RF on power to K3 question

[KD8NNU]

Dear Group,

I have determined that the majority of my RF shack problems were related
to RF on the power lead to the K3.   Winding 7 turns thru a 1" clamp on
#31 ferrite has cured the symptoms.   With this choke in place
everything is even happy on 160m.

So let me explain how I power the equipment and then ask about putting a
CAP across the power.

The radio and SGC power cube amp are powered by 5 batteries connected in
parallel.   I use a very small battery tender connected at all times to
keep the batteries at a full charge.    When using the amp I also float
a battery charger set to its mid range position with a max of 15 amps of
charge to help maintain the system.   From this perspective it works
real well for powering the system.  But I wanted to be sure that
everyone understands how I power the system as I get to my questions
below.

Plus there is the normal AC stuff like the PC and so on.

All equipment is grounded to a single point ground on one of the
negative posts of a battery.

So now to the RF problem.  If you have followed earlier posts I have
been chasing RF in my shack for quite awhile and finally started playing
around with a clamp on meter and that is what tipped me off to the power
feed of the K3.

With the power feed determined as a problem (there still could be more).
One of the tests I did was to remove all of the chargers and disconnect
all the AC equipment and connect the amp output directly to the dummy
load.  RF was still present even after I attempted to remove all
influences to verify if something was putting this on the power leads.
So now I believe it is there natively when in TX and is not from a
charger or PC or other antenna.

Based on my reading about chokes, I put 7 wraps in the 1" big snap on
ferrite.  This killed the RF and like I stated in the opening paragraph
with everything reconnected again the system is now happy at 160m.  It
now actually works real well.

In discussing what I found with others, I have learned that batteries
are not filters and all the HF energy goes right thru them.
Recommendations have been made to put a ceramic capacitor across the
batteries to filter the HF out.  I also have been cautioned that there
may be a problem with a choke on the power feed to the K3 that could put
a power spike on the feed line that could do damage when turning the
radio on and off.

So here are the questions.

Can the choke cause a problem with power spikes that could damage the
K3.

Should a CAP be placed across the batteries to filter out the HF.  If
yes how do I determine what size.

Also if yes for the CAP will this improve battery life.

Also if yes could the CAP have influence that could negatively effect my
use of chargers for floating power.

Again as always, that in advance for your help from this great group.

Cheers
Don


~73
Don
KD8NNU

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[Fred Townsend]

Hello Don:
If you have cured your RF problems I'm not sure why you are asking your
questions.
In general adding a choke or capacitors to your power lead shouldn't hurt
anything so give it a try. I will add detail to your questions below. BTW
you should indicate how much power you are running and where your antenna is
located relative to your K3. FT


-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of [hidden email]
Sent: Saturday, February 04, 2012 7:03 AM
To: [hidden email]
Subject: [Elecraft] RF on power to K3 question

Dear Group,

I have determined that the majority of my RF shack problems were related
to RF on the power lead to the K3.   Winding 7 turns thru a 1" clamp on
#31 ferrite has cured the symptoms.   With this choke in place
everything is even happy on 160m.

So let me explain how I power the equipment and then ask about putting a CAP
across the power.

The radio and SGC power cube amp are powered by 5 batteries connected in
parallel.   I use a very small battery tender connected at all times to
keep the batteries at a full charge.    When using the amp I also float
a battery charger set to its mid range position with a max of 15 amps of
charge to help maintain the system.   From this perspective it works
real well for powering the system.  But I wanted to be sure that everyone
understands how I power the system as I get to my questions below.

Plus there is the normal AC stuff like the PC and so on.

All equipment is grounded to a single point ground on one of the negative
posts of a battery.

Do you have an earth ground? That is a ground rod. Depending on your setup
that may or may not help. FT

So now to the RF problem.  If you have followed earlier posts I have been
chasing RF in my shack for quite awhile and finally started playing around
with a clamp on meter and that is what tipped me off to the power feed of
the K3.

With the power feed determined as a problem (there still could be more).
One of the tests I did was to remove all of the chargers and disconnect all
the AC equipment and connect the amp output directly to the dummy load.  RF
was still present even after I attempted to remove all influences to verify
if something was putting this on the power leads.
So now I believe it is there natively when in TX and is not from a charger
or PC or other antenna.

That suggests you may have other, as yet, undetected problems. FT

Based on my reading about chokes, I put 7 wraps in the 1" big snap on
ferrite.  This killed the RF and like I stated in the opening paragraph with
everything reconnected again the system is now happy at 160m.  It now
actually works real well.


This is good. FT

In discussing what I found with others, I have learned that batteries are
not filters and all the HF energy goes right thru them.
Recommendations have been made to put a ceramic capacitor across the
batteries to filter the HF out.  I also have been cautioned that there may
be a problem with a choke on the power feed to the K3 that could put a power
spike on the feed line that could do damage when turning the radio on and
off.

So here are the questions.

Can the choke cause a problem with power spikes that could damage the K3.

No. FT

Should a CAP be placed across the batteries to filter out the HF.  If yes
how do I determine what size.

Adding a cap won't hurt but it probably won't help much either. It might
make your battery tender happier. It should be pointed out your K3 already
has bypass caps across the input power leads. Take a look at the schematic.
As for value it is not critical as long as it is a ceramic cap, 50V or
greater. Since you are working 160M I would start with an 0.1uF. It is
useful to have a combination of values. If I were working 40M I would add a
0.01uF and for 15M and above a 0.001uF. Put them all in parallel.
FT

Also if yes for the CAP will this improve battery life.


No. FT

Also if yes could the CAP have influence that could negatively effect my use
of chargers for floating power.

Again, no. FT

Again as always, that in advance for your help from this great group.

Cheers
Don


~73
Don
KD8NNU

______________________________________________________________

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Home: http://mailman.qth.net/mailman/listinfo/elecraft
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Post: mailto:[hidden email]

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[KD8NNU]

Hi Fred,

I am asking the question simply because I was warned by another ham to
consider the possibility of a power spike on the feed to the K3 with the
choke by another ham.   He was not fully sure and suggested that I post
the question to the folks who might really know the answer.

Plus if it is good practice to put a CAP across the batteries for the
way I am doing my power to help with a clean signal, clean power and
better battery life I want use good practice.

If I had not been prompted by the ham who suggested a CAP I would have
never asked the question.

Power is an SGC power cube good for 500w.  Antennas are a 2 WL loop for
160m and a dipole and the shack is on the second floor.

Maybe the answer to the question is so obvious that it just shows my
total ignorance.  Hey but I do learn slowly at times :-).  Example I now
work split and if you remember those posts from me on that topic I think
everyone wanted to hit me in the head with a baseball bat.

Like I indicated right now everything is working real good and I have no
problems, but I dont want to be in the process of creating new ones.

Cheers
Don

~73
Don
KD8NNU


On Sun, Feb 5, 2012 at 12:32 AM, Fred Townsend wrote:

> Hello Don:
> If you have cured your RF problems I'm not sure why you are asking
> your
> questions.
> In general adding a choke or capacitors to your power lead shouldn't
> hurt
> anything so give it a try. I will add detail to your questions below.
> BTW
> you should indicate how much power you are running and where your
> antenna is
> located relative to your K3. FT
>
> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of
> [hidden email]
> Sent: Saturday, February 04, 2012 7:03 AM
> To: [hidden email]
> Subject: [Elecraft] RF on power to K3 question
>
> Dear Group,
>
> I have determined that the majority of my RF shack problems were
> related to RF on the power lead to the K3.   Winding 7 turns thru a 1"
> clamp on #31 ferrite has cured the symptoms.   With this choke in
> place everything is even happy on 160m.
>
> So let me explain how I power the equipment and then ask about putting
> a CAP
> across the power.
>
> The radio and SGC power cube amp are powered by 5 batteries connected
> in parallel.   I use a very small battery tender connected at all
> times to keep the batteries at a full charge.    When using the amp I
> also float a battery charger set to its mid range position with a max
> of 15 amps of charge to help maintain the system.   From this
> perspective it works real well for powering the system.  But I wanted
> to be sure that everyone
> understands how I power the system as I get to my questions below.
>
> Plus there is the normal AC stuff like the PC and so on.
>
> All equipment is grounded to a single point ground on one of the
> negative
> posts of a battery.
>
> Do you have an earth ground? That is a ground rod. Depending on your
> setup
> that may or may not help. FT
>
> So now to the RF problem.  If you have followed earlier posts I have
> been
> chasing RF in my shack for quite awhile and finally started playing
> around
> with a clamp on meter and that is what tipped me off to the power feed
> of
> the K3.
>
> With the power feed determined as a problem (there still could be
> more). One of the tests I did was to remove all of the chargers and
> disconnect all
> the AC equipment and connect the amp output directly to the dummy
> load.  RF
> was still present even after I attempted to remove all influences to
> verify
> if something was putting this on the power leads. So now I believe it
> is there natively when in TX and is not from a charger
> or PC or other antenna.
>
> That suggests you may have other, as yet, undetected problems. FT
>
> Based on my reading about chokes, I put 7 wraps in the 1" big snap on
> ferrite.  This killed the RF and like I stated in the opening
> paragraph with
> everything reconnected again the system is now happy at 160m.  It now
> actually works real well.
>
>
> This is good. FT
>
> In discussing what I found with others, I have learned that batteries
> are
> not filters and all the HF energy goes right thru them.
> Recommendations have been made to put a ceramic capacitor across the
> batteries to filter the HF out.  I also have been cautioned that there
> may
> be a problem with a choke on the power feed to the K3 that could put a
> power
> spike on the feed line that could do damage when turning the radio on
> and
> off.
>
> So here are the questions.
>
> Can the choke cause a problem with power spikes that could damage the
> K3.
>
> No. FT
>
> Should a CAP be placed across the batteries to filter out the HF.  If
> yes
> how do I determine what size.
>
> Adding a cap won't hurt but it probably won't help much either. It
> might
> make your battery tender happier. It should be pointed out your K3
> already
> has bypass caps across the input power leads. Take a look at the
> schematic.
> As for value it is not critical as long as it is a ceramic cap, 50V or
> greater. Since you are working 160M I would start with an 0.1uF. It is
> useful to have a combination of values. If I were working 40M I would
> add a
> 0.01uF and for 15M and above a 0.001uF. Put them all in parallel. FT
>
> Also if yes for the CAP will this improve battery life.
>
>
> No. FT
>
> Also if yes could the CAP have influence that could negatively effect
> my use
> of chargers for floating power.
>
> Again, no. FT
>
> Again as always, that in advance for your help from this great group.
>
> Cheers
> Don
>
>
> ~73
> Don
> KD8NNU
>
> ______________________________________________________________
>
> ______________________________________________________________
> 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

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[Joe Subich, W4TV-4]

Since a common mode choke as is used for RFI suppression is generally
wound with both conductors of the power cord (parallel) going through
the toroid core, there is no impact on the DC since the field from one
wire is cancelled by the field from the other wire.  Remember, in any
transmission line the currents in the two conductors are equal and
opposite!


73,

    ... Joe, W4TV


On 2/5/2012 11:31 AM, Ron D'Eau Claire wrote:

> Don, a spike is not a concern with choke for RF in the range of a few
> millihenrys such as you created winding a few turns through the ferrite
> core, but a larger value choke such as is often used for suppressing
> generator hash and noise on a d-c line can do damage.
>
> What happens is that whenever current flows through the choke a magnetic
> field is created around the windings. When the current stops, that magnetic
> field collapses producing a pulse in the winding. With small value chokes,
> such as the choke you made winding the wire through the ferrite core, the
> pulse is very tiny and of no concern.
> But that pulse can be as high as several hundred volts with larger value
> chokes, even working from a 13V supply. That would be plenty to do serious
> damage to the K3 and most other 13V electronics you may have on the circuit.
>
>
> Batteries are typically lousy conductors at RF. Putting a capacitor across
> the d-c line provides a low-impedance path for any RF on the line. That
> capacitor is usually built into any good rig, and the K3 is no exception. It
> has both a capacitor across the line and an RF choke in series with the
> power line where it enters the rig.
>
> 73,
>
> Ron AC7AC
>
> -----Original Message-----
>
> I am asking the question simply because I was warned by another ham to
> consider the possibility of a power spike on the feed to the K3 with the
> choke by another ham.   He was not fully sure and suggested that I post
> the question to the folks who might really know the answer.
>
> Plus if it is good practice to put a CAP across the batteries for the
> way I am doing my power to help with a clean signal, clean power and
> better battery life I want use good practice.
>
> If I had not been prompted by the ham who suggested a CAP I would have
> never asked the question.
>
> Power is an SGC power cube good for 500w.  Antennas are a 2 WL loop for
> 160m and a dipole and the shack is on the second floor.
>
> Maybe the answer to the question is so obvious that it just shows my
> total ignorance.  Hey but I do learn slowly at times :-).  Example I now
> work split and if you remember those posts from me on that topic I think
> everyone wanted to hit me in the head with a baseball bat.
>
> Like I indicated right now everything is working real good and I have no
> problems, but I dont want to be in the process of creating new ones.
>
> Cheers
> Don
>
>
> ______________________________________________________________
> 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
>

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[Doug Faunt N6TQS [phone]]

I saw this topic when reading older message off-line with no
connectivity, but want to put in my two-bits.

I bought some JIS screwdrivers and bits, and have used them recently on
my Elecraft gear, and find them far superior in fit to the screws to any
of my high-quality Phillips drivers.

I'm traveling, so can't see what the brands involved, but found them
using a search engine.

I strongly recommend using JIS bits on Elecraft gear.

What do they use in the factory?
73, doug



______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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[Doug Faunt N6TQS [phone]]

I saw this topic when reading older message off-line with no
connectivity, but want to put in my two-bits.

I bought some JIS screwdrivers and bits, and have used them recently on
my Elecraft gear, and find them far superior in fit to the screws to any
of my high-quality Phillips drivers.

I'm traveling, so can't see what the brands involved, but found them
using a search engine.

I strongly recommend using JIS bits on Elecraft gear.

What do they use in the factory?
73, doug



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Post: mailto:[hidden email]

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