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[TowerTalk] DX Engineering's "Non-Inductive" Resistors

To: "Tower Talk List" <>
Subject: [TowerTalk] DX Engineering's "Non-Inductive" Resistors
From: "Jim Brown" <>
Reply-to: Jim Brown <>
Date: Thu, 19 Aug 2004 11:53:59 -0500
List-post: <>
I bought two packages of DX Engineering's "non-inductive"470 ohm 2 watt 
resistors with the intent of using them to terminate Beverages, calibrate/test 
bridges, and build some dummy loads. Yesterday I wired one of them to a PL-259 
with VERY short leads and measured it with both an AEA CIA-HF and my MFJ-
259B (carefully calibrated per Tom's excellent applications note). 

I measured at 1 MHz intervals  between 1 MHz and 10 MHz (down to 2 MHz on the 
MFJ). The AEA and MFJ agree within reasonable experimental error that the 
resistor shows considerable reactance at even the lowest frequencies. 
Interestingly, the magnitude of the impedance stays fairly close to 470 ohms 
this range of frequency on both analyzers, and the typical phase angle is on 
order of 17 degrees.  And while the phase angle does increase a bit with 
frequency, the increase is not anything close to proportional. 

Has anyone measured one of these resistors with a more precise device (like a 
real  bridge)?  Is 470 ohms simply too far from 50 ohms for the CIA and MFJ to 
give acceptable measurements for X and the phase angle?  

The 200 ohm load I assembled from four 1/8w composition resistors to run 
Tom's calibration reads 200 ohms resistive at 16 MHz, and begins to show some 
inductance above 25 MHz on the CIA. The MFJ begins to see inductance well 
below that. 


Jim K9YC


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