"Tehrasha Darkon" wrote in message
...
On Thu, 15 Mar 2007 00:08:30 +0000, west wrote:

I know I can go to eham.com but I like the advice on rraa better. I also
know that this question is somewhat subjective, but if you will, please
indulge. :-)
What is flat out the best vertical HF antenna in your opinion and why?
Thanks in advance.

west
AF4GC

SteppIR. Why use a tuner to match your radio to your antenna, when you can
make your antenna match your radio?

--Teh

No Tuner i.e. TransMatch -- The SteppIRT vertical is remotely adjustable
in length, with continuous coverage from 40 meters through 6 meters - and
every frequency in between.

A vertical antenna that is precisely adjustable in length while in the air
solves the coverage problem, and in addition has vastly improved performance
over existing fixed length verticals. The ability to tune the antenna to a
specific frequency results in excellent performance on every band - and this
means the entire band, with very low VSWR. Resonant antennas must be made a
specific length to operate optimally on a given frequency. So, instead of
trying to "trick" the antenna into thinking it is a different length (traps,
coils, etc), why not just change the antenna length? This is what we have
done with the new SteppIR verticals.

http://www.steppir.com/

CL

"Caveat Lector" wrote in
:


"Tehrasha Darkon" wrote in message
...
On Thu, 15 Mar 2007 00:08:30 +0000, west wrote:

I know I can go to eham.com but I like the advice on rraa better. I
also know that this question is somewhat subjective, but if you
will, please indulge. :-)
What is flat out the best vertical HF antenna in your opinion and
why? Thanks in advance.

west
AF4GC

SteppIR. Why use a tuner to match your radio to your antenna, when
you can make your antenna match your radio?

--Teh

No Tuner i.e. TransMatch -- The SteppIRT vertical is remotely
adjustable in length, with continuous coverage from 40 meters through
6 meters - and every frequency in between.

A vertical antenna that is precisely adjustable in length while in the
air solves the coverage problem, and in addition has vastly improved
performance over existing fixed length verticals. The ability to tune
the antenna to a specific frequency results in excellent performance
on every band - and this means the entire band, with very low VSWR.
Resonant antennas must be made a specific length to operate optimally
on a given frequency. So, instead of trying to "trick" the antenna
into thinking it is a different length (traps, coils, etc), why not
just change the antenna length? This is what we have done with the new
SteppIR verticals.

This analysis is along the lines of the traditional "resonant antennas
work better" line.

Sure, a marconi antenna that is adjusted to be a physical quarter wave on
the operating frequency has a feedpoint impedance that yields a low VSWR
on the coax, and feedline losses are relatively low, but the equivalent
loss resistance of the ground connection is significant relative to the
radiation resistance. A quarter wave marconi requires an extensive earth
system for good efficiency.

My reading of Cebik's article at http://www.cebik.com/gp/gr.html is that
simple 4 radial installations have 10 ohms or so loss resistance greater
than extensive (128 radial) systems, which themselves aren't zero loss.
The modelled feedpoint R varies from 4 to 18 ohms above the radiation
resistance of a quarter wave over perfect ground, which implies a
feedpoint efficiency of 90% to 66% respectively.

On the other hand, a longer non-resonant radiator (say approaching a half
wave) has higher radiation resistance (relative to the equivalent ground
loss resistance) which more than offsets the loss expected in a matching
network needed to operate the coax at near unity VSWR for low line loss.
Not only might the longer radiator be more efficient, but it well have a
better pattern (eg higher gain at lower angles or radiation).

It isn't clear to me that the Steppir has "vastly improved
performance over existing fixed length verticals" as you put it. With
enough radials, it is about as good as good verticals get, but there are
other good verticals that don't need as extensive a radial system.

Owen

Owen Duffy wrote in
:

....
But...

What if ground resistance was 10 ohms, efficiency of the antenna and
loading coil would be 5/(10+5+0.7) or 32% (5dB loss). That will help
the line loss though, now with a feed Z of 15.7-j22, loss in the same
line is 1dB and input Z is 16+j2. ATU loss might be more like 0.4dB.
Total loss is 5+1+0.4 or 6.4dB.

I didn't want to give the impression that this isn't a significant
improvement over the unloaded vertical on 7MHz.

The Force12 page give an analysis and loosely claims 16dB improvement
over the unloaded antenna, but that is probably based on ignoring ground
resistance again.

Assuming ground resistance of 10 ohms, feedpoint Z would be 15-j460,
ground loss 5dB, line loss 12.2dB, ATU loss ~1.1dB for a total system
loss of 18.3dB.

Improvement from system loss of 18.3dB to 6.4dB is 12dB, a little less
than they might want you to think, but very worthwhile.

Of course results are very sensitive to the ground scenario.

Owen

On Thu, 15 Mar 2007 00:08:30 GMT, "west" wrote:

I know I can go to eham.com but I like the advice on rraa better. I also
know that this question is somewhat subjective, but if you will, please
indulge. :-)
What is flat out the best vertical HF antenna in your opinion and why?
Thanks in advance.

west
AF4GC

What I gather from what I read here and all the publications I can get
my hands on it is a quarter wave radiator over 130 radials that are at
least 1/4 wave long.

That may not hold true if you consider radiators longer than 1/4 wave.
"Best" is a very loose spec.

I am in the throws of constructing what I think is "Best" for me. I
started out with a 28 foot radiator and three twenty five foot
radials. It worked. It works a whole lot better now with a total of 36
radials. 14 are about 70 ft, 16 are about 36 ft, 6 are less than 36
ft.

I will work on a taller and more robust radiator next.

I feed it with a SGC-237 tuner. I can only guess the tuner losses are
similar to what a comparable tuner built from the TLW program in the
ARRL Antenna Handbook predict.

The limiting factors are the radiator, the ground and the losses.

What is "Best" for you will depend on your set of compromises.

My expectations are focused on 160-80-40 meters. It was pretty
inexpensive until I added the tuner!

John Ferrell W8CCW
"Life is easier if you learn to
plow around the stumps"

The Force12 page give an analysis and loosely claims 16dB improvement
over the unloaded antenna, but that is probably based on ignoring ground
resistance again.


Force 12 advertising has been ignoring the laws of physics since they
first went into business and started their fantasy gain baloney...
Now, that is not to take away from Tom's innovative approach to beam
design and beam construction... He has done some nice things...

denny / k8do