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KX3 & Chasing local HF noise sources

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Niel Skousen-2

KX3 & Chasing local HF noise sources

Good Evening All,

Questions and Advice sought, i will report back on results...
(cross posted to qrp-l, elecraft, and kx3)

I live in a rural area, which should be very low noise. i put up a OCFD (88:44) this afternoon, and tonite wandered on to 80m to listen and check the antenna. I had 20db over noise everywhere. 40m was showing S4 noise, and I could only copy about 4 or 5 stations above the noise on 40m (yep, NR and NB both on, 400hz wide).

nearest neighbor is 1/4mi away, and I'm the last one on a rural overhead power line.

So, Given a KX3 and internal batteries, my first thought is to build a small multi-turn electrostatically shielded loop (1ft dia, 3-5 turn in a copper pipe, 1" gap at top) and see if I can localize any local noise sources.

my office and computers are prime targets of course...

Is this overkill ?
Recommendations for a better small / near-field noise pickup ?
Any other advice for first steps ?
Anyone else chased noise sources with their KX3 ? How did it work, what antenna did you use ?
Other suggestions / recommendations ?

TIA, 73
Niel
WA7SSA
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w0mu

Re: KX3 & Chasing local HF noise sources

Run the KX3 on battery and turn off your house mains and see if the
noise goes away. If not you know to start looking elsewhere. You might
also try the RFI reflector.

Mike W0MU

On 5/1/2014 10:47 PM, Niel Skousen wrote:

> Good Evening All,
>
> Questions and Advice sought, i will report back on results...
> (cross posted to qrp-l, elecraft, and kx3)
>
> I live in a rural area, which should be very low noise. i put up a OCFD (88:44) this afternoon, and tonite wandered on to 80m to listen and check the antenna. I had 20db over noise everywhere. 40m was showing S4 noise, and I could only copy about 4 or 5 stations above the noise on 40m (yep, NR and NB both on, 400hz wide).
>
> nearest neighbor is 1/4mi away, and I'm the last one on a rural overhead power line.
>
> So, Given a KX3 and internal batteries, my first thought is to build a small multi-turn electrostatically shielded loop (1ft dia, 3-5 turn in a copper pipe, 1" gap at top) and see if I can localize any local noise sources.
>
> my office and computers are prime targets of course...
>
> Is this overkill ?
> Recommendations for a better small / near-field noise pickup ?
> Any other advice for first steps ?
> Anyone else chased noise sources with their KX3 ? How did it work, what antenna did you use ?
> Other suggestions / recommendations ?
>
> TIA, 73
> Niel
> WA7SSA
> ______________________________________________________________
> Elecraft mailing list
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Jim Brown-10

Re: KX3 & Chasing local HF noise sources

In reply to this post by Niel Skousen-2

On 5/1/2014 9:47 PM, Niel Skousen wrote:
> Other suggestions / recommendations

Hi Niel,

First, dump the off-center-fed "dipole" -- it's inherently noisy. Put up
some resonant dipoles (or even fan dipoles) and put a ferrite common
mode choke at the feedpoint of each dipole. Study k9yc.com/RFI-Ham.pdf
for lots of detailed advice on RFI issues, and how to wind common mode
chokes.

73, Jim K9YC

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JHRichards

Re: KX3 & Chasing local HF noise sources

In reply to this post by Niel Skousen-2

K9YC raises an important issue. I love my OCF dipole, but only because
I was very careful in how it went up.

My friend in Germany is making a serious study of common mode noise on
OCF dipoles, and from his work I know you must bring the transmission
line away at a 90 degree angle, and use a good 4:1 balun with common
mode choke, or the OFC Dipole can be an inherently noisy thing - in
fact, causing its own noise!

I have a very quiet OCF dipole, but I was extremely particular in how I
assembled and hung it, with a good balun-common mode choke, and making
sure I did not have have a problematic length of transmission line, etc.
Great antenna, I use it as net control of a nationwide net, but you
must be careful in how you build it. If the coax comes near the
elements, even just a little, it can become problematic - affecting SWR
if not causing audible RFI.

Even if you put up resonant half wave dipoles, follow Jim's advice and
use a common mode choke. Some guys put chokes at both ends of the
transmission line - at feed point and near the shack - and I know of no
negative or down side from doing that.

In addition to what Jim refers you to, in general, see:

www.dj0ip.de

and in particular see:

http://www.dj0ip.de/off-center-fed-dipole/what-s-wrong-ocfd/

which is all in English, and the author makes the case that many times
the 4:1 balun is poorly constructed or improperly wound to minimize
noise and effectuate the proper transformation. And he uses 2 OCF
dipoles, himself, so it can be done with good results. It seems that
some things called a "balun" are transformers and other things called a
"balun" are common mode chokes, and sometimes you need both functions,
and how yours is made matters. So, read Jim's article, and the other
references herein, and maybe check out W8JI's personal web site, for
good information on this.

Just MY take.

=============== K8JHR ================================

On 5/2/2014 1:09 AM, Jim Brown wrote:

> First, dump the off-center-fed "dipole" -- it's inherently noisy. Put up
> some resonant dipoles (or even fan dipoles) and put a ferrite common
> mode choke at the feedpoint of each dipole. Study k9yc.com/RFI-Ham.pdf
> for lots of detailed advice on RFI issues, and how to wind common mode
> chokes.
>
> ________________________________________________________

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Jim Brown-10

Re: KX3 & Chasing local HF noise sources

On 5/1/2014 11:14 PM, K8JHR wrote:
> My friend in Germany is making a serious study of common mode noise on
> OCF dipoles, and from his work I know you must bring the transmission
> line away at a 90 degree angle

It's MUCH more than that. OCF (off-center-fed) antennas (dipole implies
balance) are badly unbalanced, which places a very high common mode
voltage across a common mode choke because of their high degree of
imbalance, which tends to fry (destroy) the common mode choke with high
power.

The OCF antenna is an idea whose time is LONG past. In that long past
time, it offered a broadbanded solution that was "OK," but not great,
and in that long past time, noise was much less of a problem. Sadly,
noise is a BIG problem, and that makes OCF antennas a really bad idea.

73, Jim K9YC
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NK7Z

Re: KX3 & Chasing local HF noise sources

In reply to this post by Niel Skousen-2

Hello Niel,
Not sure if this is appropriate for this group, but I'll post a response
and see. If not, we can take off line... Your response seems right in
step with where I would be. You might consider your first step as
running your radio on batteries, and killing power to your home. If you
are lucky, the RFI will end. Then just track from there, then go for
the loop.

--
Thanks and 73's,
For equipment, and software setups and reviews see:
www.nk7z.net
for MixW support see;
http://groups.yahoo.com/neo/groups/mixw/info
for Dopplergram information see:
http://groups.yahoo.com/neo/groups/dopplergram/info
for MM-SSTV see:
http://groups.yahoo.com/neo/groups/MM-SSTV/info

On Thu, 2014-05-01 at 22:47 -0600, Niel Skousen wrote:

KM3K

Re: KX3 & Chasing local HF noise sources

In reply to this post by Niel Skousen-2

Mike W0MU gave a good beginning, only there is more to the story.

(I gave a class on RFI this past February to our club, so the topic is still
fresh in my mind.)

There may be devices in your house or on your grounds that are
battery-operated, run continuously and may emit RFI.

The batteries must be removed to stop that equipment from operating.

BTW, I wish I could figure out an easy way to reply to a posting here; I
know I must be doing this the hard way.

73 Jerry KM3K

Message: 19

Date: Thu, 01 May 2014 23:05:20 -0600

From: W0MU Mike Fatchett <[hidden email]>

To: [hidden email]

Subject: Re: [Elecraft] KX3 & Chasing local HF noise sources

Message-ID: <[hidden email]>

Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Run the KX3 on battery and turn off your house mains and see if the

noise goes away. If not you know to start looking elsewhere. You might

also try the RFI reflector.

Mike W0MU

On 5/1/2014 10:47 PM, Niel Skousen wrote:

> Good Evening All,

>

> Questions and Advice sought, i will report back on results...

> (cross posted to qrp-l, elecraft, and kx3)

>

> I live in a rural area, which should be very low noise. i put up a OCFD
(88:44) this afternoon, and tonite wandered on to 80m to listen and check
the antenna. I had 20db over noise everywhere. 40m was showing S4 noise,
and I could only copy about 4 or 5 stations above the noise on 40m (yep, NR
and NB both on, 400hz wide).

>

> nearest neighbor is 1/4mi away, and I'm the last one on a rural overhead
power line.

>

> So, Given a KX3 and internal batteries, my first thought is to build a
small multi-turn electrostatically shielded loop (1ft dia, 3-5 turn in a
copper pipe, 1" gap at top) and see if I can localize any local noise
sources.

>

> my office and computers are prime targets of course...

>

> Is this overkill ?

> Recommendations for a better small / near-field noise pickup ?

> Any other advice for first steps ?

> Anyone else chased noise sources with their KX3 ? How did it work, what
antenna did you use ?

> Other suggestions / recommendations ?

>

> TIA, 73

> Niel

> WA7SSA

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Don Wilhelm-4

Reply to an Elecraft email posting

Jerry,

You are apparently receiving posts in Digest form, and yes, replying is
difficult that way.

I have no problem replying to any posting on the Elecraft reflector - it
is just like any other email.
How?
First, I have the posts sent as individual emails.
Secondly, I have created a folder under my Inbox called Elecraft
Third, I created an email filter. Any email with [Elecraft] in the
subject line is automatically sent to the Elecraft folder.

As a result, all reflector posts are neatly sorted in my Elecraft
folder, and they do not clutter my main Inbox. When I want to read
them, there they are - sort of like my own personal "digest". My email
client will even arrange them as threaded posts should I prefer (but I
don't).
Replying is just like replying to any email - click 'Reply' to email
only the sender, 'Reply All' to email to the sender and the Electaft
list, and my email client (Thunderbird) has a button to "Reply to List"
which goes only to the list.

You can do that kind of filtering and sorting with most all email
clients. Try it, you may like it too.

73
Don W3FPR

On 5/2/2014 9:43 AM, Jerome Sodus wrote:
> BTW, I wish I could figure out an easy way to reply to a posting here; I
> know I must be doing this the hard way.
>
> 73 Jerry KM3K
>

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Vic Rosenthal

Re: KX3 & Chasing local HF noise sources

In reply to this post by JHRichards

It appears to me that "no-radial" verticals are also OCF dipoles,
vertically oriented. In my new QTH I will be limited to a vertical, and
I chose a Cushcraft (well, MFJ now) R8. It has a built-in 'balun' --
that is, a choke -- but I am taking no chances and have prepared another
choke that I will mount immediately under the antenna to ensure that it
will be decoupled from the feedline.

In addition, I am going to put yet another choke in the line where it
enters the shack. I made these according to GM3SEK's designs
<http://www.ifwtech.co.uk/g3sek/in-prac/>, so they won't cost a king's
ransom.

I hate noise!

On 5/1/2014 11:14 PM, K8JHR wrote:

> K9YC raises an important issue. I love my OCF dipole, but only because
> I was very careful in how it went up.
>
> My friend in Germany is making a serious study of common mode noise on
> OCF dipoles, and from his work I know you must bring the transmission
> line away at a 90 degree angle, and use a good 4:1 balun with common
> mode choke, or the OFC Dipole can be an inherently noisy thing - in
> fact, causing its own noise!
>
> I have a very quiet OCF dipole, but I was extremely particular in how I
> assembled and hung it, with a good balun-common mode choke, and making
> sure I did not have have a problematic length of transmission line, etc.
> Great antenna, I use it as net control of a nationwide net, but you
> must be careful in how you build it. If the coax comes near the
> elements, even just a little, it can become problematic - affecting SWR
> if not causing audible RFI.
>
> Even if you put up resonant half wave dipoles, follow Jim's advice and
> use a common mode choke. Some guys put chokes at both ends of the
> transmission line - at feed point and near the shack - and I know of no
> negative or down side from doing that.
>
> In addition to what Jim refers you to, in general, see:
>
> www.dj0ip.de
>
> and in particular see:
>
> http://www.dj0ip.de/off-center-fed-dipole/what-s-wrong-ocfd/
>
> which is all in English, and the author makes the case that many times
> the 4:1 balun is poorly constructed or improperly wound to minimize
> noise and effectuate the proper transformation. And he uses 2 OCF
> dipoles, himself, so it can be done with good results. It seems that
> some things called a "balun" are transformers and other things called a
> "balun" are common mode chokes, and sometimes you need both functions,
> and how yours is made matters. So, read Jim's article, and the other
> references herein, and maybe check out W8JI's personal web site, for
> good information on this.
>
> Just MY take.
>
>
> =============== K8JHR ================================

--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/

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Phil Kane-2

Re: KX3 & Chasing local HF noise sources

On 5/2/2014 10:12 AM, Vic Rosenthal K2VCO wrote:

> It appears to me that "no-radial" verticals are also OCF dipoles,
> vertically oriented. In my new QTH I will be limited to a vertical, and
> I chose a Cushcraft (well, MFJ now) R8. It has a built-in 'balun' --
> that is, a choke -- but I am taking no chances and have prepared another
> choke that I will mount immediately under the antenna to ensure that it
> will be decoupled from the feedline.

For a number of years I used an R8 with my K2/100 - no chokes, just a
ground wire to the antenna mast and at the entry protector for safety
even though this area does not have lightning to any degree - and was
very pleased with it.

Right now I'm in an apartment and can't put up any reasonable HF
antennas, so using 30 ft coax-fed OCF "special" sold as an emergency
antenna by the Honolulu Emergency Amateur Radio Club (I have no
financial interest in the club or the product other than satisfaction).
It's tuned by the KAT/100 and rated for 40m and down, but it will also
tune to 60m. 80/75m is something else, same as the R8. See: www.earchi.com
-- --

73 de K2ASP - Phil Kane
Elecraft K2/100 s/n 5402

From a Clearing in the Silicon Forest
Beaverton (Washington County) Oregon
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Phil Kane-2

Re: KX3 & Chasing local HF noise sources [CORRECTED]

On 5/2/2014 11:45 AM, Phil Kane wrote:

> ........Honolulu Emergency Amateur Radio Club (I have no
> financial interest in the club or the product other than satisfaction).
> It's tuned by the KAT/100 and rated for 40m and down, but it will also
> tune to 60m. 80/75m is something else, same as the R8. See: www.earchi.com

My error! The proper URL is: www.earchi.org/proj_homebrew.html.

It uses a tri-filar-wound auto-transformer as an un-un. A complete
parts list and instructions are available at the above URL but it is
also available ready-built and tested (and the 30 ft wire included) for
about $50.
-- --
73 de K2ASP - Phil Kane
Elecraft K2/100 s/n 5402

From a Clearing in the Silicon Forest
Beaverton (Washington County) Oregon
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Lynn W. Taylor, WB6UUT

Re: KX3 & Chasing local HF noise sources [CORRECTED]

Isn't this more of a Zepp than an OCF?

On 5/2/2014 11:55 AM, Phil Kane wrote:

> On 5/2/2014 11:45 AM, Phil Kane wrote:
>
>> ........Honolulu Emergency Amateur Radio Club (I have no
>> financial interest in the club or the product other than satisfaction).
>> It's tuned by the KAT/100 and rated for 40m and down, but it will also
>> tune to 60m. 80/75m is something else, same as the R8. See: www.earchi.com
> My error! The proper URL is: www.earchi.org/proj_homebrew.html.
>
> It uses a tri-filar-wound auto-transformer as an un-un. A complete
> parts list and instructions are available at the above URL but it is
> also available ready-built and tested (and the 30 ft wire included) for
> about $50.
> -- --
> 73 de K2ASP - Phil Kane
> Elecraft K2/100 s/n 5402
>
> >From a Clearing in the Silicon Forest
> Beaverton (Washington County) Oregon
> ______________________________________________________________
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> Message delivered to [hidden email]
>

Ignacy

Re: KX3 & Chasing local HF noise sources

In reply to this post by Niel Skousen-2

Perhaps KX3 is overloading from BC stations nearby as you OCF may capture stronger signals than your previous antenna. Noise from overloading goes away with lower preamp gain.
Ignacy, NO9E