Low Noise receiving Loop antenna
 

Owen Duffy wrote:

Tony Giacometti wrote in
news:aeydnehFvJBYatHanZ2dnUVZ_o2vnZ2d@hawaiiantel. net:

I guess the question is this, DX signals would be skywave, a loop is
omni directional to skywave signals I believe. Is this correct?

In free spacem the nulls are orthogoal to the plane of the loop. If you
make the plane of the loop vertical and mount it near ground, the nulls
will be modified somewhat, but the gain at high elevations (eg
ionospheric propagation from nearby) would be pretty much unaffacted by
loop orientation. That cannot be said for very low angle signals.

...
I didn't use a shielded box, I have a plastic box. The instructions
for the loop I built said either was OK.

Well, the instructions had you tuning the loop in a manner that wasn't
very effective too didn't they. Are they credible?

I am not saying a shielded box is necessary, but I wouldn't use a plastic
box without verifying it works as well as a shielded box... and the way
you do that is to build the shielded box version.

Shielded boxes are hard to come by in the middle of the Pacific Ocean.

Radio Shack has a few which I just got. I will be changing over first chance
I get.



Why do you still think that a larger loop has deeper nulls.

If I implied that I didn't intend to do so, what I mean is to "keep"
the deep nulls I now have.

I pointed out in an earlier post that you might well compromise symmetry
with a larger loop and so compromise the depth of the nulls. You only
need enough gain to swamp receiver internal noise under the best band
conditions and loop orientation.

Of course, when the loop becomes large enough, its directivity does
change, and the nulls are a little broader. Proximity to ground modifies
large loops significantly.

Owen

Lets see what happens when I change over to a shielded box.

Low Noise receiving Loop antenna
 

On Sun, 25 Nov 2007 13:15:33 -0800 (PST), wrote:

A solenoid loop is like this..
http://home.comcast.net/~nm5k/loop5.jpg

Hi Mark,

That is a really good job you did at that page.

73's
Richard Clark, KB7QHC

Low Noise receiving Loop antenna
 

On Nov 28, 12:36 am, Richard Clark wrote:
On Sun, 25 Nov 2007 13:15:33 -0800 (PST), wrote:
A solenoid loop is like this..
http://home.comcast.net/~nm5k/loop5.jpg

Hi Mark,

That is a really good job you did at that page.

73's
Richard Clark, KB7QHC

Cartoon version to avoid having to make a separate
web page.. :/ I think I just about ran out of room for
any more jibber jabber. Was made in a paint program.
MK

Low Noise receiving Loop antenna
 

On 27 Nov, 22:28, Tony Giacometti wrote:
Owen Duffy wrote:
Tony Giacometti wrote in
news:aeydnehFvJBYatHanZ2dnUVZ_o2vnZ2d@hawaiiantel .net:

I guess the question is this, DX signals would be skywave, a loop is
omni directional to skywave signals I believe. Is this correct?

In free spacem the nulls are orthogoal to the plane of the loop. If you
make the plane of the loop vertical and mount it near ground, the nulls
will be modified somewhat, but the gain at high elevations (eg
ionospheric propagation from nearby) would be pretty much unaffacted by
loop orientation. That cannot be said for very low angle signals.

...
I didn't use a shielded box, I have a plastic box. The instructions
for the loop I built said either was OK.

Well, the instructions had you tuning the loop in a manner that wasn't
very effective too didn't they. Are they credible?

I am not saying a shielded box is necessary, but I wouldn't use a plastic
box without verifying it works as well as a shielded box... and the way
you do that is to build the shielded box version.

Shielded boxes are hard to come by in the middle of the Pacific Ocean.

Radio Shack has a few which I just got. I will be changing over first chance
I get.







Why do you still think that a larger loop has deeper nulls.

If I implied that I didn't intend to do so, what I mean is to "keep"
the deep nulls I now have.

I pointed out in an earlier post that you might well compromise symmetry
with a larger loop and so compromise the depth of the nulls. You only
need enough gain to swamp receiver internal noise under the best band
conditions and loop orientation.

Of course, when the loop becomes large enough, its directivity does
change, and the nulls are a little broader. Proximity to ground modifies
large loops significantly.

Owen

Lets see what happens when I change over to a shielded box.- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -

Tony,
You just are not getting any luck with your present aproach.
Why not go out to a store and buy a hula hoop ($4)Then wire around
the 1 inch or so diameter until the wire covers 3/4 of the loop.
Repeat the winding again over the top of the previous wire but winding
in the opposite direct until you reach the end of the other wire where
you can tie them with a wire nut. Now stretch out the wire further
around the hula hoop till you get a burst at the desired signal.
Feeding at the start of the windings will give you a high resistive
impedance so you will need a transformer there. You can widen the
band
width purely by nudjing the wire further around the loop but that
probably wont be necessary as it is wide band.
Art KB9MZ

Low Noise receiving Loop antenna
 

art wrote:

On 27 Nov, 22:28, Tony Giacometti wrote:
Owen Duffy wrote:
Tony Giacometti wrote in
news:aeydnehFvJBYatHanZ2dnUVZ_o2vnZ2d@hawaiiantel .net:

I guess the question is this, DX signals would be skywave, a loop is
omni directional to skywave signals I believe. Is this correct?

In free spacem the nulls are orthogoal to the plane of the loop. If you
make the plane of the loop vertical and mount it near ground, the nulls
will be modified somewhat, but the gain at high elevations (eg
ionospheric propagation from nearby) would be pretty much unaffacted by
loop orientation. That cannot be said for very low angle signals.

...
I didn't use a shielded box, I have a plastic box. The instructions
for the loop I built said either was OK.

Well, the instructions had you tuning the loop in a manner that wasn't
very effective too didn't they. Are they credible?

I am not saying a shielded box is necessary, but I wouldn't use a
plastic box without verifying it works as well as a shielded box... and
the way you do that is to build the shielded box version.

Shielded boxes are hard to come by in the middle of the Pacific Ocean.

Radio Shack has a few which I just got. I will be changing over first
chance I get.







Why do you still think that a larger loop has deeper nulls.

If I implied that I didn't intend to do so, what I mean is to "keep"
the deep nulls I now have.

I pointed out in an earlier post that you might well compromise
symmetry with a larger loop and so compromise the depth of the nulls.
You only need enough gain to swamp receiver internal noise under the
best band conditions and loop orientation.

Of course, when the loop becomes large enough, its directivity does
change, and the nulls are a little broader. Proximity to ground
modifies large loops significantly.

Owen

Lets see what happens when I change over to a shielded box.- Hide quoted
text -

- Show quoted text -- Hide quoted text -

- Show quoted text -

Tony,
You just are not getting any luck with your present aproach.
Why not go out to a store and buy a hula hoop ($4)Then wire around
the 1 inch or so diameter until the wire covers 3/4 of the loop.
Repeat the winding again over the top of the previous wire but winding
in the opposite direct until you reach the end of the other wire where
you can tie them with a wire nut. Now stretch out the wire further
around the hula hoop till you get a burst at the desired signal.
Feeding at the start of the windings will give you a high resistive
impedance so you will need a transformer there. You can widen the
band
width purely by nudjing the wire further around the loop but that
probably wont be necessary as it is wide band.
Art KB9MZ


interesting way to make a loop.

I just finished changing the coax on my current loop, not the feedline coax
but the loop coax, its about an hour from sunset and I hear some signals on
the loop already.

I think the previous coax may have been defective. I did ohm it out for
continuity - shorts & open and I did'nt see any problem.
So, I will test this over the next few days and see if the problem I was
having is gone.

By the way, I appreciate all the input I have received from my original
post.

Low Noise receiving Loop antenna
 

"Richard Clark" wrote in message
...
On Sat, 17 Nov 2007 10:30:06 -1000, Tony Giacometti
wrote:

Richard, I use a vertical antenna, for transmitting its great, does a
fine
job, but for receive, with the noise in the neighborhood, its not the
best
option. I have tried to use an ANC-4 noise reducer but the noise isn't
reduced enough to hear the weaker signals.

Hi Tony,

Leaving that aside for others to comment....

So, what to do, I followed the instructions for building the loop from
W2YR
and KN4LF and from this link
http://www.hard-core-dx.com/nordicdx.../coaxloop.html

There is a world of opportunity in making a mistake with this monster.
It goes a long way to do something difficult that could be done vastly
easier.

As I wrote previous I have 2 good preamps but the signals are still very
weak.

You state that there is no gap.

No, he said there was a gap. Read it again.

Low Noise receiving Loop antenna
 

Tony Giacometti wrote:
My neighborhood is loaded with some kind of electrical noise which makes
working 160 & 75 meters difficult. I have tried to locate the source but
have come up empty at this point. It appears to be something other than
power line noise which may mean its coming from someones house.


Tony,
This may have already been suggested as I only got about half way
through the replies. As a test, isolate the receiver from _everything_
(ground & ac power) except for a 12 volt battery and the loop. I did
this in order to receive 600 meter test transmissions. It turned out
that most of my noise was related to underground supplied AC power. I
can now easily copy several of the WD2XSH test transmissions with a 5
foot square indoor loop with no preamp.
Note that I am not transmitting, and I am only suggesting this as a
test to verify that your AC power line isn't the problem.

Regards,

bob baldwin
bryan, texas