[SCCC] RF Noise

[Prasad VU2PTT]

Wyatt,

You may also want to look at the new ferrite cookbook from K9YC which could give you more bang with less ferrite - http://k9yc.com/2018Cookbook.pdf

73,

Prasad VU2PTT, W2PTT (ex AF6DV)


Sent from my iPhone

> On 15-Feb-2019, at 11:11 AM, Wolf Leverich, WA6I <leverich at mtpinos.com> wrote:
> 
> 
> Hi Wyatt -
> 
> Several comments:
> 
> Ferrite toroids are your friend.  I buy them in $100 lots from Kreger
> Components -- usually Mix 31 1.5"ID/2.5"OD toroids, Fair-rite 2631803802.
> 
> Note that choking resistance increases roughly with the square of the
> number of turns until you get into capacitive bleed and resonance issues,
> so you really, really want multiple turns if at all possible.
> 
> At least to a point.
> 
> 8-13 turns will put a real dent in any common-mode hash on a pair of
> wires.  (Don't do more than 13T, unless you want to sacrifice choking
> on the higher end of the HF spectrum for more on the lower -- and even
> then, you might want to use a different ferrite mix if you're a Top Band
> contester.)
> 
> If you can't get 13T through the toroid, you can use more toroids.  A
> famous coax choke is only something like 3 turns through two stacks of
> 4 toroids.
> 
> Wall warts apparently aren't your problem, but you can choke their AC
> side by buying a 6' 2-conductor extension cord at Home Depot, winding
> it around a toroid, then inserting that between the wall wart and the
> outlet.
> 
> Besides ferrites, be aware that cables matter.  Some cheap HDMI and
> USB cables are pretty efficient noise antennas.  Toroids will help
> but a better idea is to buy better cables and then choke them.
> 
> Also, Faraday cages can be your friend.  Be aware that a Faraday cage
> needs to have walls (rule of thumb) 20x the skin depth of the signal
> you want to block, so aluminum foil isn't effective at HF.  But cookie
> sheets and even disposable turkey pans are.  Also, aluminum window
> screening usually is.  If you can box the noise source, that will help.
> 
> Another thing that matters is station grounding.  That's a whole
> topic unto itself.
> 
> BTW, in my experience DX Engineering Maxi-Core® feedline current chokes
> DXE-FCC050-H05-B totally rock if you have noise coming in on your feedline.
> 
> Be aware that feedline noise ingress, if I understand what's happening
> here, really comes in 3 flavors: feedline to your rig, feedline to your
> antenna, and feedline leakage in between.  Burying your coax helps
> with everything, and choking it at both your rig and antenna helps.
> 
> And I apologize for the sorta-random core dump.  It's been a long day
> in a really, really long week and my caffeine reserves are totally 
> depleted. hihihihi
> 
> 73 de Wolf WA6I
> 
> 
> 
> 
> 
>> On Thu, Feb 14, 2019 at 09:00:13PM -0800, Wyatt Law wrote:
>> Hello all,
>> 
>> I was wondering what everyone else uses to cut down on noise. I used to
>> have a problem where whenever I did CW, it would turn off the TVs in my
>> house and make my PC monitor flicker. That has been fixed for a while with
>> ferrite beads. The only issue that I have now is that whenever my dad's PC
>> is turned on across the house, it blows out my IC-7300. It makes a ton of
>> noise all over the panadapter and significantly raises the noise level.
>> When the PC is turned off, the noise is gone. What could be done to stop
>> this? I've read online that people wrap their cables in torrids? If so what
>> size and where should I get them? I have tired different combinations of
>> beads and looping the coax with no change and was wondering if anyone has
>> had any success with torrid wrapping?
>> 
>> Thanks,
>> Wyatt
>> AI6V
>> wyattlaw4 at gmail.com
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