So what's the best plan? If I string a dipole antenna, what are the
optimum leg lengths? Are the circular indoor "amplified" units any good?
Any other ideas?
JR
Dweller in the cellar

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In article ,
JR North wrote:

So what's the best plan? If I string a dipole antenna, what are the
optimum leg lengths?

Get a copy of The Radio Amateurs Handbook (ARRL), and read the chapter
on antennas. It has lots of tables and charts and nomograms.


Are the circular indoor "amplified" units any good?

No.


Any other ideas?

If you listen to a particular station, you can make a rhomboid antenna
from copper wire, aimed directly at the station's antenna tower. This
can be done very cheaply, in the attic. The radio waves have no problem
getting through all but a metal roof, and with antennas, higher is
better.

Joe Gwinn.

JR North wrote:
So what's the best plan?

Mr. Cebik has a pretty good page on the subject.

http://www.cebik.com/vhf/fm1.html

Kevin Gallimore

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JR North wrote:

So what's the best plan? If I string a dipole antenna, what are the
optimum leg lengths?

1/4 wavelength. A good way to go is to get about 12 feet of 300 ohm twin-lead
and figure out the wavelength of 100MHz (remember the speed of light equals
frequency times wavelength, plug in speed of light and 100MHz and get out your
wavelength, pay attention to units). Then cut a piece of the twinlead to 1/4
wavelength length, strip the ends, and solder two 300 ohm resistors across each
end. Then carefully find the middle, and cut just one of the twin-lead wires
right in the middle, then cut it away from the body on each side of the cut
until your cut is the width of the twin-lead, then strip the 2 pieces and strip
the ends of another long piece of twin-lead and solder the wires so the whole
thing makes a T. Strip and attach the other end of the non-quarter-wavelength
piece to your 300 ohm antenna input, and stretch the top of the T out so you get
good reception.

Are the circular indoor "amplified" units any good?

Better than connecting the inputs to a bowl of Jell-O maybe, not really very
good antennas. But you don't need much if your desired signal is strong.

Any other ideas?

Yes. Go to Goodwill and get an old school rabbit ears with the FM antenna built
into it, and just use it for the FM antenna part. Don't spend more than a buck
or two in case you don't like it.

GWE

Ok - easy - did it in school while in the dorms at TAMU.

Take a length of twin lead - 2 meters long. strip both ends and short both
so it now becomes a long loop. At the center of one side only, cut. Cut
back each side of the cut - and splice another length of twin lead - attaching
both sides to the two wires from the center cut strip back point.

You should have a T now. The long 6' loop should be somewhat taught and held
in place by rubber bands. The angle is directive - so sweep or simply point
the perpendicular at the station. Then simply connect the twin lead.

If your radio has 75 ohm - then adapt the twin lead to the common transformer
that changes the impedance.

It worked for me over 200 miles from radio to station tower. Tower is important.
It might not be where the station is.

Martin

Martin Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
NRA LOH & Endowment Member
NRA Second Amendment Task Force Charter Founder



JR North wrote:
So what's the best plan? If I string a dipole antenna, what are the
optimum leg lengths? Are the circular indoor "amplified" units any good?
Any other ideas?
JR
Dweller in the cellar


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Folded dipole - with graphics - like I suggested.

Martin
Martin Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
NRA LOH & Endowment Member
NRA Second Amendment Task Force Charter Founder



Winston Smith wrote:
On Sat, 11 Feb 2006 09:25:08 -0800, JR North
wrote:


So what's the best plan? If I string a dipole antenna, what are the
optimum leg lengths? Are the circular indoor "amplified" units any good?
Any other ideas?
JR
Dweller in the cellar


Try something simple before you spend money. A lot of those fancy
indoor antennas are bogus.

If you are reasonably close to the transmitter, make one out of
twin-lead/lead-in. Put it broad side to the transmitter.

How to make an FM antenna
http://www.kgnu.org/howtohear/antenna.html

I'm pretty close to the transmitters and a couple feet of wire
dangling down works pretty well.

--
W§ mostly in m.s - http://members.1stconnect.com/anozira

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On Sat, 11 Feb 2006 14:19:47 -0800, Grant Erwin
wrote:

JR North wrote:

So what's the best plan? If I string a dipole antenna, what are the
optimum leg lengths?

1/4 wavelength. A good way to go is to get about 12 feet of 300 ohm twin-lead
and figure out the wavelength of 100MHz (remember the speed of light equals
frequency times wavelength, plug in speed of light and 100MHz and get out your
wavelength, pay attention to units). Then cut a piece of the twinlead to 1/4
wavelength length, strip the ends, and solder two 300 ohm resistors across each
end. Then carefully find the middle, and cut just one of the twin-lead wires
right in the middle, then cut it away from the body on each side of the cut
until your cut is the width of the twin-lead, then strip the 2 pieces and strip
the ends of another long piece of twin-lead and solder the wires so the whole
thing makes a T. Strip and attach the other end of the non-quarter-wavelength
piece to your 300 ohm antenna input, and stretch the top of the T out so you get
good reception.

You're not having a good day, Grant! Total length should be 1/2
wave, not 1/4 wave, and you just short the ends -- no resistors.

Check Cebik's site cited in another post.

Don Foreman wrote:
On Sat, 11 Feb 2006 14:19:47 -0800, Grant Erwin
wrote:


JR North wrote:


So what's the best plan? If I string a dipole antenna, what are the
optimum leg lengths?

1/4 wavelength. A good way to go is to get about 12 feet of 300 ohm twin-lead
and figure out the wavelength of 100MHz (remember the speed of light equals
frequency times wavelength, plug in speed of light and 100MHz and get out your
wavelength, pay attention to units). Then cut a piece of the twinlead to 1/4
wavelength length, strip the ends, and solder two 300 ohm resistors across each
end. Then carefully find the middle, and cut just one of the twin-lead wires
right in the middle, then cut it away from the body on each side of the cut
until your cut is the width of the twin-lead, then strip the 2 pieces and strip
the ends of another long piece of twin-lead and solder the wires so the whole
thing makes a T. Strip and attach the other end of the non-quarter-wavelength
piece to your 300 ohm antenna input, and stretch the top of the T out so you get
good reception.


You're not having a good day, Grant! Total length should be 1/2
wave, not 1/4 wave, and you just short the ends -- no resistors.

Check Cebik's site cited in another post.

Maybe. At 1/2 wavelength, yes, you can short the leads. At 1/4 wavelength, I
believe a standing wave should be terminated by what looks like an infinite
stretch of 300 ohm twinlead - a 300 ohm resistor. Maybe I'm remembering it
wrong, in any case the design cited should work for the OP.

GWE

On Sat, 11 Feb 2006 21:04:55 -0800, Grant Erwin
wrote:

Don Foreman wrote:
On Sat, 11 Feb 2006 14:19:47 -0800, Grant Erwin
wrote:


JR North wrote:


So what's the best plan? If I string a dipole antenna, what are the
optimum leg lengths?

1/4 wavelength. A good way to go is to get about 12 feet of 300 ohm twin-lead
and figure out the wavelength of 100MHz (remember the speed of light equals
frequency times wavelength, plug in speed of light and 100MHz and get out your
wavelength, pay attention to units). Then cut a piece of the twinlead to 1/4
wavelength length, strip the ends, and solder two 300 ohm resistors across each
end. Then carefully find the middle, and cut just one of the twin-lead wires
right in the middle, then cut it away from the body on each side of the cut
until your cut is the width of the twin-lead, then strip the 2 pieces and strip
the ends of another long piece of twin-lead and solder the wires so the whole
thing makes a T. Strip and attach the other end of the non-quarter-wavelength
piece to your 300 ohm antenna input, and stretch the top of the T out so you get
good reception.


You're not having a good day, Grant! Total length should be 1/2
wave, not 1/4 wave, and you just short the ends -- no resistors.

Check Cebik's site cited in another post.

Maybe. At 1/2 wavelength, yes, you can short the leads. At 1/4 wavelength, I
believe a standing wave should be terminated by what looks like an infinite
stretch of 300 ohm twinlead - a 300 ohm resistor. Maybe I'm remembering it
wrong, in any case the design cited should work for the OP.

GWE

I think you want/need a standing wave in the antenna portion of a
folded dipole. Sections of T-line terminated in Zo don't radiate
much signal, right? By reciprocity, if they wouldn't transmit they
also won't receive.

In article .com,
mechanized_robot wrote:
Try this thread -

http://audiokarma.org/forums/showthread.php?t=58057

I came across it awhile back when I was looking to improve my FM
reception. Both of these are pretty simple to build. I think I may try
the J-Pole design when the weather improves up here (Boston) and I can
get out & mount it.



I live in an area with marginal signal strength and interference from
stations in another nearby city. I had the twinlead FM antenna that
came with some radio tacked to the wall. You can buy one from Radio
Shack for a couple bucks.

I made a MUCH better antenna by cutting a piece of thin PVC pipe the
length of the antenna, about 4 ft, and taping the antenna to it with
the feedline dropping down from the middle. I got some monofilament
fishline and hung the pipe from the ceiling above the radio, at the
balance point and then at one end hung a piece of fighline down a
couple feet so I could swing the antenna around to make the best of
the signal I want to hear and minimize the interferance.

The hang point is just far enough away from the wall to allow swing
and the fishline is tied to the PVC an inch off-center so that one end
touches the ceiling just enough so that it stays where I want it.

It's all white or transparent and is almost invisible.

--
a d y k e s @ p a n i x . c o m

Don't blame me. I voted for Gore.

As Don sez, loose the resistors. The top of the "T" should be aprox. 1/2
wavelength. Characteristic Z of a folded dipole is aprox. 300 Ohms, same as
that of twin lead. This suggests your receiver has a 300 Ohm antenna
terminal on the back. Otherwise if the twin lead is fed to a 75 Ohm coaxial
port on the receiver, then (theoretically) it should be matched to that port
via a "balun" type of Z matching device.

Bob Swinney
"Don Foreman" wrote in message
...
On Sat, 11 Feb 2006 21:04:55 -0800, Grant Erwin
wrote:

Don Foreman wrote:
On Sat, 11 Feb 2006 14:19:47 -0800, Grant Erwin
wrote:


JR North wrote:


So what's the best plan? If I string a dipole antenna, what are the
optimum leg lengths?

1/4 wavelength. A good way to go is to get about 12 feet of 300 ohm
twin-lead
and figure out the wavelength of 100MHz (remember the speed of light
equals
frequency times wavelength, plug in speed of light and 100MHz and get
out your
wavelength, pay attention to units). Then cut a piece of the twinlead to
1/4
wavelength length, strip the ends, and solder two 300 ohm resistors
across each
end. Then carefully find the middle, and cut just one of the twin-lead
wires
right in the middle, then cut it away from the body on each side of the
cut
until your cut is the width of the twin-lead, then strip the 2 pieces
and strip
the ends of another long piece of twin-lead and solder the wires so the
whole
thing makes a T. Strip and attach the other end of the
non-quarter-wavelength
piece to your 300 ohm antenna input, and stretch the top of the T out so
you get
good reception.


You're not having a good day, Grant! Total length should be 1/2
wave, not 1/4 wave, and you just short the ends -- no resistors.

Check Cebik's site cited in another post.

Maybe. At 1/2 wavelength, yes, you can short the leads. At 1/4 wavelength,
I
believe a standing wave should be terminated by what looks like an
infinite
stretch of 300 ohm twinlead - a 300 ohm resistor. Maybe I'm remembering it
wrong, in any case the design cited should work for the OP.

GWE

I think you want/need a standing wave in the antenna portion of a
folded dipole. Sections of T-line terminated in Zo don't radiate
much signal, right? By reciprocity, if they wouldn't transmit they
also won't receive.

I used to make lots of FM antennas in HS - this was before everything
came with antennas in the box- take 5 feet of 300 ohm twinlead - short
both ends. cut one of the wires in the middle and splice into a fresh
piece of twinlead. takes about 2 minutes to make - somewhat
directional though







On Tue, 14 Feb 2006 09:16:00 -0600, "Robert Swinney"
wrote:

As Don sez, loose the resistors. The top of the "T" should be aprox. 1/2
wavelength. Characteristic Z of a folded dipole is aprox. 300 Ohms, same as
that of twin lead. This suggests your receiver has a 300 Ohm antenna
terminal on the back. Otherwise if the twin lead is fed to a 75 Ohm coaxial
port on the receiver, then (theoretically) it should be matched to that port
via a "balun" type of Z matching device.

Bill

www.wbnoble.com

to contact me, do not reply to this message,
instead correct this address and use it

will iam_ b_ No ble at msn daught com
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*** Encrypt your Internet usage with a free VPN account from http://www.SecureIX.com ***

Is there just one station you are trying to receive? Or do you want a
better antenna for all FM stations? And how much better of an antenna
do you need? The dipole antenna will be an improvement. Going to a
Yagi or Rhombic would be more work but a still better antenna that is
more directional.

An amplifier at the antenna is good if you need a major increase in
signal.


Dan


JR North wrote:
So what's the best plan? If I string a dipole antenna, what are the
optimum leg lengths? Are the circular indoor "amplified" units any good?
Any other ideas?
JR
Dweller in the cellar