Hi Gang, There is a European firm, LEAD that makes a continuously ferrite loaded cable. I think it is heavy in weight.
Contact: Prof. Ferdy Mayer President, LEAD 12 Avenue de la Republique 94700 Maisons-Alfort France Possible e-mail: [email protected] Telephone: 1-49-77-9400 Fax: 1-49-77-9813 Prof. Mayer is on the IEEE EMC Society Board of Directors Regards, Jim Dr. Jim Knighten e-mail: [email protected] Senior Consulting Engineer NCR 17095 Via del Campo San Diego, CA 92127 http://www.ncr.com Tel: 619-485-2537 Fax: 619-485-3788 ---------- From: Colin Brench Sent: Monday, November 16, 1998 1:47 PM To: '[email protected]'; [email protected]; [email protected]; Robert Bonsen Subject: RE: ANSI C63.4 -- ferrites Hi folks, I have a sample of just such a flexible ferrite loaded cable here in my hand. I have had it for many years the intent being to use it for a test site antenna feed. All I remember about it (and my memory is not that good!) is that I believe it is of German manufacture. Any details I had on this cable have been lost in antiquity. It is heavy, and looking at it I think it is not meant for low loss applications. Brief description based on my guestimate of dimensions.: Center conductor 7 strands of about 22 AWG plain copper (large diameter - nearly 2mm?) Dielectric solid polyethylene Single woven braid not wrapped very tightly also plain copper Thin (0.5 mm ?) layer of ferrite material under outer jacket . Overall diameter is just over 1 cm maybe 1.2 cm. Given the weight of this two meter section I would not want it used for the full length of the feed cable. There are no ID marking on this so it might be a prototype, the outer jacket is grey with a blue stripe running along it FWIW. Now the capon type ferrites do not provide much attenuation over the lower frequencies so this cable might not be effective where most needed 30 - 200 MHz. So I would think that such cables are available but I have not seen any other reference to them at least for commercial applications. So someone should be able to find it. Regards, Colin.. Compaq Maynard, MA -----Original Message----- From: [email protected] [mailto:[email protected]] Sent: Monday, November 16, 1998 11:32 AM To: [email protected]; [email protected]; Robert Bonsen Subject: RE: ANSI C63.4 -- ferrites Bob: You stress the importance of discrete ferrite absorbers placed closely along the antenna cable. The obvious extension of this thought is to have a special antenna coaxial cable which has ferrite material continuously distributed along its external surface. Is this a reasonable extrapolation of the discrete ferrites technique? Or does there have to be at least some spacing between discrete absorptive elements? If a continuous absorptive layer on a coax cable is a good idea, then has anyone ever encountered such a cable? Might there be some practical way to fabricate a flexible "add-on" absorptive sleeve, possibly like the urethane foam thermal barriers placed on water and refrigerant pipes? Regards, Ed ------------------------ From: Robert Bonsen <[email protected]> Subject: RE: ANSI C63.4 -- ferrites Date: Fri, 13 Nov 1998 17:02:52 -0600 To: [email protected], [email protected] > > In my experience when doing testing of semi-anechoic chambers for NSA > performance using ferrites is a must to avoid measurements being influenced > by the vertical drop portion on both the transmit and receive end. Using a > spacing of about half a foot inbetween individual ferrite beads has worked > best for me. Especially in the lower frequencies, up to about 150MHz, the > effect of the cable drop on vertical pol measurements is considerable > (sometimes more than 1.5 dB). Thus, in all the NSA test specifications I > write, I insist on the use of ferrites. > > Of course, not using ferrites on the vertical cable drop allows a chamber > tester to tweak the cables such that at a specific problem frequency the > vertical cable drop portion acts as a reflector to reduce or increase the > transmitted/received signal levels somewhat. This may bring a chamber/OATS > in spec which really isn't. Or bring it out if the tester is not aware of > the problem. > > For better repeatability and better NSA measurements, ferrites are > required. They do not make the cable totally RF-invisible but do > considerably reduce the influence of the cable on the measurements. > > Regards, > -Robert > > Robert Bonsen > Principal Consultant > Orion Scientific > email: [email protected] > URL: http://www.orionscientific.com > phone: (512) 347 7393; FAX: (512) 328 9240 > > > --------- > This message is coming from the emc-pstc discussion list. > To cancel your subscription, send mail to [email protected] > with the single line: "unsubscribe emc-pstc" (without the > quotes). For help, send mail to [email protected], > [email protected], [email protected], or > [email protected] (the list administrators). > > ---------------End of Original Message----------------- -------------------------- Ed Price [email protected] Electromagnetic Compatibility Lab Cubic Defense Systems San Diego, CA. USA 619-505-2780 Date: 11/16/1998 Time: 08:32:01 -------------------------- --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators). --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators). --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
