the
length of the rod.

Winding the turns farther apart will reduce the inter-winding
capacitance and the coil will have the ability to resonate at a high
frequency.

--
Telamon
Ventura, California

Something To Think About - PRICE WISE !
..
I would guess that you would have to compare this to a
Palomar Ferrite Rod Loop Antenna System.
..
Palomar LA-1 Loop Amp Base @ $135
= http://www.universal-radio.com/catalog/sw_ant/0445.html
+ Very Long Wave Loop Ferrite Rod Element
Coverage 50 kHz to 150 kHz @ $ 150
+ Long Wave Loop Ferrite Rod Element
Coverage 150 kHz to 550 kHz @ $ 135
+ Medium Wave (AM/MW) Ferrite Rod Loop Element
Coverage 530-1700 kHz @ $ 135
$ Total Cost: $455 +S&H

Also, the Quantum "QX" Pro 15" Ferrite Rod Loop Antenna System
= http://www.dxtools.com/QXPro.htm
Covers both Long Wave and Medium Wave Bands 150 kHz to 2000 kHz
$ Cost: $299 +S&H
..
Or a 'used' Kiwa MW Air-Core Loop Antenna on eBay
SEARCH = Consumer Electronics : Radios : CB/HAM/Shortwave for 'kiwa'
KIWA= http://tinyurl.com/2fcqq
..
For more information on the Kiwa MW Air-Core Loop Antenna goto:
KIWA-MW-LOOP= http://www.kiwa.com/kiwaloop.html
..
RUMOR has it that Kiwa Electronics is currently working on a
'new' AM/MW {Loop?Ferrite} Antenna for AM/MW DXers.
? ? ? Now Is That True ? ? ?
..
..
iane ~ RHF
..
..

BPNJ,

When back and checked the eBay Auction Listing.

The main Photo/Image shows Two (2) 'separate' "Individual" Ferrite
Rod Loop Antenna Heads (VLF & AM/MW) with one Base Unit.

AFAIK - The Coil is the Coil and for the same 'type' Ferrite Material
and Cross Sectional Area: The Coil will not vary too much in its size
and length for the same band of frequencies.
? Comments Please . . .

Most Ferrite Rod Antenna Coils that I have seen for AM/MW are Single
(One) Layer Wrapped: Most likely because for the at home builder
'doing-it-by-hand' this is the easiest method.
? Comments Please . . .

However - I have seen Coils that a
- Evenly "Spaced" over the 'full length' of the Ferrite Rod
- Single Coil = One Coil near one end of the Ferrite Rod
- Twin Coils = One Coil near each end of the Ferrite Rod
? Comments Please . . .

For the same 'type' Ferrite Material and Cross Sectional Area as the
Ferrite Rod gets Longer and Shorter the amount of RF EMF Energy
{Signal} gathering Increases or Decreases respectively.
? Comments Please . . .

The Ferrite Rod is used to gather and concentrate the RF EMF Energy
{Signal} and reduce the physical size of the Antenna Element for
an effective smaller antenna.
? Comments Please . . .

It is my understanding that for a given 'type' Ferrite Material with
a given Cross Sectional Area the Ferrite Rod can only be so long
before the Gains are overcome by the minuses of using a longer
Ferrite Rod. At some point as the Ferrite Rod gets longer; then
the Cross Sectional Area has to Increase too. The result is a
Longer and Thicker Ferrite Rod and these are Costly Items that
usually do not warrant the cost based on any potential or actual
improvement Signal Handling.
? Comments Please . . .

iane ~ RHF
..
..

RHF wrote:
BPNJ,

When back and checked the eBay Auction Listing.

The main Photo/Image shows Two (2) 'separate' "Individual" Ferrite
Rod Loop Antenna Heads (VLF & AM/MW) with one Base Unit.

AFAIK - The Coil is the Coil and for the same 'type' Ferrite Material
and Cross Sectional Area: The Coil will not vary too much in its size
and length for the same band of frequencies.
? Comments Please . . .

Think about that in terms of the size of coil in a GE Superadio and a
small pocket radio. They cover the same frequencies. They are a
different size. Size alone does not dictate inductance. For a given
capacitance, the inductance needs to stay the same if you are covering
the same frequencies.



Most Ferrite Rod Antenna Coils that I have seen for AM/MW are Single
(One) Layer Wrapped: Most likely because for the at home builder
'doing-it-by-hand' this is the easiest method.
? Comments Please . . .

Most antennas are mass produced so the home builder has little to do
with it. For the home builder the easiest thing to do is a jumbled mess
wrapped around the form.


However - I have seen Coils that a
- Evenly "Spaced" over the 'full length' of the Ferrite Rod
- Single Coil = One Coil near one end of the Ferrite Rod
- Twin Coils = One Coil near each end of the Ferrite Rod
? Comments Please . . .

The person designing the antenna has many choices that can be made.
Different spacing affects coupling and stray capacitance.


For the same 'type' Ferrite Material and Cross Sectional Area as the
Ferrite Rod gets Longer and Shorter the amount of RF EMF Energy
{Signal} gathering Increases or Decreases respectively.
? Comments Please . . .

If that were the case, then small portable radios would be deaf. Some
small radios are considered very sensitive.


The Ferrite Rod is used to gather and concentrate the RF EMF Energy
{Signal} and reduce the physical size of the Antenna Element for
an effective smaller antenna.
? Comments Please . . .

That is the effect of permeability of the material. (Hint: this is one
of the key magnetic properties that matter.)



It is my understanding that for a given 'type' Ferrite Material with
a given Cross Sectional Area the Ferrite Rod can only be so long
before the Gains are overcome by the minuses of using a longer
Ferrite Rod.

You are talking about design trade offs, but don't present anything
specific. An assumption is made that the length is a major driver in
performance. You don't indicate what 'minuses' you are referring to.

At some point as the Ferrite Rod gets longer; then
the Cross Sectional Area has to Increase too.

Why, what dictates that? Please present some information supports your
statement. This would indicate a magic point for length to area ratio.

The result is a
Longer and Thicker Ferrite Rod and these are Costly Items that
usually do not warrant the cost based on any potential or actual
improvement Signal Handling.
? Comments Please . . .


You seems to be trying to make a connection between the effectiveness of
a ferrite antenna and its size without any understanding of how they
actually work.

Why not spend some time using Google (or a library) and do some real
research into the topic and report your findings back to the group?
Those findings can be backed with references and proper technical
reasoning. This would be better than the usual misinformation generally
seen. By the way, I do not consider references to posts in Yahoo groups
as being credible.

craigm

iane ~ RHF
.
.

CRAIGM,
..
"Why not spend some time using Google (or a library) and do some
real research into the topic and report your findings back to the
group? Those findings can be backed with references and proper
technical reasoning. This would be better than the usual
misinformation generally seen. - craigm"
..
A Good Suggestion - Why Don't You... Write a Book and Post It Here )
..
Who Know I Might Read It Some Day - iane ~ RHF
..
..

..
..

RHF wrote:
CRAIGM,
.
"Why not spend some time using Google (or a library) and do some
real research into the topic and report your findings back to the
group? Those findings can be backed with references and proper
technical reasoning. This would be better than the usual
misinformation generally seen. - craigm"
.
A Good Suggestion - Why Don't You... Write a Book and Post It Here )
.
Who Know I Might Read It Some Day - iane ~ RHF
.
.

.
.



I wasn't the one looking for comments.