- The radio input impedance is a separate issue.
-
- Re-quoting RHF post I specifically object to the following.
-
* Use a Balun with a Dipole Antenna Another 'improved' Shortwave
Listening (SWL) Antenna design would use a Balun {Matching
Transformer} between the Dipole Antennaand the Coax Cable
feed-in-line. This is most often a 4:1 {Four-to-One} Matching
Transformer. Using the Balun will better 'match' the Dipole Antenna
to the Coax Cable feed-in-line and the Receiver across a wide
frequency range then simply using a Dipole Antenna that is directly
connected to the Coax Cable.
- - - The direct conneted Dipole Antenna is great for Hams
working on a single Shortwave (HF) Frequency Band.


- RHF wrote about matching a dipole.
- I wrote about matching a folded dipole in a follow up to his post.
- A dipole is around 72 ohms and a folded dipole is around 300 ohms.
-
- ********
-
- There are three items involved, antenna, transmission line, and radio

- input impedance. They all have to match. The 4:1 BALUN is incorrect
to
- match a dipole to 50 ohm coax what is happening on the other end of
the
- coax does not change this relationship. The closest easily attainable

- would be a 1:1 BALUN. All impedances need to match or you have
- reflections and the signal that the antenna picks up will only
- partially be used by the radio input.
-
- If the 50 ohm coax to radio input is an issue then you need another
- transform between the coax and radio input. Most radios have a 50 ohm

- input. Generally, you can figure this out by the connector used. On
- most radios the radio input may not be right at 50 ohms but will be
- somewhere in that area over the 3 to 30 MHz input range.
-
- --
- Telamon
- Ventura, California

Telemon,

Everything that you say is true -HOWEVER-

1 - The Dipole Antenna is very good for a specific single frequency
-and- most Shortwave Listeners (SWL) are tuning across the
entire range of the Shortwave Band (HF) from 1.8 MHz to 30
MHz and the majority are also using the same Antenna for
AM (Medium Wave) 530 kHz to 1700 kHz Listening too.

2 - The Folded Dipole Antenna is a good choice for the Shortwave
Listener (SWL) -but- it is effectively a 'spoiled' Antenna : Not Very
Good on any one frequency -bu-t some-what-good across the entire
range of Shortwave Frequencies.

3 - This is where the use of a Matching Transformer comes into
play with a : Dipole Antenna, Inverted "L" Antenna, Sloper Antenna,
Random Wire Antenna, Windom Antenna or a Loop Antenna.
- - - The Matching Transformer be it a Balun or UnUn can take
a good single frequency Shortwave Antenna and 'transform' it into
a Not Very Good on any one frequency -but- some-what-good
across the entire range of Shortwave Frequencies Antenna.
- - - The Matching Transformer effectively 'spoils' the Antenna.

Note - The Sensitivity and dynamic-range of most modern
Shortwave Radio makes up for this 'spoiled' Antenna.

FWIW - What I am saying (writing) is not the pure science
of Shortwave Antennas and clearly is not technically correct.
-But- For the Shortwave Listener (SWL) it generally provides
a single Shortwave Listening (SWL) Antenna that 'works'
reasonably well across the enter Shortwave (HF) Band.

LOW NOISE ANTENNA DESIGN CONCEPTS:
Uses a Random Wire Antenna Element coupled via a 9:1
Matching Transformer at the Near-End of the Antenna with
a Ground Rod and Coax Cable feed-in-line to the Receiver.
This is basically an Antenna that uses the "Low Noise Antenna"
'design concepts' that were popularized -by- John Doty.
[ Please READ These Three Links ]
.
Low Noise Antenna Connection - by John Doty
http://www.anarc.org/naswa/badx/ante...e_antenna.html
.
Shortwave Listener (SWL) Longwire Antenna - by John Doty
? WHY Use a Fixed Matching Transformer ?
http://www.anarc.org/naswa/badx/ante..._longwire.html
.
Grounding is the Key to Good Reception - by John Doty
http://www.anarc.org/naswa/badx/antennas/grounding.html
.
.
Once Again Re-Read :
Shortwave Listener (SWL) Longwire Antenna - by John Doty
? WHY Use a Fixed Matching Transformer ?
http://www.anarc.org/naswa/badx/ante..._longwire.html

To read more Rec.Radio.Shortwave postings by John Doty
Click-On = http://tinyurl.com/79tk5
.
.
shortwave listening (swl) antennas - they are all about . . .
hearing 'what's out there' across the bands - iane ~ RHF
.
Shortwave Listener Antennas = http://tinyurl.com/ogvcf
http://groups.yahoo.com/group/Shortwave-SWL-Antenna/
SWL Antenna Group = http://tinyurl.com/ogvcf
.
The Shortwave Listener's Blessing :
SWL BLESSING = http://tinyurl.com/s2bjm
May You Never Tire of Listening to the Radio and Always
have Strong Signals and Noise Free Reception ~ RHF {ibid}
http://groups.yahoo.com/group/Shortw...a/message/9233
.
Tous Sont Bienvenus ! - - - Groupe par Radio
d'auditeur d'onde courte pour des Antennes de SWL
http://groups.yahoo.com/group/Shortwave-SWL-Antenna/
.
Alle Sind Willkommen ! - - - Shortwave Radiozuhörer
Gruppe für SWL Antennen
http://groups.yahoo.com/group/Shortwave-SWL-Antenna/
.
Tutti Sono Benvenuti ! - - - Gruppo Radiofonico
dell'ascoltatore di onda corta per le Antenne di SWL
http://groups.yahoo.com/group/Shortwave-SWL-Antenna/
.
Todos São Bem-vindos ! - - - Grupo de Rádio
do ouvinte do Shortwave para Antenas de SWL
http://groups.yahoo.com/group/Shortwave-SWL-Antenna/
.
Ð’Ñ�е Ð*адушны ! - - - Группа оператора
на приеме коротковолнового диапазона
Radio дл� Aнтенн SWL
http://groups.yahoo.com/group/Shortwave-SWL-Antenna/
.
¡Todos Son Agradables! - - - Grupo de Radio del oyente
de la onda corta para las Antenas de SWL
http://groups.yahoo.com/group/Shortwave-SWL-Antenna/
.
= = = = Plain Old American-English Translation = = = =
All are Welcome - - - To Join the Shortwave Listeners
(SWL) Antenna Group on YAHOO !
http://groups.yahoo.com/group/Shortwave-SWL-Antenna/
.
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