Antenna Information needed

[foggie]

Wayne;
    If anyone replies maybe you could summarize and either post it to newsgroup 
or
email me, as I too am considering a force 12 antenna.

73,
Al KK5ZX

On 11-Jun-96 Wayne Bailey wrote:
>>I would like to hear from anyone with experience with the Force 12 Antennas,
>How do they perform in contests, comparison with your old setup, what did
>you use before, etc.
>
>Thank you in advance for any information you might provide.
>
>73 de Wayne, NX7K

____________________________________________________________________________
E-Mail: foggie at dtx.net            | Snail-Mail: Allen Fogleson
Date: 06/09/96                    |             6121-A Nowak Court
                                  |             Fort Polk, La 71459
____________________________________________________________________________
This message was sent by XF-Mail free of charge, and is 100% microsoft free!
For more information on remaining microsoft free try http://www.redhat.com/
---------------------------------------------------------------------------- 


>From fisher at hp-and2.an.hp.com (Tony Brock-Fisher)  Tue Jun 11 18:06:15 1996
From: fisher at hp-and2.an.hp.com (Tony Brock-Fisher) (Tony Brock-Fisher)
Date: Tue, 11 Jun 1996 13:06:15 -0400
Subject: Antenna Information needed
Message-ID: <9606111706.AA05817 at hp-and2.an.hp.com>

Allen-

Here's the reply I sent to Wayne:

First; my own personal conclusions, followed by the responses I received
to a similar posting:


Greetings....


You are on the distribution list because you replied to an earlier
posting of mine about the Force12 C4XL antennas. I have come to a
final conclusion regarding this subject, and thought you might be
interested in what I ultimately decided....

 I currently have a KT-34XA at 70 feet, and a 40-2CD at 80 feet, on the same
 mast. Of course what I'd REALLY like to do is put another 10 sections
 of Rohn 45 under them! But my next tower project starts at the real estate
 office! 
 
 I have observed that height makes a BIG difference; and I'd like to get
 the 20-10 antenna up that last 10 feet in anticipation of the next
 time 10 and 15 open again. The thought has crossed my mind of replacing
 both antennas with a Force 12 C4, which would cover 10-40 meters, and
 have the advantage of all cohabitating at the same height on the mast.
 
 If anyone out there has any experience with this antenna, I'd be
 interested in hearing about it. Particularly, how does it compare to
 my existing antennae in performance and windloading. I've heard lots
 of good things about other Force 12 antennas (the C3 in particular).
 
 I also wonder if the C4 has separate feedlines for 40 meters, and if both
 antennas could be used at the same time without impossible interference
 problems due to proximity of driven elements.

The above background was in my original posting. After talking to the
folks from Force12 at Dayton, and without really a lot of meaningful
consideration, I placed an order for the C4-XL at the Dayton special
price. Fortunately there was a three week lead time before the order
shipped, during which I had an opportunity to do LOTS of research
which ultimately led me to cancel the order. Please understand
that my ultimate conclusion was NOT that the C4-XL was a bad antenna;
I think it is a good antenna, it's just that I concluded that what
I had was already better... Here's my thoughts:


I have done a lot of modelling on mono-band models of the
KT-34XA (my existing antenna on 20-10), and I have modelled the C3.
My conclusion is that the C3 just cannot compete with the XA in the
forward gain department. Here are my observations:

1. Force12 C3 series antennas are well-built, using many desirable and
advanced construction techniques. Specificly rivets, and their mast-element
and mast-boom connections look really nice to me.

2. Force12 C3 series antennas are full-size, no loading 2-element beams
on 10-20. This means they can't be beat for efficiency.

3. As far as Force12 advertising claims, I'm skeptical. First, comparing
a C3 to a KT34XA, the XA is really 4 elements on 15 and 20, and 5-6 elements
on 20. If you check with the experts, or do some modelling, you'll
find that the XA comes out 4-8 dB better in the forward gain department.
4 dB is 60% of the power. To equate the two antennas' performance would
require that the XA dissipate almost 1KW in the form of heat. That would
be 100 watts per trap (there are 10 traps in an XA). I think that much power
would be enough to melt the plastic end caps out of the traps. 
The traps of the XA are made out of three materials - air, aluminum,
and polyethylene (?) capacitor caps. Air is very low loss, the aluminum
tubing is of reasonable diameter so skin effect losses are minimal, and
the capacitor end caps constitute such a minute percentage of the capacitors
that they can't dissipate 100 watts each. The
upshot is that while there is merit in the efficiency arguement, there
isn't 4 dB of merit. I'd be willing to accept that antennas with lumped
traps like a TH7 or A4 etc would have higher losses. But the XA uses
linear loading and air-capacitors - you can't get much lower loss than that.

4. Consider this - a 2-element quad would have about one dB more gain
than a two-element yagi (such as a C3). A 2-element quad would also
be at least as efficient as a C3, if not more efficient, because of the 
higher radiation resistance. I've had a 2-element quad up at the same
time as the XA, and while it comes close, the XA beats it 99% of the time
-usually by about 6 dB.

5. Force12 is very careful about making their most dramatic statement
always appear as a customer quote - they never directly state the following
as their own claim:

 "The C3 outperforms every trapped tribander, regardless of boom length"
(quote may not be exact).

6. Force12 claims that all 7 elements are active on all bands. If this
means that the current flow in an element is non-zero, I guess they
are technically correct. If it means that the other elements contribute
significantly to gain or F/B, I disagree. I modelled the C3 on 20
meters, and got reasonably close numbers for gain and F/B to their
specs. Then I removed all the 10 and 15 meter elements. The pattern
change was really slight. Much less than .5 dB.

My conclusion was that the C3 antennas are really nice, well engineered,
well-built 2-element beams. They'd be a great replacement for a TH-32,
or even an A3 (if you buy the efficiency arguement). But they will not
provide the forward gain of an antenna with truly active elements on
a boom almost twice as long. And they won't beat a 2 element quad, either.

As far as comparisons between the 2-element 40 of the C4-XL versus
the 40-2CD, the 40-2CD has much wider bandwidth (250 kHz vs 130 kHz)
and has a longer boom length. The arguement would be between linear
loading on the Force12 versus the coils on a Cushcraft. W6QHS published
measured data for the coils on the 40-2CD - 12.93uH and a Q of 161!
That's pretty high Q. And if Force12 argues that linear loading is better
than coils for a 40 meter antenna, the same argument should hold
when comparing a linear laoded XA on 20 versus a TH7.

I called and cancelled my order for the C-4XL. I'm going to work
this summer to swap the 40-2CD at 80 feet with the KT-34XA at 70 feet.
The 40-2CD will do nearly as well at the lower height, and the XA will
benefit 3 bands (if they ever open again!) with the added
10 feet of height.

In the course of this investigation, I obtained a model for the 40-2CD;
I generated a model for the C3 (from owner's manual measurements); and
I have generated 3 mono-band models for the KT-34XA at 10, 15, and 20
meters.

GL

-Tony, K1KP, fisher at hp-and2.an.hp.com

Tony,

I have a C4 on a side mount at the 55' level on my 110' Rohn 55.  I also have
a C3 at 110,  a Force 12 180S at 117 and a Mosely 2 el 40 at 125'.  I phase
the C3/C4 and they work well.  Actually just got them up in Oct, so the jury
is still out somewhat as I spent so much time changing antennas I haven't had
much time to get on except for SS both modes.  I took down two Th7DXX and so
far I think I like the Force 12's better--sure a lot easier to work with
(weight, size, adjusting ability, etc.).  I find the low 40 el on the C4 is
great for an off direction antenna.  The 40 has a seperate feed line and
seems to work very well.  Predictably down on long haul stuff and sometimes
stronger than the high 40 for local stuff (US).  It definitely takes a lot of
adjusting (entire C4) for a situation like my side mount--I had it up and
down 3-4 times.  I am in Duluth MN, so we will see how they all do this
winter.  Have had one big slush/ice storm so far and both C3/C4 went out of
horizontal (mast to boom clamps slipped).  They said only tighten enough to
flatten lock washers--wrong!!  They are now straight and very tight and I
have had no further problem.
Good luck--and would enjoy hearing any other stories you get!!  73 John K0IJL
 

Tony,

I recently purchased/installed a Force-12 C4-XL 40M-10M beam antenna. 
Like you, I had a TH6-DX and a 40CD stacked on a Rohn 56' tower. In 
spite of a number of opinions to the contrary, stacking different types 
antennas is not all that great.

What influenced me the most was actually using a (specially built) C4 
on my recent DXpedition to Lord Howe Island for the CQWW RTTY Contest. 
The antenna was a breeze to put together and worked incredibly well. 
(We came in first for Oceana.)

The C4-XL has nine elements and a boom length of about 30'. In spite of 
this, the antenna has low mass and wind loading which means that I was 
able to use my HAM IV rotator which saved another $500-$600. (Of course 
this was offset by the purchase of a US Tower MDP-472 72' motorized 
crank-up tower!)

I assembled the C4-XL in about 4 hours. Installing on the tower was a 
snap compared to any other beam antenna I have owned. They have a very 
neat boom-to-mast mounting scheme which requires that you only have to 
align one bolt hole to hold the thing in place while you attach the 
remainder of the mounting bolts.

There has been considerable controversy surrounding the gain figures 
published for the Force-12 antennas. I showed the data provided by 
Force-12 to my neighbor, who is the chief antenna scientist for a local 
company (ESL) which manufactures ultra-sophisticated equipment for the 
defense and intelligence communities, and, in his estimation, the 
figures are realistic. I suspect that the most of the disbelievers 
cannot grasp the concept that a series of random-length elements can 
produce an impedance of 50 ohms at certain frequencies.

Frankly, the only performance data that matters is what you can work 
it! In my case, the performance has been great and I racked up two new 
countries (Myanmar and Burkina-Faso) the first afternoon I had it on 
the air. Since I am only running 700 watts on SSB and the pile-ups for 
these countries were significant, I attribute my success to the 
antenna.

In summary, I would heartily recommend the C4-XL.

73's,

Steve Stark, KE6FV
 


Tony, I have a C4 up and I've used XA's and 40CD's extensively.  I like 
the C4 a lot, but it will in no way compete with those other two 
antennas.  I have no experience using both feedlines simultaneously.  
It's on the list to try, but one you see the spacing between the 
elements, you begin to wonder if it will work.

Good luck.

73, Steve  N4TQO
merchant at crl.com


I have a C4 in the air and own a DXpedition model C4 (packs in a 4 ft 
box) that I used in Lord Howe.  They work very well and mechanically are 
very strong.  Using rivets seems to be a very fine idea.  Not having any 
traps, these antennas are fairly broad-banded.  But note that the 40 
meter element is simply a rotatable dipole and is no match for a 2 or 3 
element 40m beam.  However, you might try the C4XL instead.  This antenna 
has a longer boom and a second element on 40.  KE6FV just put one up at 
70 feet and is very pleased with it.  I will send his e-mail address in a 
second message.

The 40 meter element does have a separate feed but I do not know whether 
you can drive it and the rest of the (open sleeve driver system) antenna 
simultaneously.  W6QHS, for one, thinks not.

73, Glenn, W6OTC


Tony,

I put up a C4 for k5kg a few weeks ago.  It's a nice antenna, but don't think
its going to compete with your 2-el 40 and XA.  Its only a (very) short dipole
on 40 and 2 elements on 20, 15, and 10.

I have to agree with you about height.  That's why I don't operate dx
contests very much -- kinda like beating your head against the wall
with only a 50' tower.  My next antenna project will be like yours, at
the real estate office!

73, Ed

WA2SRQ

-Tony, K1KP, fisher at hp-and2.an.hp.com

>From ab5mm at topher.net (Steve Fletcher)  Tue Jun 11 18:46:41 1996
From: ab5mm at topher.net (Steve Fletcher) (Steve Fletcher)
Date: Tue, 11 Jun 1996 12:46:41 -0500
Subject: TNX 10m Help on TL-922
Message-ID: <31BDB101.12BD at mail.topher.net>

A short note to say "Thanks" for all the response I reveived
 abt obtaining 10m use on the KW TL-922A.

 Again, Many Thanks to;
      k4sb
      k8jlf
      w4hg
      nt5c 
      kv1w
      aa5bt

 c u @ field day

 73,
 AB5MM Steve Fletcher

ab5mm at topher.net