noise canceling Elevator /HF?
 

hi

I've had some interference from 1 to 30 caused by new elevator
equipment.

my building lookes like a long but narrow rectangle

it's about (rounding off) 100ft long maybe 50ft wide i'd guess

on each far end of the rectangle is an elevator room

both throw out same type noise

my antenna a horiz dipole center tuned (SGC) is ontop of the Eastern
one

some have recomended to help cancel the noise i try a noise
canceling device like a timewave anc4(others are simular so i'll use
anc4 as example)

i happened to have one hooked up anyway and already had a small
antenna extra up there i taped to the side of the elevator room it
picks up noise fantastic

the anc never really seemed to fix the noise i am really trying to
kill thou i will say over all in general every now and then some
noise (not by my building) can really be cancled by it when it
works it's great but it works so poorly for my situation*(not the
above elevator noise) but the other far an few randum noise i wouldnt
recomend one unless you specifically know it can help your specific
instance


sorry to a side track but it leads me to so why didn't this kill my
noise

(lets forget about that 2nd elevator for a second)

so turns out these things are designed to 'null' noise a)further away
than both your main antenna and noise antenna and b) presumes you can
sepereate the noise antenna from main ant.

i sorta understood 'b' didn't know about a

further the 2nd elevator is about 80 feet i can't tell if the
noise from it is getting over to the other side/elevator where my
antenna is aka east side if it is i realize my question below
becomes very complex

so question

how does one design a device ie what kind and whom can design
essentially a anc4 like device that can create a null in the
situation i have lets assume the 2nd elevator is not causing me
issues


not even sure the theory behind it, i sorta understand how the anc 4
works thou


anyone have any ideas? any partial or total null could really help
me out if it's poss to create one w/o sacrficing my rx sensitivity
overall too much

noise canceling Elevator /HF?
 

On Wed, 27 Feb 2008 02:38:44 GMT, ml wrote:

i happened to have one hooked up anyway and already had a small
antenna extra up there i taped to the side of the elevator room it
picks up noise fantastic

the anc never really seemed to fix the noise i am really trying to
kill thou i will say over all in general every now and then some
noise (not by my building) can really be cancled by it when it
works it's great but it works so poorly for my situation*(not the
above elevator noise) but the other far an few randum noise i wouldnt
recomend one unless you specifically know it can help your specific
instance

Hi Myles,

There's the old saying that "if a little works, a lot works better."

But possibly not in this case.

If you have your sense antenna right up against the noise source, you
are certainly inducing huge noise fields into that sense antenna's
line. Much too much. Pull that sense antenna away 40 feet (put it
between the two elevator sheds). 40 feet will still be plenty close.

Also make sure you have all lines going topside CHOKED! And in
several places along the way.

73's
Richard Clark, KB7QHC

noise canceling Elevator /HF?
 

In article ,
Richard Clark wrote:

On Wed, 27 Feb 2008 02:38:44 GMT, ml wrote:

i happened to have one hooked up anyway and already had a small
antenna extra up there i taped to the side of the elevator room it
picks up noise fantastic

the anc never really seemed to fix the noise i am really trying to
kill thou i will say over all in general every now and then some
noise (not by my building) can really be cancled by it when it
works it's great but it works so poorly for my situation*(not the
above elevator noise) but the other far an few randum noise i wouldnt
recomend one unless you specifically know it can help your specific
instance

Hi Myles,

There's the old saying that "if a little works, a lot works better."

But possibly not in this case.

If you have your sense antenna right up against the noise source, you
are certainly inducing huge noise fields into that sense antenna's
line. Much too much. Pull that sense antenna away 40 feet (put it
between the two elevator sheds). 40 feet will still be plenty close.

Also make sure you have all lines going topside CHOKED! And in
several places along the way.

73's
Richard Clark, KB7QHC

hi Rich

thanks for the reply

i have a balun on both ends never thought of chokes hmmm maybe i
can rummage up some snap on of a partucular size/material think
dxengineering has nice chokes

the companies that make these noice devices say the above you
proposed won't work at all, however your idea is ceartainly worth
trying and a fun experiment only way i'll learn and know fer sure

and the chokes are easy to do can't hurt

as an aside:

i dunno why i was thinking the closer the sense at is the better but
not the case

noise canceling Elevator /HF?
 

On Wed, 27 Feb 2008 11:28:42 GMT, ml wrote:

the companies that make these noice devices say the above you
proposed won't work at all, however your idea is ceartainly worth
trying and a fun experiment only way i'll learn and know fer sure

Hi Myles,

What they may be talking about is noise that arrives over the air
(radiation) won't be materially affected by chokes - or at least not
enough. However, where chokes do work best is with noise over the
wire (conduction) and your sense antenna sitting right on top of the
elevator shack is tightly coupled (and why I suggested putting it
further away).

and the chokes are easy to do can't hurt

However, knowing their impedance characteristic is important because
you may end up thinking they weren't useful for the wrong reason (they
didn't present enough impedance).

A ferrite choke at the feed point consisting of 50 mixed beads of
Amidon types #75 and #73 (or #77) over RG58 will be about a foot
long. A couple more of these along the line (one a quarter wave away
from the feed point for a low band, and another a quarter wave away at
the high band) will help decouple it further. At a minimum, over the
HF band it will present something on the order of 1000 Ohms to those
noise currents traveling on the braid outer surface. The attenuation
ratio of this Z to your front end Z is not very considerable (low
teens of dB) but still useful. At the proximity you are with sitting
on top of the elevator shack, distance with the square law will help
far more - you only want to sense the noise, not pull it into your ham
shack.

You will need to choke ALL lines going topside in this manner (your
principle antenna, your sense antenna, your control leads to your SGC)
such that this sounds like an investment of roughly 150-450 beads.

I would move the sense antenna first as that is the cheapest test for
noise reduction that could bring the greatest return - pick the low
hanging fruit first.

73's
Richard Clark, KB7QHC

noise canceling Elevator /HF?
 

In article ,
Richard Clark wrote:

On Wed, 27 Feb 2008 11:28:42 GMT, ml wrote:

the companies that make these noice devices say the above you
proposed won't work at all, however your idea is ceartainly worth
trying and a fun experiment only way i'll learn and know fer sure

Hi Myles,

What they may be talking about is noise that arrives over the air
(radiation) won't be materially affected by chokes - or at least not
enough. However, where chokes do work best is with noise over the
wire (conduction) and your sense antenna sitting right on top of the
elevator shack is tightly coupled (and why I suggested putting it
further away).

and the chokes are easy to do can't hurt

However, knowing their impedance characteristic is important because
you may end up thinking they weren't useful for the wrong reason (they
didn't present enough impedance).

A ferrite choke at the feed point consisting of 50 mixed beads of
Amidon types #75 and #73 (or #77) over RG58 will be about a foot
long. A couple more of these along the line (one a quarter wave away
from the feed point for a low band, and another a quarter wave away at
the high band) will help decouple it further. At a minimum, over the
HF band it will present something on the order of 1000 Ohms to those
noise currents traveling on the braid outer surface. The attenuation
ratio of this Z to your front end Z is not very considerable (low
teens of dB) but still useful. At the proximity you are with sitting
on top of the elevator shack, distance with the square law will help
far more - you only want to sense the noise, not pull it into your ham
shack.

You will need to choke ALL lines going topside in this manner (your
principle antenna, your sense antenna, your control leads to your SGC)
such that this sounds like an investment of roughly 150-450 beads.

I would move the sense antenna first as that is the cheapest test for
noise reduction that could bring the greatest return - pick the low
hanging fruit first.

73's
Richard Clark, KB7QHC

ok thanks again rich, i shoulda been more specific the company made no
comments about chokes only there noise cancling device those where my
last comments about your comments which differed from their comments
so despite all the commenting i will still try what you said cause
it seems like it might work it seems logical

my coax for hf is LMR400 as far as chokes go i presume the types
wouldn't change but i guess i'll need few more chokes on roof?

come to think of it i dn't have any chokes on my temp prob, sgc
control etc i do on the shack end hmmm

i wonder if i cut power to the sgc and if i still get the noice
it can't be a deffive sgc just to be scientific to rule it out


thanks rich for helping so much