RFI 103: RFI Tips, Tricks and Techniques Q & A Session

Presentation on theme: "RFI 103: RFI Tips, Tricks and Techniques Q & A Session"— Presentation transcript:

1 RFI 103: RFI Tips, Tricks and Techniques Q & A Session
Bob Brehm, AK6R Chief Engineer Palomar-Engineers.com Copyright 2015 Palomar Engineers, Inc. 1

2 How to Choose an effective feed line choke
Suppress TRANSMITTER RFI, reduce RECEIVER RFI/NOISE 2

3 Common Mode Feed Line Choke Recommendations
Choke impedance should be > 10X feedline impedance (> 500 ohms for 50 ohm feedline) Use choke at antenna feed point to keep RF on antenna and off feedline Use choke at receiver end of feedline to choke off common mode noise from neighborhood 3

4 Ham Shack RFI Solutions
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5 RFI Chokes for feed line path
Antenna feed line choke (aka 1:1 balun, 1:1 unun, line isolator, line choke, sleeve baluns) Coax Air Wound – frequency dictates # turns for Z (5-10 turns at VHF, small diameter, turns large diameter at HF) In line (ferrite – toroids, split beads, sleeve beads) 1:1 balun (voltage (DC grounded) or current) Line isolators (w or w/o ground lug) Examples 5

6 Coax Balun (aka “Ugly” balun)
Picture: Ugly balun at 7 Mhz, 16 turns, 4.5” diameter = 3,000 Z – 20 feet of coax 6

7 Sleeve Baluns (Snap on)
RG-8X (1/4” size) ohms RG-213 (1/2” size) ohms 7

8 Large Clamp On (FSB-1) = 1” ID
3 turns = 1K ohms 8

9 Sleeve Baluns (Slip on)
Palomar BA-8 Balun on Beam Antenna (RG-213) 9

10 Super Choker (40-10 Meters)
Z = 1,500 at 7Mhz , 2.2K at 10 Mhz, 1K at 14 Mhz, 300 at 28 Mhz – 5 Turns, 3 cores 10

11 CUBE Baluns BA-1-1500 (1:1, 1500w) Z = 2k-10k
Feedline choke and noise filter Do It Yourself KIT CB (1:1, 5000w) Z = 3k-12k Feedline choke and noise filter ASSEMBLED 11

12 OCF Antenna 4:1 Balun + Choke
Palomar CB OCF Balun + Common mode choke in single enclosure 12

13 AK6R OCF Antenna 19%/81% Feedpoint
Antenna uses Palomar CB OCF Balun + Common mode choke in single enclosure. 36’ at feed point, 12’ at ends meters 13

14 OCF/Carolina Windom Notes
No vertical radiator Use 4:1 current balun & choke at feedpoint. You need at least 2000 ohms of choking. 10 bead sleeve baluns do NOT provide enough choking! With vertical radiator Use 4:1 voltage balun at feed point and > 2K feedline choke at bottom of vertical radiator to stop radiation from continuing on rest of feedline. 14

15 Palomar Engineers Porta-Pole™
Palomar Porta-Pole™ - 27 feet tall – Special unun for meters vertical operation 15

16 Palomar Engineers Porta-Pole™
Special Unun for impedance matching for higher signal strength Palomar Porta-Pole™ with CU unun 16

17 Prize Question? Who is the strangest case of RFI you have experienced?
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18 Contact Info Website: Phone: Bob Brehm, AK6R – Chief Engineer This presentation available on the website. 18