Argh. I just posted an empty message. Sorry. Please ignore.

Thanks for the info. I picked up a 300/75 ohm mini-plug adapter at the
store, but failed to get the second 75/300 ohm matching transformer to go
between it and the coax. Tomorrow.

Question: I have an odd situation, and can either install a 1/4 wave dipole
or a half-wave "random" wire loop (I think). Right now the grounding rod is
immediately below where the dipole would go, and I think I could drop the
300 ohm twin-lead down to it where I would ground one side (I think I have
this right, please correct me if I am wrong). At that same point I would
ground the shield of the coax, and hook the other side of the dipole to the
coax center conductor. Coax would travel 10 feet or so to my window and the
radio. Other option involves moving the grounding rod and doing something
similar with the twin-lead as a long loop, grounding one side of that and
coax from the other side of the window. Assuming these are workable ideas,
which do you think would work best? Again, [please don't hesitate to tell
me if I am full of crap. RF is new to me.

I really do appreciate your help. Like I said before, RF is totally new to
me.

Thanks,

Dave


"RHF" wrote in message
om...
DAVE,

At the Radio-End of the 75 Ohm Coax Cable "F" Connector you can
use a standard 75-300 Ohm Matching Transformer and then connect
it to a Mini-TV External Antenna Adapter. [ RadioShack {Canada}
Catalog #: 15-1148 = 75 to 300 Ohm Mini-Plug Adapter ]
MINI-PLUG-ADAPTER= http://tinyurl.com/23nsh

FWIW: Some RadioShacks and other electronics stores have an "Adapter"
that directly connects an "F" Connector to a /18" Mono-Phone-Jack.


Please Note: That a 'connection' to a good earthen Ground is
needed to one of the "F" Connectors of the 75 Ohm Coax Cable.

You can use a #14 Wire with a RadioShack Catalog #: 278-002
Heavy-Duty Claw Insulated Test/Jumper Cable Sets. Or, simply
use several windings of bare wire wrapped around one of the "F"
Connectors with a small metal hose clamp to secure the wire.


iane ~ RHF
.
.
= = = "Dave" wrote in message
= = = ...
Just printed your instructions in prep for a trip to the store, and have
one
question: The twin-lead is 300 ohm, connected to a 300/75 ohm matching
transformer, connected to 75 ohm coax. Then the coax is connectect to
another 75/300 ohm matching transformer, which is connected to the 1/8"
mono
plug to plug into the external antenna jack? Is the 1/8" jack a 300 ohm
impedance connection? Somehow I thought it would be 50 or 75 ohms, like
coax. Do I need some 300 ohm coax to put between the second transformer
and
the plug?

Thanks,

Dave


"RHF" wrote in message
om...
DAVE,

So you have a Sangean ATS -505 and your 'problems' are Antenna
Overload and Noise Levels.
* Consider a 'smaller' shorter Antenna will reduce the overload
problems.
* Consider a Low Noise Antenna Design will reduce the noise problems.
{LOW NOISE SWL ANTENNA - popularized by John Doty}
http://groups.yahoo.com/group/Shortw...enna/message/2
http://www.anarc.org/naswa/badx/ante...e_antenna.html

For a simple 'external' Shortwave Antenna to use with the Sangean
ATS-505 'portable' Shortwave Radio, using the 1/8" Mono-Jack
External Shortwave Antenna Input. Consider a Random Wire
Antenna using a Matching Transformer and Ground for Low Noise
and Wide Range Frequency Coverage.

PARTS: Here is a simple SWL Antenna Idea using a few common
RadioShack TV Antenna type parts:
Catalog #: 15-1174 = 25~50 Foot 300 Ohm (Flat) TV Twin-Lead
Catalog #: 15-1230 = 75 to 300 Ohm Matching Transformer (2 Ea.)
Catalog #: 274-286 = 1/8" Mono (Phone) Plug
Catalog #: Catalog #: 15-1579 = 25~50 Foot Coax Cable with F
Connectors

NOTE: This is an 'improved' Random Wire SWL Antenna using "TV"
Parts for 'reducing' Man Made Noise (RFI EMF) that is generated in
or near most modern homes/buildings.

EXTERNAL "OUTSIDE" SWL ANTENNA:

The Antenna [Loop] Element is Stretched outside Horizontally or
in the shape of an Inverted "L". The Antenna [Loop] Element is
formed by connecting the two ends of the Far-End of the 300 Ohm
TV Twin Lead. This forms a continuous single skinny horizontal
flat loop going out and back. This also represents a Balance
300 Ohm Load to match-up with the 300 Ohm Matching Transformer.
The 300 Ohm Leads of the Matching Transformer connects to the
Near-Ends of the Loop Antenna Element. The 75 Ohm F Connector
of the Matching Transformer is connected to the 75 Ohm Coax Cable.
The 75 Ohm Coax Cable acts as the Lead-In from the Outside to
inside the house to the radio shack. The other end of the 75
Ohm Coax Cable is connected to the 75 Ohm F Connector of the
Matching Transformer. The Radio-End of the Coax Cable F Connector
would connect to a 75 to 300 Ohm Matching Transformer; and then
into a 1/8" Mono-Plug to plug into the Radio.
NOTE: Using the 300 Ohm TV Twin Lead in a Skinny Flat Loop
Antenna should balance-cancel-reduce most man made noise and be
Omni-Directional.

GROUND: Find a Grounding Point within/about your dwelling.
Secure a good Grounding Point for your Radio and Antenna.
Run a Heavy & Short Ground Wire to your Radio. Locate the
Ground Terminal on your Radio. Attach/Secure the Ground Wire
to the Coax Cable and/or the Radio's Ground Terminal.

FWIW: This Antenna using common TV Antenna type parts should
be effective as SWL Antennas above 5MHz and beyond 30MHz.


iane ~ RHF
.
Some Say: On A Clear Day You Can See Forever.
http://groups.yahoo.com/group/Shortw...na/message/502
I BELIEVE: On A Clear Night...
You Can Hear Forever and Beyond - The Beyond !
.
.
= = = "Dave" wrote in message
= = = ...
I recently hooked up a thirty-six foot (plus or minus a couple of
feet)
piece of four-stranded wire with alligator clip to the internal
"whip"
antenna of my portable shortwave receiver, for the extra performance
such a
device offered. It works so well that I now cannot usually use my
"DX"
setting because of all the background noise (sounds like hundreds of
other
broadcasts vying for attention.) I don't know the frequency source
of
all
this background noise, but would like to filter out as much of it as
I
can.
One manufacturer of a similar "wind-up" antenna adds a capacitor to
the
wire
in order to lower the resonance frequency of the wire. If I were
going
to
try something similar (adding a capacitor, in series) in an attempt
to
bring
the resonance of the wire down into the 30 MHz range, what size
(roughly)
capacitor should I use? Should I just try a few with different
ranges,
or
does anyone here have any suggestions?

TIA

Cross-posted between sci.electronics.basics and rec.radio.shortwave


Dave


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