On Thursday, November 6, 2014 12:46:04 PM UTC-6, wrote:
Jeff wrote:
I would think a dipole would be a bad candidate for a "short" antenna
as you need to get the matching stuff close to the antenna to avoid
I^2R losses.

Some sort of ground mounted, or close to the ground, antenna might
make a better choice.


A dipole may be a better candidate, if you use a monopole then although
you will be able to put your matching close to the antenna, providing an
effective earth screen becomes vital and earth losses may outweigh any
advantage.

Of course if you do use a dipole it is vital that any matching is at the
feed point and not on the end of a length of coax or the losses will soar.

The issue with dipoles is height.

As the height of a dipole decreases below 1/2 wavelength the pattern
elevation angle starts increasing and very quickly has most of the
energy going straight up.

At 160M that means getting the dipole 260 feet up in the air, and if
you can do that, why would you be concerned about a short antenna
as a full 1/4 wave 160M antenna is only about 140 feet tall?



--
Jim Pennino

When I was on 160m a lot, I had both the T vertical, and I also
had a "Z" dipole, which was the only way I could fit a dipole on
this lot without loading coils. In some cases for NVIS, the Z dipole
was a bit better, but overall, I prefer being vertical on 160.
On that band, the path doesn't really have to be that far for the
vertical to do as well or better than the very low dipole. And at
farther distances, the vertical will generally outperform the low
dipole by quite a large margin.

So if I could could only have one antenna, I would generally prefer
the vertical, because a dipole on that band really needs to be pretty
high to play well. My Z dipole was only at about 40 feet at the apex,
which is only slightly above 1/16 of a wave up. It was fairly
lame overall.

W8JI plays on 160m a lot, and has lots of good info about that band
and his various antennas on his web site, if it's still around.
I haven't looked at it in a while.

wrote:
On Thursday, November 6, 2014 12:46:04 PM UTC-6, wrote:
Jeff wrote:
I would think a dipole would be a bad candidate for a "short" antenna
as you need to get the matching stuff close to the antenna to avoid
I^2R losses.

Some sort of ground mounted, or close to the ground, antenna might
make a better choice.


A dipole may be a better candidate, if you use a monopole then although
you will be able to put your matching close to the antenna, providing an
effective earth screen becomes vital and earth losses may outweigh any
advantage.

Of course if you do use a dipole it is vital that any matching is at the
feed point and not on the end of a length of coax or the losses will soar.

The issue with dipoles is height.

As the height of a dipole decreases below 1/2 wavelength the pattern
elevation angle starts increasing and very quickly has most of the
energy going straight up.

At 160M that means getting the dipole 260 feet up in the air, and if
you can do that, why would you be concerned about a short antenna
as a full 1/4 wave 160M antenna is only about 140 feet tall?



--
Jim Pennino

When I was on 160m a lot, I had both the T vertical, and I also
had a "Z" dipole, which was the only way I could fit a dipole on
this lot without loading coils. In some cases for NVIS, the Z dipole
was a bit better, but overall, I prefer being vertical on 160.
On that band, the path doesn't really have to be that far for the
vertical to do as well or better than the very low dipole. And at
farther distances, the vertical will generally outperform the low
dipole by quite a large margin.

That is exactly what one would expect from the patterns.

So if I could could only have one antenna, I would generally prefer
the vertical, because a dipole on that band really needs to be pretty
high to play well. My Z dipole was only at about 40 feet at the apex,
which is only slightly above 1/16 of a wave up. It was fairly
lame overall.

W8JI plays on 160m a lot, and has lots of good info about that band
and his various antennas on his web site, if it's still around.
I haven't looked at it in a while.

I remember him. AIR he uses 1/4 verticals at home and was very
involved in mobile antenna contests at one point.



--
Jim Pennino