[TowerTalk] yagi comments
tgstewart@pepco.com
tgstewart@pepco.com
Mon, 16 Jun 1997 15:19:32 -0400
This is all very interesting...but what we really need is an independent
third-party analysis of what happens to both of these philosophies when
loaded with 1/2" radial ice and a little wind comes along and the ice
starts shedding...one side at a time.
Both M2 and F12 suffer from the "California Antenna Syndrome". That is,
the reputation, deserved or not, that they only hold up in non-icing
climates. Wind is one thing. Ice is a whole other ballgame. I've heard
some "stories" about F12's loaded with ice springing back to life as the
ice goes...but I'd like to see some real data.
While both companies offer antennas that are electrically similar, they do
have hardware differences. For example, M2 uses solid aluminum rod for
their linear loading (and support of the element), while F12 uses an
aluminum clad stranded cable. F12 uses brackets bent out of aluminum sheet
and a type of "bug" clamp for the wires, while M2 uses machined aluminum
clamps and brackets. Which holds up better? I have no idea...
Then there is a known performer that survives by brute force. The W3LPL
3el fullsize 40m beam doesnt use drastic tapering or other recent tricks...
it uses lots of pounds of aluminum in multiple layers and in larger
diameters. How does this stack up to the "new" designs?
Here's the project and a good subject for a magazine article if it's done
correctly:
Someone take a W3LPL full size 3 el 40m beam, a Cushcraft 402CD with and
without QHS mods(or the new heavy-duty one if you can get the plans), and
the M2 and F12 3el 40's and do a real honest analysis using Yagistress
and/or similar mechanical analysis software and tell us the real story (or
as close as they can get to it).
Analyze each model for wind survival with and without 1/2" radial ice.
Frank's (LPL's) 40 uses easily over $2500 in materials alone, priced at
small-quantity wholesale! His 5 el 48' boom 20 takes about $1000 or more.
Obviously there is a wide gap in the physical construction of the mentioned
antennas. Now, which one actually delivers?
Sincerely, Tyler Stewart K3MM
ftbrady@cosmoslink.net on 06/16/97 12:31:42 PM
To: towertalk@contesting.com
cc: (bcc: Tyler G Stewart/BENN/CEC)
Subject: Re: [TowerTalk] yagi comments
John Watson wrote:
>Hi Frank;
> I don't know where you got the idea that the Force 12 antennas
>are so outrageously priced. If you compare their cost of the C-3 that I
>own to the cost of a Moseley Classic 33, (I owned a 33), the price is
>equal or slightly less than the 33.
> As to weight, I can only talk to the differences in the 2
>antennas I mentioned above, and the C-3 weighs less than the 33 by at
>least 15 pounds. This alone is a vast difference. AND the difference in
>wind load is considerably less also.
> Like you, when they first came out, I was leery as to the no
>trap idea, and the weight factor. However, after having the chance to
>see one up at 40 feet (C-3), and how well it performed, I was sold on
>the antenna. I purchased a C-3 and put it up at 40 feet, the then top of
>my tower, and it was a BIG difference from the 33 I had replaced. I was
>actually able to hear people that were just too weak to work before.
> Another consideration, the Force 12 facility is out west, where
>materials and other related manufacturing costs are higher than, say in
>the south, or the economically depressed northeast. And nobody has said
>that this "hobby" is or was cheap when it comes to equipment.
> My C-3 has been up over a year in some winds over 90mph, and it
>still performs like it came out of the box, no if's. ands, or but's.
> I suggest that if you don't like the cost of a new Force 12
>antenna, you look for a used one, maybe it might be cheaper than a new
>one.
> Don't be so pessimistic, and look for excuses, or try to
>reinvent the wheel.
> Remember, you get what you pay for. There are a lot of antenna
>manufacturers out there, and they price their products fairly close to
>their competitors. The choice is yours.
>
> John Watson/KC4TBH
John,
I'm learning a lot from the responses to my "price complaint" - thanks for
contributing. I won't go into the points I covered in my followup on the
fact that Force 12 is more and more of a bargain as the tower height
increases.
I should have mentioned the specific Force 12 models that I felt were
overpriced. Here, I have selected a simple 40m 3 element monobander from a
mfr well known for solid construction ("like a tank"). Both antennas are
on
the same boom length and advertise similar gain - the only significant
difference is the M2 contains a lot more material by weight.
The M2 40ML3 three element 40m yagi specs are:
5.6 dbd gain
30ft boom
9.5 sq ft wind load
90 pounds
$799
The Force 12 Magnum 340 three element 40m yagi specs are:
5.2 dbd gain (over a dipole at 74 ft above avg ground)
30ft boom
7.5 sq ft wind load
58 pounds
$929
I just found it curious that Force 12 was asking $130 more for 32 pounds
less material. I realize that material alone does not determine the cost,
but in a bare-bones monobander, there aren't too many tricks to design - so
I don't think the extra cost came from modeling. Of course, now I realize
that the cost comes from the design and production of the manufacturing
process that so minimizes the antenna weight without (apparently)
sacrificing strength. The low weight advantage is, unfortunately, not
nearly as beneficial to users with tower heights of 70ft and less.
Bottom line - the more you increase either tower height or wind load, the
more value you get from Force 12.
I'm sorry my query sounded pessimistic, but I honestly was only trying to
spur some debate to help me intelligently make this very important
tower-rotator-antenna system decision.
73 and thanks again John
Frank - W0ECS
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