[TowerTalk] Modeling tri-banders

[Roger (K8RI) on TT]

One thing modeling will do in spades, is show how honest the 
manufacturer is at present.  Gain figures are very difficult and 
expensive to obtain empirically,  not to mention the effort involved.  
"In general" modeling is the easiest and most accurate way to obtain 
valid numbers for comparisons between antennas and models.

Will that extra element or two be worth it?  Will the extra bands 
degrade, or enhance the figures.  In some cases they enhance the multi 
band antenna to numbers that are close to what a mono band antenna for 
each bad could do.  OTOH all this extra come with a downside.  They cost 
more and weigh more. Sometimes they weigh a lot more.  When I was 
younger, the price was more of an issue than weight.  When I had a 
degree and a good job, the price became a lesser issue, but let's face 
it.  Hams "in general" are not an affluent lot, so for some price is the 
leading factor.  Some hams are, shall we say, frugal while some are 
downright cheap! The last group is why some manufacturers can get away 
with rating amps at far more than they are capable, or with ratings 
guaranteed to be a boon for the tube industry.

Antennas are little different.  Most hams are well aware that all 
antennas are a group of compromises.  Some are inexpensive while others 
are downright "cheap".  Any high school kid should know the difference 
between inexpensive and cheap.  Alas, with today's educational lack in 
addressing practical issues, there is a strong likelihood that not many 
will.

With little to spend (the essence of hams in the "old days"), it makes 
sense to model the antennas, and follow the newsgroups to find out how 
well the antennas stand up to the tests of time. True, the new ham may 
have little knowledge of modeling, so an "Elmer" would hopefully lend a 
hand.  But be careful with glowing reports on some on-line groups. 
Antennas and Amplifiers in particular tend to have either glowing 
reports, or trash reports. Inexperienced hams and old timers alike are 
loathe to admit they made a mistake and were "screwed" by company A, or 
B with an over rated and flimsy product.

Antennas have to stand up to the weather, be it wind, heat, or ice.  We 
don't have all that many strong winds in Michigan, but we do have ice.  
It's difficult to describe that sinking feeling when you see the element 
ends of your favorite antenna pointed straight at the ground, but good 
alloy will often provide elements that snap back when the ice falls.

A new hazard is acid rain, where unprotected solder joints may dissolve 
in a few years.  It's been my experience that RHOS solder does not fare 
well, but that is only one hams experience.I've had the solder joints 
fail on several recent commercial antennas.

So, modeling, combined with user reports can be invaluable in the 
selection of that next new antenna.

73

Roger (K8RI)


On 4/9/2015 11:27 PM, Tom Osborne wrote:
> What is the purpose of modeling tri-banders, like Steps, etc.  Is it 
> just to compare antennas before purchasing one?  If I have a Step up, 
> why would I want to model it?
>
> Sure not gonna be moving elements around for more gain or F/B.
>
> Just curious.  73
>
> Tom W7WHY
>
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-- 

73

Roger (K8RI)


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