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Old June 24th 08, 09:41 PM posted to rec.radio.shortwave
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First recorded activity by RadioBanter: Jun 2006
Posts: 8,652
Default Converting the an small short Active Whip Antenna into a smallTerminated Loop Active Antenna.

On Jun 24, 5:46*am, Dave wrote:
Telamon wrote:
In article ,
*"Justis" wrote:


Tried the MFJ-1024 and it's definitely going back. *Quieter reception
and seems like more gain on my zigzag "array". I even do better with
my TPA Ameco active antenna, indoors. *Too much gain and it
overloads, backing off the gain and it's just not equal to wire mess
in my backyard.


SNIP


- - Build a loop antenna.

- As I pointed out, it (MFJ-1024) works fine out here
- in the Wild American West, where there is no HF
- to overload the mediocre active elements.
- The only problem with loops is that they work a lot
- better if they are resonated, which requires a variable
- capacitor outdoors.

? Loop Antenna +plus+ Active Whip Antenna ?

Converting the an small short Active Whip Antenna
into a small Terminated Loop Active Antenna.

Replace the MFJ-1024 Active Antenna's Whip Element with
a single turn One Metre Diameter Loop Antenna Element.

NOTE - The One Metre Diameter Loop Antenna Element
is about 10.3 Feet (124") Long and has a Signal Appeture
Area of around 8.4 Square Feet. -while- The original Whip
Antenna was only 54" Long with a relative Signal Appeture
Area of around 1.2 Square Feet.

* Near-End of the Loop Antenna Element is attached /
connected to the Mounting Stud for the Whip Element.

* The Far-End of the Loop Antenna Element is connected
via a Shunt/Bleed Resistor to the Grounded Body of the
MFJ-1024 Active Antenna's Mast Head Unit.

* Start with a 680 K Ohm Shunt/Bleed Resistor and test
for a =Balance= between RF Signal Strength Across the
MW and/or Shortwave Radio Bands and RF Signal Over
Load from 'local' AM & FM Radio Stations.
* * Adjust the Resistance Value of the Resistor :
Up -if- RF Signal Levels are Low 1.3 MŮ
2.7 MŮ, 5.6 MŮ, 11 MŮ, 22 MŮ, 44 MŮ,
* * Adjust the Resistance Value of the Resistor :
Up -if- RF Signal Levels are Low 1.3 MŮ, 2.7 MŮ, 5.6 MŮ,
11 MŮ, 22 MŮ, 44 MŮ, etc.
* * Adjust the Resistance Value of the Resistor :
Down -if- RF Signal Levels are OK but there is Overload
430 KŮ, 270 KŮ, 180 KŮ, 120 KŮ, 82 KŮ, 56 KŮ, etc.

FWIW - This is a 'small' Terminated Loop Antenna Element
and is still some what Directional. So you can position the
Loop Antenna Element to :
* Null-Out 'local' sources of RF Noise.
* Null-Out Overload from 'local' AM & FM Radio Stations.


even though you think you have it whipped . . .
it is often better to be in-the-loop - iane ~ RHF {pomkia}