This one was simplistic but it worked. I run a KW with the beam about 10
feet above the roof.
I had problems with RFI on the phones. I replaced the phones with cordless
models from Radio Shack and that did the trick! I was told they had better
filtering than most.
Steve
W2KN
----- Original Message -----
From: <rfi-request@contesting.com>
To: <rfi@contesting.com>
Sent: Saturday, June 19, 2004 16:00
Subject: RFI Digest, Vol 18, Issue 15
> Send RFI mailing list submissions to
> rfi@contesting.com
>
> To subscribe or unsubscribe via the World Wide Web, visit
> http://lists.contesting.com/mailman/listinfo/rfi
> or, via email, send a message with subject or body 'help' to
> rfi-request@contesting.com
>
> You can reach the person managing the list at
> rfi-owner@contesting.com
>
> When replying, please edit your Subject line so it is more specific
> than "Re: Contents of RFI digest..."
>
>
> Today's Topics:
>
> 1. Re: CAT 3 Cable? (Berry W6EZ)
> 2. Re: CAT 3 Cable? (Jim Brown)
> 3. Re: CAT 3 Cable? (Tom Rauch)
> 4. Re: CAT 3 Cable? (Tom Rauch)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Fri, 18 Jun 2004 11:42:21 -0700
> From: Berry W6EZ <serazin@pacbell.net>
> Subject: Re: [RFI] CAT 3 Cable?
> To: RFI List <rfi@contesting.com>
> Message-ID: <40D3378D.5060504@pacbell.net>
> Content-Type: text/plain; charset=us-ascii; format=flowed
>
> In my own quest for rf proof phone lines, I too went the CAT 5 route and
> had little
> luck. What I finally did was twist all the unused wires together at the
> ends of the runs where
> the phones are and then ground the other end at the service drop.
> That made a major improvement. The with simple el cheapo plug in filets
> at each phone I
> ended up with no rf problem at all!
> I can now run a KW or more and not have the wife yelling at me when she is
> on the phone.
> Before I did the CAT5 thing, I had go so far as to put the "well known
> brand" of filters in the phone line
> at every 1/4 wave length and had no effect.
>
> Berrry
>
>
>
>
> ------------------------------
>
> Message: 2
> Date: Fri, 18 Jun 2004 14:03:37 -0500
> From: "Jim Brown" <jim@audiosystemsgroup.com>
> Subject: Re: [RFI] CAT 3 Cable?
> To: "RFI List" <rfi@contesting.com>
> Message-ID: <20040618190349.3171D7D44@gw1.nlenet.net>
> Content-Type: text/plain; charset="us-ascii"
>
> On Fri, 18 Jun 2004 08:19:49 -0500, Jim Brown wrote:
>
> >I am able to achieve 2-6 S-units of suppression of these components
> >with multi-turn chokes wound around some big clamp-on #31 ferrites.
>
> Reading the latest (July) QST, I see that I'm not alone in recommending
this
> technique. See "Workbench" on pages 54-55, with a photo of about 10
> turns of coax wound around a toroidal core. The author hasn't quite
figured
> out how multiple turns moves the effective range of the choke down in
> frequency though. :)
>
> Jim Brown K9YC
>
>
>
>
> ------------------------------
>
> Message: 3
> Date: Sat, 19 Jun 2004 10:30:20 -0400
> From: "Tom Rauch" <w8ji@contesting.com>
> Subject: Re: [RFI] CAT 3 Cable?
> To: "Berry W6EZ" <serazin@pacbell.net>, "RFI List"
> <rfi@contesting.com>
> Message-ID: <004401c45609$f3c0a6c0$6801a8c0@akorn.net>
> Content-Type: text/plain; charset="iso-8859-1"
>
>
> > In my own quest for rf proof phone lines, I too went the
> CAT 5 route and
> > had little
> > luck. What I finally did was twist all the unused wires
> together at the
> > ends of the runs where
> > the phones are and then ground the other end at the
> service drop.
>
> What you actually did was make a crude low-pass filter.
>
> This illustrates my point perfectly!
>
> Using ONLY a series impedance is not a very wise thing to do
> unless the RFI is reasonably low to start with. In order to
> be an effective solution, there has to be a low SHUNT
> impedance and a high series impedance for RF.
>
> The type of cable or number of twists per inch makes VERY
> little if any difference in RF response, because the wires
> are so close together for distant sources they already look
> like one conductor. The increased twist helps mainly on
> pair-to-pair crosstalk, much less on cable to adjacent cable
> crosstalk, and does virtually nothing at all more than a few
> inches away. It is all really a conductor spacing to source
> distance problem of dimensional ratios, so the advice to use
> CAT5 for RFI even over close-spaced parallel untwisted lays
> is not good advice at all.
>
> Neither beads (even with multiple turns) nor in-line filters
> make much sense unless the series RF impedance is extremely
> high and very resistive, or you include a shunting
> capacitance to earth or the chassis of the protected device
> to control common mode impedances.
>
> 73 Tom
>
>
>
>
> ------------------------------
>
> Message: 4
> Date: Sat, 19 Jun 2004 11:01:43 -0400
> From: "Tom Rauch" <w8ji@contesting.com>
> Subject: Re: [RFI] CAT 3 Cable?
> To: "Jim Brown" <jimbrown.enteract@rcn.com>, "RFI List"
> <rfi@contesting.com>
> Message-ID: <005401c4560e$560deaa0$6801a8c0@akorn.net>
> Content-Type: text/plain; charset="iso-8859-1"
>
> > Before you make this statement, you should measure chokes
> built with some of
> > these cores. I have done so, and in a disciplined way.
>
> I already have Jim. I just completed measurements a few
> weeks ago on 31 material using identical size samples to my
> standards of other materials.
>
> I always do this as an approval process.
>
> I can also read catalogs, and FairRite corps catalog shows
> 31 has a Q=1 at about 3MHz. 44 material, the most common now
> for snap-on beads from many sources, has Q=1 at 20MHz. 43
> material has Q=1 at 10MHz, and has noticeably less impedance
> per unit length of core against the conductor.
>
> All of those materials are the most common. 31 and 44
> actually have similar performance at upper HF, but 31 has a
> slight edge especially down low (around 1.8 MHz). 31,
> however, is a newer material and not well stocked.
>
> In contrast, 73, 75, and 76 materials have Q=1 at 2, 0.7,
> and 0.2MHz respectfully with 73 or 75 material probably
> providing the best RFI suppression of any material over the
> HF region for a give core material length.
>
> My points are that:
>
> 1.) Throwing a few beads (even with multiple turns) at a
> problem and "assuming" the world is filled with devices that
> have modest or low common mode impedances so the beads
> actually work is not really a good RFI-proofing protocol. It
> is one that many people use, and they need to be educated as
> to how poorly this method actually works.
>
> 2.) People also assume a distributor's suggestion (like
> Amidon) for "frequency range" are good, but they almost
> always are NOT. For HF, the best performance generally comes
> from 73 material. You want an impedance peak at HF, and
> hopefully with very low Q over a very wide bandwidth.
>
> 3.) Snap on cores are really are not all that good at best,
> and the worse ones really are next to doing nothing.
>
> 4.) A few small bypass capacitors and series chokes will do
> significantly more and do it much cheaper. If you don't want
> to cut wires at LEAST install some bypass caps or ground
> unused pairs in the cable to add capacitance to the
> equipment ground with your beads!!
>
> 5.) The type of cable or number of twists per inch has
> little to do with RF ingress from sources more than a few
> dozen conductor spacings away.
>
> The single most effective thing anyone can do is make
> everything in the room around the affected device have the
> same RF potential.
>
> 73 Tom
>
>
>
>
>
>
>
>
> ------------------------------
>
> _______________________________________________
> RFI mailing list
> RFI@contesting.com
> http://lists.contesting.com/mailman/listinfo/rfi
>
>
> End of RFI Digest, Vol 18, Issue 15
> ***********************************
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
|