"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
out of phase we have Va-Vb=0 . A loaded loop has a cardioid patter and two
in phase , like the horizontal WF , have over 90 dB attenuation on vertical
polarized signals at the front lobe and at same time has 11.5 to 1332 dB
directivity for horizontal signals
The main lobe is near 40 degree and + - 20 degree for 3db, it means deep
null from 90 degree plane, not only from the side , also with a 5 to 8
degree difference in phase you can enjoy 20 to 40 F.B.
So the HWF can null the noise in all direction coming from ground wave,
simple as that. You can turn the HWF and aim to the DX with good directivity
like a 3 elements full size beam from 160, 80, 40 and 30m in one single
feed line.
The HWF needs to be at least 30 Ft. high for 80m and 60 Ft high for good
performance on 160m. Even on 40m and 30m the HWF offer the same noiseless
performance.
I called noiseless because with 90 dB attenuation on ground wave, mainly man
made noise, the noise level during the day without propagation noise or sky
wave is below the noise floor of the receiver.
The challenger is to avoid any common mode noise pickup from the feed line,
the feed line is a vertical antenna and it will deteriorate the vertical
attenuation if you don't choke it, not that shield is our enemy for that.
Quad shield just increase the common mode noise problems.
I recorded some signals comparing a good RDF vertical HF, is my main antenna
for almost 10 years, I built on in 2006. The results speak for itself, it
is a booring 10 minutes video and at the end somebody started a huge
intentional QRM on top of the DX, unbelievable bad in all aspects. It is my
Drop box
https://www.dropbox.com/s/xqrtj86jout29ph/MVI_0075.MP4?dl=0
Another solution not so efficient because does not have directivity, but
works very well is the old K6STI loop >>
http://www.angelfire.com/md/k3ky/page45.html
Same issue , you need to use unshielded twisted pair to feed the loop, no
shield !!! you don't what that on the feed line.
73's
N4IS
_________________
Topband Reflector Archives - http://www.contesting.com/_topband
|