(OT) - Unplanned Discovery

[hhoyt]

Hi Stan,

One thing we have learned in supplying thousands of Kx33s to hams is the
importance of minimizing or eliminating common-mode currents in the
antenna system.  The transverse mode RFI output of the Kx33 is extremely
low and has never been the cause of noise to our customers, but if the
antenna system has significant common-mode potential, it will always
seek a current path through whatever is attached to the rig...through
the power supply, your body, as well as grounds.  The outside of the
coax shield, the rig, the power supply and AC mains are all in a series
path for common-mode currents.

The most direct cure is to place a high common-mode impedance in the
antenna feedline.  The DC power lead on the Kx33 is smaller in diameter
than most RF coax lines, so it may be easier to form a choke on that
cable.  You mentioned "YES, I HAD CHOKES ON ALL SUPPLIES, CABLES,
WIRE."  The exact core material used and number of turns is important in
constructing common-mode chokes.  Jim Brown, K9YC has excellent
tutorials on this subject: http://audiosystemsgroup.com/RFI-Ham.pdf

Another measure which will shunt common mode currents away from other
paths is a low impedance ground on the rig.

Something else I want to mention, as it is an issue which has cropped up
recently: There are several sellers on both eBay and Amazon stating "Pro
Audio Engineering  Kx33 power supply" in their ads, but no supplies
other than those sold directly from us are the actual Kx33.  We know
this because we worked with one such customer to resolve noise issues
and it turned out the unit he had was not a Kx33.  eBay and Amazon both
state they can not do anything, since the other vendors are claiming
they use our part number and name only to state an equivalency, which
they most assuredly are not.  Our Kx33 has less than 70 pF of input to
output coupling vs. 1000 pF or more for most other supplies, making it
far easier to choke common-mode currents.  This was the most difficult
spec of the supply to arrive at, but considering we knew it could be
used with temporary antenna systems with common-mode potential it was
important to achieve.

As we unconditionally guarantee everything we sell, please contact us at
[hidden email] and I am sure we can help you eliminate this noise
or refund your purchase price.

Cheers & 73,

Howard Hoyt - WA4PSC
www.proaudioeng.com

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[Edward R Cole]

Up here in Alaska its not unusual to experience loss of commercial
power (often due to Inclement wx or avalanche).  I've noted how quiet
my radio is when no one around us has power.  Even running our 6500w
Honda invertor-generator its very quiet (which also tells my noise is
coming from neighbors and not my appliances).

Also, I have found the IBM Think pad (laptop) is very quiet (even
with charger).  I think this largely because the case is metallic and
not plastic.

This story does remind us to periodically check our house for noise
sources - might be pleasantly surprised.

I have been plagued by S9 level interfering noise on 144-MHz for 3-4
years.  Recently I checked coax loss on some lines when I had to roll
up all for some house work.  I found excessive loss in my two
130-foot LMR-400 Rx lines (runs from preamps on tower to transverter
in house).  Since replacing the lines I think I have lessened the
interference, making suspect some may have been due to passive
intermod in those lines.  Loss was probably moisture caused corrosion
which might interact with out of band signals.  Passive IM is tested
by the cellular industry at their tower sites.

I still see occasional noise interference but its less often and less
problem-some.

73, Ed - KL7UW
   http://www.kl7uw.com
Dubus-NA Business mail:
   [hidden email]

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[JT Croteau-3]

Thanks for address this thread Howard!

73

On Mon, Nov 20, 2017 at 1:35 AM, Howard Hoyt <[hidden email]> wrote:

> Hi Stan,
>
> One thing we have learned in supplying thousands of Kx33s to hams is the
> importance of minimizing or eliminating common-mode currents in the antenna
> system.  The transverse mode RFI output of the Kx33 is extremely low and has
> never been the cause of noise to our customers, but if the antenna system
> has significant common-mode potential, it will always seek a current path
> through whatever is attached to the rig...through the power supply, your
> body, as well as grounds.  The outside of the coax shield, the rig, the
> power supply and AC mains are all in a series path for common-mode currents.
>
> The most direct cure is to place a high common-mode impedance in the antenna
> feedline.  The DC power lead on the Kx33 is smaller in diameter than most RF
> coax lines, so it may be easier to form a choke on that cable.  You
> mentioned "YES, I HAD CHOKES ON ALL SUPPLIES, CABLES, WIRE."  The exact core
> material used and number of turns is important in constructing common-mode
> chokes.  Jim Brown, K9YC has excellent tutorials on this subject:
> http://audiosystemsgroup.com/RFI-Ham.pdf
>
> Another measure which will shunt common mode currents away from other paths
> is a low impedance ground on the rig.
>
> Something else I want to mention, as it is an issue which has cropped up
> recently: There are several sellers on both eBay and Amazon stating "Pro
> Audio Engineering  Kx33 power supply" in their ads, but no supplies other
> than those sold directly from us are the actual Kx33.  We know this because
> we worked with one such customer to resolve noise issues and it turned out
> the unit he had was not a Kx33.  eBay and Amazon both state they can not do
> anything, since the other vendors are claiming they use our part number and
> name only to state an equivalency, which they most assuredly are not.  Our
> Kx33 has less than 70 pF of input to output coupling vs. 1000 pF or more for
> most other supplies, making it far easier to choke common-mode currents.
> This was the most difficult spec of the supply to arrive at, but considering
> we knew it could be used with temporary antenna systems with common-mode
> potential it was important to achieve.
>
> As we unconditionally guarantee everything we sell, please contact us at
> [hidden email] and I am sure we can help you eliminate this noise or
> refund your purchase price.
>
> Cheers & 73,
>
> Howard Hoyt - WA4PSC
> www.proaudioeng.com
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

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[stan levandowski]

Howard, I received the core and the replacement choke earlier today.


I put the core on the 25' RG174 feedline right at the 9:1 UNUN and was
able to wind 10 turns.  Then I connected a 33' counterpoise wire to the
output BNC using a hose clamp.  This was just a quickie "temporary"
installation as it was getting dark here in NY.


With no other changes made, I tried tuning up on 80, 40, 30 and 20 with
my K2/10 and its internal KAT2 tuner.


My 80 meter SWR which had been 1.1:1 was now an unusable 2.8:1.  This
makes sense to me if the choke was now keeping the common mode currents
from using "everything" connected to the K2!!  I would EXPECT 80 meters
to have a high SWR for a 33' wire and it did!  My 40 meter SWR went from
1.2:1 to 1:1.  My 30 meter SWR went from 1.7:1 to 1:1 and my 20 meter
SWR went from 1.1:1 to 1:1.  I was only able to make one quick contact
but that was a pretty good one - Corsica - on 20M QRP.


Then I put the new choke you sent me on the DC cable IN ADDITION to the
cracked one that I already had on.  I detected NO NOISE at this point. 
Switching back and forth from battery to Kx33 did NOT change the noise
level.


Of course, I'm going to keep experimenting through radial placement,
elevation and number of radials but for now, it looks like you solved my
"noise problem."


That's a nifty sized little Kx33 power supply you sell and I'm glad I
didn't give up on it.  I'm very pleased with the personal support you
provided to me.


Well, the CQWW starts in 15 minutes and I'm looking forward to a 'no
noise' weekend!


73, Stan WB2LQF


On Tue, Nov 21, 2017 at 03:07 PM, [hidden email] wrote:


Hi Stan,

That is great news regarding the antenna being outside, it is my
       experience and that of many customers that a common-mode (CM)
       choke at the feedpoint of an end-fed outside is highly effective
       at decoupling the feedline as part of the active antenna.



In my opinion, and those of another expert in the field Jim
       Brown, it is money wasted purchasing a CM choke.  If you had not
       taken a look at his excellent paper on the subject here is the
       link: http://audiosystemsgroup.com/RFI-Ham.pdf 
<http://audiosystemsgroup.com/RFI-Ham.pdf>

Before I was able to measure the performance of chokes I had
       purchased both a W2DU and  DX Engineering choke myself, and
       thought they worked OK, but had no way to tell.  Once I started
       merely winding coax on mix 31 ferrites, I noticed they worked
       better than the ones I bought, and the cores are cheap.  I ended
       up selling the DX Engineering unit and in it's place I have two
       2.4" mix 31 cores stacked (for higher power handling) with 8
turns
       of RG-8X, and it is superior.  Here is a chart showing how
       effective winding as many as 6-14 turns around that core can be,
I
       suggest 8-10 turns depending on the size of coax you are using:



I will send you a replacement for the small choke which broke in
       shipment, I am sorry for that.  I will also send you a 2.4"
       diameter mix 31 toroid core so you can make your own CM choke at
       the feedpoint.  The core is weatherproof, so don't worry about it
       getting wet.  I look forward to getting reports from you as to
the
       progress taming this CM noise pickup, and thank you for your
       patience!  Ease of choking CM RFI is the real advantage to the
       Kx33 you purchased relative to other switchers, it is a
       characteristic we worked hard to engineer into the supply.



Cheers & 73,

Howie - WA4PSC






       On 11/21/2017 2:30 PM, stan levandowski wrote:





Howard, thank you for the info
         and the offer.  


 


YES, I would love to have a new
         ferrite.  The one that was shipped was neatly cracked in half! 
         I used it anyway; didn't figure it mattered that much as the
         mass was still there.






And YES, I am going to install
         additional counterpoises right at the 9:1 UNUN and spread them
         out.  The antenna is not in the attic, it is outside as a
sloper
         from the rear of my townhouse up to the top of a 35' pine
tree. 
         It's working great so far.  Worked Paraguay last night on 20M
         and Belgium this morning also on 20M.  K2@5 watts. 






Do you have a recommendation for
         an effective choke at the UNUN?  Beads, a coax choke, something
         from DX Engineering like their 1:1 isolator??  






Thanks and 73, Stan WB2LQF





         On Tue, Nov 21, 2017 at 01:28 PM, [hidden email]
<mailto:[hidden email]>  wrote:





Hi Stan,

Thank you for the reply!  Regarding antennas; I feel your
             pain!  I have had to endure less-than-optimum antenna
setups
             many times as well.

One of the aspects of common-mode currents is they are
             reciprocal between transmit and receive.  In transmit they
             cause feedline radiation and a radiation pattern which is
             the combination of the desired antenna radiation and the
             feedline radiation.  In receive the feedline becomes part
of
             the receiving antenna pattern, and since it leads right
into
             your house, it is receiving any and all of the RF noise in
             your place.  The Kx33 has very low radiated noise, however
             if an antenna is placed close to it hooked to a sensitive
             receiver like that in the KX2/KX3, some noise may be heard.




If you were to choke the feedline at the feedpoint/balun
             and add an additional counterpoise wire in the attic to
help
             balance the antenna currents, you would achieve two goals:
             the antenna pattern would no longer be disturbed in receive
             or transmit by unwanted feedline currents, and your receive
             could potentially be much quieter than even now running
from
             batteries.  I make this last point because even running
from
             a battery I guarantee there are devices in your house which
             generate RFI like LEDs and fluorescent lights, not to
             mention the numerous little chargers we all seem to have
             scattered around for phones, toothbrushes, etc. and your
             counterpoise/antenna is close to them.



As is obvious from its size, the ferrite included with the
             Kx33 is designed for 3-5 turns of the DC cable only.  I
             would be glad to send you at no charge a more substantial
             ferrite core which would allow multiple turns of coax, just
             let me know if you are interested.

Cheers & 73,

Howie - WA4PSC




On 11/20/2017 3:56 PM, stan
             levandowski wrote:



           Howard,
             I certainly didn't mean to impugn your company or its
             product.  I think I made that clear in the second of the
two
             posts I made to the Reflector.  I fall into the category of
             hobbyist ham and self-educated and I simply wanted to
remind
             fellow Listers that noise problems could literally be right
             under our noses and *not* because of crummy propagation or
             easily blamed on our neighbors.





             In my case, yes I have an end fed antenna with a 9:1 UNUN
             and yes it uses the coax shield as a ground return and
             absolutely yes there are common mode currents involved. 
             However, Howard, when I disconnected the Kx33 power supply
             from my K2 and connected the SLA battery using an 18 inch
             twisted pair, there was then NO connection other than the
             paddle cable, the battery connection and the antenna
             connection for the  common mode currents to "...seek a
             current path through whatever is attached to the rig..." as
             you stated.  It wasn't until I UNPLUGGED the Kx33 that the
             noise went away.  I can only assume that the Kx33, while
             powered up, was sending RFI out via it's AC and/or DC
cables
             which were lying on the floor about 5 feet away from the K2
             even though unplugged from the K2 





             Please also note that in my post, when I reconnected my old
             Samlex 1235M, I also had noise.  And the darn computer
             supply added noise also.





             I will fall on my sword here and admit that I've had high
             noise for the last couple of years, ever since giving up my
             old fashioned analog supply but I never realized it.  I
             never made the connection.   I was a lousy problem solver
             and fell into the trap of ASSuming it was either my attic
             antenna picking up all kinds of stuff inside the house, or
             just the falling propagation conditions.  And I lived with
             it and still made contacts.  And that darn Laptop of mine
             was ALWAYS plugged in and turned on for QRZ.com, the
reverse
             beacon network, or just so I could use Notepad with N1EA's
             "MILL" font to copy CW (I'm a former Navy Radioman and it's
             easier to type CW).





             But I have to say here that now that I'm totally on
             batteries, it's amazingly quiet.  I'm hearing QRP signals
             that were previously lost in the noise. After living with
             baseline S4 noise for so long, this is like heaven!! 





             I'm not going to return the Kx33.  It's the right size,
puts
             out a full 14 volts and I'm confident I can ultimately
solve
             the problem with the proper chokes, physical placement and
             perhaps even some shielding.





             I'm retired and we live in a townhouse.  Installing a
proper
             ground is not possible for me.  It would be so far away
that
             the connection would just be antenna.  For safety I
             disconnect my antenna when not operating.  





             73, Stan WB2LQF











             On Mon, Nov 20, 2017 at 01:35 AM, Howard Hoyt wrote:



             Hi Stan,



               One thing we have learned in supplying thousands of Kx33s
               to hams is the importance of minimizing or eliminating
               common-mode currents in the antenna system.  The
               transverse mode RFI output of the Kx33 is extremely low
               and has never been the cause of noise to our customers,
               but if the antenna system has significant common-mode
               potential, it will always seek a current path through
               whatever is attached to the rig...through the power
               supply, your body, as well as grounds.  The outside of
the
               coax shield, the rig, the power supply and AC mains are
               all in a series path for common-mode currents.



               The most direct cure is to place a high common-mode
               impedance in the antenna feedline.  The DC power lead on
               the Kx33 is smaller in diameter than most RF coax lines,
               so it may be easier to form a choke on that cable.  You
               mentioned "YES, I HAD CHOKES ON ALL SUPPLIES, CABLES,
               WIRE."  The exact core material used and number of turns
               is important in constructing common-mode chokes.  Jim
               Brown, K9YC has excellent tutorials on this subject:
http://audiosystemsgroup.com/RFI-Ham.pdf 
<http://audiosystemsgroup.com/RFI-Ham.pdf>




               Another measure which will shunt common mode currents
away
               from other paths is a low impedance ground on the rig.



               Something else I want to mention, as it is an issue which
               has cropped up recently: There are several sellers on
both
               eBay and Amazon stating "Pro Audio Engineering  Kx33
power
               supply" in their ads, but no supplies other than those
               sold directly from us are the actual Kx33.  We know this
               because we worked with one such customer to resolve noise
               issues and it turned out the unit he had was not a Kx33. 
               eBay and Amazon both state they can not do anything,
since
               the other vendors are claiming they use our part number
               and name only to state an equivalency, which they most
               assuredly are not.  Our Kx33 has less than 70 pF of input
               to output coupling vs. 1000 pF or more for most other
               supplies, making it far easier to choke common-mode
               currents.  This was the most difficult spec of the supply
               to arrive at, but considering we knew it could be used
               with temporary antenna systems with common-mode potential
               it was important to achieve.



               As we unconditionally guarantee everything we sell,
please
               contact us at [hidden email]
<mailto:[hidden email]>  and I am
               sure we can help you eliminate this noise or refund your
               purchase price.



               Cheers & 73,



               Howard Hoyt - WA4PSC

               www.proaudioeng.com <http://www.proaudioeng.com>


















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