Noise level between two ant types
 

Take 2 antennas on 6m - one is an inverted V and the
other a 3el quad. Both are mounted at near the same
height and fed with about the same length of coax.

Is it normal for the quad to be quieter?

Signals are louder on the quad - it's just the background
noise is higher on the V.

Just curious.....

--
73's de Ken KG0WX - Kadiddlehopper #11808,
Flying Pigs #-1055, Grid EM17io, FT-857D, AL-84,
Elecraft XG2, 4SQRP Tenna Dipper, Heath GD-1B

Noise level between two ant types
 

Ken Bessler wrote:
Take 2 antennas on 6m - one is an inverted V and the
other a 3el quad. Both are mounted at near the same
height and fed with about the same length of coax.

Is it normal for the quad to be quieter?

Noise almost always arrives from multiple directions and from different
directions than the desired signal.

It is normal for ANY antenna to be quieter when it is more directional.
As a matter of fact, it is expected that S/N ratio is a direct function
of directivity of the antenna as long as the noise and signal are not
coming from the same direction.

To answer your question, it would be very abnormal if your quad (or
Yagi or any other directional antenna) was noisier than a broad pattern
antenna like your Inverted Vee dipole.

By the way, a real Inverted V is a longwire array fed at one end. I'm
assuming you really have an Inverted Vee dipole, and not a true
Inverted V.

73 Tom

Noise level between two ant types
 

Not to mention that noise is normally a phenonmen
of the Vertical Plane (which , depending on how
steep your inverted "vee" is, will contain some
vertical component, while the yagi/quad is
Horizontal to the plane. This has been a factor
on vhf for years, as noise levels tend to peak
at 6 meters (50 MHz). The MAIN reason that F.M.
is Vertical polarized is that for mobiles, it is
easy to construct an omni-directional antenna.
Most vhf manuals detail this effect! Jim NN7K

wrote:
Ken Bessler wrote:

Take 2 antennas on 6m - one is an inverted V and the
other a 3el quad. Both are mounted at near the same
height and fed with about the same length of coax.

Is it normal for the quad to be quieter?


Noise almost always arrives from multiple directions and from different
directions than the desired signal.

It is normal for ANY antenna to be quieter when it is more directional.
As a matter of fact, it is expected that S/N ratio is a direct function
of directivity of the antenna as long as the noise and signal are not
coming from the same direction.

To answer your question, it would be very abnormal if your quad (or
Yagi or any other directional antenna) was noisier than a broad pattern
antenna like your Inverted Vee dipole.


73 Tom

Noise level between two ant types
 

Jim - NN7K wrote:
Not to mention that noise is normally a phenonmen of the Vertical Plane
(which , depending on how steep your inverted "vee" is, will contain some
vertical component, while the yagi/quad is Horizontal to the plane.

Quads are a lot less noisy than Yagis when the wind
is blowing in the Arizona desert. Quads have a DC
short across the feedpoint that reduces noise from
static buildup.
--
73, Cecil http://www.qsl.net/w5dxp

Noise level between two ant types
 

Cecil Moore wrote:
Quads are a lot less noisy than Yagis when the wind
is blowing in the Arizona desert. Quads have a DC
short across the feedpoint that reduces noise from
static buildup.

Virtually all Yagi's have dc paths to discharge the elements.

The primary reason a quad is quiter is it has no sharp protruding ends
that are sticking way out in the air.

As a matter of fact if you research the quad, it was initially used to
eliminate corona at radio station HCJB.

Try this test, wire a small 2.5 MHh RF choke across your antenna and
check the before and after noise levels. They will not change.

73 Tom

Noise level between two ant types
 

wrote:
As a matter of fact if you research the quad, it was initially used to
eliminate corona at radio station HCJB.

Yep, designed by my distant cousin, BTW.

Try this test, wire a small 2.5 MHh RF choke across your antenna and
check the before and after noise levels. They will not change.

Obviously a false statement based on limited knowledge and
experience. Any ham living around Phoenix will be glad to
enlighten you.

That's exactly how I eliminated the noise and arcing on my
first bare-wire G5RV installed in Arizona. I didn't measure
the change in noise level but it went from arcing at the coax
connector to not arcing at the coax connector which was
acceptable to me.

If the driven element on a Yagi is an uninsulated dipole, it
is susceptible to wind driven noise on the driven element just
like my G5RV was.

Just because you have never experienced that type of noise in
Georgia doesn't mean it doesn't exist in Arizona. I dare say
you haven't experienced a lot of things that exist in reality.
Mary G. comes to mind. :-)
--
73, Cecil http://www.qsl.net/w5dxp

Noise level between two ant types
 

Cecil Moore wrote:
Try this test, wire a small 2.5 MHh RF choke across your antenna and
check the before and after noise levels. They will not change.

Obviously a false statement based on limited knowledge and
experience.

When did you do that test?

When did you compare other antennas, like noise on plummer's delight
antennas?

How many Yagi's have floating driven elements without ground paths?

Noise level between two ant types
 

Noise level between two ant types
 

Tom Ring wrote:
wrote:

How many Yagi's have floating driven elements without ground paths?


None on VHF/UHF/SHF that I build and anyone I know builds. Maybe on HF
it's different. I don't know why it should be, though.

Although normally all the other elements float on anything but 6 meters.

You're both over-generalizing. In VHF/UHF/SHF yagi construction it's
quite common to find driven elements connected to the boom or floating.
The same choice or a different choice may be made for the parasitic
elements.

There are many different reasons for these choices, including:
* size of elements and boom
* mechanical strength requirements
* effect of boom on element resonance (depends on mounting method)
* long-term effect stability of element resonance
* feed impedance of driven element (affects choice of feed method)
* number of elements involved
* perceived or actual effects of "static".

This makes the choices quite complex, and makes generalization
impossible. Quote an example, and someone else will quote you a
counter-example.

Just one other thing: PLEASE let's not talk about elements being
"grounded", way up there at the top of a tower.



--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

Noise level between two ant types
 

Ian White GM3SEK wrote:

This makes the choices quite complex, and makes generalization
impossible. Quote an example, and someone else will quote you a
counter-example.

Just one other thing: PLEASE let's not talk about elements being
"grounded", way up there at the top of a tower.

The entire topic and people's reactions about precepitation noise is
fascinating.

People actually seem to think the little particles voving through the
air charge the antenna to a different potential than the air around the
antenna, and that a "dc" path to earth or "dc" path around an element
somehow magically stops RF noise.

Certainly it is possible for a conductor very well insulated from earth
to charge to the potential of the static field around the antenna, and
flash over to "ground" through some path that breaks down. Of course
only a fool would have equipment that allows that to happen while large
antennas are being used or connected. This is an entirely different
thing than the corona discharge that makes what people typically call
"P-static".

73 Tom