Top Loading Butternut HF2V for 160m
 

Hi thanks for reading.
I'm trying to maximise the DX capabilities of my new HF2V/160S on top band.
Butternut recommend top loading wires, mainly for increasing the bandwidth
but some say this reduces the effective height, leading to detrimental
effects as a DX antenna?
Also, mine sways around like a whip in the wind so I'd imagine the loading
wires would have to be very slack?
I dont particularly need extra bandwidth so am unsure whether to go to the
bother?

Do you have any experience of top loading this or similar LF antennas?
Thanks in advance for any tips. 73 Dave G4GED

HF2V/160S means nothing to me. I assume it is a coil loaded vertical.

Extending a loading wire from the top will seriously lower the top-band
resonant frequency. Unless the loading coil is variable the loading wire
will shift the resonant frequency right outside the band.

Assuming the coil inductance can be reduced, eg., shorted turns, then top
capacitance loading will work nicely.

Extending the top sideways, even at an angle of 45 degrees below the
horizontal, will considerably improve all-round performance. The longer the
loading wire the better. If possible come downwards at the remote end to
make an inverted-U out of it.

But a lot depends on the local environment.

The ground connection/system is just as important as the antenna. A single
ground rod is not of any use unless it is all you have got. With good
garden soil a system equivalent to half-dozen shortish radials, preferably
shallow buried, will get you somewhere. Include the incoming water main and
domestic plumbing system in the ground system. On 160m include all you can
find.

Amuse yourself with program LOADCOIL.
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.................................................. ..........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
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"Dave Richardson"
Hi thanks for reading.
I'm trying to maximise the DX capabilities of my new HF2V/160S on top
band.
Butternut recommend top loading wires, mainly for increasing the bandwidth
but some say this reduces the effective height, leading to detrimental
effects as a DX antenna?
Also, mine sways around like a whip in the wind so I'd imagine the loading
wires would have to be very slack?
I dont particularly need extra bandwidth so am unsure whether to go to the
bother?

Do you have any experience of top loading this or similar LF antennas?
Thanks in advance for any tips. 73 Dave G4GED

"Dave Richardson" wrote in message ...
Hi thanks for reading.
I'm trying to maximise the DX capabilities of my new HF2V/160S on top band.
Butternut recommend top loading wires, mainly for increasing the bandwidth
but some say this reduces the effective height, leading to detrimental
effects as a DX antenna?

Effective height? I don't see where they get that at...The height of
the vertical radiator is still the same. Top loading by wires is very
effective. It's much less lossy that inductive loading, and you will
need fewer coil turns to tune than without the top loading wires. But
there is another advantage. The current distribution is improved, and
will be much more constant along the vertical section, than without
the top loading.

Also, mine sways around like a whip in the wind so I'd imagine the loading
wires would have to be very slack?

I'd use them as extra guy wires, and tighten them up a bit to cut the
swaying.

I dont particularly need extra bandwidth so am unsure whether to go to the
bother?

The improved current distribution alone is worth it on 160m.

Do you have any experience of top loading this or similar LF antennas?

I run one here. It's actually my 80m turnstile and 40 dipole fed with
a single coax feedline. On 160m, I short the coax together at the
shack, and feed as a top loaded vertical. Mine is appx 42 ft tall, and
uses four 60 ft loading wires, along with the two 32 ft wires. I've
modeled it, and the current distribution along the vertical section is
nearly constant, and it has an overhead null and pattern much the same
as a monopole. How does it work? I have a 1/4 wave inverted L about 45
ft up a tree. Only very early in the evening when the skip is straight
up and back down is it ever better than the top load antenna. "due to
the horizontal componant of the inv L" Most all other times, the top
load vertical is better. Usually by about 5-10 db on the average
radio's meter. I'm fairly sure the increase in performance is due to
the improved current distribution. Both antennas are the same appx
height. This also reduces ground losses a bit since the current level
near the ground is lower.
MK

Changing the current distribution and changing the effective height are one
and the same thing.

Reg Edwards wrote:
Changing the current distribution and changing the effective height are one
and the same thing.

I can lower my angle of maximum radiation by raising the height of
my low 75m dipole. Is there a way for me to accomplish the same thing
by changing the current distribution?
--
73, Cecil http://www.qsl.net/w5dxp



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Reg, G4FGQ wrote:
"Changing the current distribution and changing the effective height are
one and the same thing."

Could be. Antennas are reciprocal. A common definition of "effective
height" for receiving antennas is simply the ratio of volts out of the
antenna versus the field volts per meter acting upon the antenna.
Constants provide effective height in feet, meters, or in the units of
your choice.

Best regards, Richard Harrison, KB5WZI