ENDFEDZ
EF-QUAD
10M/15M/20M/40M END FED DIPOLE
ASSEMBLY
1. This antenna is essentially a half wave radiator on 7 MHz / 1 wave on 14 MHz /1.5 wave
on 21 MHz and 2 wavelengths on 28 MHz with one important difference– the feedline is
at the end of the antenna. The antenna is suspended at its ends by the two included
insulators – one of which is integral to the matchbox.
2. In order to have the least possible influence on the antenna, insulated lines are
recommended for attachment to the insulators. The antenna may be suspended
horizontally or sloping. Portable operation is easily accomplished by suspending the far
end from a tree limb and letting the matchbox hang just above the ground. It is important
that the radiator be suspended so that the tuning stubs hang away from the main radiator.
TAKE THE TIME TO PROPERLY TUNE THE ANTENNA
3. Tuning is most easily accomplished by using an antenna analyzer attached to the far end
of the coaxial cable that will be used with the antenna. Alternatively, of course, a suitable
VSWR meter may be employed. This should be done at the lowest power setting that
yields reliable VSWR readings.
HOW TO TUNE THIS ANTENNA– A MUST READ
The EF-QUAD uses a novel method of tuning the individual bands that we believe is
unique to this antenna. Take a moment to review how this works. The center of a half
wave antenna is low impedance (minimum voltage/maximum current) and thus is
virtually unaffected by grounding or metal (think of the boom of a classic Yagi– it is not
“seen” by the elements). In the case of the EF-QUAD, a wire placed at the center
(approx. 33’) would have very little effect on 40 and 15M (33’ is a point of current
maxima on both bands), but would have a large effect on 20M and 10M which are points
of current minima or high impedance. Similarly, a wire at 16.5’ would have some
lengthening effect on 40M and 15M (in between a low and high impedance point),
virtually no effect on 20M (current maxima) and a large effect on 10M (current minima)
You can see, by strategically placing stubs of wire we can more or less independently
tune the different bands. Note that it is not necessary to get each band perfectly centered.
The on-air difference between say 1.6:1 and 1:1 is absolutely unrecognizable. In addition,
the EF-QUAD being a full half wave, or multiple thereof on each band displays excellent
BW- See the specification box on the last page.
4. Set the tuning stub with the #10 lug (706) aside– you likely will NOT need it.
5. Because the stubs are required to hang away from the main radiator, vertical deployment
is discouraged– a sloper or horizontal configuration should be used. Hang the antenna as
it will be in its final deployment.
6. If the three stubs are not already attached to the main radiator, plug them in now. Refer to
Figure 1 for their placement.
7. Tuning will be MUCH faster with an antenna analyzer. Find the frequency of lowest
VSWR. Search around 7 MHz for the lowest VSWR. This should be low in the band or
even below the band. Trim the far end of the radiator in short lengths until the 40M
VSWR is acceptable
8. Go to 20M and again find the frequency of lowest VSWR, which again should be low in
the band. Cut the 20M stub to achieve acceptable VSWR on 20M.
9. Repeat for 15M and 10M with their appropriate stubs.
10. In order to reduce end loading effects– the guys at each end should be non-conducting
material.
11. If you find you have initially cut the main radiator too short– install the tuning stub (706)
onto the matchbox. This will lower the best VSWR a bit on ALL bands
NOTE: If one or both ends use a tree for support, make sure to strain relieve the antenna
with a pulley+ weight or a bungy if this is temporary installation. No antenna can hold
up to thousands of pounds of force exerted by a moving tree.
SPECIFICATIONS
Polarity: Depends on mounting configuration
Design Z: 50 Ohms
V.S.W.R. Bandwidth 40M: 300KHz 1.5:1
V.S.W.R. Bandwidth 20M: 450KHz 1.5:1
V.S.W.R. Bandwidth 15M: 350KHz 1.5:1
V.S.W.R. Bandwidth 10M: 500KHz 1.5:1
Power Handling: 200W CW/SSB 50W A.M.
Weight: 2 lbs.
Length: 65’
Hardware: Stainless Steel
Connector: Silver/Teflon SO-239
Radiator #18 black poly coated copper clad
Par EndFedz ®
Vibroplex LLC
1001 N. Broadway St.
Knoxville, TN 37917 USA
(865) 309-5073
www.vibroplex.com vibroplex@vibroplex.com
NOTE:
The EF-QUAD may be used as a monobander on ANY band between 40M and 10M. This is
can be accomplished by removing the factory radiator and installing the appropriate 1/2
wavelength wire. Calculate the approximate length from L= 468/F(MHz). As an example, a
25’ 10” wire will allow operation on 17M as a monobander. Initially, cut the wire a bit long
and trim for best V.S.W.R.
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