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[TowerTalk] C4XL vs. TH-6 (Wilson SYS-36) - looong

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Subject: [TowerTalk] C4XL vs. TH-6 (Wilson SYS-36) - looong
From: (
Date: Tue, 23 Mar 1999 18:19:09 EST
In a message dated 99-03-23 17:54:57 EST, writes:

> Have checked the archives and found little.....purchased the
>  tribander comparison......but still feel a little hesitant abt going from
>  the Wilson Sys-36 (TH-6) to the C4XL.....Wud really like to see the C31xr
>  with 2 el on 40m.......

     Force 12 does have some new antennas. Natan, W6XR, Force 12 East made the
recent following announcement:

>> Several have asked for specifications of our new additions to the XR
Below are the electrical/mechanical specs for those antennas.  Pricing will
soon be available.


Natan W6XR/2
FORCE12 East


1999 introduces an expanded line of XR series antennas. Last year was the
first ?XR? series antenna, the C-31XR, named after Natan, W6XR/2 (Force 12,
East), who politely pushed for its completion. The C-31XR 31? boom no-trap
tribander has become the antenna of choice for those who want the best. The
basic design goals have been carried throughout the entire line that
includes the C-19XR, C-31XR, C-36XR and C-51XR.

The XR series utilizes an overlaid Yagi technique for 20-15-10 mtrs. This is
an extension of the Force 12 designs that have been in production for
several years, such as the C-3, C-3S, C-3SS, 5BA, 4BA, 15/10 duobanders and
the C-3XL. Besides utilizing the experience and knowledge of our successful
designs, some of the groundwork was based on additional testing using models
at 2-6GHz. The XR tribanders use three monoband Yagis that are placed onto
the same boom, one on  top of the other. This must be done carefully;
otherwise, the antenna will not perform properly. One key is the right
design that will pass energy through elements that are otherwise
?unfriendly.? Another key is the feed system. The three-band open sleeve
developed by Force 12 for the C-3 and C-3S was modified for more
flexibility. The XR triband feed is a combination of both the open sleeve
and the ?closed sleeve? (used on the C-3SS).

Design features on the XR series include:
No traps for the highest efficiency (no need to estimate trap losses)
High forward gain and excellent Front to Rear (front to side and F/B)
Stepped gain on 10 mtrs to assist in stacking
Low profile, riveted elements and tapered booms
Standard 100 mph design (120 mph optional), with standard booms rated for
Minimal mast torque
Open space at the center for side mounting
5KW+ rating (no traps to be concerned about)

Force 12, Inc. logically expanded the XR line for 1999 to meet the needs and
dreams of more amateurs. A challenge was to add a 2el 40 Yagi to the
tribander(s) without disturbing the excellent performance. The overlaid Yagi
design on 20-15-10 does not allow ?dropping? 40 mtr elements into the
antenna. The most effective method is to add the 40 mtr Yagi in an area that
does not impact the tribander, which is behind the reflectors. This adds to
the boom length, but the results are what was desired: excellent quad-band
performance on a single boom Yagi.

This is a great tribander that can be installed by everyone. The C-19XR
shares the C-31XR technology in a smaller footprint. The 19? boom contains
three overlaid monoband Yagis: 3el on 20, 3el on 15 and 5el on 10 mtrs, with
a single feedline. The patterns are excellent, as are the forward gain
figures. Simple assembly, open area at the center, 100 mph standard, with an
overbuilt boom. It is designed specifically for optimum performance on
20-15-10 mtrs, 11 elements.

This magnificent tribander is the product of about 2 years development to
provide an antenna that exceeded the C-3. It is the first to be released in
the XR series. The C-31 XR is composed of three overlaid monobanders: for 20
mtrs, there is a wide-spaced 3 element; on 15, it has a wide spaced 4
element; and, on 10 mtrs, there are 7 elements, for a total of 14. The feed
system is a new development by FORCE 12, utilizing both open sleeve and
closed sleeve systems. It can be used as a single feedline and be changed in
the field to separate feedlines to make maximum use of the new transceivers
and for multi-operator contesting (remember to use bandpass filters!). 120
mph optional, with no increase in windload.

The first of the quad-banders, the C-36XR is on a 36? boom. Using the C-19XR
for 20-15-10, the 2el 40 mtr Yagi is placed to the rear of the 20 mtr
reflector. The pattern on the close-spaced 40 is excellent and the operating
bandwidth is about 130 kHz, with an optional relay box to switch between CW
and phone. This relay box is the same as used on the 80 mtr dipoles and
Yagis. The C-36XR is rated for 100 mph, optional at 120.

This is the largest quad-bander ever built. The 51? boom has the entire
C-31XR for 20-15-10, plus a 2el 40 mtr Yagi installed behind the 20 mtr
reflector. This antenna is crated, having 20? of 4? boom at the center,
tapering down to the ends. It comes with the Force 12 drop-in tilt cradle
mount for easier installation. The 2el 40 has the optional relay boxes
available to work both modes. The 20-15-10 can use a single feedline, or
separates, just like the C-31XR. The C-51XR is built in standard form for
120 mph. The first two C-51XR?s are being installed in a stack with a C-31XR
at VE1JF, for what he calls, ?Excessive Force 12!?

                      Boom       Wind       Frequency        Gain
Net         F/B           VSWR                  Turning            Mast
Antenna Length  Load          in mHz @74?       Gain Ratio (max) Radius Wt.

C-19 XR 19? 9.1sqft 14.000-14.350 13.3dBi 5.2dBd 23dB <1.6:1 20.3? 58# <150
11 el, one 50 ohm feedline 21.000-21.450 13.1 5.0 24 <1.8:1  100 mph rating
21? open space at center  28.000-29.300 14.1 5.9 20 <1.4: (28.0-29.1)

C-31 XR 31? 10.5 14.000-14.350 14.0dBi 6.0dBd 20dB <1.7:1 23.8? 82# <200
14 el, 1, 2 or 3, 50 ohm feedlines 21.000-21.450 14.3 6.3 22 <1.7:1  100 mph
30? open space at center  28.000-29.300 15.6 7.4 21 <1.7: (28.0-29.1)  120
mph optional

C-36 XR 36? 13.8   7.000-7.300 12.1dBi 4.0dBd 20dB pk 130kHz, 2:1 29.2? 108#
<120 in/lb
13 el, two 50 ohm feedlines 14.000-14.350 13.3dBi 5.2dBd 23dB <1.6:1  100
mph rating
30? open space at center  21.000-21.450 13.1 5.0 24 <1.8:1
40 mtr adjustable in band 28.000-29.300 14.1 5.9 20 <1.4: (28.0-29.1)

C-51 XR 51? 15.5   7.000-7.300 12.1dBi 4.0dBd 20dB pk 130kHz, 2:1 34.2? 173#
<800 in/lb
15 el, 40 mtr feedline  14.000-14.350 14.0dBi 6.0dBd 20dB <1.7:1  120 mph
1, 2, or 3 feedlines 20-15-10 21.000-21.450 14.3 6.3 22 <1.7:1
70? open space at center  28.000-29.300 15.6 7.4 21 <1.7: (28.0-29.1)
40 mtr adjustable in band

1.  Gain is achieved by redistributing the available energy into a preferred
direction at the expense of other directions. It is usually measured at the
point of most energy in the preferred lobe of an antenna. Gain is expressed
in a relative term, ?dB something?, where ?something? is the important
reference (what it is compared to). Horizontal antennas are specified in two
GAIN @ 74? is given in dBi at the computed gain of the antenna at a height
of 74? (over average, real ground), as compared to the theoretical isotropic
source (reference). This dBi figure will be familiar to those who do
computer modeling and is numerically much larger than the ?apples to apples?
dBd comparison, by roughly 7-7.5dB. This comes from two places. One is from
the difference between the theoretical isotropic source in free space to a
dipole in free space, which accounts for 2.14dB (the pattern is changed from
a sphere in free space to a figure 8 above ground, which indicates how the
energy is redistributed). The second is from ?ground reflection gain,? which
is the enhancement for a horizontal antenna installed above real ground, due
to the effect of the ground. Values for ground reflection gain on horizontal
antennas depend on the height in wavelengths above ground and average
4.5-5.8dB. If 2.14 (isotropic source) and 5.9 (maximum ground reflection
gain) are subtracted from the dBi figure, one will arrive at approximately
the dBd ?apples to apples? number.
NET GAIN is given in dBd as compared to the full size, resonant reference
dipole at the same height, in the same location. This is the ?apples to
apples? comparison and is labeled, ?NET GAIN.?
Computations are performed using state of the art modeling software: NEC-4,
EZNEC, AO, YO and are validated using consultants. Force 12 does not use
traps, so there are no assumptions needed about possible Q of the traps
(coils) and associated losses.
2.  F/B ratio is the peak (minimum) difference between the forward and
reward pattern.  A high F/B at a single point (180 degrees to the rear) does
not necessarily means the antenna has good rejection to the sides and rear
quadrants (F/R).  FORCE 12 antennas have excellent F/R.
3.  VSWR is the highest value (usually at the band edges) for a typical
installation through an RF choke or 1:1 balun. Within the band, the VSWR
will usually approach 1:1. The actual VSWR measured might be lower than
these values, because coax has a small amount of loss and this acts to
smooth out the VSWR curve.  If the frequency of the lowest VSWR shifts with
a change in coax length, the balun or RF choke is not effective. Proximity
to other antennas or other objects (i.e. roof and ground), can change these
values. >>

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