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[Towertalk] Re. HF2V

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Subject: [Towertalk] Re. HF2V
From: (Tom Rauch)
Date: Sun, 7 Jul 2002 13:13:30 -0400
> N4KG:  OK, are you suggesting that a guy on a CITY LOT
>  would be well advised to use a BASE LOADED HF2V
>  over a limited (<35') radial field and expect to be competitive?

Don't know. 

I'd sure try one or something else vertical with a chance of working 
(NOT a Gap or similar no-radial or small radial system dummy load) if 
I was serious about doing the best I could without moving.

When a situation has many unknowns, it makes little sense to limit 
our options with preconceived ideas based on results in other system 
with unknown variables.

When I lived in Rockdale county, despite having a uphill slope 
towards Europe and rocky ground, a 35 foot vertical almost always 
tied my 120 foot or so high dipole for long DX on 80. When I think of 
the work in getting a 120 foot tower in the city, or the odds of 
finding a 100 foot tree, it might be worth a shot.

Will it work the same? Who knows. 
> N4KG:  I assume your comparison is over a LARGE radial field
>  (30 or more radials 70 ft long).  How do the HF2V and
>  MFJ 1792 compare over a 1/8 WL (35 ft) radial field
>  that can be realized on a conventional city lot?

I had 60 1/4 wl radials. That was the only ground system I used, 
other than a test of a small elevated system that wound up being 5-6 
dB down from those radials. I do things reasonably as best as I can, 
and once I learned the elevated system didn't work I just left the 60 
radials in.
> N4KG: SO, you AGREE that a TOP LOADED Vertical is superior
>  to a BASE LOADED vertical over a limited radial field
>  typical for most city lot limited users?

Depends. Like many things, it is a juggling act.

As the loading coil height is increased in a basically uniform cross 
section radiator, coil loss for a given design generally increases 
while ground loss decreases. The change in efficiency depends on how 
poor the ground system is, how poor the coil is, and if the antenna 
has a top-hat of significant dimensions.

There will be some point that optimizes the results.

The larger the top hat, the less critical the coil becomes, so I 
would agree that top hat loading is a better choice, but 
unfortunately that also means the coil location is NOT important!

In other words, I'd be really careful to look at things before just 
moving the coil up high. I would not hesitate to add a large 
capacitance hat at top, because that makes everything less critical.

 >  In other words, a short tower / tribander, shunt fed
>  (or even set up as an Elevated GP) would be a 
>  MUCH better antenna than a Base Loaded (HF2V)
>  vertical on a small city lot.   (N4KG)

I don't know how you would feed a grounded tower as a groundplane, 
since by definition it is grounded and the ground path can have a 
large effect on efficiency. My choice would be to do something 
predictable, like install a good ground system and use traditional 
shunt feeding. 
> N4KG:  OK.  So your recommendation to all the city dwellers
>  on TowerTalk is to install 40 radials 70 ft in length, right?
>  And to keep any other large vertical conductors (towers)
>  WELL away from their verticals (>500 ft).

I am not recommending anything, other than people do the best they 
can and experiment. Some people, as unbelievable as it might seem, 
will do pretty well with a short vertical whether base loaded or 
not..even if they can not get in a perfect or near perfect ground.

My only point is to add technical accuracy to some points of this 
discussion, not to tell people what will work when there are dozens 
of unknowns.

People generally can make better decisions with facts or 
understanding of HOW something interacts, rather than anecdotal 
> N4KG: What do you recommend to the guy who lives on a 60 by 120 ft
> lot?

I only recommend they look at what is around them, try to the 
understand any resources they have, and decide what they want to try 
in order to get the results they might want.

They only clear thing in any of this is to avoid magic antennas, and 
use systems with good engineering.

73, Tom W8JI 

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