Shortwave random-wire antenna question

[CW]

Good advice. No need to over design something if your not sure it will work.
"Frank Dresser" <analogdial@worldnet.att.net> wrote in message
news:NTBdc.1512$K_.34795@bgtnsc05->

I'll suggest you try the alligator clip and wire first. It will be alot
easier to do any modifications. Also, you might find the whole experiment
isn't particularly helpful in your situation. If so, you might as well
find
out right away.

Frank Dresser

 

[Rich Grise]

"Dave" <db5151@hotmail.com> wrote in message
news:c5483e$6am@library2.airnews.net...

The antenna does indeed seem to be working great, and the radio is not
operating too shabily either as it is only the "background noise" I am
trying to reduce. I hooked a 100 mH RF choke up to it with good results,
and am planning on adding another one or two similar devices in an effort
to
cut down on higher frequency interference. Question: how would I ground
this antenna?

Uh, you don't ground the antenna. You ground ground. The ground is like
a "return" path for the current induced in the antenna by the radio wave.

I have a grounding rod right outside the window, but don't
know what to hook it too. The negative battery terminal?

Probably. Any handy chassis ground will be fine.

This radio does
have an external antenna input, but that has a plastic ring around the
outside. Open to suggestions.

The radio might be grounded through the power cord, if it's a 3-prong.
Otherwise, just a wire from the radio's chassis to the ground rod, or
even to one of the mounting screws of a grounded outlet.

And thanks for the input RE purchasing a
new/used tuner.

dave

As you seem to have mentioned, you have lots & lots of signal
strenth, so you actually might want to make your antenna even _less_
sensitive. What it sounds like you're looking for is selectivity,
and you do that with tuned circuits. Or you did back when I was
learning this stuff. ;-)

Hope This Helps!
Rich

 

[Dave]

"Rich Grise" <null@example.net> wrote in message
news:LGKdc.21046$TS3.19724@nwrddc02.gnilink.net...

"Dave" <db5151@hotmail.com> wrote in message
news:c5483e$6am@library2.airnews.net...
The antenna does indeed seem to be working great, and the radio is not
operating too shabily either as it is only the "background noise" I am
trying to reduce. I hooked a 100 mH RF choke up to it with good
results,
and am planning on adding another one or two similar devices in an
effort
to
cut down on higher frequency interference. Question: how would I ground
this antenna?

Uh, you don't ground the antenna. You ground ground. The ground is
like
a "return" path for the current induced in the antenna by the radio wave.

I have a grounding rod right outside the window, but don't
know what to hook it too. The negative battery terminal?

Probably. Any handy chassis ground will be fine.

This radio does
have an external antenna input, but that has a plastic ring around the
outside. Open to suggestions.

The radio might be grounded through the power cord, if it's a 3-prong.
Otherwise, just a wire from the radio's chassis to the ground rod, or
even to one of the mounting screws of a grounded outlet.

And thanks for the input RE purchasing a
new/used tuner.

dave

As you seem to have mentioned, you have lots & lots of signal
strenth, so you actually might want to make your antenna even _less_
sensitive. What it sounds like you're looking for is selectivity,
and you do that with tuned circuits. Or you did back when I was
learning this stuff. ;-)

Hope This Helps!
Rich

Yes, a tuned circuit, I am thinking. There is currently much more signal
than I need. Is an antenna tuner what I am looking for?

I hooked up 300 microhenries worth of RF choke, which reduces the entire
signal just a hair, but that is enough to knock the noise level down
considerably. I am not yet sure, but this *may* be all I need. BTW, did
some fiddling withe the anchor of the random wire, and decided it is more
like 45 - 50 feet total. I am planning on moving it, however, and placing
it under the eaves and off to the side of the aluminum rain gutter, which
may deflate it some. Right now I have signal to waste. That may change.

Thanks for the input. Working with RF is new to me.

Dave
db5151@hotmail.com

 

[Rich Grise]

"Dave" <db5151@hotmail.com> wrote in message
news:c5825g$8eb@library1.airnews.net...

As you seem to have mentioned, you have lots & lots of signal
strenth, so you actually might want to make your antenna even _less_
sensitive. What it sounds like you're looking for is selectivity,
and you do that with tuned circuits. Or you did back when I was
learning this stuff. ;-)

Hope This Helps!
Rich



Yes, a tuned circuit, I am thinking. There is currently much more signal
than I need. Is an antenna tuner what I am looking for?

I hooked up 300 microhenries worth of RF choke, which reduces the entire
signal just a hair, but that is enough to knock the noise level down
considerably. I am not yet sure, but this *may* be all I need. BTW, did
some fiddling withe the anchor of the random wire, and decided it is more
like 45 - 50 feet total. I am planning on moving it, however, and placing
it under the eaves and off to the side of the aluminum rain gutter, which
may deflate it some. Right now I have signal to waste. That may change.

Thanks for the input. Working with RF is new to me.

Actually, if you've got good electrical conductivity, the aluminum
rain gutters themselves might make a passable antenna. Ground _one_
of the downspouts at the bottom end, and experiment with different
pickoff points along the length of the gutter. An antenna has
different impedances at different points along its length, based on
the wavelength of interest. And you'd add inductance and capacitance
as needed to make the whole thing resonant at the freq. you want.
(that's the philosophy of an "antenna tuner.")

It really wouldn't do any harm to look up some books on antennas
and stuff, like "The ARRL Antenna Book", and talk with practically
any radio amateur - those guys do this stuff all day long.

Cheers!
Rich

 

[Telamon]

In article <c5825g$8eb@library1.airnews.net>,
"Dave" <db5151@hotmail.com> wrote:

"Rich Grise" <null@example.net> wrote in message
news:LGKdc.21046$TS3.19724@nwrddc02.gnilink.net...
"Dave" <db5151@hotmail.com> wrote in message
news:c5483e$6am@library2.airnews.net...
The antenna does indeed seem to be working great, and the radio is not
operating too shabily either as it is only the "background noise" I am
trying to reduce. I hooked a 100 mH RF choke up to it with good
results,
and am planning on adding another one or two similar devices in an
effort
to
cut down on higher frequency interference. Question: how would I ground
this antenna?

Uh, you don't ground the antenna. You ground ground. The ground is
like
a "return" path for the current induced in the antenna by the radio wave.

I have a grounding rod right outside the window, but don't
know what to hook it too. The negative battery terminal?

Probably. Any handy chassis ground will be fine.

This radio does
have an external antenna input, but that has a plastic ring around the
outside. Open to suggestions.

The radio might be grounded through the power cord, if it's a 3-prong.
Otherwise, just a wire from the radio's chassis to the ground rod, or
even to one of the mounting screws of a grounded outlet.

And thanks for the input RE purchasing a
new/used tuner.

dave

As you seem to have mentioned, you have lots & lots of signal
strenth, so you actually might want to make your antenna even _less_
sensitive. What it sounds like you're looking for is selectivity,
and you do that with tuned circuits. Or you did back when I was
learning this stuff. ;-)

Hope This Helps!
Rich



Yes, a tuned circuit, I am thinking. There is currently much more signal
than I need. Is an antenna tuner what I am looking for?

I hooked up 300 microhenries worth of RF choke, which reduces the entire
signal just a hair, but that is enough to knock the noise level down
considerably. I am not yet sure, but this *may* be all I need. BTW, did
some fiddling withe the anchor of the random wire, and decided it is more
like 45 - 50 feet total. I am planning on moving it, however, and placing
it under the eaves and off to the side of the aluminum rain gutter, which
may deflate it some. Right now I have signal to waste. That may change.

Thanks for the input. Working with RF is new to me.

Anytime you have to much signal and want to reduce it you employ an

attenuator. For coax it would be composed of three resistors in a pie
network. You would select values that would cause the input and output
resistance of the attenuator to appear 50 ohms using the source and load
impedance of the antenna and receiver so it would not generate
reflections. Additionally the resistor values would provide the voltage
division required. All calculations use ohms law. Since the radios S
meter basically is a reflection of the signal voltage a 6 dB attenuator
would cause the meter deflection to be about half what it was without
the attenuator.

If you don't care about reflections then you can make a quick and dirty
variable attenuator using a potentiometer from Radio Shack. The outer
shield of the coax goes to the same radio connection and one end of the
potentiometer, the other end of the potentiometer goes to the coax
center conductor and the potentiometer wiper goes to the radio input
where the coax center conductor would normally go. A 10K potentiometer
would be good to use.

--
Telamon
Ventura, California

 

[-=jd=-]

On Sat 10 Apr 2004 04:27:52p, Telamon
<telamon_spamshield@pacbell.net.is.invalid> wrote in message
news:telamon_spamshield-CF8279.13274610042004@news.sf.sbcglobal.net:

{snippage}

If you don't care about reflections then you can make a quick and dirty
variable attenuator using a potentiometer from Radio Shack. The outer
shield of the coax goes to the same radio connection and one end of the
potentiometer, the other end of the potentiometer goes to the coax
center conductor and the potentiometer wiper goes to the radio input
where the coax center conductor would normally go. A 10K potentiometer
would be good to use.

I just made one of these. I got a 10k and a 100k pot because I didn't know
which one I would need, ad Rat-Shack had both. It turns out the 100K pot
suits me better. However, they're so cheap, get both and try each to see
which one works best for your situation/receiver.

So far, it works like a charm for me. I can either have no attenuation
(signal at full strength) or I can reduce the signal strength as much as I
need.

I haven't noticed any "reflections"... yet... I may have them... ummm...
ok, I don't even know what they are... Are they like harmonics?

-=jd=-
"Stumbling through SWL like a 4-year old in the dark..."
--
My Current Disposable Email:
jd770YOUR@HATpostmark.net
(Remove YOUR HAT to reply directly)

 

[Dave]

"Rich Grise" <null@example.net> wrote in message
news:J1Xdc.8306$F9.5818@nwrddc01.gnilink.net...

"Dave" <db5151@hotmail.com> wrote in message
news:c5825g$8eb@library1.airnews.net...

As you seem to have mentioned, you have lots & lots of signal
strenth, so you actually might want to make your antenna even _less_
sensitive. What it sounds like you're looking for is selectivity,
and you do that with tuned circuits. Or you did back when I was
learning this stuff. ;-)

Hope This Helps!
Rich



Yes, a tuned circuit, I am thinking. There is currently much more
signal
than I need. Is an antenna tuner what I am looking for?

I hooked up 300 microhenries worth of RF choke, which reduces the entire
signal just a hair, but that is enough to knock the noise level down
considerably. I am not yet sure, but this *may* be all I need. BTW,
did
some fiddling withe the anchor of the random wire, and decided it is
more
like 45 - 50 feet total. I am planning on moving it, however, and
placing
it under the eaves and off to the side of the aluminum rain gutter,
which
may deflate it some. Right now I have signal to waste. That may
change.

Thanks for the input. Working with RF is new to me.

Actually, if you've got good electrical conductivity, the aluminum
rain gutters themselves might make a passable antenna. Ground _one_
of the downspouts at the bottom end, and experiment with different
pickoff points along the length of the gutter. An antenna has
different impedances at different points along its length, based on
the wavelength of interest. And you'd add inductance and capacitance
as needed to make the whole thing resonant at the freq. you want.
(that's the philosophy of an "antenna tuner.")

It really wouldn't do any harm to look up some books on antennas
and stuff, like "The ARRL Antenna Book", and talk with practically
any radio amateur - those guys do this stuff all day long.

Cheers!
Rich

I thought about trying to use the rain gutter as an antenna, but decided
against it for a number of reasons. The main reason was that I didn't want
to fiddle with trying to get good electrical connections between the many
pieces. Anything I did to it would have to be most asthetically appealing,
or I would never hear the end of it from my wife. She absolutely hates
having a piece of wife laying across the roof, and can't wait until I fix it
in place underneath the eaves.

I have a copy of the latest edition of Joe Carr's Practical Antenna Handbook
(I think that's what it's called) but don't have a tremendous amount of time
to spend with it. So much else to do... I need to set aside a couple hours
every night and just plow through it.

Thanks again for your input.

Dave
db5151@hotmail.com

 

[Dave]

"Telamon" <telamon_spamshield@pacbell.net.is.invalid> wrote in message
news:telamon_spamshield-CF8279.13274610042004@news.sf.sbcglobal.net...

In article <c5825g$8eb@library1.airnews.net>,
"Dave" <db5151@hotmail.com> wrote:

"Rich Grise" <null@example.net> wrote in message
news:LGKdc.21046$TS3.19724@nwrddc02.gnilink.net...
"Dave" <db5151@hotmail.com> wrote in message
news:c5483e$6am@library2.airnews.net...
The antenna does indeed seem to be working great, and the radio is
not
operating too shabily either as it is only the "background noise" I
am
trying to reduce. I hooked a 100 mH RF choke up to it with good
results,
and am planning on adding another one or two similar devices in an
effort
to
cut down on higher frequency interference. Question: how would I
ground
this antenna?

Uh, you don't ground the antenna. You ground ground. The ground is
like
a "return" path for the current induced in the antenna by the radio
wave.

I have a grounding rod right outside the window, but don't
know what to hook it too. The negative battery terminal?

Probably. Any handy chassis ground will be fine.

This radio does
have an external antenna input, but that has a plastic ring around
the
outside. Open to suggestions.

The radio might be grounded through the power cord, if it's a 3-prong.
Otherwise, just a wire from the radio's chassis to the ground rod, or
even to one of the mounting screws of a grounded outlet.

And thanks for the input RE purchasing a
new/used tuner.

dave

As you seem to have mentioned, you have lots & lots of signal
strenth, so you actually might want to make your antenna even _less_
sensitive. What it sounds like you're looking for is selectivity,
and you do that with tuned circuits. Or you did back when I was
learning this stuff. ;-)

Hope This Helps!
Rich



Yes, a tuned circuit, I am thinking. There is currently much more
signal
than I need. Is an antenna tuner what I am looking for?

I hooked up 300 microhenries worth of RF choke, which reduces the entire
signal just a hair, but that is enough to knock the noise level down
considerably. I am not yet sure, but this *may* be all I need. BTW,
did
some fiddling withe the anchor of the random wire, and decided it is
more
like 45 - 50 feet total. I am planning on moving it, however, and
placing
it under the eaves and off to the side of the aluminum rain gutter,
which
may deflate it some. Right now I have signal to waste. That may
change.

Thanks for the input. Working with RF is new to me.

Anytime you have to much signal and want to reduce it you employ an
attenuator. For coax it would be composed of three resistors in a pie
network. You would select values that would cause the input and output
resistance of the attenuator to appear 50 ohms using the source and load
impedance of the antenna and receiver so it would not generate
reflections. Additionally the resistor values would provide the voltage
division required. All calculations use ohms law. Since the radios S
meter basically is a reflection of the signal voltage a 6 dB attenuator
would cause the meter deflection to be about half what it was without
the attenuator.

If you don't care about reflections then you can make a quick and dirty
variable attenuator using a potentiometer from Radio Shack. The outer
shield of the coax goes to the same radio connection and one end of the
potentiometer, the other end of the potentiometer goes to the coax
center conductor and the potentiometer wiper goes to the radio input
where the coax center conductor would normally go. A 10K potentiometer
would be good to use.

--
Telamon
Ventura, California

Thanks for the info. Not really sure which avenue I am going to persue at
this point. Trying to sort out all the options. I appreciate the input.

Dave
db5151@hotmail.com

 

[-=jd=-]

On Sun 11 Apr 2004 01:39:04a, "Dave" <db5151@hotmail.com> wrote in message
news:c5amel$qnk@library2.airnews.net:

She absolutely hates
having a piece of wife laying across the roof, and can't wait until I
fix it in place underneath the eaves.

There's a few different ways I could interpret that!!


-=jd=-
--
My Current Disposable Email:
jd770YOUR@HATpostmark.net
(Remove YOUR HAT to reply directly)