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Capicator Size for filtering across battery power

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KD8NNU

Capicator Size for filtering across battery power

Gents,

My setup uses four ()4 12v batteries in parallel for powering my K3 and
SGC powercube amp that I float with a battery maintainer.

I believe that I have an RF problem with the power setup. I have put
chokes in the power leads to the equipment but at certain times I can
hear the ferrites buzzing with either the digital code being sent of
matching my voice with SSB. The chokes are clamp on types. I am not
observing any RF problems or reported problems on the air. But I think
that something is not right as of yet so I want to go after it to make
my shack even better.

It has been suggested to me by a ham on the air that batteries just pass
this thru as they have no filtering capability. His suggestion is to
but a bit CAP across the batteries to kill this phenomenon.

So my question as I am not an EE by education is how would I properly
pick a CAP size and would different materials that CAPS are made out of
make any difference.

It would be easy to go out and get a large CAP like used on car stereo
systems but I want to have a better shot of fixing it right than just
hacking away.

As always thanks in advance for your help.

~73
Don
KD8NNU
FH#4107
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Eric Sluder

Re: Capicator Size for filtering across battery power

I typically use a high uF cap that is rated at 70-80 volts DC. My current
installation utilizes a 44,000 uF cap and all is quiet for my DC power
needs when running off of the battery fed by a charger.

73,
Eric
W9WLW
On Oct 6, 2012 5:36 PM, <[hidden email]> wrote:

>
> Gents,
>
> My setup uses four ()4 12v batteries in parallel for powering my K3 and
> SGC powercube amp that I float with a battery maintainer.
>
> I believe that I have an RF problem with the power setup. I have put
> chokes in the power leads to the equipment but at certain times I can
> hear the ferrites buzzing with either the digital code being sent of
> matching my voice with SSB. The chokes are clamp on types. I am not
> observing any RF problems or reported problems on the air. But I think
> that something is not right as of yet so I want to go after it to make
> my shack even better.
>
> It has been suggested to me by a ham on the air that batteries just pass
> this thru as they have no filtering capability. His suggestion is to
> but a bit CAP across the batteries to kill this phenomenon.
>
> So my question as I am not an EE by education is how would I properly
> pick a CAP size and would different materials that CAPS are made out of
> make any difference.
>
> It would be easy to go out and get a large CAP like used on car stereo
> systems but I want to have a better shot of fixing it right than just
> hacking away.
>
> As always thanks in advance for your help.
>
> ~73
> Don
> KD8NNU
> FH#4107
> ______________________________________________________________
> 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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David Cutter

Re: Capicator Size for filtering across battery power

The car stereo situation is different in that the battery is charged from a
high frequency 3 phase supply ie the vehicle alternator. The ripple
frequency is quite high, from low kHz at tickover to 10s of kHz when you
are motoring. In either case it's a lot higher than the 120Hz ripple
frequency of your home charger, ie it's much longer between current bursts
injected into the battery. Your vehicle supply is voltage limited to around
13.8V average and the peak of this voltage under normal conditions is
probably around 15V - 16V or so, though it can have considerable nasty
spikes on it during engine starting and when large solenoids pull in and
drop out. That makes a vehicle supply quite aggressive but not hard to
filter. Your home supply can have nasty spikes as well but more important
is the on-load, off-load and line voltage variations you can experience.
For this reason, you need a much higher voltage rating capacitor than you
might think at first sight. I would take a compromise on size and cost and
go for 25V minimum and feel fairly safe at 35V as big uF as you like.
Caution: when you first apply volts to your cap, it will suck an enormous
current, possibly enough to weld the open ends as they touch, so, I would
charge it up first with a modest resistor.

Ideally, the place to put the cap is near the radio so it absorbs
fluctuations in resistive drop of the supply cables, but that is sometimes
inconvenient electrically and mechanically.

David
G3UNA

----- Original Message -----
From: "Eric Sluder" <[hidden email]>
To: <[hidden email]>
Cc: "elecraft list" <[hidden email]>
Sent: Sunday, October 07, 2012 3:29 PM
Subject: Re: [Elecraft] Capicator Size for filtering across battery power

>I typically use a high uF cap that is rated at 70-80 volts DC. My current
> installation utilizes a 44,000 uF cap and all is quiet for my DC power
> needs when running off of the battery fed by a charger.
>
> 73,
> Eric
> W9WLW
> On Oct 6, 2012 5:36 PM, <[hidden email]> wrote:
>
>>
>> Gents,
>>
>> My setup uses four ()4 12v batteries in parallel for powering my K3 and
>> SGC powercube amp that I float with a battery maintainer.
>>
>> I believe that I have an RF problem with the power setup. I have put
>> chokes in the power leads to the equipment but at certain times I can
>> hear the ferrites buzzing with either the digital code being sent of
>> matching my voice with SSB. The chokes are clamp on types. I am not
>> observing any RF problems or reported problems on the air. But I think
>> that something is not right as of yet so I want to go after it to make
>> my shack even better.
>>
>> It has been suggested to me by a ham on the air that batteries just pass
>> this thru as they have no filtering capability. His suggestion is to
>> but a bit CAP across the batteries to kill this phenomenon.
>>
>> So my question as I am not an EE by education is how would I properly
>> pick a CAP size and would different materials that CAPS are made out of
>> make any difference.
>>
>> It would be easy to go out and get a large CAP like used on car stereo
>> systems but I want to have a better shot of fixing it right than just
>> hacking away.
>>
>> As always thanks in advance for your help.
>>
>> ~73
>> Don
>> KD8NNU
>> FH#4107
>> ______________________________________________________________
>> 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
>>
> ______________________________________________________________
> 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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Eric Sluder

Re: Capicator Size for filtering across battery power

Very good tips David... also to note a good source for used caps in great
condition here in the states is Telecom gear. The "rectifiers" as they
call them use a nice cap and its usually over-sized on purpose by the
manufacture for reliability needs. I bought a very clean unit for $3 U.S.
and had four nice caps that have served me well.

Eric
W9WLW
On Oct 7, 2012 12:25 PM, "David Cutter" <[hidden email]> wrote:

> The car stereo situation is different in that the battery is charged from
> a high frequency 3 phase supply ie the vehicle alternator. The ripple
> frequency is quite high, from low kHz at tickover to 10s of kHz when you
> are motoring. In either case it's a lot higher than the 120Hz ripple
> frequency of your home charger, ie it's much longer between current bursts
> injected into the battery. Your vehicle supply is voltage limited to
> around 13.8V average and the peak of this voltage under normal conditions
> is probably around 15V - 16V or so, though it can have considerable nasty
> spikes on it during engine starting and when large solenoids pull in and
> drop out. That makes a vehicle supply quite aggressive but not hard to
> filter. Your home supply can have nasty spikes as well but more important
> is the on-load, off-load and line voltage variations you can experience.
> For this reason, you need a much higher voltage rating capacitor than you
> might think at first sight. I would take a compromise on size and cost and
> go for 25V minimum and feel fairly safe at 35V as big uF as you like.
> Caution: when you first apply volts to your cap, it will suck an enormous
> current, possibly enough to weld the open ends as they touch, so, I would
> charge it up first with a modest resistor.
>
> Ideally, the place to put the cap is near the radio so it absorbs
> fluctuations in resistive drop of the supply cables, but that is sometimes
> inconvenient electrically and mechanically.
>
> David
> G3UNA
>
>
> ----- Original Message ----- From: "Eric Sluder" <[hidden email]>
> To: <[hidden email]>
> Cc: "elecraft list" <[hidden email]>
> Sent: Sunday, October 07, 2012 3:29 PM
> Subject: Re: [Elecraft] Capicator Size for filtering across battery power
>
>
> I typically use a high uF cap that is rated at 70-80 volts DC. My current
>> installation utilizes a 44,000 uF cap and all is quiet for my DC power
>> needs when running off of the battery fed by a charger.
>>
>> 73,
>> Eric
>> W9WLW
>> On Oct 6, 2012 5:36 PM, <[hidden email]> wrote:
>>
>>
>>> Gents,
>>>
>>> My setup uses four ()4 12v batteries in parallel for powering my K3 and
>>> SGC powercube amp that I float with a battery maintainer.
>>>
>>> I believe that I have an RF problem with the power setup. I have put
>>> chokes in the power leads to the equipment but at certain times I can
>>> hear the ferrites buzzing with either the digital code being sent of
>>> matching my voice with SSB. The chokes are clamp on types. I am not
>>> observing any RF problems or reported problems on the air. But I think
>>> that something is not right as of yet so I want to go after it to make
>>> my shack even better.
>>>
>>> It has been suggested to me by a ham on the air that batteries just pass
>>> this thru as they have no filtering capability. His suggestion is to
>>> but a bit CAP across the batteries to kill this phenomenon.
>>>
>>> So my question as I am not an EE by education is how would I properly
>>> pick a CAP size and would different materials that CAPS are made out of
>>> make any difference.
>>>
>>> It would be easy to go out and get a large CAP like used on car stereo
>>> systems but I want to have a better shot of fixing it right than just
>>> hacking away.
>>>
>>> As always thanks in advance for your help.
>>>
>>> ~73
>>> Don
>>> KD8NNU
>>> FH#4107
>>> ______________________________**______________________________**__
>>> Elecraft mailing list
>>> Home: http://mailman.qth.net/**mailman/listinfo/elecraft<http://mailman.qth.net/mailman/listinfo/elecraft>
>>> Help: http://mailman.qth.net/mmfaq.**htm<http://mailman.qth.net/mmfaq.htm>
>>> Post: mailto:[hidden email].**net <[hidden email]>
>>>
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html
>>>
>>> ______________________________**______________________________**__
>> Elecraft mailing list
>> Home: http://mailman.qth.net/**mailman/listinfo/elecraft<http://mailman.qth.net/mailman/listinfo/elecraft>
>> Help: http://mailman.qth.net/mmfaq.**htm<http://mailman.qth.net/mmfaq.htm>
>> Post: mailto:[hidden email].**net <[hidden email]>
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>
>
>

ve3dvy

Re: Capicator Size for filtering across battery power

In reply to this post by KD8NNU

On 10/6/2012 5:15 PM, [hidden email] wrote:
> I believe that I have an RF problem with the power setup. I have put
> chokes in the power leads to the equipment but at certain times I can
> hear the ferrites buzzing with either the digital code being sent of
> matching my voice with SSB.
That is interesting. I suspect that they are reacting to the
elecromagnetic field created by rapid current fluctuations in the DC
lines rather than picking up RF. RF would be far to high a frequency
to cause a ferrite to audibly buzz or rattle.

I too run batteries on my K3 when I am at the cabin. and cant say that I
am aware of ever suspected RF issues in the DC power system other than
with the charger which is horrible for noise on the reciever and any
attempts to tame it have failed so I just disconnect it when I'm on the
air.
As far as RF in the power system if it really is a problem I would
put a small cap across the input terminals to the rig. for RF id say
.01mf ceramic disk. if you are attempting to filter ripple from a
generator or charger which is not an RF issue I would first connect
the charger as close if not directly to the battery terminals. then
add a large say 50000 mf 16 to 20V capacitor near the power terminals
at the rig. this will filter ripple but wont filter RF well so add to
it a small .01mf ceramic capacitor for any RF.
> I am not
> observing any RF problems or reported problems on the air.
If you are not having any issues than I wouldn't worry about it. RF
issues in the power source like batteries are not often a problem so
long as things are wired and grounded properly

73 Dave
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Jim Brown-10

Re: Capicator Size for filtering across battery power

On 10/7/2012 7:06 PM, David Moes wrote:
> That is interesting. I suspect that they are reacting to the
> elecromagnetic field created by rapid current fluctuations in the DC
> lines rather than picking up RF.

NOT electromagnetic fields, just simple Ohm's Law. There's IR drop on
the power cable between the battery (or power supply) and the rig, and
if the rig is running full power, peaks of at least 20A, with an
envelope that follows SSB modulation. If you are powering accessories
from that same battery and have audio connections between those
accessories and the rig, the IR drop (modulated SSB envelope) will
appear between the chassis of the accessory and the chassis of the K3,
and will be added to the audio. That will SOUND like RF feedback, but
it is NOT. W8JI told me about this several years ago.

There are at least four good fixes for this issue. I've set up and
tested all of these, and all of them work.

1) Don't power accessories from the same supply that feeds your rig.
Instead use a separate wall wart for them.

2) Power accessories from the same supply, but use a simple power
splitter (Y-cord) at the RIG end of the power cable to get the accessory
power.

3) Power the accessories from the battery or big power supply, but bond
from chassis to chassis of all interconnected equipment with short, fat
copper.

4) Power the accessories from the battery or big supply, but use a
monster capacitor across the terminals right at the rig. When I say
monster cap, I'm talking at least 10,000 uF. That's big, and it ain't
cheap.

73, Jim K9YC
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Joe Subich, W4TV-4

Re: Capicator Size for filtering across battery power

> That will SOUND like RF feedback, but it is NOT.

True - it's good old amplitude modulation. Put two signals though
a common impedance and each will modulate the other. This is the
principle behind Heising (choke) modulation.

> 1) Don't power accessories from the same supply that feeds your rig.
> Instead use a separate wall wart for them.

Kenwood have documented this for "data mode controllers" in their
manuals for 10+ years although they do not explain the reasons
properly.

> 2) Power accessories from the same supply, but use a simple power
> splitter (Y-cord) at the RIG end of the power cable to get the
> accessory power.

Or use the "Accessory" power output if the rig provides one with enough
current capacity. microHAM have been designing their interface cables
for this solution since the first microKEYER (more than 8 years).

Unfortunately, Yaesu and Elecraft limit the available current from the
accessory power output which limits the utility of the Accessory output.

> 3) Power the accessories from the battery or big power supply, but
> bond from chassis to chassis of all interconnected equipment with
> short, fat copper.

Better yet, bond the transceiver chassis to the power supply with
large, *bolted* connections rather than rely on small friction fit
connectors (e.g., "Molex" pins, low current "PowerPoles", etc). Keep
the resistance in the power supply return much less (0.01 x) than the
effective resistance of all the other parallel paths. The current
will go where it should and any residual current will be small enough
to not cause problems because it can't generate a significant voltage.

> When I say monster cap, I'm talking at least 10,000 uF. That's big,
> and it ain't cheap.

10,000 uF is marginal with rigs drawing upward of 20A on voice peaks.
10 F would not be too small! However, it must be *at the rig* to be
effective. The batteries are already the best filter capacitors one
can have adding a few thousand uF across the battery is like putting
an inflatable boom on the seashore and expecting it to stop the tide.

73,

... Joe, W4TV

On 10/8/2012 3:52 PM, Jim Brown wrote:

> On 10/7/2012 7:06 PM, David Moes wrote:
>> That is interesting. I suspect that they are reacting to the
>> elecromagnetic field created by rapid current fluctuations in the DC
>> lines rather than picking up RF.
>
> NOT electromagnetic fields, just simple Ohm's Law. There's IR drop on
> the power cable between the battery (or power supply) and the rig, and
> if the rig is running full power, peaks of at least 20A, with an
> envelope that follows SSB modulation. If you are powering accessories
> from that same battery and have audio connections between those
> accessories and the rig, the IR drop (modulated SSB envelope) will
> appear between the chassis of the accessory and the chassis of the K3,
> and will be added to the audio. That will SOUND like RF feedback, but
> it is NOT. W8JI told me about this several years ago.
>
> There are at least four good fixes for this issue. I've set up and
> tested all of these, and all of them work.
>
> 1) Don't power accessories from the same supply that feeds your rig.
> Instead use a separate wall wart for them.
>
> 2) Power accessories from the same supply, but use a simple power
> splitter (Y-cord) at the RIG end of the power cable to get the accessory
> power.
>
> 3) Power the accessories from the battery or big power supply, but bond
> from chassis to chassis of all interconnected equipment with short, fat
> copper.
>
> 4) Power the accessories from the battery or big supply, but use a
> monster capacitor across the terminals right at the rig. When I say
> monster cap, I'm talking at least 10,000 uF. That's big, and it ain't
> cheap.
>
> 73, Jim K9YC
> ______________________________________________________________
> 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
>

Mel

Re: Capicator Size for filtering across battery power

In reply to this post by Jim Brown-10

Good points Jim,

I would like to add a clarification and results that I use.

1. On point 2) I would rather power the accessories on the battery end of the rig power cord as the voltage regulation will not have the rig IR losses.

2. On point 4) I have used a 5 Farad cap with 3 inch leads to the rig. It does the best of trying to cancel out the IR losses on voice pikes and does a great job. This is the one used by the car monster audio amps. Cost is around $50 direct and less on eBay.

Mel, K6KBE

--- On Mon, 10/8/12, Jim Brown <[hidden email]> wrote:

From: Jim Brown <[hidden email]>
Subject: Re: [Elecraft] Capicator Size for filtering across battery power
To: [hidden email]
Date: Monday, October 8, 2012, 12:52 PM

On 10/7/2012 7:06 PM, David Moes wrote:
> That is interesting. I suspect that they are reacting to the
> elecromagnetic field created by rapid current fluctuations in the DC
> lines rather than picking up RF.

NOT electromagnetic fields, just simple Ohm's Law. There's IR drop on
the power cable between the battery (or power supply) and the rig, and
if the rig is running full power, peaks of at least 20A, with an
envelope that follows SSB modulation. If you are powering accessories
from that same battery and have audio connections between those
accessories and the rig, the IR drop (modulated SSB envelope) will
appear between the chassis of the accessory and the chassis of the K3,
and will be added to the audio. That will SOUND like RF feedback, but
it is NOT. W8JI told me about this several years ago.

There are at least four good fixes for this issue. I've set up and
tested all of these, and all of them work.

1) Don't power accessories from the same supply that feeds your rig.
Instead use a separate wall wart for them.

2) Power accessories from the same supply, but use a simple power
splitter (Y-cord) at the RIG end of the power cable to get the accessory
power.

3) Power the accessories from the battery or big power supply, but bond
from chassis to chassis of all interconnected equipment with short, fat
copper.

4) Power the accessories from the battery or big supply, but use a
monster capacitor across the terminals right at the rig. When I say
monster cap, I'm talking at least 10,000 uF. That's big, and it ain't
cheap.

73, Jim K9YC
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KD8NNU

Re: Capicator Size for filtering across battery power

Gents,

Thanks for all the information regarding my request for how to size a
capacitor across my batteries to fix my perceived problem of RF.

>From what I understand is that this is just the normal current flow during
voice peaks or digital peaks when transmitting and not RF.

So my options as I understand them are to put a large cap like the car
stereo guys do across the batteries. These are large cap's and since I
have both the amp and radio on the same batteries I will need two cap's one
at each device.

If I have this wrong then please correct me.

Again as always thanks for the replies on the topic as there was more behind
a simple question than I realized.

Thanks
Don

~73
Don
KD8NNU
-----Original Message-----
From: Mel Farrer
Sent: Monday, October 08, 2012 5:24 PM
To: [hidden email] ; [hidden email]
Subject: Re: [Elecraft] Capicator Size for filtering across battery power

Good points Jim,

I would like to add a clarification and results that I use.

1. On point 2) I would rather power the accessories on the battery end of
the rig power cord as the voltage regulation will not have the rig IR
losses.

2. On point 4) I have used a 5 Farad cap with 3 inch leads to the rig. It
does the best of trying to cancel out the IR losses on voice pikes and does
a great job. This is the one used by the car monster audio amps. Cost is
around $50 direct and less on eBay.

Mel, K6KBE

--- On Mon, 10/8/12, Jim Brown <[hidden email]> wrote:

From: Jim Brown <[hidden email]>
Subject: Re: [Elecraft] Capicator Size for filtering across battery power
To: [hidden email]
Date: Monday, October 8, 2012, 12:52 PM

On 10/7/2012 7:06 PM, David Moes wrote:
> That is interesting. I suspect that they are reacting to the
> elecromagnetic field created by rapid current fluctuations in the DC
> lines rather than picking up RF.

NOT electromagnetic fields, just simple Ohm's Law. There's IR drop on
the power cable between the battery (or power supply) and the rig, and
if the rig is running full power, peaks of at least 20A, with an
envelope that follows SSB modulation. If you are powering accessories
from that same battery and have audio connections between those
accessories and the rig, the IR drop (modulated SSB envelope) will
appear between the chassis of the accessory and the chassis of the K3,
and will be added to the audio. That will SOUND like RF feedback, but
it is NOT. W8JI told me about this several years ago.

There are at least four good fixes for this issue. I've set up and
tested all of these, and all of them work.

1) Don't power accessories from the same supply that feeds your rig.
Instead use a separate wall wart for them.

2) Power accessories from the same supply, but use a simple power
splitter (Y-cord) at the RIG end of the power cable to get the accessory
power.

3) Power the accessories from the battery or big power supply, but bond
from chassis to chassis of all interconnected equipment with short, fat
copper.

4) Power the accessories from the battery or big supply, but use a
monster capacitor across the terminals right at the rig. When I say
monster cap, I'm talking at least 10,000 uF. That's big, and it ain't
cheap.

73, Jim K9YC
______________________________________________________________
Elecraft mailing list
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Mel

Re: Capicator Size for filtering across battery power

In reply to this post by KD8NNU

A couple of added comments. In my mobile installation, the lines to the transceiver are directly to the battery, maybe 6-7 feet #10 AWG. The lines to the amp are #2 welders cable 4 feet long. I do not use the cap on either. The ir losses are minimal on both.

What I was referring to with the large cap was in the home installation where it is not possible to run short lines, they have to be about 20 feet long, hence I use the cap. The house amp is on 220 VAC, no problem.

If you want to understand the numbers. Let's assume you are using #10 wire 20 feet long to the transceiver. Thats 40 feet of IR lossHope that clears it up a little.

--- On Mon, 10/8/12, KD8NNU <[hidden email]> wrote:

From: KD8NNU <[hidden email]>
Subject: Re: [Elecraft] Capicator Size for filtering across battery power
To: [hidden email]
Date: Monday, October 8, 2012, 5:18 PM

Gents,

Thanks for all the information regarding my request for how to size a
capacitor across my batteries to fix my perceived problem of RF.

>From what I understand is that this is just the normal current flow during
voice peaks or digital peaks when transmitting and not RF.

So my options as I understand them are to put a large cap like the car
stereo guys do across the batteries. These are large cap's and since I
have both the amp and radio on the same batteries I will need two cap's one
at each device.

If I have this wrong then please correct me.

Again as always thanks for the replies on the topic as there was more behind
a simple question than I realized.

Thanks
Don

~73
Don
KD8NNU
-----Original Message-----
From: Mel Farrer
Sent: Monday, October 08, 2012 5:24 PM
To: [hidden email] ; [hidden email]
Subject: Re: [Elecraft] Capicator Size for filtering across battery power

Good points Jim,

I would like to add a clarification and results that I use.

1. On point 2) I would rather power the accessories on the battery end of
the rig power cord as the voltage regulation will not have the rig IR
losses.

2. On point 4) I have used a 5 Farad cap with 3 inch leads to the rig. It
does the best of trying to cancel out the IR losses on voice pikes and does
a great job. This is the one used by the car monster audio amps. Cost is
around $50 direct and less on eBay.

Mel, K6KBE

--- On Mon, 10/8/12, Jim Brown <[hidden email]> wrote:

From: Jim Brown <[hidden email]>
Subject: Re: [Elecraft] Capicator Size for filtering across battery power
To: [hidden email]
Date: Monday, October 8, 2012, 12:52 PM

On 10/7/2012 7:06 PM, David Moes wrote:
> That is interesting. I suspect that they are reacting to the
> elecromagnetic field created by rapid current fluctuations in the DC
> lines rather than picking up RF.

NOT electromagnetic fields, just simple Ohm's Law. There's IR drop on
the power cable between the battery (or power supply) and the rig, and
if the rig is running full power, peaks of at least 20A, with an
envelope that follows SSB modulation. If you are powering accessories
from that same battery and have audio connections between those
accessories and the rig, the IR drop (modulated SSB envelope) will
appear between the chassis of the accessory and the chassis of the K3,
and will be added to the audio. That will SOUND like RF feedback, but
it is NOT. W8JI told me about this several years ago.

There are at least four good fixes for this issue. I've set up and
tested all of these, and all of them work.

1) Don't power accessories from the same supply that feeds your rig.
Instead use a separate wall wart for them.

2) Power accessories from the same supply, but use a simple power
splitter (Y-cord) at the RIG end of the power cable to get the accessory
power.

3) Power the accessories from the battery or big power supply, but bond
from chassis to chassis of all interconnected equipment with short, fat
copper.

4) Power the accessories from the battery or big supply, but use a
monster capacitor across the terminals right at the rig. When I say
monster cap, I'm talking at least 10,000 uF. That's big, and it ain't
cheap.

73, Jim K9YC
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k6dgw

Re: Capicator Size for filtering across battery power

In reply to this post by KD8NNU

Not quite ... the capacitor goes as close to the rig as you can manage.
Putting it "across the batteries" does nothing, the batteries are
already a far massively larger capacitor than anything the boom box guys
next to you at the traffic signal ever dreamed of. Your goal is to
"smooth out" the IR drop in the power circuit to the rig, and you can
only do that from the load end.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2013 Cal QSO Party 5-6 Oct 2013
- www.cqp.org

On 10/8/2012 5:18 PM, KD8NNU wrote:

>
> Gents,
>
> Thanks for all the information regarding my request for how to size a
> capacitor across my batteries to fix my perceived problem of RF.
>
>>From what I understand is that this is just the normal current flow during
> voice peaks or digital peaks when transmitting and not RF.
>
> So my options as I understand them are to put a large cap like the car
> stereo guys do across the batteries. These are large cap's and since I
> have both the amp and radio on the same batteries I will need two cap's one
> at each device.
>
> If I have this wrong then please correct me.
>
> Again as always thanks for the replies on the topic as there was more behind
> a simple question than I realized.
>
> Thanks
> Don
>
>
> ~73
> Don
> KD8NNU
> -----Original Message-----
> From: Mel Farrer
> Sent: Monday, October 08, 2012 5:24 PM
> To: [hidden email] ; [hidden email]
> Subject: Re: [Elecraft] Capicator Size for filtering across battery power
>
> Good points Jim,
>
> I would like to add a clarification and results that I use.
>
> 1. On point 2) I would rather power the accessories on the battery end of
> the rig power cord as the voltage regulation will not have the rig IR
> losses.
>
> 2. On point 4) I have used a 5 Farad cap with 3 inch leads to the rig. It
> does the best of trying to cancel out the IR losses on voice pikes and does
> a great job. This is the one used by the car monster audio amps. Cost is
> around $50 direct and less on eBay.
>
> Mel, K6KBE
>
> --- On Mon, 10/8/12, Jim Brown <[hidden email]> wrote:
>
>
> From: Jim Brown <[hidden email]>
> Subject: Re: [Elecraft] Capicator Size for filtering across battery power
> To: [hidden email]
> Date: Monday, October 8, 2012, 12:52 PM
>
>
> On 10/7/2012 7:06 PM, David Moes wrote:
>> That is interesting. I suspect that they are reacting to the
>> elecromagnetic field created by rapid current fluctuations in the DC
>> lines rather than picking up RF.
>
> NOT electromagnetic fields, just simple Ohm's Law. There's IR drop on
> the power cable between the battery (or power supply) and the rig, and
> if the rig is running full power, peaks of at least 20A, with an
> envelope that follows SSB modulation. If you are powering accessories
> from that same battery and have audio connections between those
> accessories and the rig, the IR drop (modulated SSB envelope) will
> appear between the chassis of the accessory and the chassis of the K3,
> and will be added to the audio. That will SOUND like RF feedback, but
> it is NOT. W8JI told me about this several years ago.
>
> There are at least four good fixes for this issue. I've set up and
> tested all of these, and all of them work.
>
> 1) Don't power accessories from the same supply that feeds your rig.
> Instead use a separate wall wart for them.
>
> 2) Power accessories from the same supply, but use a simple power
> splitter (Y-cord) at the RIG end of the power cable to get the accessory
> power.
>
> 3) Power the accessories from the battery or big power supply, but bond
> from chassis to chassis of all interconnected equipment with short, fat
> copper.
>
> 4) Power the accessories from the battery or big supply, but use a
> monster capacitor across the terminals right at the rig. When I say
> monster cap, I'm talking at least 10,000 uF. That's big, and it ain't
> cheap.
>
> 73, Jim K9YC
> ______________________________________________________________
> 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
> ______________________________________________________________
> 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
>
>
> ______________________________________________________________
> 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
>
>
>
>
> -----
> No virus found in this message.
> Checked by AVG - www.avg.com
> Version: 2013.0.2677 / Virus Database: 2591/5802 - Release Date: 10/01/12
> Internal Virus Database is out of date.
>
>

Jim Brown-10

Re: Capicator Size for filtering across battery power

In reply to this post by KD8NNU

On 10/8/2012 5:18 PM, KD8NNU wrote:
> So my options as I understand them are to put a large cap like the car
> stereo guys do across the batteries.

NO! I listed four good options, all of which cost a lot less than that
large cap. Why is it that folks gravitate toward the option that
involves BUYING a solution when the best solutions are often nothing
more than simple wring?

And, as has been noted, the cap, if you choose to use it, goes AT THE
RIG with zero length leads, NOT at the battery.

On 10/8/2012 2:24 PM, Mel Farrer wrote:
> On point 2) I would rather power the accessories on the battery end
> of the rig power cord as the voltage regulation will not have the rig
> IR losses.

That's OK -- IF you do the chassis bonding noted. Or if you waste money
on a big cap. I put a big cap across the K3 power terminals ONLY as a
test to prove that what I was hearing was that modulated IR drop, not as
a solution. Simple bonding requires nothing more than a few feet of
wire, works just as well, and is a lot cheaper.

73, Jim K9YC
______________________________________________________________
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