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.
End Fed Off Center Fed Antenna
Need a high performance, multi-band, stealthy antenna system that is easy to setup and use? Get the Bullet antenna matcher with the antenna wire, insulator and feed line choke all in one convenient package (great for HOA restricted areas, camping and portable operations, etc.)
Why is this end fed OCF antenna a better choice than and End Fed Half Wave (EFHW)? More bands, shorter length and no dangerous high voltage at antenna feed point from VOLTAGE FED 49:1 TRANSFORMERS!!!
Off Center Fed (OCF) antennas are very convenient as they will allow multiple bands of operation with a simple wire antenna which is fed off center. The Palomar Engineers 8010 OCF is a very popular antenna and consists of an off center fed dipole with sides of 95 feet and 40 feet and it will work all bands from 80-6 meters.
The BULLET-8006 uses the same dimensions but the wire section is 95 feet as in the OCF and the coax outer braid is used for the “other” part of the OCF dipole. We place a choke on the coax at the 40 foot distance from the matching unit and we essentially have an OCF antenna with its great frequency range, but with only a 95 foot wire length instead of the 135 feet required by the regular OCF or EFHW. You feed the antenna from one end which may be more convenient for some installations. This antenna will work on 80-40-30-20-17-15-12-11-10 and 6 meters. Most bands are under 3:1 SWR and easily tuned by your transceiver’s internal antenna tuner or external tuner used with an amplifier.
This antenna is a great stealthy primary or backup antenna and works exceptionally well for apartments, condominiums, homeowner, mobile home parks, RV applications and ARES, RACES, MARS, EMCOMM, NVIS, First Responders and Emergency Preparedness. Compact, Stealthy and Light weight for back packing and portable use.
The antenna is simple to deploy, folds up easily for transport, and with the 95 foot included wire, can work the 80-6 meter bands easily with the built in antenna tuner of most current day transceivers. Some bands may not even require a tuner if the antenna length and counterpoise choke position is adjusted correctly. (see SWR graph in gallery).
These antennas are MUCH BETTER PERFORMERS than End Fed Half Wave antennas using 49:1 transformers that are by their very design frequency limited at the high end. Our end feds work the WARC bands, DO NOT HAVE A DANGEROUS HIGH VOLTAGE at the antenna connection and are shorter to fit in smaller spaces yet provide more band coverage up to 6 meters!
Make the right choice - use and end fed OCF and enjoy the expanded band coverage, additional safety and smaller footprint!
Part #'s:
BULLET-8006-100 for 100 watts PEP/100 watts digital
BULLET-8006-500 for 500 watts PEP/250 watts digital
BULLET-8006-1500 for 1500 watts PEP/750 watts digital
BULLET-8006-5000 for 5000 watts PEP/2.5KW watts digital
The antenna can be used as a up or down sloper, “L” with a vertical section (at either end) and a horizontal section, or as a horizontal antenna between two trees or supports.
Our antenna matching network is called the “Bullet” because of it shape and its effectiveness at taking down or contacting distant (DX) stations all over the world under the right conditions.
For best results we recommend that the coax feed line be at least 50 feet. We also recommend a coax noise filter near radio end of the coax feed line to reduce RFI common mode current from interfering with the radio operation.
Installation
For best results raise the Bullet matching unit as high as possible (use a tree or vertical support) and then extend the antenna wire horizontally or as an “L” (horizontal with vertical end drop). The antenna may also be deployed as a sloper with the Bullet matching unit at the top (best) with the wire sloping toward the ground (with the end high enough to avoid contact by humans or animals), or at the bottom of the sloper with the antenna wire rising to a higher point.
Any length of 50 ohm feed line ok (over 50 feet minimum recommended) but longer feed lines over 50 feet may show reduced SWR on some bands due to soil conductivity, nearby objects, etc. Due to local ground conditions, antenna height and feed line length, SWR may vary and an antenna tuner may be required or some bands to bring SWR at end of feed line to acceptable levels. Position a feed line choke (part# SOFLC) 12 feet from the matching unit.
Use a good quality 50 ohm cable adequate for the power level of your station.The Bullet matching unit is rated for 100, 500 or 1500 watts PEP (depending on model) for SSB and 50% for CW or digital modes. If the matching unit becomes warm to the touch after transmitting at high power, reduce the power output or the internal matching unit may become damaged.
NOTE: The matching unit output is DC grounded to bleed off static electricity, however it is not RF grounded.
Need a shorter antenna for portable or stealth installation? Check out the BULLET-2006 at 25 feet length and still works 20-6 meters or the BULLET-4006 at 55 FT which works 40-6 meters!
TECH NOTE: If you use LMR-400 or 1/2" coax cable you will need to use a larger diameter ring choke (part# F400-31) so you can get 6-10 turns thru the center to provide enough choking on 40 and 80 meters. If you use RG-8X size cable (which will work up to 1500 watts), then the two included SOFLC with this kit are sufficient if you have 6 turns thru the center of each one in two separate loops as pictured.
NOTE: due to the nature of antenna systems and the modifications many users perform and the transmitter power levels that may be applied higher then the specifications, the antenna systems are NOT RETURNABLE unless they are unused, in the original packing with the original invoice and a return request is made withing 30 days of original purchase.
SWR TECH NOTE:The SWR graphs shown are specific to the conditions listed including antenna height, configuration (flat top, inverted V, inverted L, etc.) and direction, feed line length and type, geographic location and soil condition, calibration and accuracy of SWR instruments used. Your SWR measurements will probably be different and manufacturer takes no responsibility or liability for these differences beyond the purchase price of the antenna.
