Flexible DF Antennas
for
Permanent Mounting
LFA-16 Antenna Kit
The LFA Series antennas have NMO style bases which go through holes in the vehicle’s roof for permanent installations. The antenna bases screw into the mount and have an O ring gasket for a weather tight seal. When used with the LL or LH Series portable units, they give either fore-aft or left right DF, depending on how they are mounted.
The LFA Series antennas are equivalent in operation to the LVA Series Magnetic Antennas but are designed for continuous outdoor exposures They can be mounted on non-magnetic surfaces or even on fiberglass or other composite structure if a metal foil ground plane is put inside.
Antennas for one frequency band (121 MHz for example), consist of two whips and bases with a connecting cable harness, molded diode switchbox, 10 feet of cable and a BNC connector to fit the receiver. Dual band sets have an additional center antenna as shown above.
The antennas are placed on a vehicle aligned in one of two ways: front and back (fore aft) or left and right. When connected to the matching BNC jack on top of the LL series receiver (or on the single BNC jack on top of the LH series receiver), the L-Per
meter will give
directional information. Since the LL Series has a four position pointer, it will
automatically give the appropriate indication. In the older style LH Series receiver, in
the DF mode, the meter will show left right indications if antennas are positioned left
and right on the vehicle. If the antennas are oriented fore-aft, in DF mode, meter
indications to the left of center indicate a "fore" direction and deflections to
the right indicate an "aft" direction to the transmitter. Installation pictures.
We strongly recommend antennas be placed in the fore-aft configuration. This will allow you to continue toward the signal source and when you pass by it, the meter will show the source to the rear of the vehicle. Turn right or left and you resolve left-right ambiguity. If you orient your antennas left-right, you can drive right past the ELT/EPIRB and not know it for some time.
The LFA-10 is the single band antenna set used for tracking signals in the aircraft band (118-136 MHz, including 121.5).
If your L-Per is capable of receiving 243 MHz and you wish to track that frequency, the LFA-16 allows you that capability. It consists of the LFA-10 plus a single base and whip that has no cable connection. It is placed between the two "outboard" antennas connected with the cable. This extra antenna acts as a reflector to give a proper DF response on the higher frequency. This is NOT a "spare" antenna and nothing should be connected to it.
If you have an LFA-10 and wish to upgrade to an LFA-16, you can purchase the center whip and base separately.
The new LL Series Little L-Per
has the capability of "four quadrant" DF on the LCD display. In order to give
you left-right and fore-aft directional information at the same time, two sets of the
LFA-10 antennas are used. One is placed in the fore-aft position and the other in the
left-right position on the vehicle. Coax cable from the antenna pairs are plugged into the
proper (marked) BNC connectors on top of the receiver. The display will now automatically
show both a left-right and a fore-aft indication on the direction indicating bars. This is
the model LFA-100 LL.
If you wish to also track signals on 243 MHz, you add a center antenna in the middle, as before.
This same system can be used on the older LH Series Little L-Pers. A second set of
LFA-10 antennas is added to give four antennas: one pair mounted fore-aft and the second
left-right. Since the LH Series units have only one BNC jack on the receiver, a small
manual switchbox is provided (LASW-1) that plugs in to the antenna jack. This switchbox
has two BNC connections on top and the coax from each pair of magnet antennas is plugged
in to the appropriate jack, according to its alignment (fore-aft or left-right). The L-Per is run in the DF
mode and the operator manually switches between the left-right and the fore-aft pair, with
the meter indicating as explained above. This is the LFA-100.
If you wish to also track signals on 243 MHz, you add a center antenna in the middle, as before.
Complete and detailed installation instructions are provided with each order and can also be found under Antenna Installations.
Damage to the DF antenna system or to the receiver can result from placing a transmitting antenna too near them. This is true whether the DF receiver is turned on or not. The RF field from the transmitter will travel down the rods to the switchbox and destroy the switching diodes. To be safe, separation should be 3 feet from a 5 watt transmitter in the same frequency range, 4.5 feet from 10 watts, 7 feet for 25 watts 10 feet for 40 watts, and 15 feet for 80 watts. If the frequency ranges are different, such as 121.5 for the DF and 150 MHz for the transmitter, half of the above distances should be used.
If you wish to operate on another frequency band (150 MHz, for example), we have all of the above options for you. In some cases, a short "tuning stub" of coaxial cable will be connected to the center antenna.
These antennas are NOT TSO approved for aircraft, but have been used with local approval for temporary installations or where their shallow inside penetration or greater flexibility with ground impact are an advantage. Some additional information can be found in the Antenna Installation section.