On 10/14/2015 9:20 PM, K2CB wrote:
>
> While we are discussing 80m antennas, can someone shed some light on
> the radiation pattern of the SteppIR dipole option for the larger
> DB36 and DB42 models?
The SteppIR is a shortened dipole (end loaded). Radiation pattern
would typically be within 0.5 to 1 dB of a "flat" full size dipole
at the same height.
> Is the maximum radiation towards the front and back of the antenna
> elements, or off the left and right sides of the boom?
Maximum radiation is broadside to the boom - at right angles to the
beam on the other bands.
> I also have legs for 160m fed off the same feed point, which sit/hang
> 2 or 3 feet above the 80m legs. They are tied to the same end posts
> as the 80m legs. I just leave the ropes for the 80 m legs a little
> bit looser so they sag down below the 160 m legs by a few feet on the
> way down from the tower.
The 80m legs are redundant and most certainly couple with the SteppIR
when the SteppIR boom is parallel to the inverted V. I would get rid
of the 80m legs and make the inverted V a 160 meter only antenna or
consider shunt feeding the tower for 160 and get rid of the wire all
together.
As a non-scientific comparison, my buddy (N2II) up the road a few
miles with only a two element 24ft boom linear loaded 40m yagi at the
same 89ft height seems to do equally as good, if not slightly better,
as I do with the three element 36ft boom SteppIR on 40 m.
The difference between a two and three element yagi is only a couple
dB. If your buddy has a slightly better ground elevation (think HFTA)
in some directions, he will most likely make up a dB or two very
easily.
73,
... Joe, W4TV
On 10/14/2015 9:20 PM, K2CB wrote:
While we are discussing 80m antennas, can someone shed some light on
the radiation pattern of the SteppIR dipole option for the larger
DB36 and DB42 models?
Is the maximum radiation towards the front and back of the antenna
elements, or off the left and right sides of the boom?
Also, what would you consider this design? Some sort of "H" dipole?
Anyone know of any good write ups on this sort of "H" antenna design
(the 80m portion, obviously) on the web?
Finally, has anyone compared this to an 80m inverted V at similar
heights?
I have the DB36 with the dipole option at 91 ft, and an inverted V
80m dipole with the feed point/ apex just below it at 89 feet. The
end of the two legs of the inverted v are at approximately 45ft above
ground.
I also have legs for 160m fed off the same feed point, which sit/hang
2 or 3 feet above the 80m legs. They are tied to the same end posts
as the 80m legs. I just leave the ropes for the 80 m legs a little
bit looser so they sag down below the 160 m legs by a few feet on the
way down from the tower. Unfortunately I have no trees on the
property, so the only tie offs are two posts in the far corners of my
property.
I am sure there is some severe interaction, so it really is hard for
me to tell which one works better sometimes.
My experience with both seems to show that the StrppIR "H" dipole is
a little better for the long haul stuff into Europe, while the
inverted V is much better (by 10db) for the close in (200-300 mile)
and rag chew type contacts on 80 m.
On a related note, I believe I am having some noticeable interaction
with these inverted V's when I have the SteppIR on 40 m. As a
non-scientific comparison, my buddy (N2II) up the road a few miles
with only a two element 24ft boom linear loaded 40m yagi at the same
89ft height seems to do equally as good, if not slightly better, as I
do with the three element 36ft boom SteppIR on 40 m.
I have no experience with modeling, unfortunately. My area of
expertise in the hobby is radio and amplifier repair. FWIW, I am
willing to trade repair services for modeling services if anyone is
ever interested in modeling my antenna set up.
Eric K2CB
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