Loop antennas may be constructed in many forms including horizontal full wave loops in square, rectangle or triangle (delta) shapes. They can also be in the vertical plane and are most often in the same shapes with the delta being very popular as it has both vertical and horizontal polarization. The impedance at the loop resonant frequency is approximately 100 ohms but will very slightly on harmonics. Loops are “quiet” antennas compared to verticals and dipoles and are omni-directional. The also exhibit gain on harmonic bands. Once you try a loop antenna you will know why they are so popular with old timers but still a secret to newcomers. Shown below are some typical designs:
Full Wave Horizontal Loop Antenna (a.k.a Skyloop)
This antenna is horizontally polarized and should be mounted as high as possible but works well at low heights of 10-30 feet. They are quieter than a dipole or a vertical, have a broader bandwidth and will usually out perform a dipole antenna.To determine the approximate circumference in feet of a full wave loop antenna use the formula:
1005/Freq in Mhz = length in feet.
The feed point impedance of a full wave loop antenna is theoretically in the vicinity of 120 ohms and requires a 2:1 impedance transformer (for single band loops or a 4:1 balun to match on multiple bands) with 50 ohm line. You will also need a feed line choke or better yet, just get the Hybrid 4:1+1:1 in a single box.
Vertical Delta Loops
Vertical delta loops can be oriented several way but the most popular is to have the “pointy” end at the top (usually a single support) and the lower horizontal ends just out of reach of humans and animals. Best feed point is 1/4 wavelength (246/f(mhz)) from the top point down one side. Vertical delta loops use the same 2:1 baluns as the horizontal loops or 4:1 for multi-band operation.
PURPOSE
These kits are designed to choke common mode currents going into or exiting from your amplifier cables.Filters are supplied for the RF In, RF Out, Relay Cable/control lines, and AC power line.Use of the filters often helps cure SWR problems between amp exciter and amp and between amp and antenna tuner or direct to antenna.The AC power line choke helps keep common mode current out of the power line which could cause interference to other devices connected to the same power line if not suppressed.
USE
Standard kit for amplifiers with single input, single output, relay keying and AC input
Deluxe Kit for amplifiers with dual inputs/outputs, frequency/keying control lines
KIT INCLUDES
|
Filter Type |
Usage |
Standard Kit |
Deluxe kit |
|
F240 Ring (1.4” ID) |
RF Exciter input |
1 |
2 |
|
Snap On (1/2” ID) |
Ethernet, PTT control |
2 |
2 |
|
Snap On (1” ID) |
RF Output |
1 |
2 |
|
Snap On (1” ID) |
120/240 VAC Input |
1 |
1 |
|
Total Filters |
5 |
7 |
INSTALLATION GUIDELINES
Standard Kit - Part# RFI-LA-FLEX-1
RF Input:Ring Filter (1.4” ID) – 5-9 turns of RG-58/8X size through center
RF Output:Snap On Filter (1” ID) – 3 turns of coax cable through center
PTT Relay Cable:Snap On Filter (1/2” ID) – multiple turns through center
Ethernet Cable:Snap On Filter (1/2” ID) – multiple turns through center
AC Power:Snap On Filter (1” ID) – 3 turns of power cord through center
Deluxe Kit - Part# RFI-LA-FLEX-2
RF Input (2)Ring Filter (1.4” ID) – 5-9 turns of RG-58/8X size through center
RF Output: (2)Snap On Filter (1” ID) – 3 turns of coax cable through center
PTT Relay Cable:Snap On Filter (1/2” ID) – multiple turns through center
Ethernet Cable:Snap On Filter (1/2” ID) – multiple turns through center
AC Power:Snap On Filter (1” ID) – 3 turns of power cord through center
Also make sure you connect a good RF ground to the amplifier ground post.
