[RFI] Snap on split beads; coax high-pass filter recommendati ons

EDWARDS, EDDIE J EDWARDS, EDDIE J" <eedwards@oppd.com
Wed, 1 Dec 1999 16:38:08 -0600

> -----Original Message-----
> From:	Pete Smith [SMTP:n4zr@contesting.com]
> At a hamfest a couple of months ago, a guy was selling some neat split
> ferrite beads.  The idea is a little like the snap-on rectangular ferrites
> that Radio Shack et al were selling, except that these involve a split
> bead
> 1/2-3/4" long enclosed in a plastic shell that can be snapped open and
> closed.  He had 2 sizes, for different sized cable.  Does anyone know of
> an
> economical source for these?
	[Ed-K0iL]  Radio Shack does sell both types of ferrites: split bead
snap-on in a white plastic case, and rectangular core wind-on type in black
plastic that you mentioned.  Both are in the 273-series (-104 & 105 I think)
and are probably 43-mix.  
	These can also be had at Surplus Sales of Nebraska, Palomar, Amidon,
MFJ, Kilo-Tec, Ocean State Electronics, and direct from some of the
manufacturers like Fair-Rite.  

> Strikes me it would be really handy to bring
> a bag of them along on my next RFI-hunting project, because they would let
> me assess and maybe cure lead pickup without ever having to disconnect any
> of the neighbor's wires.
	[Ed-K0iL]  Yea, but they clamp-on split beads do not have the same
attenuation as multiple turns thru a torroidal core.

> Second topic -- I'm looking for recommendations on a high-pass filter for
> 75-ohm TV leadin.  I have one neighbor who is not on cable, and with my
> antennas pointing toward him he has moderate fundamental overload TVI but
> (thank goodness) no telephone or other RFI.  What do people think is the
> most cost-effective high-pass unit out there?  The best at any
> (reasonable)
> cost?
	[Ed-K0iL]  I've had trouble with the Rad Shack models (15-579 or
580?) due to the cheap cable & connector they used in it.  The ARRL sweep of
the filter shows it is one of the better electrically though; more than 70dB
attn at 30MHz.  Just don't try to hang a large ferrite torroid off of it.
It'll yank on the cable to hard.

	There's a listing of HP filters in the FCC's Interference Handbook
which is free from the FCC (888-CALL-FCC).  Get a few copies of this book.
Give one to the neighbor.  The old ARRL RFI book had graphs (ARRL & FCC
data) comparing various filters.  The new one might too, but I haven't had
time to even skim it yet (I'm trying to get thru my new DX-Aku book!).  

	Here's the FCC's HP filter list by name: Channel Master, Cornel
Dublier Electronics (CDE), Industrial Comm. Engineers (ICE), N6YHY TVI
Filters, Radio Shack, Ten Tec, and Winegard.

> Sometimes a tower is just a tower
	[Ed-K0iL]  I just wish mine was vertical instead of laying in my

	de ed -K0iL

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