> -----Original Message----- > From: Knighten, Jim L [SMTP:[email protected]] > Sent: Friday, December 17, 1999 9:55 AM > To: emc-pstc list server (E-mail) > Subject: 50/75 Ohm pads > > > Does anyone know where I can purchase 50 Ohm to 75 Ohm coaxial impedance > matching pads, with low loss that are fixtured for SMA to SMA, or APC > 3.5mm > to APC 3.5mm connectors? > > Jim > ________________________________________________________ > Dr. Jim Knighten e-mail: [email protected] > <mailto:[email protected]> > Senior Consulting Engineer > NCR > 17095 Via del Campo > San Diego, CA 92127 http://www.ncr.com <http://www.ncr.com> > Tel: 858-485-2537 > Fax: 858-485-3788 > > ***** Notice the Area Code change from 619 ***** > > Jim:
I'm assuming that you mean resistive T or PI matching pads. There's a forgotten formula for calculating the minimum loss when matching Z1 to Z2, but IIRC, for 50 to 75, the minimum loss is around 2.5 dB. So the fact that you loose about half your power must be remembered. Resistive pads are best for low power applications. For low frequencies, you could just build some discrete resistors into a little box. But SMA connectors is implying operating frequencies well into the GHz region, so you need a cleaner technique. Most of the attenuators that I have torn apart use a thin slab of ceramic as a carrier for thick film printed resistors. So the resistors offer easy adjustment (only the bold should try this; there is a host of little springs and gold plated spacers and caps and shims inside). But the manufacturer certainly realizes that he could make an attenuator which also could function as a resistive match. Demand is probably low, but try places like Weinschel, Mini Circuits Labs, Agilent, Kay, Microlab, JFW, RLC and Pasternack. Regards, Ed :-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-) Ed Price [email protected] Electromagnetic Compatibility Lab Cubic Defense Systems San Diego, CA. USA 858-505-2780 (Voice) 858-505-1583 (Fax) Military & Avionics EMC Services Is Our Specialty Shake-Bake-Shock - Metrology - Reliability Analysis :-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-) --------- 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).
