[TowerTalk] Please Help Me Decide on a Tribander or Monobanders

[k2qmf at juno.com]

Go for the SkyHawk tribander.
Much better than the Force 12 and less expensive too...
Longer boom etc.

73,
Ted  K2QMF

 
On Thu, 18 Apr 2013 17:24:31 -0500 Richard Thorne <rthorne at rthorne.net>
writes:
> I sure like my C31XR at 79' with a Delta 240 mounted 10' above it. I 
> 
> plan on changing out the 240 with a Delta 230/240  and lower it to 
> about 
> 7' above the C31xr then add a WARC 2/2 at the 10' level.  That will 
> give 
> me a rotatable 10 through 40 solution.
> 
> I also have a C3 tribander (going on 17 years old) mounted on a 
> rotatable swinging side gate at 40'.
> 
> I really like the F12 antennas, instant band change and made in 
> America.
> 
> Rich - N5ZC
> 
> 
> On 4/18/2013 4:06 PM, Wayne Willenberg wrote:
> > My 86 or 89 foot crank-up tower project seems to be progressing 
> through my
> > County review boards.  So now I am getting really excited for my 
> first
> > tower.
> >
> > I am now in ham nirvana because I have to start making up my mind 
> on which
> > antenna(s) to put on the 15’ mast.  Here is my first dilemma.  
> Should I put
> > up a tribander (10, 15 and 20M) or 3 monobanders.  My intuition 
> said there
> > was no way a tribander with the same 20M boom length could beat 3
> > monobanders having a 20M antenna with the same boom length.
> >
> > So, just as an exercise, I looked at Force 12 antennas.  (I am 
> not
> > endorsing Force 12 antennas, although they do seem to have a good
> > reputation.  I am also aware that the performance specs of 
> antenna
> > manufacturers need to be taken with a grain of salt –this is not 
> meant to
> > be a criticism of Force 12.)
> >
> > I started with the Force 12 model C-31XR tribander.  It has 14 
> elements on
> > a boom length of 31’, a wind load of 10.7 sqft and published 
> figures of:
> >
> > 20M gain: 14.0dBi, a F/B of 20dB,
> >
> > 15M gain: 14.3dBi, a F/B of 22dB, and
> >
> > 10M gain: 15.6dBi, a F/B of 21dB.  Published price: $2,970
> >
> > Then, I looked for monobanders from Force 12 that had a boom 
> length for the
> > 20M monobander close to the C-31XR and a gain in the vicinity of 
> the of the
> > tribander for each of the 3 bands.  Here is what I found:
> >
> > EF-420 (20M with 4 elements) has a boom length of 30’, a gain of 
> 14.5Dbi,
> > a  F/B of 22dB, a wind load of 5.5 sqft, and a cost of $1,300.
> >
> > EF-415 (15M with 4 elements) has a boom length of 20’, a gain of 
> 14.6Dbi, a
> > F/B of 22dB, a wind load of 2.8 sqft, and a cost of $869.
> >
> > EF-510 (10M with 5 elements) has a boom length of 18’, a gain of 
> 15.1dBi, a
> > F/B of 23, a wind load of 2.5 sqft, and a cost of $799.
> >
> > The total wind load of the 3 monobanders is 10.8 sqft and a total 
> cost of
> > $2,968.
> >
> > So, at first glance, the price and wind load of the tribander is
> > practically the same as the sum of the 3 monobanders.  There is no 
> more
> > than an additional 0.5dB of gain (and 0.5 dB loss of gain on 10M) 
> with
> > monobanders;  a gain of 2dB F/B (and 2dB more F/B on 10M) for 
> monobanders.
> >
> > However, I am aware that there will be a degradation of the 
> performance of
> > at least the middle monobander if I put 3 of them, in a Christmas 
> tree
> > fashion, on a 15’ mast.  I haven’t been able to find a good 
> discussion of
> > the amount of degradation—even the 22nd Edition of the Antenna 
> Book has
> > only a few words to say about this.  Please direct me to a 
> discussion of
> > this topic if you know one.  I may have to model these antennas on 
> EZNEC to
> > see the impact of 3 antennas confined to a 15 foot mast.
> >
> > On the other hand, there has to be a compromise when 3 antennas 
> are mounted
> > on a single boom.
> >
> > I would really appreciate your help in finding all of the specs I 
> should be
> > looking at in making this decision.  Any other comments that would 
> push me
> > one way or the other would also be appreciated.
> >
> > Please help me with my first tower!
> >
> > 73, Wayne KK6BT
> > _______________________________________________
> >
> >
> >
> > _______________________________________________
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> > TowerTalk at contesting.com
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> >
> 
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> 
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