From: Ken Javor [mailto:ken.ja...@emccompliance.com]
Sent: Sunday, June 10, 2007 12:22 PM
To: emc-p...@ieee.org
Subject: Antenna factor calibration question
Forum Members,
This is a simple question with a long intro. The question mainly concerns the
use of coax at frequencies higher than what it was designed for. What effects
are to be expected?
I just completed checking an antenna factor calibration per SAE ARP-958. The
antenna separation was one meter. The antenna was a microwave log-conical or
log-spiral used from 1 - 10 GHz. Measurements were made at every GHz.
A few observations:
1. I would have used a 3-dB attenuator at each coax / antenna junction. The
two attenuators would have been jumpered with a female / female adapter for
the direct path.
2. Semi-rigid coax would have been best, but I use United Microwave Type
AA-190 low-loss miniature flexible coax up to 18 GHz. (A 20' length, with a
pair of SMA's, is only about $250.) RG-214 needs very careful connector
assembly, and even then, I would limit it to about 10 GHz.
3. Maybe you should put some ferrite absorbers on the coax near the
antennas.
4. I don't use log spirals or log-periodics in the GHz range. I stick with
horns.
Ed Price
<mailto:ed.pr...@cubic.com> ed.pr...@cubic.com WB6WSN
NARTE Certified EMC Engineer & Technician
Electromagnetic Compatibility Lab
Cubic Defense Applications
San Diego, CA USA
858-505-2780 (Voice)
858-505-1583 (FAX)
Military & Avionics EMC Is Our Specialty
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