140 FOOT T3FD ANTENNA ASSEMBLED WITH BROADBAND MATCHING TRANSFORMER AND ROPE
AMERICAN MADE PARTS
T3FD-140-BUILT 500 Watt version (Available in 1500 Watt version)
You will receive:
4 @ Outer loop wires (coiled) 14 awg stranded Insulated
2 @ Center wires (coiled) 14 awg stranded Insulated
2 @ End insulators
10 @ 4’ Spreader insulator 3/8 inch
3 @ Middle insulators
1 @ Load resistor
1 @ Broad Band Matching Transformer (1.8-61 MHz)
12 @ 5/16” Crimp type connectors (Eye)
2 @ #10 Crimp type connectors (Eye)
2 @ Stainless Steel #10 machine screw, lock nut, flat washer (for resistor and feedline at cage)
6 @ 5/16” -18 x ½” Stainless Steel bolt, lock washer, flat washer, and nut
16@ 1” pieces of Outdoor Heat shrink
18 @ 3 ½ ” Aluminum Wire (3 per spreader)
1 @ 35’ 600 ohm open-wire feedline
1 @ 250’ Spool 5/32” Dacron DUSA rope black
2 @ 100’ Hanks 5/32” Dacron DUSA rope black
1 @ Roll of Coax Seal
1 @ Roll Black Electrical Tape
The purpose of a T3FD antenna is to obtain frequency agility (broadband 50 ohm minimally reactive load) so a transmitter (and amplifier) will not require an external tuner to maintain a safe VSWR.
Frequency agile modes: ALE scanning; rapid frequency change radio checks during voice nets.
"Safe" also means a critical digital transmission does not get interrupted due to an unexpected automatic retuning sequence.
The T3FD is a "terminated" antenna, which means you add resistance that improves the VSWR by increasing the "return loss".
You make a conscious decision to trade dB of efficiency for dB return loss!
Efficiency can be recovered by re-inserting amplification.
We are not talking about "saving fuel or saving the environment" efficiency
The T3FD has characteristics of a magnetic loop antenna.
It is less susceptible to E-field noise according to users of the antenna.
Voltages are no maximum at the end insulators, rather, current is maximum.
Much less corona effect and static noise.
The noise floor is reported to be anywhere from 1 to 5 S-units (30dB) less than with a similar voltage dipole antenna.
The physical size of the T3FD antenna directly affects the efficiency and radiation pattern just the same as a classic dipole.
The elevation profile of the T3FD antenna affects the efficiency and radiation pattern, just the same as a classic dipole.
However, for the T3FD, the more you bend the wire, such as make an inverted-V the less efficient the antenna becomes, but the VSWR remains low. This means the load resistor absorbs more reflected energy and gets hotter, but the communications mission continues.
A classic dipole impedance changes, and the user must intervene with different antenna tuner values, which takes time.
An auto-tuner intervention is unanticipated and during a transmission, which at power levels can compromise the tuner components, or tuner cost (high power).
The radiation pattern of a T3FD antenna is the same as a classic dipole when they are equal in size, length, elevation profile, and near the same reflective and RF absorbing object space according to models.
There appear to be advantages over a single-wire dipole, advantages which are related to the array occupying more physical space due to caging and "triple the amount" of wire. Electrically small antenna designs leverage this property and the T3FD exhibits these properties. Multi-path and selective fading issues appear to be less with the T3FD. This science exploration is ongoing.
Expect the R10CA and Dipoles USA LLC RF design of the T3FD antenna to be optimized where-ever possible, so as to not sacrifice efficiency by choice; Those factors include:
the actual termination resistance value,
wire spacing and geometry,
broadband matching transformer design
The Dipoles USA LLC kit design sacrifices material robustness for achieving lowest cost wherever possible and is not Mil-Spec.
The T3FD will operate with low VSWR under stressed deployment conditions (having sustained battle or environmental damage) where a classic dipole will fail. For example:
a support fails and part of the antenna is laying on the ground,
an outer-loop wire break
if middle wire or load resistor fails, the antenna can be tuned with a tuner
the load resistor can be removed and jumpers
Weather conditions change rain, snow, ice loading will not raise the VSWR
Feedline lengths between the feed-cage and the broadband matching transformer (aka balun) do not de-tune the antenna.
You do not tune the T3FD by "cutting and trying" the open-wire feedline length to the BBMT.
The environmental survivability of the T3FD is less than a standard dipole when the exact same insulator and wire components are compared.
This is due to the array being 3x larger in wire quantity. The 160m half-wave 266 foot long T3FD-288 has 820 feet of wire hanging in the air!
The additional weight, wind and ice loading will place a higher demand on the support structures
The addition of lateral spacer insulators can last 10 to 30 years by proper material choice
The overall design should be "repairable" and "upgradeable" or should be "permanent quality" where the original installation team won't be around in the future.
The material choices (design approach) should be made with the understanding of cost vs robustness is a conscious customer decision.
Constructing a T3FD is more complex than a standard dipole. You either have the time or the money. Take the time to put quality effort in your "homebrew kit" T3FD...If you absolutely want the antenna to survive massive QRO stress, or gale force winds, consider upgrading to the Mil-Spec version offer by R10CA.