Topband: Looking for 160m narrow beam RX advice - an interesting combination of ideas

[JC]

> I am going to try to get a horizontal loop aimed at 70 degrees up < 

Hi Rick

It is not recommended to tilt  and elevate the loop. There is two reasons it
improve the signal to noise ratio, First is the attenuation of the vertical
component at the same direction you are receiving the DX signal, Second is
the directivity for horizontal  signal. Her the first one is the most
important to kill local ground noise. I used to tune the HWF for best RDF,
but I've seen better results tuning it for max attenuation of the vertical
field. Since I did that I rarely use my vertical WF, including for signals
coming due north.
 
Horizontal signals get very attenuated near the ground, that's why you
should install the loops or the loop as high you can. Different from dipoles
the takeoff angle is the same for any height above ground. 

Long path propagation SSE SSW is the most interesting observation of
polarization coming horizontal polarized. Since I install the first HWF back
in 2009 I started to copy long path signals from South Asia in a daily base
during Fall and Winter. 6 month season. On 160m, the activity is a key
factor, like I heard Peter from HS0ZAI the only day he was active on 160m, I
can’t say the propagation is not open if there is no activity.  There have
been several reports of long path propagation this year on 160m , on 80 m is
it pretty common.

The HWF because the difference in polarization , the interaction with TX
antenna is 25 to 27  dB reduced. But not the same for low dipoles, elevated
radials or any other resonant wire or structure at the same band,, Remember
the HWF has the same performance  on 160 . 80. 40 and some good usability on
30m, However the gain is different, like 160m -50 dB,  80m -30 dB  , 40m -10
dB e almost some gain on 30m, these figures depend on the size of the HWF.
This also means the same preamp is not recommended for all bands, it needs
to be tuned and what I use is preamp tuned per band with the adequate gain.
Just few days ago I measure signal from two local broadcast in South
Caroline, Radio Martã aimed for Cuba, on 11.930 MHz  signal at the receiver
-13dBm (s9+60) and 13.820 MHz, -20 dBm , the preamp can/may  handle it but
these numbers can overload any receiver if you don't adjust the gain. Also
the IM or PIM became a problem ,  the product of 1890 can be very strong.  

Regards
JC
N4IS

 

-----Original Message-----
From: Richard (Rick) Karlquist [mailto:richard at karlquist.com] 
Sent: Thursday, January 08, 2015 2:36 PM
To: JC; 'topband'
Subject: Re: Topband: Looking for 160m narrow beam RX advice - an
interesting combination of ideas

On 1/8/2015 5:36 AM, JC wrote:
>
> "An array of loops is two loops for two directions.
>
> Hi guys
>
> The simple solution that is working very well since 2009 is the HWF. Why
not
> two  horizontal loaded loops end-fire.   Two identical horizontal loops
see
> the ground wave signal at the same way  Va=Vb  and because the 180 
> degree

I have been modeling horizontal loops recently.  The idea is to reject
vertically polarized ground wave noise.  As far as I can tell, a horizontal
loop rejects vertically polarized noise from any direction.
As opposed to a dipole that receives vertically polarized signals from the
ends.  You can make the loop just about any size or shape and terminate the
side opposite the feed with a resistor of around 1000 ohms to get a cardioid
pattern.  There is a resonance when the perimeter of the loop is a half wave
long, so you need to stay somewhat below this length, which would be
something like 260 feet on 160 meters.
That's a huge loop.  The higher the loop and the bigger the loop, the more
signal you get (that is gross signal, not SNR).  You need to overcome your
preamp noise.

As JC says, these loops can be the building blocks of an array.

I am going to try to get a horizontal loop aimed at 70 degrees up for the
upcoming CQWW contests as a proof of concept.  In the recent SP, I tried a
horizontal dipole, but it was no better than the transmit vertical.  In the
past, dipoles have been good receiving antennas.  I am thinking it is a
matter of what direction the dominant noise is coming from as to whether
they work.  The loop doesn't have that issue.

Rick N6RK