Anyone have a way of measuring the varying efficiencies of the
following? Let's say 5 to 20 MHz frequency range.

This would be the base number for comparison, assign it a one:

a: Straight connection of a random long wire antenna


The others...

b: The same long wire connected through a television (75/300 ohm variety)

c: Same antenna with a 9:1 ratio transformer

I'm assuming everything else remaining the same. I'm interested in the
variation, shown ratio wise, between the above. Are there any handy
online calculators for this?


mike

m II wrote:
Anyone have a way of measuring the varying efficiencies of the
following? Let's say 5 to 20 MHz frequency range.

This would be the base number for comparison, assign it a one:

a: Straight connection of a random long wire antenna


The others...

b: The same long wire connected through a television (75/300 ohm variety)

c: Same antenna with a 9:1 ratio transformer

I'm assuming everything else remaining the same. I'm interested in the
variation, shown ratio wise, between the above. Are there any handy
online calculators for this?


mike
http://amateur-radio-wiki.net/index....le=Calculators

In article , m II wrote:
Anyone have a way of measuring the varying efficiencies of the
following? Let's say 5 to 20 MHz frequency range.

This would be the base number for comparison, assign it a one:

a: Straight connection of a random long wire antenna


The others...

b: The same long wire connected through a television (75/300 ohm variety)

c: Same antenna with a 9:1 ratio transformer

I'm assuming everything else remaining the same. I'm interested in the
variation, shown ratio wise, between the above. Are there any handy
online calculators for this?


The problem is that the variations come from characteristics (like
properties of materials and the physical construction) that are easier
to measure than to model. Buzzword: Network Analyzer.

Mark Zenier
Googleproofaddress(account:mzenier provider:eskimo domain:com)

dave wrote:


http://amateur-radio-wiki.net/index....le=Calculators


dammit, dave. If I felt like working at it, I would have gone across
the room and picked out a BOOK. Then on to finding the HP41...Why
can't we just be spoon fed all the time? It works for all the News I
get these days.


On a more serious note, this link was in there..thank you.

http://www.g8ajn.tv/balun.ht



mike

On Jun 26, 1:16*am, m II wrote:
- Anyone have a way of measuring the varying
- efficiencies of the following?
- Let's say 5 to 20 MHz frequency range.
-
- This would be the base number for comparison, assign it a one:
-
- a: Straight connection of a random long wire antenna


OK so this is your starting point "Basic Standard"
with an assigned Unit Value of One [1]

Therefore this is not about 'efficiency' but Relative Merit.

- The others...
-
- b: The same long wire connected through
- a television (75/300 ohm variety)

Depends on the relative quality a design of the
TV Matching Transformer. Plus the quality of
the Coax Cable and a good earthen Ground.

1 - A 'good-one' will reduce some of the apparent
noise coming from the basic long wire antenna :
So that is a +One-Half [+1/2]

2 - A 'good-one' will reduce some of the AM/MW
Band Signals coming from the basic long wire
antenna : So that is a +One-Half [+1/2]

Relative Merit Unit Value of One + One-Half + One-Half
for a Total of Two [2] --- to One

- c: Same antenna with a 9:1 ratio transformer

First most of the very broadband 9:1 Matching
Transformers that are shown for Shortwave Radio
Listening (SWL) are also designed to cover the
AM/MW/BCB down to 500 kHz and SW Bands
up to 30 MHz. These usually recommend about
a 10-Turn Primary for the Feed-Line to the Radio
and about a 30-Turn Secondary for the Antenna
side.

Note - That you set a 5 MHz lower 'limit' so you
might want to cut the number of turns in half and
have a 5 -Turn Primary with a 15 Turn Secondary.

A good 9:1 Matching Transformer :

1 Will reduce much of the apparent noise coming
from the basic long wire antenna : So that is a
+One [+1]

2 - Will reduce much of the AM/MW Band Signals
coming from the basic long wire antenna : So that
is a +One [+1]

Relative Merit Unit Value of One + One + One
for a Total of Three [3] --- to One

- I'm assuming everything else remaining the same.

As am I : Same Long Wire Antenna +plus+

* Same good earthen Ground#
# Note - Many SWL'ers only use an in the house
Water Pipe Ground with their Long Wire Antenna
-so- Going from an in the house Water Pipe Ground
to a good outside 8-Ft earthen Ground Rod may be
another +One [+1] all by itself for those who make
the switch to an outside 8-Ft earthen Ground Rod.

* Same Coax Cable#
# Note - Many SWL'ers only use an Insulated Wire
for their Feed-in-Line from their Long Wire Antenna
-so- Going from an Insulated Wire to a Coax Cable
may be another +One [+1] all by itself for those who
make the switch in the Feed-in-Line.

- I'm interested in the variation, shown ratio wise,
- between the above. Are there any handy
- online calculators for this?

Online Calculators will give you Generated Numbers
for a given set of parameters; and not Relative Ratios
{side-by-side comparisons -aka- Relative Merit} .
-
- mike

iane ~ RHF

RHF wrote:

- c: Same antenna with a 9:1 ratio transformer

First most of the very broadband 9:1 Matching
Transformers that are shown for Shortwave Radio
Listening (SWL) are also designed to cover the
AM/MW/BCB down to 500 kHz and SW Bands
up to 30 MHz. These usually recommend about
a 10-Turn Primary for the Feed-Line to the Radio
and about a 30-Turn Secondary for the Antenna
side.

Note - That you set a 5 MHz lower 'limit' so you
might want to cut the number of turns in half and
have a 5 -Turn Primary with a 15 Turn Secondary.



Both the examples you give have a three to one ratio. If this is a
nine to one example, I must be missing something in your explanation.

Please enlighten me.



mike

On 6/27/10 13:07 , m II wrote:
RHF wrote:

- c: Same antenna with a 9:1 ratio transformer

First most of the very broadband 9:1 Matching
Transformers that are shown for Shortwave Radio
Listening (SWL) are also designed to cover the
AM/MW/BCB down to 500 kHz and SW Bands
up to 30 MHz. These usually recommend about
a 10-Turn Primary for the Feed-Line to the Radio
and about a 30-Turn Secondary for the Antenna
side.

Note - That you set a 5 MHz lower 'limit' so you
might want to cut the number of turns in half and
have a 5 -Turn Primary with a 15 Turn Secondary.



Both the examples you give have a three to one ratio. If this is a
nine to one example, I must be missing something in your explanation.

Please enlighten me.


The impedance ratio is what matters, here. More or less uniform
impedance across the desired spectra produces more or less uniform
performance at the radio input. The impedance ratio of a transformer
is equal to the square of the turns ratio.

A 3:1 turns ratio produces a 9:1 impedance ratio.

Now, a transformer's optimum frequency range will depend on a
number of factors. The specific material used in the core is one.
That's why there are so many different types of core material. The
actual number of turns is another. The type of wind is a third. For
these reasons, and that the impedance ratio is too narrow for the SW
bands, a 75-300 TV transformer is not exactly a good choice for
shortwave listening. Although it may produce passable results at
some frequencies if there are no other options.






mike

On Jun 27, 11:07*am, m II wrote:
RHF wrote:
- c: Same antenna with a 9:1 ratio transformer

First most of the very broadband 9:1 Matching
Transformers that are shown for Shortwave Radio
Listening (SWL) are also designed to cover the
AM/MW/BCB down to 500 kHz and SW Bands
up to 30 MHz. *These usually recommend about
a 10-Turn Primary for the Feed-Line to the Radio
and about a 30-Turn Secondary for the Antenna
side.

Note - That you set a 5 MHz lower 'limit' so you
might want to cut the number of turns in half and
have a 5 -Turn Primary with a 15 Turn Secondary.

- Both the examples you give have a three
- to one ratio. If this is a nine to one example,
- I must be missing something in your explanation.
-
- Please enlighten me.
-
- mike

Mike [M II],

Basically the Ratio is the Square of the Turns
-ex- 1x1 = 1 & 3x3 = 9
-so- 10T & 30T = 100:900 ~ 1:9

Many/most Shortwave Listeners(SWL) Matching
Transformers use a Ratio of 9:1 for Random {Long
Wire} Antennas and for Dipole Antennas a Ratio
of 4:1
http://en.wikipedia.org/wiki/Balun

Please note that your standard TV Matching
Transformer is 300 Ohms to 75 Ohms ~ 4:1
-so- the 300 Ohms side is 4
* The Square Root of 4 is 2
* * the 300 Ohms side would have 2-Turns [2X]
-and- the 75 Ohms side is 1
* The Square Root of 1 is 1
* * the 75 Ohms side would have 1-Turns [1X]
-note- Usually for VHF&UHF TV Signals not
many Turns are required as for the lower HF
Radio Signals of 30 MHz and all the way down
to 500 kHz in the AM/MW BCB.

-fwiw- some SWL'ers will take the very small TV
Matching Transformer Ferrite Binocular Cores
{Two Holes} and rewind them with very thin Wire
to make them into SWL Matching Transformers.
http://www.surplussales.com/Inductor...FerMisc-5.html
Since these are Ferrite Binocular Cores {Two Holes}
they require half the turns as the common One Hole
http://www.surplussales.com/Inductor...FerToro-3.html
Round Donuts {Toroidal}.
http://en.wikipedia.org/wiki/Toroida...d_transformers

Some claim to get 5T & 15T on one of these
very small TV Matching Transformer Ferrite
Binocular Cores going through each of the
Two Holes. I however have only been able
to get 3~4 & 9~12 in these very small cores.
http://www.hard-core-dx.com/nordicdx...eed/feed1.html

Making your own Shortwave Listeners(SWL)
Matching Transformers :

RHF wrote:


Thanks to both of you for the 'square of the turns ratio' bit. I have
found some old computer mother boards and these things are crawling
with ferrite cores suitable for rewinding. Some of them have a
trifiliar (weird word) wrap on them which will be coming off.

I've pulled them out and will be winding them soon.


tertiary mike III

m II wrote:

trifiliar


When I use non existent words like that , I have to pay them extra and
make them mean what I want.


michael lewis carroll II