Astron VS-35M Powwer Supply V-

How much power cable twist is needed to be effective for reducing RFI/EMI?

John KK9A

Jim Brown K9YC wrote:

I find #10 to be the largest cable that I can reasonably
fit into the 45A insert, so I run twisted pairs of that.


73, Jim K9YC


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[Jim Wilson]

Buck,

Running a heavy power supply line with a lighter gauge wire at
the radio end OR a lighter wire at the power supply end, the
overall net supply resistance (and voltage drop) will be the same.
For example, 100 Ohms in series with 1 Ohm equals 101 Ohms net total
resistance.

Likewise 1 Ohm in series with 100 Ohms is still 101 Ohms.

It doesn't matter if you take the voltage drop at the input or
at the output end of the power run if the total load is at the
end of the run.

I checked with Dr. Ohm to verify this.  :-)

Jim - W4RKS
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[Jim Brown-10]

On 4/12/2018 4:04 AM, [hidden email] wrote:
> How much power cable twist is needed to be effective for reducing RFI/EMI?

More is better. :)  I put black and white #10 in a vise on one end and a
drill motor on the other and twist it a lot, then let it sit overnight
so that it will at least partially learn its new position. :)  I'd have
to look, but I'd guess I'm getting 3-5 turns per foot, and it will vary
from one end to the other.

Note that twisting power conductors only helps prevent coupling to and
from those conductors.

73, Jim K9YC

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[Joe Subich, W4TV-4]

 > Running a heavy power supply line with a lighter gauge wire at
 > the radio end OR a lighter wire at the power supply end, the
 > overall net supply resistance (and voltage drop) will be the same.
 > For example, 100 Ohms in series with 1 Ohm equals 101 Ohms net total
 > resistance.

Use *realistic* resistance values.  For example, a 10 foot piece of
of #8 wire (0.63 milli-Ohms per foot) with a six inch "pigtail" of
#12 wire (1.5 milli-Ohms per foot) is equivalent to 11' 3" of #8
wire or less than one foot of #12 wire.

The *contact resistance* in a 15A Power Pole (0.88 milli-Ohms) is,
*by itself,* is equivalent to more than six inches of #12 wire.

Ohm's Law is *exactly* why we would all be better off if the power
jack on the K3/K3S was doubled up and the power cable replaced with
#6 or #8 wire even if it were necessary to splice in some 4" pieces
of #10 or #12 wire to mate with the 15A Power Pole connectors.

#10 or 1/4" bolts for the power terminal with #8 wire and ring
terminals on both ends would reduce the voltage drop in the power
cable by 75%, if the bolted connections were torqued properly,
compared to #12 wire and 15A Power Pole connectors.

73,

    ... Joe, W4TV


On 2018-04-12 11:19 AM, James Wilson wrote:

> Buck,
>
> Running a heavy power supply line with a lighter gauge wire at
> the radio end OR a lighter wire at the power supply end, the
> overall net supply resistance (and voltage drop) will be the same.
> For example, 100 Ohms in series with 1 Ohm equals 101 Ohms net total
> resistance.
>
> Likewise 1 Ohm in series with 100 Ohms is still 101 Ohms.
>
> It doesn't matter if you take the voltage drop at the input or
> at the output end of the power run if the total load is at the
> end of the run.
>
> I checked with Dr. Ohm to verify this.  :-)
>
> Jim - W4RKS
> ______________________________________________________________
> Elecraft mailing list
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> Message delivered to [hidden email]
>

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[Jim Brown-10]

On 4/12/2018 10:07 AM, Walter Underwood wrote:
> Cat 5 cable has a different twist on each set of pairs. Those range from 52 to 72 turns per meter or 1.94 to 1.38 cm per turn. That works out to 15 to 22 turns per foot.

Yes. This is done to minimize inductively coupled crosstalk between
pairs, which is critical to Ethernet transmission. A pair from CAT5/6
cable used to carry audio or RF provides very good rejection of
differential mode coupling to/from the cable. It's a great choice for
telephone wiring if RFI to the phone line (including DSL) is a problem.
A CAT5/6 pair is also a great choice for adding a ferrite common mode
choke to a low band receive antenna. I've completed a set of
measurements on this and will publish an applications note in the near
future.

73, Jim K9YC

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[Edward R Cole]

I run all my 12v equipment (almost anyway) on a 50A Astron PS.  Since
the PS is rack-mounted in a half-height cabinet the dc cable is about
12-foot long, so I used #4 welding cable that terminates on a 30A
Fuse holder.  That feeds two HD barrier strip terminal blocks (for
pos and neg rails).  The terminals accommodate No. 10 awg cables to
the heaviest current loads.  A secondary strip handles small stuff
(under 5A total).

The PS runs 13.71v and drops to 13.5v at the fuse holder.  K3 sees
about 13.35v (radio is 10w version).  I have only two PowerPole
equipped pieces; the rest use terminals or other connectors like
Molex, etc. (even one Cinch-Jones).  I count 14 loads connected to
the 13v power distribution (not all are used simultaneously).

In the case of running to a regular-sized PP connector I just add a
few inches of no.14 awg (splice is two wires soldered and covered
with heat shrink)

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

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[Charlie T, K3ICH]

You need to deploy the Ohm Eater to get rid of those pesky, excess Ohms....

BUT, be careful....their "droppings" can be toxic to the ruby throated
Ampere.
The hairy clawed Volt is however,  immune.

Charlie k3ICH




-----Original Message-----
From: [hidden email] <[hidden email]> On
Behalf Of James Wilson
Sent: Thursday, April 12, 2018 11:19 AM
To: [hidden email]
Subject: Re: [Elecraft] Astron VS-35M Powwer Supply V-

Buck,

Running a heavy power supply line with a lighter gauge wire at the radio end
OR a lighter wire at the power supply end, the overall net supply resistance
(and voltage drop) will be the same.
For example, 100 Ohms in series with 1 Ohm equals 101 Ohms net total
resistance.

Likewise 1 Ohm in series with 100 Ohms is still 101 Ohms.

It doesn't matter if you take the voltage drop at the input or at the output
end of the power run if the total load is at the end of the run.

I checked with Dr. Ohm to verify this.  :-)

Jim - W4RKS


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[Josh Fiden]

I believe his point was that a fat and skinny cable in series provides
the same net resistance regardless of the ordering of the pieces. Not
that a real world cable would be 100 ohms.

73
Josh W6XU

On 4/12/2018 9:55 AM, Joe Subich, W4TV wrote:

>
> > Running a heavy power supply line with a lighter gauge wire at
> > the radio end OR a lighter wire at the power supply end, the
> > overall net supply resistance (and voltage drop) will be the same.
> > For example, 100 Ohms in series with 1 Ohm equals 101 Ohms net total
> > resistance.
>
> Use *realistic* resistance values.  For example, a 10 foot piece of
> of #8 wire (0.63 milli-Ohms per foot) with a six inch "pigtail" of
> #12 wire (1.5 milli-Ohms per foot) is equivalent to 11' 3" of #8
> wire or less than one foot of #12 wire.
>

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