It appears this has become a "I love my antenna" pile-on, so here's my .02.
Since the original question was for multiple beams on a very tall crank up
(89'), You can get almost all bands on one boom...get the biggest Tennadyne log
you can afford and laugh all the way to bank!!! The HD versions cover 30m and
they still make some that cover 40m as well. No traps, no moving parts to wear
out, covers WARC bands too, good SWR and MUCH less expensive solution. Yes the
gain is a hair less. You won't notice it. Particularly when your buddy with
the SteppIR is calling the crane guy to do a repair and you're working the P5.
:-)
Chris
KF7P
On Apr 18, 2013, at 16:24 , Richard Thorne wrote:
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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