MuZak
Active Member
Hey all...
I'm beginning an antenna project, after much research.
I'll share it because it may be useful for some, and I'll
begin with describing my circumstances, which are likely
fairly typical and are the reason for doing it.
I live in a ground floor condo apartment with no possibility
of mounting anything outdoors.
Its RF hell, with all manner of garbage spewing apliances
the neighbors seem to use most of the time.
Its unbelievable. Some days it completely wipes out
AM, and even strong FM stations have distorted audio
cuz of it.
Its worst on weekends... naturally.
I've had good luck (to a point) for AM, with loops.
The untuned loop described here in several other threads,
but ONLY IF used together with a nearby large Tuned
loop.
The large tuned loop with pickup coil wired to tuner in
is best.
The challenge right now, is usable quality FM.
Specificially, good enough sound quality to justify a
good tuner in the main system.
ONLY on the lowest end of the band..
Ie: 88-92Mhz, I've recently discovered a handful of good
stations, with several really nice programs on them.
Enough that, if they'd come in well, I'd be more than
satisfied with that.... and I'd be able to have full time
music from radio while totally ignoring the commercial
stations above 92 on the dial.
All of the ones I like have no commercials as well.
Some NPR-music, some schools, etc.
I've read most if not all the J-pole threads and some web
sites on the topic.
I've determined that FOR ME.. a jpole is NOT the way to go.
Firstly because its hard to tune one correctly without an
FM transmitter. I don't happen to have one on hand.. heh..
Second, because I need a directional antenna.
Jpole is omni.
I need that for several reasons, including rejecting the
noise that comes from within the building.
Next, I need some gain... at least a little bit.
Size is also somewhat of an issue..
The equipment I use is:
MD base loaded whip thingy--> MD Signal-Sleuth-->
MD FT-101 tuner-->downstream is irrelevant to the
topic so I'll spare you all. :nerd:
The base loaded whip thingy is...
first of all, inadequate.
I know... big surprise.
Its mounted to a piece of wood and sitting on a table
near a window.
Actually a corner area, with 2 windows 90 degrees apart.
Its the best place in the appartment for reception.
In that area, it gets most of the signal comming from
outside, and the least of the RF garbage from within.
I can (and DO) stick it out the window sidewise.. ie: horizontal
polarization, and this makes a BIG improvement... again
not much of a surprise.
Whats a slightly bigger surprise, is that there's almost no
multipath with it that way... a big problem when its inside
and vertical.
This applies to the low-band stations I want, and not so much
to the big commercials up the band.
The point is.... I've been able to experiment enough to
know what works and what is the wrong direction, both
literally and in terms of what kind of 'tenna config I need.
The bottom line is, if I can get just a few more DB of signal,
together with a bit of noise attenuation, I'll be able to
achieve my goal.
Every last uV of signal counts!
A jpole will pickup all the noise and limit placement.
In the window area, I'm close to line of site to all the
stations I want.
Out the window just barely gives me line of sight, though
there must be some bounce off the building sides...
My first (recent) attempt at a new antenna, was a failure.
It was to be a folded dipole tuned to 90Mhz, to tailor it to
the range of stations I need..
That way, peak resonance would give me a couple of DB
where I need it.
Also, directional, so it would tend to reject stuff from the
sides... ie: inside the building.
Seemed the best I could do.
It failed because of the following.
I chose to make it from something found at HomeDepot/Lowes.
I noticed, in the wire section, whats called grounding wire.
Its just thick bare copper... either 4 or 6 ga IIRC.
First prob was that its fairly flexible.. or.. easy to bend.
Since I chose to mount it by hanging it from a ceiling fixture,
it wanted to sag... and not hold shape.
The other problem... also mounting related..
is that the coax feeder puts torque on it.
It looks like the driven section of a TV antenna.
Wide radius folds.. about 2 1/4in.
In other words, a thick bare copper wire curved back 180
degrees at the ends, to almost touching at the center.
Since its a folded dipole, it needs 300R cable, and to be
end fed.
Since my tuner has only 75R connector, I needed to use
a balun.
So I soldered a typical mast mount balun to the ends
where they almost touch, and zip-tied the balun to it.
As soon as it moved, the solder joints.... no, the thin
flatlead wires themselves broke.
Not to mention it took forever to heat up the copper enuff
for the solder to flow...
Hence...
Back to the drawing board.
I pondered and pondered... how to make it work.
I finally realized it won't... not easily at least, and began
to look elsewhere.
Problematic tho, since the folded dipole config gives me
everything I need.
Mounting remains the problem, as there will always be
the need for the coax (with its torque effect) which makes
it impossible to turn, and difficult to add a needed balun to.
My first thought, was to cut it down to a single dipole, but
with less efficiency, and still the need to fabricate a mounting
arrangement... still with the coax torque had me perplexed.
I stumbled upon something else coincidently, and only as
something
I decided to click on, just after deciding to give up and go
to bed.
Providence caused me to click just that one more time.
Its something I've never seen discussed before...
Not for FM at least, and that I know of it at all has to do
with distant past recollections of ham stuff.
Its a "cubical-quad/single-turn-loop!
HUH?!?!
AKA: "simple FM loop".
I'll cut to the chase...
Check it out here:
http://www.skywaves.info/index.php?entityType=HTML&id=139
I HIGHLY recommend reading the brief article.
It will help to understand all this immensly!
I think this might be a "breakthru" for some of us.
Naturally, the proof is in the testing, and I've only just begun.
Got the parts yesterday, and stuck em together.
Still needs a lot of work.
I'm making mine out of 1/2in copper tubing (jpole style ;-)
for reasons I'll explain below.
4 sections of tubing + 4 90 degree elbows.
First I have to clean the pieces then solder em..
Clean for good contact, and cuz they're filthy and a bit
oxidized.
The main reason is mounting... which remains the prinicpal
problem.
1/2in copper tubing will allow using a PVC T-section at
the bottom.
That gives the opportunity to have a section of an otherwise
square to have an electrical "break-point".
A point where there are ends... that don't touch.
Also a place to connect the wires to.
As well as a mounting provision.. ie: PVC tube stuck into
the bottom of the T.
You can then run the coax down the inside of the PVC tube.
The PVC T section will electrically seperate the 2 halves
of the cut section, and join them, as well as providing
routing for the wires, and something non-electrical to
use the clamp on.
It will look basically like the one in the above pic... except
in copper tubing.
Might use a PVC cross section rather than a T.
Then I could add another upright length of PVC for bracing.
Then it would really be like in the pic.
I'm thinking of putting a cap on the end of the PVC tube
and putting a chassis mount F connector in the cap.
That way, one end of the coax can be soldered to the
antenna "element" and the other to the F connector.
All the wiring would be invisible, as all would be inside the
tube and the T.
That would leave a PVC tube "stub" for mounting.
So far, the best I've come up with as a "stand" is a micorphone
stand with a mic clamp to hold the PVC.
That is the main remaining challenge, and I'd be greatful
for suggestions!
Its fairly big.. at 33in across, but managable.
Plus, its flat. So you can shove it behind the record
cabinet when not in use.
When I first spotted that article I thought: Whoah! a loop..
For FM no less...
Well a loop has worked best for AM here so... I'd best
read on..
For me, this provides the few DB of gain that would help
push the noise down and directionality.
I'd likely not even have to put it out the window anymore.
And if I did.. it can be used horizontally like the article says.
Its also natively 75R so no baluns with associated problems
needed.
This time, I hope it works out, and provides a good solution
for others who share my FM difficulties!
Also hope the above makes sense, and I appologize for
the length of the post!
Greg
I'm beginning an antenna project, after much research.
I'll share it because it may be useful for some, and I'll
begin with describing my circumstances, which are likely
fairly typical and are the reason for doing it.
I live in a ground floor condo apartment with no possibility
of mounting anything outdoors.
Its RF hell, with all manner of garbage spewing apliances
the neighbors seem to use most of the time.
Its unbelievable. Some days it completely wipes out
AM, and even strong FM stations have distorted audio
cuz of it.
Its worst on weekends... naturally.
I've had good luck (to a point) for AM, with loops.
The untuned loop described here in several other threads,
but ONLY IF used together with a nearby large Tuned
loop.
The large tuned loop with pickup coil wired to tuner in
is best.
The challenge right now, is usable quality FM.
Specificially, good enough sound quality to justify a
good tuner in the main system.
ONLY on the lowest end of the band..
Ie: 88-92Mhz, I've recently discovered a handful of good
stations, with several really nice programs on them.
Enough that, if they'd come in well, I'd be more than
satisfied with that.... and I'd be able to have full time
music from radio while totally ignoring the commercial
stations above 92 on the dial.
All of the ones I like have no commercials as well.
Some NPR-music, some schools, etc.
I've read most if not all the J-pole threads and some web
sites on the topic.
I've determined that FOR ME.. a jpole is NOT the way to go.
Firstly because its hard to tune one correctly without an
FM transmitter. I don't happen to have one on hand.. heh..
Second, because I need a directional antenna.
Jpole is omni.
I need that for several reasons, including rejecting the
noise that comes from within the building.
Next, I need some gain... at least a little bit.
Size is also somewhat of an issue..
The equipment I use is:
MD base loaded whip thingy--> MD Signal-Sleuth-->
MD FT-101 tuner-->downstream is irrelevant to the
topic so I'll spare you all. :nerd:
The base loaded whip thingy is...
first of all, inadequate.
I know... big surprise.
Its mounted to a piece of wood and sitting on a table
near a window.
Actually a corner area, with 2 windows 90 degrees apart.
Its the best place in the appartment for reception.
In that area, it gets most of the signal comming from
outside, and the least of the RF garbage from within.
I can (and DO) stick it out the window sidewise.. ie: horizontal
polarization, and this makes a BIG improvement... again
not much of a surprise.
Whats a slightly bigger surprise, is that there's almost no
multipath with it that way... a big problem when its inside
and vertical.
This applies to the low-band stations I want, and not so much
to the big commercials up the band.
The point is.... I've been able to experiment enough to
know what works and what is the wrong direction, both
literally and in terms of what kind of 'tenna config I need.
The bottom line is, if I can get just a few more DB of signal,
together with a bit of noise attenuation, I'll be able to
achieve my goal.
Every last uV of signal counts!
A jpole will pickup all the noise and limit placement.
In the window area, I'm close to line of site to all the
stations I want.
Out the window just barely gives me line of sight, though
there must be some bounce off the building sides...
My first (recent) attempt at a new antenna, was a failure.
It was to be a folded dipole tuned to 90Mhz, to tailor it to
the range of stations I need..
That way, peak resonance would give me a couple of DB
where I need it.
Also, directional, so it would tend to reject stuff from the
sides... ie: inside the building.
Seemed the best I could do.
It failed because of the following.
I chose to make it from something found at HomeDepot/Lowes.
I noticed, in the wire section, whats called grounding wire.
Its just thick bare copper... either 4 or 6 ga IIRC.
First prob was that its fairly flexible.. or.. easy to bend.
Since I chose to mount it by hanging it from a ceiling fixture,
it wanted to sag... and not hold shape.
The other problem... also mounting related..
is that the coax feeder puts torque on it.
It looks like the driven section of a TV antenna.
Wide radius folds.. about 2 1/4in.
In other words, a thick bare copper wire curved back 180
degrees at the ends, to almost touching at the center.
Since its a folded dipole, it needs 300R cable, and to be
end fed.
Since my tuner has only 75R connector, I needed to use
a balun.
So I soldered a typical mast mount balun to the ends
where they almost touch, and zip-tied the balun to it.
As soon as it moved, the solder joints.... no, the thin
flatlead wires themselves broke.
Not to mention it took forever to heat up the copper enuff
for the solder to flow...
Hence...
Back to the drawing board.
I pondered and pondered... how to make it work.
I finally realized it won't... not easily at least, and began
to look elsewhere.
Problematic tho, since the folded dipole config gives me
everything I need.
Mounting remains the problem, as there will always be
the need for the coax (with its torque effect) which makes
it impossible to turn, and difficult to add a needed balun to.
My first thought, was to cut it down to a single dipole, but
with less efficiency, and still the need to fabricate a mounting
arrangement... still with the coax torque had me perplexed.
I stumbled upon something else coincidently, and only as
something
I decided to click on, just after deciding to give up and go
to bed.
Providence caused me to click just that one more time.
Its something I've never seen discussed before...
Not for FM at least, and that I know of it at all has to do
with distant past recollections of ham stuff.
Its a "cubical-quad/single-turn-loop!
HUH?!?!
AKA: "simple FM loop".
I'll cut to the chase...
Check it out here:
http://www.skywaves.info/index.php?entityType=HTML&id=139
I HIGHLY recommend reading the brief article.
It will help to understand all this immensly!
I think this might be a "breakthru" for some of us.
Naturally, the proof is in the testing, and I've only just begun.
Got the parts yesterday, and stuck em together.
Still needs a lot of work.
I'm making mine out of 1/2in copper tubing (jpole style ;-)
for reasons I'll explain below.
4 sections of tubing + 4 90 degree elbows.
First I have to clean the pieces then solder em..
Clean for good contact, and cuz they're filthy and a bit
oxidized.
The main reason is mounting... which remains the prinicpal
problem.
1/2in copper tubing will allow using a PVC T-section at
the bottom.
That gives the opportunity to have a section of an otherwise
square to have an electrical "break-point".
A point where there are ends... that don't touch.
Also a place to connect the wires to.
As well as a mounting provision.. ie: PVC tube stuck into
the bottom of the T.
You can then run the coax down the inside of the PVC tube.
The PVC T section will electrically seperate the 2 halves
of the cut section, and join them, as well as providing
routing for the wires, and something non-electrical to
use the clamp on.
It will look basically like the one in the above pic... except
in copper tubing.
Might use a PVC cross section rather than a T.
Then I could add another upright length of PVC for bracing.
Then it would really be like in the pic.
I'm thinking of putting a cap on the end of the PVC tube
and putting a chassis mount F connector in the cap.
That way, one end of the coax can be soldered to the
antenna "element" and the other to the F connector.
All the wiring would be invisible, as all would be inside the
tube and the T.
That would leave a PVC tube "stub" for mounting.
So far, the best I've come up with as a "stand" is a micorphone
stand with a mic clamp to hold the PVC.
That is the main remaining challenge, and I'd be greatful
for suggestions!
Its fairly big.. at 33in across, but managable.
Plus, its flat. So you can shove it behind the record
cabinet when not in use.
When I first spotted that article I thought: Whoah! a loop..
For FM no less...
Well a loop has worked best for AM here so... I'd best
read on..
For me, this provides the few DB of gain that would help
push the noise down and directionality.
I'd likely not even have to put it out the window anymore.
And if I did.. it can be used horizontally like the article says.
Its also natively 75R so no baluns with associated problems
needed.
This time, I hope it works out, and provides a good solution
for others who share my FM difficulties!
Also hope the above makes sense, and I appologize for
the length of the post!
Greg
:nutz::drunk::grnbounce: