Coaxial Connectors,
Coaxial Cable, Feed Line,
and a Simple Antenna.
By: David E. Rudd, CET WC
Walton County Emergency Radio Club
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Coaxial Connectors
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Properly mate cables to equipment
Properly mate cables to cables
Can be easily adapted to other types
Maintain impedance
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PL-259
(Childrens Band’ers favorite)
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Coaxial Connectors
• PL-259 aka UHF Connector (50 ohms)
• WWII threaded connector intended for use
as a video connector in RADAR
applications.
• It later saw use as an RF connector and is
generally used at HF and VHF
frequencies.
• These do NOT work well over 300 MHz!
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BNC Connector
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Coaxial Connectors
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BNC Connector (50 or 75 ohms)
Aka (Bayonet Neill-Concelman)
Very common RF coaxial connector
Used for audio, video, RF and networking
Commonly found in radio and television
Typically good from 0MHz – 3 GHz
Supports voltages up to 500 volts.
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F Connector
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Coaxial Connectors
• F connector (75 ohms)
• Commonly used for over the air terrestrial
television, cable television, satellite
television and cable modems.
• Best with RG-6/U cable.
• Good up to 1 GHz.
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N Connector
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Coaxial Connectors
• N Connector (50 and 75 ohms)
• Designed for 0-11GHz, but found works
well up into the 18GHz range!
• Can handle 5000 watts at 20MHz and 500
watts at 2GHz.
• Mil-Spec and widely used in the
infrastructure of land mobile, wireless
data, paging and cellular communications
systems.
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SMA Connector
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Coaxial Connectors
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SMA Connector (50 ohms)
Good from DC to 18GHz.
Commonly found on portable radios.
Rated for only 500 mating cycles if
properly torqued to 3-5 in-lbf.
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Mini-U
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Coaxial Connectors
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Miniature UHF (mini-u) (50 ohms)
Designed for use in mobile phones
Good for up to 2.5 GHz.
Became popular for commercial mobile
transmitter applications.
• Commonly found on public safety radio
equipment.
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Coaxial Cable
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Commonly found in 50 and 75 ohms
Thin, thick, shielded, double shielded.
Flexible, rigid, semi-rigid, superflex, heliax.
Air dielectric, foam dielectric, teflon.
Silver or nickel plated, solid or copper clad
Solid conductor, braided conductor, hollow
conductor and twisted conductor.
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Coaxial Cables
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Belden 9913/U
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Coaxial Cable
• An inner conductor surrounded by a
flexible, tubular insulating layer,
surrounded by a tubular conducting shield
and covered by a weather-proof material.
• Used as a transmission line for radio
frequency signals.
• The thicker the cable, the less loss and
more power handling capabilities.
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Commercial Coaxial Cables
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Commercial Coaxial Cables
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Coaxial Cable and Loss
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Coax Cable has attenuation, both ways!
RG-8/U, 100’ @ 10 MHZ = .55 dB
RG-8/U, 100’ @ 50 MHz = 1.3 dB
RG-8/U, 100’ @ 144 MHz = 2 dB
RG-8/U, 100’ @ 400 MHz = 4.1 dB
9913, 100’ @ 50 MHz = .9 dB
9913, 100’ @ 144 MHz = 1.5 dB
9913, 100’ @ 400 MHz = 2.6 dB
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Gain and Loss Chart
Gain / Loss Multiplier ERP if 100 watts
1db
1.2
120 w
2db
1.6
160 w
3db
2.1
210 w
6db
4
400 w
9db
8
800 w
12db
15.9
1590 w
15db
31.6
3160 w
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Coaxial Cable and Loss
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LMR-400, 100’ @ 10MHz = negligible
LMR-400, 100’ @ 50MHz = .9 dB
LMR-400, 100’ @ 144MHz = 1.4 dB
LMR-400, 100’ @ 440MHz = 2.7 dB
LDF4-50, 100’ @ 10MHZ = negligible
LDF4-50, 100’ @ 144MHz = .4 dB
LDF4-50, 100’ @ 440MHz = 1.5 dB
LDF4-50, 100’ @ 900MHz = 2.2 dB
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Coaxial Cable and Loss
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LDF5-50, 100’ @ 50MHz = .25 dB
LDF5-50, 100’ @ 144MHz = .4 dB
LDF5-50, 100’ @ 440MHz = .8 dB
LDF5-50, 100’ @ 900MHz = 1.2 dB
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Ladder Line
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No loss.
Does not leak.
Not prone to radiate.
Requires a BALUN to work with standard
50 ohm equipment.
• Must be kept clear of surrounding metal.
• Very easy to work with.
• Does not require expensive connectors.
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450 ohm Ladder Line
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Simple Dipole Connection
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Ladder Line J-Pole Antenna
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Home Made Ladder Line
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The Doublet Antenna
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½ Wave Doublet Formula
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Doublet Advantages
• Cut to lowest frequency you intend to use.
• Must use a tuner.
• Must have a 4:1 Balun in the tuner.
(usually will have 2 or 3 insulated binding
posts for connecting wires on back)
• Will tune ANY frequency in the HF bands.
• Will tune 6 meter band.
• Will give you GAIN in the upper HF bands!
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The End
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