> 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
evidence.
> 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
W8JI@contesting.com
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